Learn How To Plant And Care for Your Delphiniums

Adding splendor and architectural height to borders, Delphiniums (Larkspurs) are elegant and stately perennials, biennials or annuals, which form incredibly eye-catching spikes of single or double flowers in early-mid summer and often rebloom in late summer or early fall. Profuse bloomers, their regal blooms come in an array of gorgeous colors including blue, white, pink and violet; the blue varieties being highly prized by gardeners. Rising from a mound of divided, pale to dark green foliage, hummingbirds are endlessly attracted to them – as are most onlookers!

Planting Delphinium

  • Delphiniums may be planted in spring
  • Delphiniums grow best in cool and moist summer climates, and do not fare well in hot, dry summers
  • Delphiniums need at least a half-day of sun (minimum of six hours of sun a day). Full sun is ideal as Delphiniums bloom best in sunny spots except in the South, where afternoon shade is appreciated.
  • These plants require excellent drainage. In poor or heavy soil, add organic matter at planting time to improve drainage.
  • Delphiniums love fertile, rich, moist soils. They are heavy feeders so the more compost you add to your flower bed the more spectacular your Delphiniums are likely to be.
  • Provide a site sheltered from strong winds and sufficient space to ensure good air circulation. Don’t let your Delphiniums be shaded or crowded by their vigorous neighbors.
  • Loosen your garden soil with a garden fork or tiller to a depth of 12-15 in. (30-37 cm), then mix in 2-4 in. (5-10 cm) of compost.
  • Space your plants 1 to 3 ft. apart (30-90 cm), depending on the variety.
  • Dig a hole twice the diameter of the pot your Delphinium is in
  • Place your plant in the hole so the top of the root ball is level with the soil surface.
  • Backfill the hole and firm the soil gently. Water thoroughly.
  • Delphiniums may be grown from seed, but this can be quite challenging. Seed should be started indoors early in the year, and those plants will flower the first year. If seeds are sown directly in the ground, those plants will not flower until the following year.

‘Black Eyed Angels’

‘Princess Caroline’

‘Guardian Lavender’

Caring for Delphinium

  • Delphiniums require regular watering, specifically during the dry summer months. Soil should stay just barely moist and never dry out, nor become soggy.
  • Apply a balanced liquid fertilizer every 2-3 weeks.
  • Apply a thin layer of compost in the spring as well as a 2 in. layer of mulch to keep moisture and control weeds.
  • Stake tall varieties, no later than mid-spring or when the plants reach 12 in. high (30 cm) to prevent the flower spikes from flopping over due to high winds. Grow-through supports work well for Delphiniums, as do cages.
  • Thin shoots when 3 in. high to ensure good-quality flower spikes. Leave at least 2-3 shoots on young plants and 5-7 shoots on well-established plants
  • Remove spent flower spikes to promote additional blooms.
  • After the first killing frost, cut stems back to the ground.
  • Divide plants every 3 to 4 years as new growth begins in the spring, lifting plants and dividing them into clumps.

‘Guardian Blue’

‘Magic Fountains White’

‘Highlander Blueberry Pie’

Pests & Diseases

  • Susceptible to slugs and snails as well as cyclamen mites.
  • Powdery mildew, Southern blight, bacterial and fungal spots, gray mold, crown and root rot, white rot, rust, white smut, leaf smut
  • To avoid most of these diseases and pests, practice good sanitation around the plants and keep their area well drained and clear of debris.
  • All parts of the plant may cause severe discomfort if ingested.

‘Pagan Purples’

‘Magic Fountain Sky Blue’

‘Summer Nights’

Delphiniums

How to grow Delphiniums

We have all got to grow delphiniums – the most statuesque towering spires for any garden. They make brilliant cut flowers too.

Flowers: June-July and August-September. Height: 1.5-1.7m

Growing from seed

Sow under cover in a seed tray March-April, then grow on and plant out in summer.

Or sow under cover in August, overwintering in a cold frame, to plant out the following spring.

Planting out seedlings

Choose a site in full sun or dappled shade, with well-drained soil. Add plenty of grit to heavy soils to help with drainage. If delphiniums sit wet in their dormant winter season, they can die, so make sure you prevent this.

Add plenty of organic matter to the planting hole; choose something slow-release, like Blood, Fish and Bone, or a scattering of bone meal.

They look at their best in groups of three or more, but plant seedlings 60-75cm apart to help prevent mildew.

Delphiniums will need sturdy staking to keep their hollow stems upright. You could use bamboo canes to create a ‘cage’, or if you prefer your supports to be nearly invisible, use canes to create a horizontal grid placed at 4-5ft for your delphiniums to grow through.

Aftercare

Slugs love delphinium shoots, so a dose of Nemaslug will help protect your plants.

Thin out shoots emerging from crowns early in the season to increase air circulation and help prevent powdery mildew forming.

Delphiniums are hungry feeders, so feed again with Blood, Fish and Bone a couple of times through the summer, then again in autumn before the plants die down.

Delphiniums will flower June-July. Cut to the ground after their first flowering to get a second flush August-September.

Read more from Sarah about different methods of slug and mildew prevention in her Caring for Delphiniums article.

Cut Flowers

Delphiniums make great cut flowers in June, when most flowers are open, and will last up to 7 days in a vase.

For tall spires, insert a cane into the hollow stem to avoid it bending and breaking.

Keep your arrangement away from fruit bowls as they are sensitive to ethylene gas which is omitted when fruit ripens.

Growing Delphiniums from seed and caring for them

Store the seed in the refrigerator in a sealed container until ready to plant. Delphinium seed germination is sensitive to high moisture and temperature. You should use a disease free seed sowing mix to avoid “damping off” to which delphiniums are susceptible. Cover the seed lightly.

Keep in an airy, light place. Water only enough to keep the surface from drying out. It is very important not to overwater or the seed and/or seedlings will quickly rot.

Germination for most species is best between 18 and 24°C (65 – 75°F). Do not allow temperatures to exceed 26°C (80°F). Once germinated, the seedlings will grow on happily in cooler temperatures. Watering the seed in with a general fungicide can be beneficial in helping to prevent disease problems.

Give a further treatment when most of the seedlings have emerged after about 10 days. (These applications are precautions only but help to reduce damping off when conditions favour the disease).

Pot each seedling individually into a small pot when the first true leaves appear.

It is not necessary to germinate delphinium seed in the dark. But if you do, you must be very careful to remove the seedlings to the light once they are germinated. A delay of just a day or two, when temperatures are warm (say above 18°C) will result in elongated, white seedlings which will stand little chance of survival. It is therefore a good idea to place the seeds in the light after the very first sign of germination. Warm temperatures (21-25°C) give a fast, even germination.

Caring for your plants

Situation:

Full sun preferred but successful in up to 50% shade. Delphiniums are very hardy and tolerant of frosts. They will stand and even benefit from winter freezing. Permeable shelter (tall loose shrubs or small trees) is required.

Soil:

Must be rich as delphinium are gross feeders. Mulch and sheep manure work wonders.
PH neutral 6.5-7.0 but successful over a wide range. Well drained, particularly in warm areas. Delphiniums must not get warm, very wet feet. Keep as cool as possible with thick mulch (sawdust also helps prevent slug and snail attack).

Planting:

Plant in raised beds in Spring & Autumn. Space each delphinium ½ m2 to 1 m2 apart. Wide spacing helps control height; with close spacing plants will grow taller.

Care:

Keep young plants moist. Staking is essential for best results. If grown in a bed, grow through raised, wide netting or other framework. Properly supported delphiniums will stand a lot of wind. Don’t plant right up against a wall – the wind will thrash them.

Plant Maintenance:

After flowering cut each flower spike down to 5 cm above ground; reduce water, gradually increasing again when new growth begins. Cut down and tidy in mid-winter, put slug bait down and mulch. Start feeding again when new growth is 5-10 cm high.

Watering:

Water well when in full leaf and growth is rapid. Take care not to over water when cut down after flowering, but increase water again when new shoots are 5-8 cm high.

Diseases and Pests:

Powdery Mildew can be a problem and regular spraying with sulphur, backed up with a systemic fungicide in hot humid weather, should keep them clean.

Slugs and snails are the only major pests – use slug pellets to control these especially when plants are small and during winter.

Goto to this page for more detailed description of dealing with diseases and pests.

Learn About Delphiniums

Common Delphinium Disease Problems

Aster Yellows: Leaf-like tissue forms where flower parts should be located. Petals turn green and become deformed. This virus-like condition is spread by leafhoppers. Burpee Recommends: Remove infected plants and control leafhoppers. Remove weeds in the area which serve as alternate hosts to the disease.

Bacterial Crown and Stem Rots: Leaves turn yellow and plants are stunted. Foul smelling ooze forms under wet conditions and stems may topple.Burpee Recommends: Remove and destroy infected plants.

Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Contact your Cooperative Extension Service for fungicide recommendations.

Root Rots: A number of pathogens cause root rots of seedlings as well as mature roots. Burpee Recommends: Pull up and discard infected plants. Make sure your soil has excellent drainage.

Virus (Various causes): This causes conspicuous rings and line patterns appear on foliage and plants are stunted. Burpee Recommends: Remove and destroy infected plants. Never smoke in the garden as Tobacco Mosaic Virus can be transmitted from a smoker’s unwashed hands while handling plants

Delphinium Common Pests and Cultural Problems

Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps who feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.

Cyclamen Mite: These mites damage plants by sucking juice from stems and leaves. They multiply rapidity in hot, dry weather. They can only be seen using a magnifying glass. Plants will look distorted and stunted, and may not bloom. Flowers will be distorted, streaked and blotched. Leaves can become cupped, curled, dwarfed and thickened. Burpee Recommends: Discard plants that are severely infested. Avoid working with infested plants. Keep plants watered in dry weather. For heavy infestations consult your Cooperative Extension Service for insecticide recommendations.

Leafhoppers: Leafhoppers cause injury to leaves and stunt growth. They also spread disease. Burpee Recommends: Remove plant debris. Use insecticidal soaps. Consult your Cooperative Extension Service for other insecticide recommendations.

Leafminers: These insects bore just under the leaf surface causing irregular serpentine lines. The larvae are yellow cylindrical maggots and the adults are small black and yellow flies. They do not usually kill plants, but disfigure the foliage. Burpee Recommends: Remove affected foliage.

Stalk Borer: The larvae of this insect tunnel up and down inside the plant stem causing the plants to wilt. By the time the plant wilts it is too late to save it. The larva is 1.5 inches long, greyish brown with one dorsal stripe and two lateral stripes on each side. The lateral stripes on the front half are interrupted and the lower brown stripe extends forward onto the side of the head. The eggs hatch in May to early June, after the moth lays them the previous September or October. Burpee Recommends: Remove and destroy all plant debris and nearby weeds.

Delphinium Seed Planting: When To Sow Delphinium Seeds

Delphinium is a striking flowering perennial. Some varieties can grow up to eight feet (2 m.) tall. They produce spikes of stunning small flowers in blue, deep indigo, violent, pink, and white. Delphinium is popular for cut flowers and cottage style gardens, but they do require a good deal of work. If you’re prepared to put in the time, start with seeds.

Growing Delphiniums from Seed

Delphinium plants are known for being high maintenance, but they reward you with stunning flowers. Knowing how and when to sow delphinium seeds will set you on the right path to growing tall, healthy, flowering plants.

Germinating delphinium seeds requires a cold start so put your seeds in the refrigerator for about

a week before planting. Start seeds indoors about eight weeks before the last frost of spring. Alternatively, sow seeds directly in flower beds in early summer.

If sowing outside, you may want to let the seeds germinate first. Put the seeds on a wet coffee filter and fold in half so that the seeds are inside. Place this in an out of the way place but not necessarily in the dark. In about a week you should see little roots emerging.

Whether you’re sowing delphinium indoors or out, cover the seeds with about an eighth of an inch (one-third cm.) of soil. Keep the soil moist and at a temperature of about 70-75 F. (21-24 C.).

How to Plant Delphinium Seedlings

Delphinium seed planting should lead to seedlings in about three weeks. Make sure they get plenty of light at this point if indoors. The seedlings should have two or more pairs of true leaves before they are transplanted outdoors.

When they’re ready for transplanting, harden off your seedlings by putting the seed trays outside in a sheltered area for about a week. Plant them in the flower bed with a spacing of at least 18 inches (46 cm.) between each one. Delphinium is a heavy feeder so it’s a good idea to add compost to the soil before putting in the seedlings.

Care Of Delphinium Flowers: Tips For Growing Delphinium Plants

Delphinium flowers beautify the summer garden with showy, spiky blooms on a tall, sometimes towering stem. Delphiniums come in a range of shades. Many gardeners wonder how to grow delphinium and some avoid planting them after hearing that the plant is difficult to grow. What are the secrets to the correct care of delphinium? Read more for tips about delphinium planting and how to get the best performance from growing delphinium plants.

About Delphinium Plants

One commonly thinks of delphinium plants (Delphinium) as having true blue flowers, which is the most common color. But numerous hybrids are available in shades of pink, lavender, red, white and yellow. Blooms may be single or double.

Delphinium planting is normally at the back of the bed, where flower spikes can reach 2 to 6 feet (.6-2 m.) tall. Delphinium flowers are often planted in masses or groups. Shorter varieties are useful in other areas of the garden.

How to Grow Delphinium

Grow delphinium plants in a sunny area with soil that is consistently moist. Don’t let them dry out. Mulch helps retain moisture and keeps roots cool. Performance of this specimen is enhanced when growing delphinium plants in neutral to slightly alkaline soil pH. Soil should be well-draining.

Care of delphinium should include regular fertilization in spring when the plant begins to grow, and during the flowering period. Work in well-composted organic material such as rotted cow manure, or use a basic 10-10-10 granular fertilizer. Yellowing foliage or stunted growth often indicates the plant needs more fertilizer.

Sun exposure is another aspect of care of delphinium that the gardener must get right for the showy blooms to appear. Gentle morning sun is preferable to the delphinium plants, which are picky about extreme differences in temperatures. Provide afternoon shade, especially when planted in hotter zones.

Special Tips for Delphinium Plants

An important aspect of caring for the thought to be difficult delphinium is deadheading the first blooms in early summer. Remove flower stalks when blooms are spent. When all blooms are removed and moisture and fertilization requirements are met, the gardener can expect a bountiful blast of blooms in late summer or early autumn. This is when delphinium flowers are at their most beautiful. Often, this may be the final show for the short-lived perennial, but the striking beauty and long lasting blooms are worth the effort.

Taller varieties may require staking, especially when planted in areas with heavy rain or wind. Stems are hollow and break easily under this type of stress.

Some disease and insect pests may attack delphiniums, keep an eye on young plants and when planting delphiniums, make sure soil conditions are right for the plant. Delphiniums may be propagated from seed or basal cuttings; however, don’t propagate from diseased plants.

Now that you’ve learned how to grow delphiniums, get started with delphiniums grown from seed, starting indoors in late winter. Add a few new delphinium plants each year so you’ll always have the showy blooms in your yard.

It’s around this time of year when delphiniums begin to stand tall and proud as they bloom amongst our borders. With their vibrant colours and bold heights, these are certainly a flower we look forward to seeing every year.

We asked Chief Horticultural Advisor from RHS Wisley, Guy Barter, to share his top care tips.

Growing and planting…

  • There are two ways to begin your delphinium journey – through seed raising and through propagation by cutting.
  • Barter prefers cutting a shoot in spring as opposed to raising seeds every time as this is more likely to result in beautiful, tall flowers.
  • If you prefer to plant seeds, make sure they are fresh – Delphinium Societies are a great place to purchase.
  • For optimal results, it is best to grow them like cabbages and have a dedicated patch with very fertile (slightly alkaline) soil, lots of sun and water.
  • It is very important to keep delphiniums constantly moist and not to let the plant dry out – this could cause mildew to grow which can ruin the plant.

Dan KitwoodGetty Images

As they grow…

  • Support delphiniums with canes as they grow tall, such as these 120cm bamboo canes from Gardman.
  • They are very heavy feeders and require a lot of nutrients. At the start of the season, use mulch with manure to help keep them nourished.
  • Thinning is very important for the plant’s health. A newly planted one-year-old should have one spike, two-year-olds should have three spikes and an eight-year-old can have anywhere from 20 to 50 spikes.

Getty Images

Pests…

Slugs are a major problem for delphiniums. To find out how best to deter slugs, read our guide.

Barter recommends performing a garlic drench. You can either purchase this or make your own by boiling two pints of water and adding crushed garlic cloves. Boil for half an hour and then strain into a bottle. Keep the liquid in a cool place and add two teaspoons to a gallon of water and use to water the plants once a week.

To prevent powdery mildew from ailing the plants – a common problem in dry years – try planting them widely and thinning out the shoots as they emerge from the crowns early on.

What’s next…

Once your delphiniums have finished flowering, cut them to ground level and give them a sprinkling of fertiliser to help them grow healthily the following year. Continue this process for some years and they will blossom annually until they eventually get too tired.

Delphinium Is the Flower Your Garden Has Been Missing

AndreaAstes/Getty Images

They’re striking—and unmistakable. Delphiniums are towering columns of bright blooms that can reliably add a dose of drama to any landscape. They’re often found in classic English cottage gardens, and their distinctive blooms are great additions to cutting gardens across the U.S. too. While these flowers have developed a reputation for being finicky plantings in the Southern states—they balk at the heat and humidity of our summers—they’re just plain gorgeous, which is why we’ve figured out ways to keep planting them. Read on to learn how to make delphiniums feel at home in your garden.

About Delphiniums

Delphiniums get their name from the Greek delphinion, meaning “dolphin,” as some species are said to resemble the saltwater swimmers. Delphiniums usually bloom during the spring and early summer months, and they produce tall columns of brightly colored flowers in shades of blue, pink, lavender, yellow, red, and white. The native species are reliably perennial, and some of the striking (though more difficult to tend) hybrid species can be treated as annuals if necessary.

Delphinium or Larkspur?

The genus delphinium includes several species that also go by the common name larkspur, so the names are often used interchangeably. Larkspur is also a common name used for flowers in the genus Consolida, including Consolida ajacis, a relative of plants in the genus delphinium. Both of the genera are part of the family Ranunculaceae.

Why You Should Grow Delphiniums

Aside from the fact that the tall stems of brightly colored blooms are just gorgeous in the garden, certain delphinium species are also known to attract butterflies and bees. In a garden design, they can add visual interest with height, shape, and color. If you have many low-to-the-ground plantings in your cutting garden, consider adding delphiniums for an infusion of vertical variety. While most delphinium species reach heights from 1 to 6 feet tall, some hybrids grow much higher.

Types of Delphiniums

Candle delphinium (Delphinium elatum)
Also known as candle larkspur, this delphinium species blooms in shades including blue, purple, pink, and white. This group is where you’ll find many hybrid selections, including the Pacific strain hybrids, which have been known to grow to 8 feet tall. Selections include ‘Percival,’ which is white with a black center; ‘Summer Skies,’ which blooms in light blue hues; and ‘Blue Bird,’ which has bright blue flowers.

Carolina larkspur (Delphinium carolinianum)
This plant is native to the Southeast and Midwest. It has a narrow form and bursts into a heavy showing of blue or white blooms in spring. Afterward, during the summer months, it goes dormant. Prairie larkspur (previously Delphinium virescens), also called white larkspur, is a sub-species that’s native from Texas to Canada. It’s heat-tolerant and produces tall stalks of delicate, widely spaced white flowers that bloom from spring into summer.

Chinese delphinium (Delphinium grandiflorum, D. chinense)
Also known as bouquet delphinium or Siberian larkspur, this heat-tolerant species produces large, deep blue flowers that grow in bushy masses of loose, asymmetrical formations. Selections include ‘Dwarf Blue Mirror,’ which grows to 1 foot tall, and ‘Tom Thumb,’ which grows to 8 inches tall.

Delphinium x belladonna
This delphinium group produces full, dense forms with light and delicate clusters of flowers. Selections include ‘Belladonna’ (light blue), ‘Bellamosum’ (dark blue), ‘Casa Blanca’ (white), and ‘Cliveden Beauty’ (deep turquoise).

Tall larkspur (Delphinium exaltatum)
Tall larkspur is native to the U.S. and grows north to Pennsylvania and south to Alabama. It produces bright blue flowers and reaches heights of 3 to 6 feet tall. It’s both a drought- and shade-tolerant planting.

How To Grow Delphiniums

These plants need rich soil that’s very porous, and they do best with regular watering and feeding in a spot where they can receive full sun. Because they grow to considerable heights, these flowers also require staking to ensure stability in the garden. To get them started, per The Southern Living Garden Book, “Delphiniums are easy to grow from seed. In the Middle, Lower, and Coastal South, sow fresh seed in flats or pots filled with potting soil in July or August, and set out transplants in October for bloom in late spring and early summer. In the Upper South, sow seed in March or April and set out transplants in June or July for first bloom by September (and more bloom the following spring).”

Bloom-Boosting Tip

According to The Southern Living Garden Book, “If you live in the Upper South, you can set off a burst of delphinium blooms like those you see in English gardens. When new stalks appear in spring, remove all but the strongest two or three, tie to stakes, and apply a bloom-booster fertilizer. After blooms fade, cut stalks nearly to the ground, leaving foliage at the bottom. Fertilize again and you may get a second bloom.”

Careful!

All parts of the delphinium plant (especially the very young delphinium plants) are toxic to humans and animals, so take care not to ingest them, and keep them away from children, pets, and livestock.

WATCH: Easy Wow with Buffy Hargett Makes the Perfect Blue Centerpiece

What flowers are you adding to your garden this year? Let us know your favorite flowers to plant for stunning spring blooms.

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