Culture, Production December 2012

Perennial Solutions: Erysimum ‘Fragrant Star’
By Paul Pilon

Many growers seek spring flowering perennials with attractive foliage characteristics. Erysimum ‘Fragrant Star’ is an exciting stable variegated spring blooming wallflower, destined to earn a place in many perennial programs. ‘Fragrant Star’ is easy to grow and has great potential for use in spring programs as well as in the landscape.

Erysimum ‘Fragrant Star’ is a compact selection forming 15- to 18-inch high by 18- to 24-inch wide dense, evergreen mounds of striking creamy yellow and green variegated foliage. In mid spring, it develops chocolate-purple flower buds that contrast well with the variegated foliage and golden flower clusters. The bright yellow scented blooms last several weeks; the extended bloom time is attributed its sterile nature.

‘Fragrant Star’ is a stable sport of erysimum ‘Fragrant Sunshine’ which was discovered in the United Kingdom by David Tristram. It thrives in locations with full sun throughout USDA Hardiness Zones 6 to 9. This variegated wallflower is versatile and performs well in perennial beds, borders, rock gardens and containers. Additionally, ‘Fragrant Star’ attracts butterflies into the landscape, is deer resistant and drought tolerant once established, and can be used as a cut flower.

With its variegated evergreen foliage and cheerful blooms, ‘Fragrant Star’ nicely compliments most containerized perennial programs and is a particularly nice choice for landscape uses.

Propagation

Erysimum ‘Fragrant Star’ is vegetatively propagated by tip cuttings. It is a patented cultivar; asexual propagation without a license is prohibited.

Before sticking the unrooted cuttings (URCs), moisten the rooting medium in the liner trays. After the cuttings are stuck, place them under a moderate misting regime. To accelerate rooting and improve uniformity, spray the cuttings with 1,000-ppm IBA soluble salts within 24 hours of sticking. Fungus gnat larvae can often become problematic; a preventative program to control them is recommended after the cuttings are stuck.

Maintain moderate to high mist frequencies for the first few days of propagation, then slightly reduce the amount of misting until rooting begins. Once roots are present, further reduce the misting frequency and apply 75- to 100-ppm nitrogen at least once per week. Remove the cuttings from the mist once they are rooted.

The cuttings usually take approximately three weeks to root with soil temperatures ranging from 68 to 72° F. It is beneficial to pinch the terminal shoots when the plants reach three inches tall to promote branching. Liners take approximately five to seven weeks from sticking to become fully rooted and ready for transplanting.

Production

Growers commonly produce erysimum in 1-quart to 1-gallon sized containers. ‘Fragrant Star’ performs best in well drained growing mixes. When planting, the liners should be planted so the original soil line of the plug is even with the surface of the growing medium of the new container. If the liners were not pinched prior to transplanting, it is beneficial to soft pinch the plants when they have approximately 2 inches of new growth to promote lateral branching and improve fullness. Avoid pinching or cutting them too low or they will not develop branches very well.

During production, wallflowers require light to moderate fertility levels. Nutrients can be delivered using water soluble or controlled-release fertilizers. Growers using water-soluble fertilizers apply 100- to 150-ppm nitrogen with every irrigation or use 250 ppm as needed. Controlled-release fertilizers are commonly applied as a top-dress onto the media surface using the medium recommended rate on the fertilizer label or incorporated into the growing medium prior to planting at a rate equivalent to 1.0 to 1.25 pounds of elemental nitrogen per yard of growing medium. The pH of the media should be maintained between 5.8 and 6.4.

‘Fragrant Star’ should be kept moist, but not saturated, during production. In general, they require average amounts of irrigation; however, as crops matures they will require slightly more irrigation than they used early in the production cycle. When irrigation is required, water them thoroughly and allow the substrate to dry slightly between waterings.

With its naturally compact growing habit, controlling plant height should not be necessary. Under certain circumstances, it may be necessary to use chemical plant growth regulators to control the growth of Erysimum. When the crop needs to be toned, spray applications of 5-ppm uniconazole (Concise or Sumagic) are effective. Otherwise, growing them with adequate spacing between the plants is usually sufficient.

Insects and Diseases

Wallflowers are susceptible to several insect pests and diseases during production and in the landscape. Aphids, spider mites and thrips are the most prevalent pests growers observe. The primary pathogens which infect erysimum are Botrytis, downy mildew, powdery mildew, Rhizoctonia, and rust diseases. None of these insect pests or diseases requires preventative control strategies. Insects and diseases can be detected with routine crop monitoring; control strategies may not be necessary unless the scouting activities indicate actions should be taken.

Scheduling

With its attractive foliage, erysimum ‘Fragrant Star’ can be marketed as a foliage perennial or in full flower. Typically, growers market flowering plants in the mid spring. To produce the fullest containers with the most bloom, it is best to bulk ‘Fragrant Star’ in the final container prior to overwintering. Allow a minimum of six weeks for quart-sized containers and up to 10 weeks for bulking 1-gallon sized containers.

Erysimum has an obligate cold requirement for flowering. They can be vernalized in the final container or as large plugs (72-cell or larger) for a minimum of six weeks at 35 to 44° F. It is best to bulk up large container sizes prior to overwintering. Planting vernalized liners into large containers in the late winter or early spring usually results in plants with few flowers. However, small container sizes can be planted in the spring using vernalized liners and will generally have enough flowers for this sized plant.

After vernalization, growers most commonly grow them under natural lengths and cool temperatures. When they are grown at 60 to 65° F, ‘Fragrant Star’ takes about six to seven weeks to flower. Non-flowering plants can be produced throughout the growing season from spring to fall by planting unvernalized liners and allowing approximately 10 to 12 weeks to fill out the container.

Availability

Erysimum ‘Fragrant Star’ was brought to the market by Plant Haven Inc. (www.planthaven.com). Rooted liners are available from several licensed propagators including Green Leaf Plants (www.glplants.com), Pacific Plug & Liner (www.ppandl.com) and Skagit Gardens Inc.
(www.skagitgardens.com).

Paul Pilon

Paul Pilon is a horticultural consultant, owner of Perennial Solutions Consulting (www.perennialsolutions.com), and author of Perennial Solutions: A Grower’s Guide to Perennial Production. He can be reached at 616.366.8588 or

Erysimum (Wallflower)

One of the most popular early flowering biennials grown in the UK. It can be seen putting on a colourful show in municipal bedding schemes and public parks all over the country, during spring time.

Family: Brassicaceae or Cruciferae (cabbage/mustard)
Botanical Name: Erysimum (syn. Cheiranthus)
Common Names: Wallflower
Foliage: Evergreen, narrow, dark grey-green leaves.
Flowers: Dense spikes of bright fragrant blooms, in shades of white, pink, yellow, orange, purple and red.
Flowering Period: Late spring to early summer.
Soil: Well-drained fertile soil (sand, loam, chalk), alkaline to neutral pH.
Conditions: Best in full sun.
Habit: Bushy.
Type: Hardy biennial or short lived evergreen perennial.
Origin: Europe.
Hardiness: Hardy through most of the UK (down to -10).

Planting and Growing Erysimum

These late-spring, free flowering gems, provide a first class display in beds, borders and containers. Best grown in a south, east or west-facing aspect, in a sheltered location. Plant 1ft apart and protect young plants from cold winds.

Wallflowers are actually perennials but because they can deteriorate rapidly (becoming woody over time), they are traditionally grown as biennials; by sowing seed in summer for a spring display. Several more robust modern hybrids (such as ‘Bowles’s Mauve’) are now available, which will provide a good show for many years.

Taking Care of Erysimum

Pinch out the growing tips when the plants are about 6in (15cm) tall to stimulate a more bushy shape.

Pruning

Trim perennials lightly after flowering. Remove biennial plants once the flowers have faded.

Pests and Diseases

Susceptible to slugs, snails and flea beetles. May be affected by downy mildew, club root or leaf blight.

Propagating Erysimum

Biennials are very easy to grow from seed, sown in late spring or early summer. However, you will need plenty of space in a nursery bed to grow-them-on ready for planting out in the autumn. Take semi-hardwood cuttings of perennials in spring or summer.

These popular spring plants used to be widely available in the autumn from market stalls and garden centres, as bunches of bare rooted plants. These days they are mostly sold as plug plants or in bedding trays in the spring. However, traditional bare rooted bunches can still be purchased online from several major stockists, such as Mr. Fothergill’s.

Popular Varieties of Erysimum Grown in the UK

There are numerous varieties available from tall (2ft) plants to shorter dwarf (9in) forms, in a wide range of colours.

‘Blood Red’ is a tall variety with deep red flowers. Height to 2ft (60cm).

‘Cloth of Gold’ has golden yellow flowers. Height to 2ft (60cm).

‘Rose Queen’ lovely rose pink blooms. Height to 2ft (60cm).

‘Fair Lady’ series is a shorter variety in a mix of colours. Height to 18in (45cm).

‘Persian Carpet’ has a lovely pastel mix of colours. Height to 15in (38cm).

‘Primrose Monarch’ has rich yellow flowers. Height to 15in (38cm).

‘Ivory White’ has cream-white flowers. Height to 15in (38cm).

‘Tom Thumb’ is one of the best dwarf mixes. Height to 9in (23cm).

Q: My big Erysimum ‘Bowles Mauve’ looks dry and brown on one side but is greening up and starting to bloom on the other. Can I cut back the dry side (or the whole thing) to rejuvenate it? Same question for my scraggly lavender bushes — can I whack them back, fertilize and get them looking better again?

A: Wallflowers like your ‘Bowles Mauve’ flower continuously for so many months that they literally bloom themselves to death after a couple of years. Because they establish and grow quickly, it makes most sense to replace wallflowers that are past their prime. But it wouldn’t hurt to cut your plant back severely and see if it comes on strong with a new flush of growth. I grow lots of wallflowers, and some are already greened up, and some look like brittle dry skeletons. I’ll cut the stick-looking ones to the ground, water and fertilize well and see if they sprout again — sometimes they do.

You’ll want to be more careful with your lavender, which looks its rattiest now on the cusp of springtime. But lavender resents being clipped back too hard before the weather warms up. When plants begin to show signs of new growth, cut back the old stems by no more than a third, which will encourage more flowers and liven up the plant. I never fertilize lavender, but if you feel you must, midspring is the time to top-dress with a little organic fertilizer — but not too much, because lavender does best in lean soil.

Q: What is a feeding mulch?

A: It’s a mulch with manure mixed in to “feed” or fertilize the plants. Most often feeding mulches consist of well-rotted manure mixed with bark, so they look black and rich when laid down several inches deep in spring and/or fall. Feeding mulches improve the look of beds and borders, keep down weeds, prevent water evaporation and over time break down and improve the soil as they feed the plants.

Q: I want to plant a weeping flowering cherry tree by the pond in our garden, but I’ve been told they get diseased. Are there any other trees as pretty in springtime that won’t need to be sprayed? I want an easy-care weeping tree with flowers.

A: While weeping crabapples are perhaps not as ethereally lovely as weeping cherries, they are more disease-resistant. Malus ‘Louisa’ is a weeper that has shown no sign of scab growing in Western Washington. It has blush pink flowers, graceful arched branches and lemon-gold fruits. Malus ‘Molten Lava’ is a wider, more vigorous weeper with white flowers, proven disease resistance and a cascade of bright-orange berries that earned its name. If you’re not set on a flowering tree, take a look at a weeping katsura, which has lovely heart-shaped leaves and fabulous golden fall color.

Valerie Easton also writes about Plant Life in Sunday’s Pacific Northwest Magazine. Write to her at P.O. Box 70, Seattle, WA 98111 or e-mail [email protected] with your questions. Sorry, no personal replies.

We were talking, in the aftermath of the catastrophic events in America, about how much, if anything, had changed. And someone said that things like gardening and cooking seemed unbearably trivial at times like these, almost disrespectful. But I think this is a real misreading of the times. Certainties will now seem doubly precious. Verifiable honesty matters more than ever. The flash, the glib and all things phoney will be exposed in this new, raw light as the dross that they are. Growing things, making something beautiful, eating simple, fresh food matter now more than ever. I often think of how Aldous Huxley, after years of intense exploration, came to the conclusion that all religious and spiritual learning could be summarised into two words: pay attention.

I have no embarrassment in elevating the goals and rewards of gardening to the spiritual. It seems self-evident in the sheer power of the life force that fills every cell of the smallest backyard to great estates. The trick is to pay attention to it, to notice things, to be fully alive yourself. I always know when I am not functioning properly when I lose the rhythm of the garden. This is a hard thing to define as on the one hand the garden gets along fine without me and on the other there are plenty of still moments to relish.

But it is not enough just to wander around admiring the catch of light on a leaf or the arch of a stem against the green. There has to be a commitment to the rolling future of the place. The best way that I know how to do this is a kind of controlled business where one is always spending time on next season, spending time, effort and perhaps money in making the future. And this week it seems better to deal with where we are going rather than where we have wound up. Which, and at this point I feel like a vicar peering from the pulpit on three old ladies and a snoring colonel, brings me to wallflowers.

For a start I will come clean. I have grown wallflowers before but have never really paid attention to them. In the way that lots of things in my life do, they just sort of happened. But this year I have paid attention to them. Sowed them, pricked them out and transplanted them to various points of the garden to mature. They are, of course, biennials, which, to the uninitiated have the following timetable. You sow them in May/June, plant them in October and they flower the following spring. Biennials, by definition, establish themselves as plants in their first growing season and flower in the second, producing seed which will start the cycle again.

We call wallflowers Cheiranthus cheiri , although they are reckoned to be part of the Erysimum family. The basic wallflower has yellow flowers and will seed itself in seemingly solid walls and stone. I have a friend who has a castle – ruined but dead cool all the same – and the wild wallflowers – or gillyflowers – grow 30ft up on the sheer sides of the keep. It is said that they were planted deliberately on the walls of grand medieval houses so the scent would waft in the windows of the bedchambers.

The truth is that wallflowers are really perennial, but it suits gardeners to treat them as biennial to get the best from them, otherwise they tend to become leggy and sprawly, and the florification diminishes. The fact that they get into the lime-mortar of old walls is a pretty good indication of their preference for chalky, very well-drained soil, which is almost the opposite of what we have here but was exactly what I grew up on. The musty, heavy scent of wallflowers outside the front door is as much part of my childhood as the school I went to or beech woodlands. They seem to take the warmth of the sun on an April day and process it into fragrance, a scent of dry earth on a chill spring day.

I was going to start planting ours out today, but have paused precisely because of this need for dryness and drainage, and have ordered a load of sharpsand to rotovate into the soil before planting. This should do more than make them happy. It could mean survival if we get another very wet autumn followed by an intensely cold week, as we did at the end of last year.

Wallflowers are most likely to die over winter, in very wet, cold ground. Fresh new growth can also be hit by hard frosts and it is a good idea to pinch out the growing tips around the end of August – but it is never too late – to create bushy plants and to get rid of any late, vigorous growth. It is a mistake to over-feed the soil, which will only make for this late spurt of growth and; of course, never give wallflowers any kind of fertiliser. The poorer the conditions (think stone walls) the longer they will last, and they can keep going perfectly happily for five years or more.

Many wallflowers are sterile hybrids that can only be reproduced by cuttings, or buying more seed; but many seed themselves easily and you can buy seed for about 30 different varieties (all of ours are ‘Blood Red’). You don’t need a greenhouse to grow them – a line or two in a seed bed in the vegetable garden is fine, thinning them to an inch or so apart, and then again to 6in, transplanting the thinnings to another line.

There are three groups of Erysimum varieties. Our ‘Blood Red’ come from the tallest group, which has 12 colours. The Bedder Series are much shorter and compact, with flowers in four hues: bright yellow, primrose, orange or scarlet. These can be bought as individual colours if you shop around, but you are much more likely to find them as a random mixture. If you are going to grow them in containers, try the Prince Series. They come from Japan and have five colours. Again, you are likely to buy them as mixed colours. We have ‘Bowles’ Mauve’, a genuine perennial that flowers for ages from March to June, and although not something to be treated as part of any kind of block-bedding scheme, is a good permanent addition to a border.

You can buy wallflowers as plants this year if you do not have any from seed. I remember them being sold in the local greengrocer in bundles wrapped up in damp newspaper. I don’t know if this is still done, but you should look for healthy plants with a good root system in some kind of container. Try lifting one out of its plug or pot – there should be a good rootball with the soil firmly attached to it. Anything planted now that is less than robust will not do very well next spring.

Although they raise easily from seed and you buy them as quite small, lush plants, they are very shrub-like in behaviour, and have a tendency to sprawl and submerge themselves, so keep them quite close together so they support each other when it comes to planting out. This kills two birds with one stone, because they are much better planted in blocks rather than as singletons. Each plant produces flowers sporadically and you need the massed effect to make the most of the colour.

The traditional accompaniment for wallflowers are tulips and they work well, flowering at around the same time, the tall goblets of tulip rising above the massed foliage of the wallflowers. Daffodils also look good set against the massed foliage, although the early daffs will be in flower before the wallflowers. The tazetta Narcissus ‘Geranium’ is very long flowering and will allow the wallflowers to catch up. Always plant your wallflowers first, otherwise half the bulbs will be chopped up by your trowel as you go.

There is no rush to get tulips in the ground yet – I have planted bulbs as late as January and got a perfectly good spring display, but November is ideal, dotting the bulbs in among the wallflowers. There are two clear schools of thought on tulip planting. The conventional approach is to plant really deep to ensure long life. The other, which I favour, is to plant an inch or two down. This gives them access to the best soil and makes them less likely to sit in wet soil. But it does mean digging most of them up each year. If your wallflowers are a raging success, sow more, even if the plants look entirely content and ready to do it all again next year. Sooner or later they will get a virus, clubroot, grey mould or some such disaster. That is their way. But there is always next year.

My roots: A week in Monty’s garden

I did my annual apple stint. I am on my third year of it now. This involves trying to find the labels I carefully attached to each tree last year, with the variety written bold in indelible ink. One year it proved all too delible and was, literally, a wash out. Last year I used tarred twine to secure the labels and half of these rotted so the tags fell off and were chewed up by the grass cutter. Then there is the process of nagging doubt. Is this really ‘Rev Wilks’ or could it be ‘Tydemans Early’? So I get all the apple books out and cross reference what they tell me with what my garden diary says. This year I drew a plan, but I’m still baffled by three that do not fit any of the varieties I planted.

Heedless of name, the apples have grown and grown this year. A bumper crop. We have nowhere to store them and too few mouths to eat them as they ripen, especially the earlies, which will not keep long. In my last garden the windfalls lay by the thousand, feeding all the birds and foxes until Christmas. That would seem a criminal waste here.

I mattocked the weeds around the base of each tree that had grown on last year’s mulch, attended by half a dozen fat hens, scratching and wallowing in the powdery dry soil. The chickens look wonderful in the orchard, but are driving me insane with their destructive scratching. Sarah says the whole point of having hens is that they should look decorative in the orchard, give or take an egg or two. The solution is containment. I shall make hen-proof, suitably arcadian fencing so they can be seen to be beautiful but strictly within their harmless limits.

Last week I said that we had planted out all our wallflowers. There was a bit of artistic licence there. We started to plant as I wrote, but about an hour into the job I changed my mind and they were all unplanted and gathered. Instead of letting the cardoons grow back, we have decided to remove them all and make this long, narrow strip into a garden for annuals and bulbs.

The cardoons have made it a passageway and now that it is cleared it has real form and balance that is entirely lost if the planting is too big. So all six beds are in the middle of being dug over, compost and sharpsand being added by the barrowload and rotovated in, and then the wallflowers can properly go in, followed by jonquils and tulips and alliums. This is a dramatic change and really exciting. I can’t wait to see it next spring.

Thorny Problems

I hope Susan reads this, finds a garden society or club locally and that it is helpful. It all depends on the nature of that society. As a member of one, new president (that is, the hander-out of cups) of another, and regular speaker to many – and with a great friend who is the run-ragged show secretary of yet another, I would like to make the following (doubtless inflammatory) observation: modern garden societies should not be all about the shows – the perfect onions, the best jam, flower arrangement or whatever – they should spend an equal amount of time and energy encouraging younger, perhaps less confident gardeners to join and hand on skills and information to help them.

And there are another couple of things (while on my high horse): most garden societies have hopelessly low membership fees that may have scarcely increased in 30 years. Members in work should pay more. Big-name gardeners should, however, stop trying to charge ridiculous fees to speak to the amateurs of this nation who made them “celebrities” in the first place. As a post script for webby people – many, but not all, garden societies are affiliated to the RHS and there are links to some on the RHS website: www.rhs.org.uk Local garden centres are also often a starting point.

Bracken invasion

My greenhouse is adjacent to a (very) uncultivated field. Two summers ago bracken started appearing inside the greenhouse. At first I pulled it up, but in due course I covered the floor with old compost bags hoping they would choke it. On removal of these to plant tomatoes, I discovered a full-scale invasion was under way, and pulling up the stems revealed a mass of huge rhizomes. What can I do? Val Foster-Smith, Anglesey

This is a tricky one – controlling bracken is hard in normal circumstances when it is growing through hedges into garden beds and borders. Normally, you can weaken it by pulling the stems consistently or, if it is in grass, by mowing it regularly. As far as weed killers are concerned: farmers have access to a selective weed killer that deals with the problem effectively, while gardeners have to resort to a strong glyphosate (there is now an extra powerful Round Up), but, of course, this is non-selective. You are going to have a big fight on your hands.

Since I understand you cannot tackle the bracken in the field, I feel that to stop a continuing invasion you will have to dig down vertically at the point where the bracken is coming into the greenhouse, sever the connections and put in a vertical barrier – something really tough like a double layer of pond liner might do the trick. I don’t see that you have any choice but to abandon the greenhouse for a while, or, if it is not too late, grow your tomatoes in large containers that can be moved while you tackle the problem. Allow the bracken to grow for a few weeks and spray the fronds with glyphosate once they are unfurled. When you have the problem under control, you should perhaps decide to cover most of the greenhouse floor with a proper heavy-duty woven plastic membrane and gravel – and keep your eyes open for ever more, just in case.

In praise of wall flowers

Elizabeth Pegram, from Cheshire, bemoans that wallflowers last too long. She picks them for the house because she loves the smell and this (like deadheading), encourages them to flower on and on. However, she ends up throwing them away when there is still plenty of (rather untidy) colour left in them, principally because she wants to replace them with summer annuals grown from seed. This year she has kept one or two creamy red ones of which she is particularly fond in situ. Can she encourage them to become shrub-like and behave like her purple Erysimum ‘Bowles Mauve’?

Perennial wallflowers such as the ‘Bowles Mauve’ are just that: almost shrubby perennials and no, the ordinary wallflowers we use for late-spring bedding containers (Erysimum cheiri) can’t be persuaded to do the same thing at all. However, they are biennials – of the type that will readily flower in their first year (most biennials don’t), but will die after flowering for a second time the following year. If Elizabeth cut the first-year plants that she particularly likes right down after they have finished flowering, leaving just a few leaves at their base, she will find that although they will not flower again this year, they will make a lot of leafy growth and put on an excellent show next year. This will not solve her space problem though. Which is why most of us treat these lovely plants ungraciously and chuck them out before they reach their prime.

Gareth Martin asks why his wallflowers, bought last autumn virtually bare-rooted from the same supplier as usual, didn’t do well. He says there is no sign of dreaded club root (that is, sickly growth and lumpy roots), they just looked wan. I can’t say with any certainty what is wrong. How long they hang around bare-rooted has some bearing on performance; obviously if you buy them this way there is a risk they could have started to dry out or (probably worse), may have been sitting with their roots in water for too long. And the weather has something to do with it. Mine did quite well this year, planted in containers of good rich compost and – most importantly, as my father used to tell me – I always firm them in really well. (For more on wallflowers, see Sarah Raven’s story on biennials, 30 May issue.)

Off with their heads?

Should you deadhead alliums after flowering? Last year I left seed heads on as advised on television. This year we have fewer flowers with smaller heads. Sheila Waring, via email

I have also found that alliums deteriorate. It is partly a function of leaving the heads on (for aesthetic reasons and for birds), and partly because, I suspect, their leaves get swamped within our unnaturally packed borders and are unable to act as ”solar panels” for the creation of the following year’s flower buds within the bulbs. The answer? Remove half the old heads (and stems), leave the rest on; try to keep the dying leaves, ugly though they are, clear of other growth, and also top up your allium population with fresh bulbs each autumn.

  • Write to Thorny Problems at [email protected] or Gardening, The Daily Telegraph, 111 Buckingham Palace Road, London SW1W 0DT. Helen Yemm can answer questions only through this column.

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