Prune with sharp garden shears, 0.5-1 cm above the set of two healthy leaf buds. Always remove all withered leaves and either whole stems or just the parts that died down (e.g. because of freezing).

During the first year all clematis should be cut not higher than 30 cm from the base, to encourage the growth of new stems at the base of the vine. Similar, or even better result can be obtained by laying the stems flat on the ground and covering them with mulch, just as you did when planting clematis. It will foster the strength of the plants and thus ensure better flowering and higher immunity to diseases. In subsequent years, pruning depends on the variety and the season in which it blooms. (refer to the last column in a catalogue chart and drawing 1 and drawing 2).
When it comes to pruning, clematis can be roughly divided into three groups, which we’ll call
1 (none), 2 (light) and 3 (hard).

Notice: By December 2004 we have adopted an international classification of clematis pruning groups. Pruning group 1 corresponds to the former group C, group 2 to the former group A, group 3 to the former group B.

Group 1 (none)- are varieties that flower only on growth produced the previous year: Clematises from Montana and Atragene Group. They are generally not pruned at all, but if it is necessary to prune some overgrowth, cut immediately after flowering, usually not lower than 1 m above the ground.

Popular varieties which should not be pruned:

  • Clematis armandii ‘Apple Blossom’
  • Clematis ‘Albina Plena’
  • Clematis ‘Lemon Dream’PBR
  • Clematis ‘Markham’s Pink’
  • Clematis ‘Purple Dream’PBR
  • Clematis ‘Stolwijk Gold’
  • Clematis cirrhosa var. purpurescens ‘Freckles’
  • Clematis japonica
  • Clematis montana ‘Elizabeth’
  • Clematis montana var. rubens
  • Clematis sibirica

Group 2 (light) – are the large-flowered varieties that begin to bloom in May or early June with the first flush of flowers appearing on the previous year’s growth, followed by a smaller flush on new growth. Pruning should consist of cutting shoots at a height of 100-150 cm from the base (the younger a plant the lower it should be cut). This is a safe way of pruning if we are unsure which category our plant falls into.

Popular varieties which should be pruned at a height of 100-150 cm:

Group 3 (hard) – are later flowering species and varieties that bloom on new growth from the end of June to July e.g. cultivars from Viticella Group and Jackmanii Group. These should be hard pruned above second or third set of the buds, 20-50 cm from the ground. This pruning pattern should also be applied to vigorous vines if you want to reduce their growth: Clematis from Tangutica Group. As for herbaceous perennial clematis and cultivars from Texensis Group remove all dead stems just above the base, cut the rest 5-10 cm above the ground.

Popular varieties which should be pruned at a height of 20-50 cm:

  • Clematis ‘Błękitny Anioł’ BLUE ANGEL
  • Clematis ‘Comtesse de Bouchaud’
  • Clematis ‘Etoile Violette’
  • Clematis ‘Jackmanii’
  • Clematis ‘Krakowiak’ PINK MINK
  • Clematis ‘Mme Julia Correvon’
  • Clematis ‘Prince Charles’
  • Clematis ‘Princess Diana’
  • Clematis ‘Romantika’
  • Clematis ‘Rouge Cardinal’
  • Clematis ‘Sweet Summer Love’PBR
  • Clematis ‘Venosa Violacea’
  • Clematis crispa
  • Clematis fusca
  • Clematis x triternata ‘Rubromarginata’

Known and Probable Human Carcinogens

In general, the American Cancer Society does not determine if something causes cancer (that is, if it is a carcinogen). Instead, we rely on the determinations of other respected agencies, such as the International Agency for Research on Cancer (IARC) and the US National Toxicology Program (NTP).

The lists below are from IARC and NTP, and more information on each of these known and probable human carcinogens can be found on their websites.

To learn more about these agencies and how they study and classify cancer causes, see Determining if Something Is a Carcinogen.

What you should know

  • The IARC and NTP act independently. Many known or suspected carcinogens appear on both organization’s lists; however, if a substance or exposure is only on one agency’s list, this it does not necessarily mean there is a controversy, as one agency may not have evaluated it.
  • These lists are alphabetical, but many of the substances and exposures here can go by different names. This can make it hard to find a particular substance on one or both of these lists.
  • These lists include only those agents that have been evaluated by the agencies. These agencies tend to focus on substances and exposures most likely to cause cancer, but there are many others that have not been fully studied yet.
  • These lists include agents that have been classified as known and probable human carcinogens. The lists do not include substances that have been classified as possible carcinogens, for which the evidence is not as strong. These lists also do not include substances evaluated as “not classifiable as to its carcinogenicity in humans.”
  • Most of the agents on the lists have been linked only with certain kinds of cancer, not all cancer types. See each agency’s website for more details about the substances and exposures on their lists.
  • The lists describe the level of evidence that something can cause cancer, not how likely it is that something will cause cancer in any person (or how much it might raise your risk). For example, IARC considers there to be strong evidence that both tobacco smoking and eating processed meat can cause cancer, so both are listed as “carcinogenic to humans.” But smoking is much more likely to cause cancer than eating processed meat, even though both are in the same category.
  • Carcinogens do not cause cancer at all times, under all circumstances. In other words, a carcinogen does not always cause cancer in every person, every time there is any kind of exposure. Some may only be carcinogenic if a person is exposed in a certain way (for example, swallowing it as opposed to touching it). Some may only cause cancer in people who have a certain genetic makeup. Some of these agents may lead to cancer after only a very small exposure, while others might require intense exposure over many years. Again, refer to the agencies’ reports for specifics.
  • Even if a substance or exposure is known or suspected to cause cancer, this does not necessarily mean that it can or should be avoided at all costs. For example, sunlight is a major source of ultraviolet (UV) rays, which are a known cause of skin cancer, but it’s not practical (or advisable) to completely avoid the sun. (See How to Interpret News About Cancer Causes for more about this.)
  • These lists also include many commonly used medicines, particularly some hormones and drugs used to treat cancer. For example, tamoxifen increases the risk of certain kinds of uterine cancer, but it can be very useful in treating some breast cancers, which may be more important for some women. If you have questions about a medicine that appears on one of these lists, be sure to ask your doctor.

Known human carcinogens

International Agency for Research on Cancer
Group 1: Carcinogenic to humans

  • Acetaldehyde (from consuming alcoholic beverages)
  • Acheson process, occupational exposure associated with
  • Acid mists, strong inorganic
  • Aflatoxins
  • Alcoholic beverages
  • Aluminum production
  • 4-Aminobiphenyl
  • Areca nut
  • Aristolochic acid (and plants containing it)
  • Arsenic and inorganic arsenic compounds
  • Asbestos (all forms) and mineral substances (such as talc or vermiculite) that contain asbestos
  • Auramine production
  • Azathioprine
  • Benzene
  • Benzidine and dyes metabolized to benzidine
  • Benzopyrene
  • Beryllium and beryllium compounds
  • Betel quid, with or without tobacco
  • Bis(chloromethyl)ether and chloromethyl methyl ether (technical-grade)
  • Busulfan
  • 1,3-Butadiene
  • Cadmium and cadmium compounds
  • Chlorambucil
  • Chlornaphazine
  • Chromium (VI) compounds
  • Clonorchis sinensis (infection with), also known as the Chinese liver fluke
  • Coal, indoor emissions from household combustion
  • Coal gasification
  • Coal-tar distillation
  • Coal-tar pitch
  • Coke production
  • Cyclophosphamide
  • Cyclosporine (ciclosporin)
  • 1,2-Dichloropropane
  • Diethylstilbestrol (DES)
  • Engine exhaust, diesel
  • Epstein-Barr virus (EBV) (infection with)
  • Erionite
  • Estrogen-only menopausal therapy
  • Estrogen-progestogen menopausal therapy (combined)
  • Estrogen-progestogen oral contraceptives (combined) (Note: There is also convincing evidence in humans that these agents confer a protective effect against cancer in the endometrium and ovary)
  • Ethanol in alcoholic beverages
  • Ethylene oxide
  • Etoposide
  • Etoposide in combination with cisplatin and bleomycin
  • Fission products, including strontium-90
  • Fluoro-edenite fibrous amphibole
  • Formaldehyde
  • Haematite mining (underground)
  • Helicobacter pylori (infection with)
  • Hepatitis B virus (chronic infection with)
  • Hepatitis C virus (chronic infection with)
  • Human immunodeficiency virus type 1 (HIV-1) (infection with)
  • Human papilloma virus (HPV) types 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59 (infection with) (Note: The HPV types that have been classified as carcinogenic to humans can differ by an order of magnitude in risk for cervical cancer)
  • Human T-cell lymphotropic virus type I (HTLV-1) (infection with)
  • Ionizing radiation (all types)
  • Iron and steel founding (workplace exposure)
  • Isopropyl alcohol manufacture using strong acids
  • Kaposi sarcoma herpesvirus (KSHV), also known as human herpesvirus 8 (HHV-8) (infection with)
  • Leather dust
  • Lindane
  • Magenta production
  • Melphalan
  • Methoxsalen (8-methoxypsoralen) plus ultraviolet A radiation, also known as PUVA
  • Methyl-CCNU
  • 4,4′-Methylenebis(chloroaniline) (MOCA)
  • Mineral oils, untreated or mildly treated
  • MOPP and other combined chemotherapy including alkylating agents
  • 2-Naphthylamine
  • Neutron radiation
  • Nickel compounds
  • N’-Nitrosonornicotine (NNN) and 4-(N-Nitrosomethylamino)-1-(3-pyridyl)-1-butanone (NNK)
  • Opisthorchis viverrini (infection with), also known as the Southeast Asian liver fluke
  • Outdoor air pollution (and the particulate matter in it)
  • Painter (workplace exposure as a)
  • 3,4,5,3′,4′-Pentachlorobiphenyl (PCB-126)
  • 2,3,4,7,8-Pentachlorodibenzofuran
  • Pentachlorophenol
  • Phenacetin (and mixtures containing it)
  • Phosphorus-32, as phosphate
  • Plutonium
  • Polychlorinated biphenyls (PCBs), dioxin-like, with a Toxicity Equivalency Factor according to WHO (PCBs 77, 81, 105, 114, 118, 123, 126, 156, 157, 167, 169, 189)
  • Processed meat (consumption of)
  • Radioiodines, including iodine-131
  • Radionuclides, alpha-particle-emitting, internally deposited (Note: Specific radionuclides for which there is sufficient evidence for carcinogenicity to humans are also listed individually as Group 1 agents)
  • Radionuclides, beta-particle-emitting, internally deposited (Note: Specific radionuclides for which there is sufficient evidence for carcinogenicity to humans are also listed individually as Group 1 agents)
  • Radium-224 and its decay products
  • Radium-226 and its decay products
  • Radium-228 and its decay products
  • Radon-222 and its decay products
  • Rubber manufacturing industry
  • Salted fish (Chinese-style)
  • Schistosoma haematobium (infection with)
  • Semustine (methyl-CCNU)
  • Shale oils
  • Silica dust, crystalline, in the form of quartz or cristobalite
  • Solar radiation
  • Soot (as found in workplace exposure of chimney sweeps)
  • Sulfur mustard
  • Talc containing asbestiform fibres
  • Tamoxifen (Note: There is also conclusive evidence that tamoxifen reduces the risk of contralateral breast cancer in breast cancer patients)
  • 2,3,7,8-Tetrachlorodibenzo-para-dioxin (TCDD); “dioxin”
  • Thiotepa
  • Thorium-232 and its decay products
  • Tobacco, smokeless
  • Tobacco smoke, secondhand
  • Tobacco smoking
  • ortho-Toluidine
  • Treosulfan
  • Trichloroethylene
  • Ultraviolet (UV) radiation, including UVA, UVB, and UVC rays
  • Ultraviolet-emitting tanning devices
  • Vinyl chloride
  • Welding fumes
  • Wood dust
  • X- and Gamma-radiation

National Toxicology Program 14th Report on Carcinogens
“Known to be human carcinogens”

  • Aflatoxins
  • Alcoholic beverage consumption
  • 4-Aminobiphenyl
  • Analgesic mixtures containing phenacetin
  • Aristolochic acids
  • Arsenic and inorganic arsenic compounds
  • Asbestos
  • Azathioprine
  • Benzene
  • Benzidine
  • Beryllium and beryllium compounds
  • Bis(chloromethyl) ether and technical-grade chloromethyl methyl ether
  • 1,3-Butadiene
  • 1,4-Butanediol dimethylsulfonate (also known as busulfan)
  • Cadmium and cadmium compounds
  • Chlorambucil
  • 1-(2-Chloroethyl)-3-(4-methylcyclohexyl)-1-nitrosourea (MeCCNU)
  • Chromium hexavalent compounds
  • Coal tar pitches
  • Coal tars
  • Coke oven emissions
  • Cyclophosphamide
  • Cyclosporin A
  • Diethylstilbestrol (DES)
  • Dyes metabolized to benzidine
  • Epstein-Barr virus (EBV)
  • Erionite
  • Estrogens, steroidal
  • Ethylene oxide
  • Formaldehyde
  • Hepatitis B virus
  • Hepatitis C virus
  • Human immunodeficiency virus type 1 (HIV-1)
  • Human papilloma viruses (HPVs): some genital-mucosal types
  • Human T-cell lymphotropic virus type 1 (HTLV-1)
  • Kaposi sarcoma-associated herpesvirus (KSHV) (also known as human herpesvirus 8, or HHV-8)
  • Melphalan
  • Merkel cell polyomavirus (MCV)
  • Methoxsalen with ultraviolet A therapy (PUVA)
  • Mineral oils (untreated and mildly treated)
  • Mustard gas
  • 2-Naphthylamine
  • Neutrons
  • Nickel compounds
  • Radon
  • Silica, crystalline (respirable size)
  • Solar radiation
  • Soots
  • Strong inorganic acid mists containing sulfuric acid
  • Sunlamps or sunbeds, exposure to
  • Tamoxifen
  • 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD); “dioxin”
  • Thiotepa
  • Thorium dioxide
  • Tobacco smoke, environmental
  • Tobacco, smokeless
  • Tobacco smoking
  • o‑Toluidine
  • Trichloroethylene (TCE)
  • Ultraviolet (UV) radiation, broad spectrum
  • Vinyl chloride
  • Wood dust
  • X-radiation and gamma radiation

Probable carcinogens

International Agency for Research on Cancer
Group 2A: Probably carcinogenic to humans

  • Acrylamide
  • Adriamycin (doxorubicin)
  • Androgenic (anabolic) steroids
  • Art glass, glass containers, and press ware (manufacture of)
  • Azacitidine
  • Biomass fuel (primarily wood), emissions from household combustion
  • Bitumens, occupational exposure to oxidized bitumens and their emissions during roofing
  • Bischloroethyl nitrosourea (BCNU), also known as carmustine
  • Captafol
  • Carbon electrode manufacture
  • Chloral
  • Chloral hydrate
  • Chloramphenicol
  • alpha-Chlorinated toluenes (benzal chloride, benzotrichloride, benzyl chloride) and benzoyl chloride (combined exposures)
  • 1-(2-Chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU)
  • 4-Chloro-ortho-toluidine
  • Chlorozotocin
  • Cisplatin
  • Cobalt metal with tungsten carbide
  • Creosotes
  • Cyclopentapyrene
  • DDT (4,4′-Dichlorodiphenyltrichloroethane)
  • Diazinon
  • Dibenzacridine
  • Dibenzanthracene
  • Dibenzopyrene
  • Dichloromethane (methylene chloride)
  • Dieldrin, and aldrin metabolized to dieldrin
  • Diethyl sulfate
  • Dimethylcarbamoyl chloride
  • N,N-Dimethylformamide
  • 1,2-Dimethylhydrazine
  • Dimethyl sulfate
  • Epichlorohydrin
  • Ethyl carbamate (urethane)
  • Ethylene dibromide
  • N-Ethyl-N-nitrosourea
  • Frying, emissions from high-temperature
  • Glycidol
  • Glyphosate
  • Hairdresser or barber (workplace exposure as)
  • Human papillomavirus (HPV) type 68 (infection with)
  • Hydrazine
  • Indium phosphide
  • IQ (2-Amino-3-methylimidazoquinoline)
  • Lead compounds, inorganic
  • Malaria (caused by infection with Plasmodium falciparum)
  • Malathion
  • 2-Mercaptobenzothiazole
  • Merkel cell polyomavirus (MCV)
  • 5-Methoxypsoralen
  • Methyl methanesulfonate
  • N-Methyl-N´-nitro-N-nitrosoguanidine (MNNG)
  • N-Methyl-N-nitrosourea
  • Nitrate or nitrite (ingested) under conditions that result in endogenous nitrosation
  • 6-Nitrochrysene
  • Nitrogen mustard
  • 1-Nitropyrene
  • N-Nitrosodiethylamine
  • N-Nitrosodimethylamine
  • 2-Nitrotoluene
  • Non-arsenical insecticides (workplace exposures in spraying and application of)
  • Petroleum refining (workplace exposures in)
  • Pioglitazone
  • Polybrominated biphenyls (PBBs)
  • Procarbazine hydrochloride
  • 1,3-Propane sultone
  • Red meat (consumption of)
  • Shiftwork that involves circadian disruption
  • Silicon carbide whiskers
  • Styrene
  • Styrene-7,8-oxide
  • Teniposide
  • Tetrabromobisphenol A
  • 3,3′,4,4′-Tetrachloroazobenzene
  • Tetrachloroethylene (perchloroethylene)
  • Tetrafluoroethylene
  • 1,2,3-Trichloropropane
  • Tris(2,3-dibromopropyl) phosphate
  • Very hot beverages (above 65 degrees Celsius)
  • Vinyl bromide (Note: For practical purposes, vinyl bromide should be considered to act similarly to the human carcinogen vinyl chloride.)
  • Vinyl fluoride (Note: For practical purposes, vinyl fluoride should be considered to act similarly to the human carcinogen vinyl chloride.)

National Toxicology Program 14th Report on Carcinogens
“Reasonably anticipated to be human carcinogens”

  • Acetaldehyde
  • 2-Acetylaminofluorene
  • Acrylamide
  • Acrylonitrile
  • Adriamycin (doxorubicin hydrochloride)
  • 2-Aminoanthraquinone
  • o-Aminoazotoluene
  • 1-Amino-2,4-dibromoanthraquinone
  • 1-Amino-2-methylanthraquinone
  • 2-Amino-3,4-dimethylimidazoquinoline (MeIQ)
  • 2-Amino-3,8-dimethylimidazoquinoxaline (MeIQx)
  • 2-Amino-3-methylimidazoquinoline (IQ)
  • 2-Amino-1-methyl-6-phenylimidazopyridine (PhIP)
  • Amitrole
  • o-Anisidine and its hydrochloride
  • Azacitidine (5-Azacytidine, 5-AzaC)
  • Basic Red 9 Monohydrochloride
  • Benzanthracene
  • Benzofluoranthene
  • Benzofluoranthene
  • Benzofluoranthene
  • Benzopyrene
  • Benzotrichloride
  • 2, 2-bis-(bromoethyl)-1,3-propanediol (technical grade)
  • Bromodichloromethane
  • 1-Bromopropane
  • Butylated hydroxyanisole (BHA)
  • Captafol
  • Carbon tetrachloride
  • Ceramic fibers (respirable size)
  • Chloramphenicol
  • Chlorendic acid
  • Chlorinated paraffins (C12, 60% chlorine)
  • Chloroform
  • 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea
  • Bis(chloroethyl) nitrosourea
  • 3-Chloro-2-methylpropene
  • 4-Chloro-o-phenylenediamine
  • Chloroprene
  • p-Chloro-o-toluidine and p-chloro-o-toluidine hydrochloride
  • Chlorozotocin
  • Cisplatin
  • Cobalt and cobalt compounds that release cobalt ions in vivo
  • Cobalt-tungsten carbide: powders and hard metals
  • p-Cresidine
  • Cumene
  • Cupferron
  • Dacarbazine
  • Danthron (1,8-dihydroxyanthraquinone)
  • 2,4-Diaminoanisole sulfate
  • 2,4-Diaminotoluene
  • Diazoaminobenzene
  • Dibenzacridine
  • Dibenzacridine
  • Dibenzanthracene
  • 7H-Dibenzocarbazole
  • Dibenzopyrene
  • Dibenzopyrene
  • Dibenzopyrene
  • Dibenzopyrene
  • 1,2-Dibromo-3-chloropropane
  • 1,2-Dibromoethane (ethylene dibromide)
  • 2,3-Dibromo-1-propanol
  • 1,4-Dichlorobenzene
  • 3,3′-Dichlorobenzidine and 3,3′-dichlorobenzidine dihydrochloride
  • Dichlorodiphenyltrichloroethane (DDT)
  • 1,2-Dichloroethane (ethylene dichloride)
  • Dichloromethane (methylene chloride)
  • 1,3-Dichloropropene (technical grade)
  • Diepoxybutane
  • Diesel exhaust particulates
  • Di(2-ethylyhexyl) phthalate
  • Diethyl sulfate
  • Diglycidyl resorcinol ether
  • 3,3′-Dimethoxybenzidine
  • 4-Dimethylaminoazobenzene
  • 3,3′-Dimethylbenzidine
  • Dimethylcarbamoyl chloride
  • 1,1-Dimethylhydrazine
  • Dimethyl sulfate
  • Dimethylvinyl chloride
  • 1,6-Dinitropyrene
  • 1,8-Dinitropyrene
  • 1,4-Dioxane
  • Disperse blue 1
  • Dyes metabolized to 3,3′-dimethoxybenzidine
  • Dyes metabolized to 3,3′-dimethylbenzidine
  • Epichlorohydrin
  • Ethylene thiourea
  • Ethyl methanesulfonate
  • Furan
  • Glass wool fibers (inhalable)
  • Glycidol
  • Hexachlorobenzene
  • Hexachloroethane
  • Hexamethylphosphoramide
  • Hydrazine and hydrazine sulfate
  • Hydrazobenzene
  • Indenopyrene
  • Iron dextran complex
  • Isoprene
  • Kepone (chlordecone)
  • Lead and lead compounds
  • Lindane, hexachlorocyclohexane (technical grade), and other hexachlorocyclohexane isomers
  • 2-Methylaziridine (propylenimine)
  • 5-Methylchrysene
  • 4,4′-Methylenebis(2-chloroaniline)
  • 4-4′-Methylenebis(N,N-dimethyl)benzenamine
  • 4,4′-Methylenedianiline and its dihydrochloride salt
  • Methyleugenol
  • Methyl methanesulfonate
  • N-methyl-N’-nitro-N-nitrosoguanidine
  • Metronidazole
  • Michler’s ketone
  • Mirex
  • Naphthalene
  • Nickel, metallic
  • Nitrilotriacetic acid
  • o-Nitroanisole
  • Nitrobenzene
  • 6-Nitrochrysene
  • Nitrofen (2,4-dichlorophenyl-p-nitrophenyl ether)
  • Nitrogen mustard hydrochloride
  • Nitromethane
  • 2-Nitropropane
  • 1-Nitropyrene
  • 4-Nitropyrene
  • N-nitrosodi-n-butylamine
  • N-nitrosodiethanolamine
  • N-nitrosodiethylamine
  • N-nitrosodimethylamine
  • N-nitrosodi-n-propylamine
  • N-nitroso-N-ethylurea
  • 4-(N-nitrosomethylamino)-1-(3-pyridyl)-1-butanone
  • N-nitroso-N-methylurea
  • N-nitrosomethylvinylamine
  • N-nitrosomorpholine
  • N-nitrosonornicotine
  • N-nitrosopiperidine
  • N-nitrosopyrrolidine
  • N-nitrososarcosine
  • o-Nitrotoluene
  • Norethisterone
  • Ochratoxin A
  • 4,4′-Oxydianiline
  • Oxymetholone
  • Pentachlorophenol and by-products of its synthesis
  • Phenacetin
  • Phenazopyridine hydrochloride
  • Phenolphthalein
  • Phenoxybenzamine hydrochloride
  • Phenytoin and phenytoin sodium
  • Polybrominated biphenyls (PBBs)
  • Polychlorinated biphenyls (PCBs)
  • Polycyclic aromatic hydrocarbons (PAHs)
  • Procarbazine and its hydrochloride
  • Progesterone
  • 1,3-Propane sultone
  • beta-Propiolactone
  • Propylene oxide
  • Propylthiouracil
  • Reserpine
  • Riddelliine
  • Safrole
  • Selenium sulfide
  • Streptozotocin
  • Styrene
  • Styrene-7,8-oxide
  • Sulfallate
  • Tetrachloroethylene (perchloroethylene)
  • Tetrafluoroethylene
  • Tetranitromethane
  • Thioacetamide
  • 4,4′-Thiodianaline
  • Thiourea
  • Toluene diisocyanates
  • Toxaphene
  • 2,4,6-Trichlorophenol
  • 1,2,3-Trichloropropane
  • Tris(2,3-dibromopropyl) phosphate
  • Ultraviolet A (UVA) radiation
  • Ultraviolet B (UVB) radiation
  • Ultraviolet C (UVC) radiation
  • Urethane
  • Vinyl bromide
  • 4-Vinyl-1-cyclohexene diepoxide
  • Vinyl fluoride

Clematis montana var. rubens


One of the most floriferous and rapid growing clematis varieties.

Rubens is a pinkish form of the usual white Clematis montana. All forms are vigorous rambling climbers, with twining stems that produce a mass of scented flowers in May and June. May also produce a second smaller flush of blooms in late summer.

Awarded the RHS Award of Garden Merit (AGM).


  • Habit: tall spreading climber with long twining stems.
  • Leaves: deciduous, mid-green with bronze tints.
  • Flowers: rose-pink buds opening to 2.25 inches (6 cm), pale pink/white star shaped flowers, with four open petals and a central cluster of yellow stamens.
  • Eventual Height: 26ft (8m)
  • Spread: 7ft (2.5m)
  • Aspect: full sun or partial shade. Sheltered or exposed sites.
  • Hardiness in UK: hardy (h4)
  • Soil Requirements: any good, moist but free draining garden soil (sandy, loam, chalk or clay).
    Alkaline or neutral pH

Planting Clematis Montana Rubens

Soak the root ball well before planting. Dig a hole at least twice the size of the root ball. Back-fill with a planting mixture of equal parts soil and soil improver/compost. Water thoroughly. Provide initial climbing supports (such as canes, mesh or wire) until the plant is well established.

Best planted with the roots in the shade and the stems in the sun.

Planting Context

Ideal for rambling over walls and fences or up through large trees and conifers. Also makes an effective cover for old buildings and sheds.


Water thoroughly during dry weather until well established. Mulch with organic matter in spring and add a general fertilizer such as bonemeal.

Pruning Clematis Montana Rubens

Clematis group 1. Can be pruned lightly just after the main flowering period has finished (June/July). Prune back harder if untidy or to remove excessive growth.

Propagating Clematis Montana Rubens

Layer or take semi-hardwood cuttings in February to March.

Clematis montana, or Mountain Clematis, is a vine that is simply beautiful.

Core Clematis montana facts

Name – Clematis montana
Family – Ranunculaceae
Type – vine

Height – 20 to 25 feet (6 to 8 m)
Exposure – full sun
Soil – deep and cool

Foliage – deciduous
Flowering – May

Described here are the right practices to bring out the best in your Clematis montana, a plant full of vigor bearing many flowers.

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Planting Clematis montana

Clematis montana is planted indifferently in fall or in spring.

Clematis montana, like all other clematis flowers, loves being rooted in a shaded spot while the head basks in the sun.

  • It the base is in direct sun, as in, if sunlight will hit the root collar, then cover it with for example an old tile or a few odd rocks.

Clematis requires some kind of structure to climb up along, it must be set at a distance of about 8 inches (20 cm) away from the root collar.

  • Dig a hole more or less 16 inches (40 cm) in diameter.
  • Lean the young seedling towards the wall or lattice that is will hang from later on.
  • Backfill the hole with a blend of soil mix and garden soil. If the soil is very heavy, add in ⅓ river sand.
  • Fertilize the plant right at the moment of planting with a little compost or dehydrated manure: this will allow for stronger growth.

Propagating Clematis montana

Clematis montana is quite easily multiplied, either through layering of young stems or via cuttings.

Layering in spring, herbaceous cuttings end of spring, semi-hardened cuttings in summer, sowing in fall under a cold frame.

  • Layering is most successful in spring.
  • Cutting preparation is best performed in spring on young stems or at the end of summer on semi-hardened stems.

Potted Clematis montana

Growing clematis in a pot is as simple as ABC. Several Clematis montana varieties are well suited to container growing, although other Clematis varieties like Clematis alpina are better suited to it because of their slow growth.

  • Proper flower plant soil mix is required.
  • The pot must have a drainage hole at the bottom and must be wide enough.
  • Repotting every 2 or 3 years will be a necessity for your potted clematis to keep growing and blooming.

Pruning and caring for Clematis montana

The right time to prune Clematis montana is after the blooming, most often during summer. But since it is rather hardy, pruning in fall is also possible.

The more Clematis montana is pruned, the more it bears flowers!

  • Cut back stems, but not too drastically.
  • Cut to the shortest stems that have died off and weak stems.

Watering Clematis montana

Watering Clematis montana is important in case of extended dry spell and/or intense heat.

Clematis can’t withstand drought, and neither can it cope with excess water that might make the roots rot away.

  • Regular watering is recommended over the first year after planting.
  • Maintain moisture in the soil.
  • Always protect the base of the plant to keep it cool. For example, you might lean an old tile against it, or use mulch.

Types and varieties of Clematis montana

Clematis montana ‘Alexander’

This is one of the Clematis montana cultivars that bears the largest flowers. These come in a cream-white color. If it doesn’t bear flowers immediately, don’t worry: it needs a few years before reaching the point of blooming.

Clematis floribunda ‘Lilacina’

Lilac violet-colored flowers, as its name shows. It is particularly interesting for the size of its flowers that can grow as large as saucers, over 6 inches (15 cm) across. It bears flowers all summer long.

Clematis montana grandiflora

Its blooming is immaculate white, simply magnificent against its gray-green leafage. It adapts particularly well to shaded areas.

Speed is what stands out about its growth, and its leafage and very interesting lilac pink flowers are remarkable.

Clematis montana var. wilsonii

Its blooming comes late, but patience is rewarded when the superb fragrant white flowers appear: some say they have chocolatey smell!

Smart tip about Clematis montana

You can attach your clematis to a lattice to ensure it grows the way you hope it will as it develops!

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Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
Two white clematis blooms by 阿橋 HQ under © CC BY-SA 2.0
Pink clematis montana bush by WillowGardeners under © CC BY 2.0
Newly opened Clematis montana blooms by Josh Egan-Wyer under © CC BY 2.0

How to Prune Columbine

Prized for its bicolor blooms, columbine requires very little maintenance to stay healthy. While an end-of-season pruning will help prevent disease and encourage growth next spring, other pruning decisions will depend on your goals for the plants. Summer removal of spent blooms, known as deadheading, will result in larger blooms next year. Refraining from summer pruning will mean smaller flowers, but more of them as they further seed the bed. A happy medium is to prune most of the spent flowers but leave a few to go to seed.

Snip off dead or damaged leaves throughout the growing season. Use a sharp pair of gardening scissors or shears. Snip off the leaf where it joins the main stem.

Cut off spent blooms if desired. Snip terminal flowers–the blooms at the top of the central stem–1/4 inch above the nearest leaf set.

Snip off spent lateral flowers where their stems join the main stem of the plant. If the terminal bloom is already removed and the spent lateral is above a second healthy lateral flower on the main stem, cut the main stem to just above where the lowest healthy flower joins it.

Prune the plant down to its basal set of leaves in the fall. Basal leaves are the larger leaves at the base of the columbine that emerge from the stem near soil level. This encourages the columbine to produce more roots as opposed to sending nutrients to stems that are no longer producing flowers.

Columbine Flowers: How To Grow Columbines

The columbine plant (Aquilegia) is an easy-to-grow perennial that offers seasonal interest throughout much of the year. It blooms in a variety of colors during spring, which emerge from its attractive dark green foliage that turns maroon-colored in fall. The bell-shaped flowers are also a favorite to hummingbirds and may be used in cut-flower arrangements as well.

How to Grow Columbines

Columbine plants aren’t too particular about soil as long it’s well-draining and not too dry. While they enjoy full sun in most areas, they don’t like it very hot, especially during summer. Therefore, in warmer areas like the south, grow them in partial shade and give them plenty of mulch to help keep the soil moist.

Mulch will also help insulate and protect these plants during winter in other regions.

Columbine Planting Tips

Columbines start easily from seed and will readily multiply once established. Columbine flower seeds can be directly sown in the garden anytime between early spring and mid-summer. There’s no need to even cover them as long as they receive plenty of light.

Put pre-established plants in the ground at the same time, with the crown placed at soil level. Spacing for both seeds and plants should be anywhere from 1 to 2 feet (.3-.6 m.). Note: Blooms will not appear on seed-grown plants until their second year.

How to Care for Columbine Plant

Keep the plants moist following columbine planting until well established. Then only weekly watering is necessary with exception to extended periods of drought in which they will require additional watering.

Provide a water-soluble fertilizer monthly. Regular fertilizing will help produce brighter blooms and thicker foliage.

Regular deadheading can also be performed to encourage additional blooming. If self-seeding becomes an issue, both the foliage and remaining seedpods can be cut back in the fall. While some people prefer not to allow them to self-sow, it is often recommended, as columbine plants are generally short-lived with an average lifespan of about three or four years. If desired, these plants can also be divided every few years.

Although columbine doesn’t suffer from too many problems, leaf miners can become an issue on occasion. Treating plants with neem oil is a good way to control these pests. Pruning columbine plants back to the basal foliage just after blooming can usually help alleviate any problems with insect pests as well. You may even be lucky enough to get a second set of stem growth within a few weeks so that you may enjoy another wave of blooms.

How to choose and grow the best clematis varieties

I f plants are like people, then clematis are comparable with the Hollywood movie stars of the Technicolor era, combining cinematic good looks with high-wattage charm. Used to cloak a wall, pergola, obelisk or arbour, to scramble through the branches of a companion plant, or as container specimens, clematis add great swathes of colour to gardens, while some varieties also offer scent and/or evergreen foliage.

In April, as the soil finally begins to warm up, is one of the best times to plant them. But with several thousand different varieties in cultivation, the problem for many gardeners has been the abundance of choice. Step forward the Royal Horticultural Society’s Award of Garden Merit (AGM), the equivalent of an Oscar for luminaries of the plant kingdom, given only to plants of exceptional quality and sturdy constitution that are vigorous, easily cultivated, disease-resistant and readily obtainable.

The big difference between an Oscar and an RHS AGM, however, is that the latter is not for life. Once-prized cultivars are ruthlessly demoted if they no longer make the grade or are superseded by better varieties, which is what happened this spring when the society unveiled its newly revised list of more than 7,000 AGM plants, its first comprehensive review in 10 years.

Of those clematis which had held the coveted AGM in 2011, 15 were deleted, and six new varieties were added. A total of 79 clematis now hold the award, a testimony to the great variety of different garden-worthy plants. Some of these such as the evergreen early-flowering Clematis cirrhosa ‘Freckles’ C. Wisley Cream’ and Clematis armandii ‘Apple Blossom’ have a new RHS hardiness rating of H4, making them suitable only for warmer gardens.

Tougher by far are the many varieties of C. alpina and C. macropetala. Hardy and floriferous, these will happily tolerate a shady north or east-facing spot as long as the soil is free-draining, while their small, bell-shaped flowers, which appear in April-May, have a discreet beauty a world away from that of the flashier, large-flowering types. Look out for the award-winning ‘Frances Rivis’, ‘Constance’ and ‘White Columbine’ amongst others.

Clematis montana is one of the clematis that Irish gardeners know best, with pink/white flowers that are often seen festooned through the branches of trees or draped along the roofs of garden sheds in late spring/ early summer. Of the various cultivars available, the RHS singles out five – C. ‘Mayleen’, C. ‘Elizabeth’, C. ‘Freda’, C. montana var. grandiflora and C. montana var. rubens ‘Tetrarose’. With the exception of the relatively well-behaved ‘Freda’ (cherry-pink flowers), the rest of these shade-tolerant clematis varieties will romp through any garden, so beware of planting in a confined space . Neither, with a hardiness rating of only H4, are they suitable for cold or exposed gardens.

By May, clematis belonging to what’s known as the early large flowered group will take centre stage. Gone from the RHS list are ‘Henryi’, ‘Josephine’, ‘Miss Bateman’, ‘Mrs Chalmondeley’ and ‘Royalty’ but plenty of other old favourites still make the grade including the candy-striped ‘Nelly Moser’, ‘Niobe’ (red) and ‘The President’ (purple). Compact and colourful, this group make wonderful wall or container-grown specimens.

Summer marks the peak of the clematis season, beginning with a wealth of large, late flowering cultivars (LLs) such as the ever-popular C. ‘Jackmanii’ (purple), ‘Comtesse de Bouchaud’ (pale pink), ‘Ernest Markham’ (crimson-red) and the freshly-AGM-anointed C. ‘Aotoroa’ (purple). These are joined by varieties of Clematis texensis (the pink-flowering ‘Princess Diana’ is the only AGM variety), C. tangutica and orientalis cultivars as well as the herbaceous integrifolia and diversifolia types. And then, in early autumn comes the spreading, sun-loving C. rehderiana, with its elegant clusters of small, creamy-yellow flowers that smell like cowslips.

But if I had to grow only one clematis, I would choose a variety from the hardy viticella group, probably the longest-flowering (July-September), most floriferous, vigorous, versatile and garden-worthy of all the categories. Many feature in the RHS’s updated list (see, with classics such as C. ‘Purpurea Plena Elegans’ (double, magenta) , C. ‘Etoile Violette’ (blue-purple), ‘Mme Julia Correvon (red) and ‘C. Venosa Violacea’ (purple-white) included alongside new additions such C. ‘Poldice’ (violet-blue, white centre) and C. ‘Walenburg’ (red-purple) .

Viticellas belong to Group 3 of the clematis genus and along with so many of the other plants in this category, they look wonderful growing through or up a vigorous companion plant to extend or add to its season of interest.
How to plant clematis
Before planting, soak the plant’s rootball in a bucket of water. Dig a hole 45-60cm deep and wide (45-60cm away from the base of a wall, 60cm away from the base of a host tree). Fork over the base of the hole, then cover with a layer of well-rotted organic matter (compost, manure) followed by a thin layer of soil (clematis don’t like manure touching their roots or stems). Mix homemade garden compost/John Innes compost and a couple of handfuls of slow-release fertiliser with the remaining loose soil, then take the soaked rootball and gently loosen some of the coiled roots before placing the plant in the hole. Excluding herbaceous and evergreen types, the traditonal advice is to plant deeply to avoid clematis wilt, ensuring the top of the rootball is roughly eight centimetres below the finished level of the soil. If it’s a dry spot, consider placing an open-ended pipe (7.5cm diameter) in the hole, which will allow you to water the plant effectively until established. Backfill, water, and protect against slugs. Continue to water regularly until well established. If growing against a wall/support, plants will need to be tied to horizontal wires, or a trellis fixed on battens. All clematis should be hard-pruned at some point within the first year of planting. For Group 1, prune immediate after flowering while for Group 2 and Group 3 types, prune in February/March the following spring. Mulch established plants with manure in early spring, making sure that it doesn’t rest against the stems. To ensure good flower production, add a handful of sulphate of potash to the surrounding soil in April and water in.

For ease of cultivation, clematis are divided into three main groups. Group 1 comprises the earliest flowering types. These plants should only be pruned to tidy them up/restrict their size, immediately after flowering has finished. Group 2 comprises the early-large-flowered types that flower on last year’s growth. Lightly prune in February and again after flowering to encourage a second flush. The final category, Group 3, encompasses the late large-flowered hybrids as well as the viticella, texensis and orientalis types that flower on new growth. Each stem should be hard pruned back to 45cm above ground and a pair of strong buds. The only other time to prune clematis is if they are struck with the fungal disease known as clematis wilt, which mainly affects the early-large-flowered types. If this happens, cut growth to the ground and dispose carefully of the pruned material.

April 10th-24th: Powerscourt Tulip Festival. Events include walking tour with head gardener Michael Byrne (April 12th, 11.30am) and garden design with Tim Austen (April 13th, 12.30-3pm), see April 13th-14th : Mount Venus Nursery ‘Flowers In the Shade’, 11am-6pm, see
April 14th : Start of week-long Tulip Fest, based around gardens in Birr, Co Offaly, pre-booking essential, see

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