Nothing beats the riot of colour of Delphiniums, which fit the glorious English summer perfectly!
The effort put into establishing them now will pay off when they create vivid spikes in your garden in June and July; really worth it, even from the perspective of encouraging pollinators.
If the goal of growing classic Delphiniums is to enjoy the sapphire blue, red, pink, mauve colours, then the types of information here will enable you to be successful growing these stylish perennials.
All About Delphiniums
The genus Delphinium includes over 300 species of flowering perennials and belongs to the buttercup family (Ranunculaceae).
Delphinium sounds very similar to the word dolphin and is derived from the Greek term delphinos, perhaps as a reference to the shape of the flower.
Delphiniums grow mostly in the Northern Hemisphere and have been cultivated in Britain for centuries and are commonly called Larkspur, from the Tudor era.
Delphinium Description
Similar to many other garden perennials planted by gardeners and designers, such as hollyhocks or foxgloves, delphiniums produce tall spikes of inflorescence made up of single or double flowers which are the most standard vivid blue colour you’ve probably ever seen.
The delphiniums shown in the group below, vary by flower colour, the height of the delphinium plants themselves and numbers of flowers per plant;
Some delphiniums are not just perennials, they are also annuals and biennials as well.
The tallest variety within delphiniums, the Elatum group can grow up to two metres tall; while, other types of delphiniums, like “Belladonna” are shorter, much more branched stems and do have delphinium flowers, like in the Elatum grouping; although they are more individualized flowers
The Delphinium Flower and Foliage
Gardeners admire the tall upright stems and the palmate deeply lobed leaves of Delphinium.
During the summer months, Delphinium produces an impressive raceme of bilaterally symmetrical flowers that have numerous stamens.
The flowers show five petal-like sepals forming a hollow pocket with a spur at the tip, and four true petals inside.
The spur on the upper, backward-facing sepals encloses the nectar-containing spur of the upper petals, thus attracting butterflies and bees.
Once it is pollinated, the plant develops small, tiny black seeds.
Delphinium Toxicity
Delphinium poses a threat to humans and livestock due to its toxicity. However, certain varieties of moths and butterflies are capable of consuming this plant without any adverse effects.
Perfect for the English Country Garden
Delphiniums are a beautiful addition to herbaceous borders and give gardens that treasured cottage garden look.
They are definitely worth adding to the plant palette, especially if you would like year-round colour in your garden. They are also a hardy perennial that provides an eye-pleasing cut flower in a vase.
Delphiniums look lovely with:
- English roses
- Lupins
- Foxgloves
- Stocks
- Peonies
- Verbascum
How to Grow Delphiniums
The optimal time to plant delphiniums is in autumn or spring, when the soil is warmer, although they can be planted at any time of year.
Delphiniums prefer soil that is moist but well-drained. When you plant, prepare your soil by adding a handful of grit to the planting hole.
This will help your Delphiniums survive the winter when the soil tends to become waterlogged.
Remove delphiniums from the pot and plant at a similar depth, adding a rich manure feed. Back-fill with soil and water again.
They will need full sun, so make sure to position them where they will be in the sun and not under shade.
When planting them along a border, you can position them at the back of the border, as they are taller than other plants.
Make sure to not plant them in very windy spots, as the tall stems can be blown over. Most gardeners use one stake per stem that runs from the base of the plant to just beneath the flower heads.
You will need to be careful of young shoots and protect them from slugs until the plant has some height. Delphinium specialists “Blackmore & Langdon” have their own potent garlic drench as a slug deterrent.
You can make your own by soaking garlic cloves in hot water and then cooling the water, straining it and putting it in spray bottle to drench your young delphiniums in.
Your young plants will need to be staked, do this in the early spring as they begin to shoot. This is very important as sacks of wind, storms or heavy summer rain can snap the stems.
The tall stems will also need to be staked again to support when the blooms become heavy with dew/rainwater.
Use canes to stake up the taller varieties of delphinium you are growing or erect frames that your plants can grow and rise up in.
You will also need to feed your delphiniums with a high potash fertiliser.
All the growth and flowering makes for very hungry delphiniums over summer they should be fed at least twice with a good slow-release fertiliser.
Seaweed fertiliser is another excellent choice.
The flowering season of Delphiniums is quick and colourful!.
If you cut back the stems of your delphinium after their first flowering, they will then have some chance of a second flowering between late August and early September.
You should cut back as soon as your first blooms start to fade.
When the flower spikes start to look tatty, cut your delphinium back right to the soil, this will be your final cut for your delphinium.
Do try and leave any shoot that is developing from the side.
You can water and feed your dephinium preparing for winter.
Growing Delphiniums from Seed
It’s possible to successfully sow and grow any variety of delphinium seeds you would like to use.
If you already have existing delphinium plants, you can harvest the seeds from these plants.
Growing from seed takes more time and care compared to buying plants in a nursery, however, it can be cheaper.
Seeds can be sown from February through June or later in September or October.
Here is a way to do it:
- Start your seed in a seed tray using warm, moist potting compost.
- Delphinium seeds require a cold start, so you can place them in the refrigerator before planting.
- Cover your seeds with a light covering of soil.
- Keep the seedlings in a dark place at a temperature of 50°-60°F.
- Once established, so they can continue to grow vigorously, pot on your delphinium cuttings.
- To encourage the best growth, use nutrient-rich compost.
In warmer weather, (late spring/early summer), you can direct sow the seeds outside.
You can germinate them first by putting them on a moist paper towel or coffee filter.
Propagating Delphiniums
Delphiniums can be propagated through basal cuttings (cut off at the base of the plant).
This should take place when the plant is beginning its spring growing process.
Here’s How to Take a Basal Cutting from a Delphinium
Here is the process:
- When you spot new shoots from a plant, you can take stem cuttings of individual shoots with a sharp clean knife just below the soil level.
- You should only take two shoots from each plant and place both shoots into a plastic bag to keep them moist.
- The cuttings should be prepared by cutting excessive foliage off and leaving one to two leaves remaining to feed the developing roots from the cut cutting.
- You can then pot up your cutting into some good multipurpose compost.
- Be sure to water the cutting and cover it with a plastic bag, and mist the developing plant regularly to prevent drying out, and look a sunny spot until transplanting outside.
Frequently Asked Questions for Growing Delphiniums
Can Delphiniums Cope with High Temperatures?
Although they love to be in the sunshine, delphinium flowers prefer cooler relative ambient temperatures.
On hot summer days, be sure to check that your potted flowering plants do not dry out by making sure the soil remains moist at all times.
What are the Main Pests to Look Out for When Growing Delphiniums?
In the early spring, delphinium’s tender braches may be vulnerable to damage from pests that can persist until the summer months.
You will need to feathers up strong to avoid having the stem eaten caused by bugs or having older flower stalks worn to the ground from pests.
Typical delphinium pests include:
- Slugs and snails: these gastropods can cause damage to young plants by feeding on their tender new growth and leaving leaves with ragged holes. Slugs and snails may be controlled by a liberal garlic drench or trapping them using beer.
- Aphids: Aphids and other sapsucking insects can congregate on the undersides of delphinium leaves or around the flower buds. The effects of aphid feeding are stunted growth, yellowed and brown leaves and distortion. Affected plants should be treated with fatty acids, neem oil and other insecticidal sprays.
- Cyclamen mites: cyclamen mites are tiny mites that cause black spots on the leaves and stems of delphiniums and are also sapsucking insects. Insecticidal soap sprays can be helpful in controlling these insects.
- Nematodes: there are some nematode species that can damage the root, resulting in yellowed and stunted plants. The solution to this problem may be to inoculate the soil with materials to increase beneficial fungi that feed on nematodes.
- Leafminers: leaf miners can damage and feed on the leaves resulting in discoloration, blighting and collapse, a soap spray treatment may help in eradicating them.
What are Delphinium Diseases to Look Out for?
Delphiniums are susceptible to several common plant diseases including:
- Powdery mildew can manifest during dry weather. Maintaining moist soil around your delphiniums will help but make sure the leaves are dry.
- Rust produces rust-like pustules on the leaves of the delphinium. Prevent rust by pruning off affected leaves and cleaning dead foliage in the fall.
- Delphinium black blotch is a bacterial disease that produces large black blotches on the leaves. It occurs more often during wet summers and has the potential to overwhelm a plant. The best management is to use secateurs and cut off the affected parts of the plants to reduce the spread of the disease.
What Should I Look Out for When Buying Delphiniums?
Purchasing a young plant from a respected nursery or reputable online store is a simple and quick way to have the gorgeous flowers of the delphinium in your garden by summer.
You should also make sure that the variety you purchase grows to a manageable height for you because of how big and tall delphiniums can become.
If you are able to see the plants before you purchase them, look at the quality of the foliage and look for signs of some of the pests and diseases that are common to all plants.
What are the Best Delphinium Varieties to Grow?
Growing some of the popular types of delphiniums will create a great display in the garden.
Here are some of the most popular varieties.
Delphinium ‘Amadeus’
Delphinium ‘Amadeus’ is a well-known delphinium cultivar noted for its deep blue/violet flower colour and velvet petals with a dark brown ‘eye’. Amadeus reaches a height of just over 1.5 metres and a spread of 1 metre.
Delphinium ‘Pacific Hybrids’
This amazing variety features heavy single or double flower head in a wide range of colours.
These tall flower spikes can be stunning cut and placed into a vase and used as a feature in your home! Backed by the horticulturalists at “Pacific Giants” these selections can reach 1.5 metres tall and spread to 75 centimeters.
Delphinium ‘Rising Stars Mixed’
Delphinium ‘Rising Stars Mixed’ is a top quality variety that produces somewhat smaller, more compact plants, ideal for smaller gardens.
This hardy perennial is available in a range of colours, including blues and pinks and different flower types.
‘Rising Stars Mixed’ reaches a height of approximately 1.2 meters and a spread of 75 centimeters.
Delphinium ‘Magic Fountain Series’
The ‘Magic Fountain Series’ produces compact plants that are suitable for a small garden or balcony.
This colorful type will grow to a height of 90 centimeters and spread of 60 centimeters.
Delphinium elatum ‘Faust’
Add some drama to your garden with these impressive 2.5 metre high flower spikes which are packed with brilliantly colourful double blue flowers with a dark centre.
Delphinium elatum ‘Cinderella’
This is a smaller pink delphinium plant, which is just as lovely.
It has a strong stem and triple blooms. Cinderella reaches a height of 1.2 metres and a spread of 80 centimetres.
Top tip!
You can continue to enjoy delphiniums throughout the summer months by dividing them regularly in spring.
Rounding Up
Delphiniums are true English flowers with their abundance of character and colour.
With a little care during the year, you will enjoy that leggy lady this year and for many more years to come!