Delphinium

Most of us remember delphiniums in Grandma’s garden. This article will discuss many species of delphinium. including our native species, though the hybrid forms are most popular in gardens. They need a sunny, sheltered site with fertile soil and abundant moisture. Delphiniums are not long lived, and will self sow if allowed to do so. The offspring of hybrids often reverts back to the simple, single (and usually blue or purple) flowers of their ancestors.  These are the delphiniums you are most likely to find offered for sale at your local garden center, and they are for the most part, superb garden plants.

There’s quite a lot to this group of plants and both novice and advanced gardeners can benefit from having them in their gardens and getting to know them a bit better. Delphiniums belong in the buttercup family (Ranunculaceae), and as such, they are related to clematis, anemones, pasque flower, monkshood, baneberry, hellebores, columbines, and globe flower.

The word delphinium is derived from the Greek word Delphos, meaning dolphin. It refers to the shape of the buds. They are often called larkspurs, in reference to the distinctive spur on the back of the flower, but true larkspurs belong in the closely related genus Consolida. There are about 300 species of Delphinium, nearly all of them native to the northern hemisphere but with a few species coming from high altitudes in the mountains of tropical Africa.

Usually they have deeply lobed, palmate leaves and hollow stems. Flowers appear in late spring or early summer and while blues and purples are very predominant, there are also species with white, red, yellow, and pink blooms. Bees are the primary pollinators but butterflies also play a role, and several North American species rely on hummingbirds.

Like many members of their family, delphiniums are considered poisonous. Interestingly, the toxins of delphiniums have been studied and analyzed more than almost any other group of poisonous perennials since their toxins affect different creatures in such different ways. In humans, delphiniums cause stomach upset and severe discomfort if ingested. In both sheep and deer, the effects vary greatly. They are extremely poisonous to cattle and bison, usually causing death within a few hours of ingestion. In places like Utah and Wyoming, ranchers will often wait until the native delphiniums are finished blooming before moving their cattle to the pastures in the high country to lessen the risk of consumption. As garden plants, delphiniums are seldom eaten by browsing animals (including rabbits and deer) and have very few pest or disease problems.

In wetter climates, powdery mildew can be an issue but with the exception of one very specialized moth, there isn’t really anything that eats them. That moth is the golden plusia (Polychrysia moneta), and its larvae are commonly called delphinium worm. The moth is native throughout the northern hemisphere and in their juvenile stage, they feed on delphiniums of all kinds, larkspur, and sometimes globe flower or monkshood as well. There is only one generation per year, and this makes them somewhat easier to control. Adults emerge in late spring or early summer, usually right when the delphiniums are budding. Small green caterpillars that blend in so beautifully as to be nearly invisible will chew the tips and leaves, causing the whole plant to take on a ragged, shredded appearance with no flower buds. The caterpillars overwinter in the hollow stems and pupate in early spring, emerging in late spring or early summer as adults.

Be very alert to the appearance of these creatures; the first sign is usually a blackened, collapsed leaf near the tip of the plant. Things get progressively shabbier looking from there. Carefully examine your plants (daily) and crush and squish the caterpillars as you find them. You should also cut back delphinium in the fall, thereby eliminating their wintering grounds.

You would think that with several hundred species available, these plants would positively fill our gardens, but the truth is that very few species of delphinium are cultivated. Nearly all of the garden forms are hybrids, and nearly all of the hybrids are quite tall. This has led many gardeners to place them in the category of “large things that require staking” but this is not true of all of them; there are a large number that are very short and compact and can easily be grown without support of any kind.

To grow delphiniums well, there are a couple of things you need to be aware of. Firstly, they need full sun. This is not optional because they become magnets for fungal infections in partly shady or shady locations. You also need excellent air circulation around them and they shouldn’t be overly crowded. A rich, moist soil with good drainage suits them best. They are very fond of compost and well rotted manure, and they respond well to fertilizer and love.

Delphiniums ideally should be grown in a sheltered location for two reasons. Since their stems are hollow, they are easily smashed by a strong wind. It’s very disheartening to come home from work and find your delphiniums lying on the ground in pieces! Secondly, they will be absolutely demolished by hail, something that we often get when they are just about to bloom. With abundant nutrients, they recover fairly quickly and if they are deadheaded, they sometimes flower again in late summer, though less profusely. Try to plant them in as protected a location as you can.

If not deadheaded, delphiniums will self seed abundantly but should not be problematic. Hybrids normally revert to the parent species, so if you have successive generations of delphinium in your garden, your doubles will likely become singles and your pinks and whites will produce blue and purple offspring. They have a tendency to be short lived (usually three or four years) but they are easy to start from seed and will often flower the first year if you sow them indoors in February or March. They hybridize quite freely as well, so if you have more than one color in the garden, you’ll sometimes get interesting results.

Established plants can also be divided, and this sometimes lengthens their life by a season or two. Delphiniums are for the most part inexpensive, and they flower for several weeks. They are worth planting in nearly any garden, and they grow fast and establish quickly.

Types of delphinium

We’re going to look at a few of the native species and some of the more unusual things that the genus Delphinium has to offer, and then we’re going to look at some of the hybrids. There will undoubtedly be a few things here you weren’t expecting!

Delphinium bicolor- Found native throughout western and central North America, from BC all the way to South Dakota. This beautiful little plant, sometimes called low larkspur, will often bloom en masse where conditions suit it - usually moist, sunny meadows and pastures. The flowers range from dark blue to purple and it’s very showy. If you find a small delphinium growing wild in Saskatchewan or Alberta, this is probably it. Growing only 8-12” tall, this makes an excellent garden plant as long as you are prepared for it to go dormant in the heat of summer.

Delphinium cardinale- From southern California and northern Mexico, this species grows up to 6 ft. tall and produces beautiful scarlet flowers that are pollinated by hummingbirds. This species is hardy only to about zone 5, but it has been used in several breeding programs in attempts to introduce its coloring to modern hybrids.

Delphinium elatum- Found throughout Europe and western Asia, this species is the most important in terms of developing garden delphiniums. Growing 3-4 ft. tall, it produces single or double flowers that are usually blue or violet but can also be purple, lavender, or white. It is the grandfather of all modern delphiniums found in gardens. Famous French horticulturalist Victor Lemoine (best known for his work with lilacs) was the first person to hybridize delphiniums for garden use, well over 100 years ago. He crossed this species with D. formosum, and the resulting plants were showy and flowered profusely. Using his hybrids as a starting point, the British began to produce their own garden delphiniums. They were soon a staple of the English cottage garden and border, and they have been popular ever since. Hybrid delphiniums will revert back to this species after several generations (or very close to it) and have occasionally naturalized in North America.

Delphinium formosum- Native to the northern parts of Turkey, this is a gorgeous species that is sometimes grown, with large, showy flowers that range from lilac to blue. It was extremely important in developing the first garden hybrids of delphinium and is still sometimes used in breeding programs.

Delphinium glaucum- If you have hiked in the Rockies, you may have encountered this species. Growing anywhere from 3-7 ft. tall and favoring moist to wet soils at moderate to high elevations, this is a very beautiful delphinium with smallish, light purple flowers. It can be found native throughout the western half of North America and is sometimes cultivated, although it has a preference for cooler temperatures. It is particularly gorgeous when it grows with cow parsnip (Heracleum lanatum).

Delphinium grandiflorum- Sometimes listed as Delphinium grandiflorum var. chinensis, and often sold as dwarf Chinese delphinium. If you’ve ever said to yourself that you would love to grow delphiniums but that you find them too tall, this is the plant for you! This is a very recommended plant. It will self sow profusely if allowed to do so and you should let it because it is very short lived and the spread is not problematic. It can also be grown as annual, and it’s wonderful as a container plant. Growing only 18-20” tall, this species is native to northern China and Siberia. The flowers are quite large for the size of the plant and are produced in loose clusters. They are very finely divided. Although the flowers can be violet or purple, they are usually an incredibly vivid, brilliant sapphire blue. It rivals even the best gentians for “true blue” coloring, and it attracts myriads of bees. A number of cultivars have been developed from it, and some are highly desirable and some are not. ‘Blue Elf’ is very compact, and ‘Blue Butterflies’ is similar. ‘Blue Mirror’ is a striking shade of blue but the flowers lack the distinctive spur that delphiniums are so famous for. ‘Blue Bees’ is a soft, powdery blue but does not bloom as profusely as the others and is not as showy. There are also white and soft pink flowered forms but they are not especially vigorous or garden worthy.

Delphinium luteum- I mention this species because it is one of the most unusual species, and it is also the rarest and most critically endangered, with an estimated population of only about 200 individual specimens left. Found only on a few rocky, foggy hillsides in Sonoma County in California, it is very difficult to cultivate and was probably never a very common plant to begin with. The flowers are a gorgeous shade of lemon yellow.

Delphinium nudicaule- Sometimes called scarlet larkspur, this species hails from California and Oregon and produces unusual flowers that range from orangey-red to scarlet. It grows only 8-12” tall but is unfortunately a poor garden plant- neither vigorous nor heavy blooming, and prone to mildew. There are, however, two cultivars of it that are worth growing as annuals. ‘Laurin’ is easy from seed and makes an excellent container plant, producing brick red flowers over a long period and is much more vigorous than the species. ‘Fox’ is a British cultivar in bright, cherry red with good disease resistance. Both are worth having.

Delphinium nuttallianum- Another species native to western North America, this one is very hardy and garden worthy although it is quite slow to establish. Growing 8-16” tall, it has gorgeous blue to lilac blooms and while it prefers moisture, it can tolerate significantly dry soil once it is established. It is occasionally available from native plant specialists.

Delphinium zalil- Coveted by collectors and highly prized, this stunning species from Iran grows 1-3 ft. tall and produces long wands of brilliant, clear yellow flowers over a long period. It needs very sharp drainage and can be quite difficult to establish, but it is longer lived than other species and is probably worth experimenting with. Officially it is hardy to about zone 4, but you might get away with it in the right location. In its homeland, the flowers were traditionally used for dying silk. 

Hybrid Delphiniums

These are the delphiniums you are most likely to find offered for sale at your local garden center, and they are for the most part, superb garden plants.

‘Pacific Giants’- These might be the most famous delphiniums in the world, and they were developed in California by Frank Reinelt. A Czech immigrant who arrived in America in 1925, Frank was one of the most prolific gardeners and plant breeders ever to try his hand at hybridization. Finding the blues of delphiniums “rather cold”, he started his breeding program trying to introduce the genes of D. nudicaule to the offspring of D. elatum. His success was unprecedented, and his delphiniums have been grown all over the world since their introduction in the 1930’s. Frank was always modest about his accomplishments (“there is always room for improvement!” he said) and he didn’t consider delphiniums his best work. He also did ground breaking work with dahlias and begonias. Regrettably, his delphiniums have deteriorated from their original forms and what is now offered is often inferior. Consider these varieties “hit or miss”,  you may or may not wind up with something spectacular. They normally grow about 6 ft. tall.

• ‘Black Knight’- deep purple
• ‘Galahad’ – pure white
• ‘Lancelot’- lilac with a hint of blue
• ‘Guinevere’- mauve
• ‘Astolat’- lavender
• ‘King Arthur’- royal blue
• ‘Percival’- white with a distinct black center 

‘Magic Fountains’- This series resembles ‘Pacific Giants’ but is much shorter and more compact, reaching only 3-5 ft. Available in light blue, dark blue, white, lavender, purple and pink. This series also has a strong tendency to re-bloom if deadheaded. The variety ‘Cherry Blossom’ in this series is a gorgeous light pink, and the best pink delphinium on the list.

‘New Millenium’- Developed by Dowdeswell Delphiniums in New Zealand, these  are considered by many to be the best series ever developed. Producing larger flowers on stronger stems than ‘Pacific Giants’, they also flower for up to 10 days longer and have the best heat and disease resistance of any strain yet introduced. They are vigorous growers and flower profusely. They are also considerably more expensive than many of the older strains, but they are definitely worth the money. All of them grow 6-7 ft. tall. The series includes:

‘Royal Aspirations’- electric blue.

‘Purple Passion’- rich plum.

‘Pagan Purples’- deep violet.

‘Misty Mauves’- purples through lavenders and pale pinks.

‘Morning Lights’- pale blues to soft purples. (*this strain is also a bit shorter than the others in the series.)

‘Dusky Maidens’- light purples through lilacs and pinks.

‘Green Twist’- Beautiful ivory to cream flowers with very distinct, apple-green markings. Quite unusual. ‘Green Expectations’ is an inferior, seed-grown strain. If you are looking for a “green” delphinium, this is the one you want.

‘Blushing Brides’- A really excellent blend of pinks and soft purples.

‘Lilac Ladies’- The very best lilacs, mauves, lavenders, violets, and light purples.

‘Moonlight Blues’- The very best light to pale blue selections.

‘Innocence’- Purest, snowy white.

‘Guardian’-  This is an extremely compact series that maxes out at about 3 ft. Heavy blooming and available in several colors (white, light blue, dark blue, lavender), this delphinium makes a fantastic annual and can also be really excellent as a container plant. Originally developed for the cutflower trade, this series also performs well in the garden but is particularly short lived. It is usually the first delphinium to bloom; generally in full flower when the others are still in bud.

‘Bruce’- 6 ft. Brilliant royal blue flowers. Won the RHS award of merit in 1993.

‘Emily Hawkins’- 6 ft. Introduced in the late seventies. Pale lavender flowers. If you like pastels, you’ll love this one. Award winner.

‘Galileo’- 6 ft. Brilliant blue with black centers. Very similar to ‘Loch Lomond’.

‘Faust’- 5 ft. Stunning deep blue. Excellent bloomer.

‘Lord Butler’- 6 ft. An old variety, but still very popular. Brilliant turquoise blue flowers. Prone to mildew. ‘Summer Skies’ is quite similar but with much better disease resistance.

‘Spindrift’- Large lilac blooms distinctly tinged with blue and mauve. Another good one for those who like soft pastel colors. Vigorous grower.

Red delphiniums - A few words need to be said about the “red” delphiniums. The first one to really arrive on the scene was ‘Red Rocket’ in 1997. Reaching only 2 ft. tall, it was promoted as being the first really “red” garden delphinium and demand for it was crazy! Unfortunately, taking its genes from the red flowered Californian species, it did not prove hardy here, nor could it tolerate heat or humidity. It was very disease prone and did not flower well even where it was hardy. It was followed sometime later by ‘Red Caroline’, which was a vast improvement. Reaching 3 ft., it produces reddish pink, showy blooms but it too, lacks hardiness and does not flower profusely. The sister to it is ‘Princess Caroline’, which although is promoted as being hardy to zone 3, it still may not overwinter well. The flowers are a very rich salmon pink and it is very showy, but it is also extremely prone to powdery mildew.

‘Atlantis’- A favorite of mine with loosely clustered, single flowers of pure blue marked with purple. Only 3 ft. tall, no staking required.

‘Pink Sensation’- Apparently the result of a chance cross between D. elatum and D. nudicaule that took place in Holland, and sometimes listed as Delphinium x ruysii in honor of its discoverer. The flowers are a very rich, salmon pink on 3 ft. tall plants. Widely considered the best pink delphinium. Hardiness is questionable.

You’d think that someone, somewhere along the way, would have thought to cross D. elatum with D. grandiflorum. Well, they did. In fact, not only has this cross been done a few times (with multiple backcrosses with more seedlings), quite a number of nice varieties have come out of this. These are sometimes listed as Delphinium x belladonna. Normally these hybrids have loose clusters of blooms with a flower shape and growth habit similar to D. grandiflorum, but with the flowers arranged in a spike like D. elatum. They come in a range of colors and some are very garden worthy and some are not. Two of my favorites are ‘Casablanca’, which is the best white delphinium on this list, and ‘Cliveden Beauty’, which has large, lovely, light blue flowers. There are others; some are good and some are not. Experiment and see what you like!

Finally, we have perhaps the most unusual of modern delphiniums; a cultivar introduced by Thompson and Morgan. Over 20 years of breeding and selection went into creating ‘Phantom’, a stunning, very compact strain growing 3-4 ft. tall and producing white to ivory blooms heavily brushed and marked in a dark, chocolatey maroon color. It is absolutely stunning and not like any other delphinium you will grow. It is not especially hardy, but will flower the first year if started indoors in February. You will also have to deal with powdery mildew in wet, rainy conditions. The effort, however, is well worth it.