Delphiniums bring a wealth of height and color into any garden, although they do have a reputation of being difficult to look after.
This is due to the way that delphiniums can be easily broken by heavy winds, but there are tricks to stop this from happening, even in the most exposed garden.
Their popularity has been cemented by their huge flower spikes, producing many blooms in the most vivid blues, purples, pinks, whites, reds, and yellows imaginable.
Here’s everything you need to know about Delphiniums, including how to grow them, how to stake them, where to plant them, and different varieties you should try at least once.
Delphinium At a Glance
Where do Delphiniums Come From?
Delphiniums hail from many parts of the Northern Hemisphere, as well as the mountains of the tropical parts of Africa.
Delphinium andersonii, or the Anderson’s Larkspur, is only found in the Sierra Nevada Mountains in the US, while Delphinium exaltatum, the tall larkspur, comes from the Appalachian Mountains.
Delphinium refers to a genus encompassing around 300 species of flowering perennials in the Ranunculus family.
The name is derived from the Greek delphis, which means dolphin, referring to the flower bud shape.
The Difference between Larkspur and Delphiniums
The names larkspur, and delphinium, are often used interchangeably, making things very confusing.
Larkspur refers to annuals which fall under the Consolida genus, as well as the common name for Delphinium, and while they are related, they are entirely different plants.
Delphiniums are perennials, though their flowers are short-lived, while Consolida larkspurs only last for a single season.
You can tell the difference between the two not only in their lifespan but in several ways.
Larkspurs have much smaller flower (see also Larkspur Flower Meaning and Symbolism) spikes, producing much fewer flowers than Delphiniums.
Delphinium Hybrids
Like a lot of plants, valued for their beauty and producing many flowers, delphiniums have been highly hybridized over the years.
Most delphiniums available are a result of these crosses, where they have successfully been bred to flower for longer periods of time, produce more blooms, in many new colors, or even bicolors.
Some are suitable for specific climates, including Delphinium elatum, which is extremely cold-hardy, down to 14°F or -10°C, and a very reliable bloomer, ensuring that you get colorful displays year after year.
How to Use Delphiniums in the Garden
Delphiniums produce such displays of color that they have become synonymous with summer and days filled with colorful blooms, some of the very best we can grow during the season.
They’re often referred to as the ‘Queen of the Border’, referring to the dramatic flowers which can outshine others in a mixed border.
Despite their short-lived nature, the flowers make an excellent and impressive cut flower, perfect for arrangements, gifts, or as wedding decorations.
For a captivating display, dedicate a whole bed to growing delphiniums, or mix them with contrasting heights and colors to really show them off, with garden phlox, tithonia, chrysanthemums and asters.
Other Uses
Delphiniums were used to make blue dye, as well as one of the primary sources of a bright blue ink.
While the flowers of a delphinium don’t last a hugely long time, they can also be dried, making for gorgeous decoration or unique gifts.
Toxicity
It’s worth mentioning that every part of a delphinium is very toxic to both humans and animals. The seeds especially contain the most alkaloids.
Where they are found naturally, ranchers wait until late summer to move their cattle into fields with delphiniums, as they are much less toxic at this point.
While the plant won’t cause any damage to your skin, it will cause you serious harm if you ingest it.
You can recognize signs of poisoning which include vomiting, the throat going numb, a weaker pulse, muscle spasms, diarrhea, convulsions among others, which will lead to death if ingested in large amounts and left untreated.
How to Recognize a Delphinium
Delphiniums are classed as herbaceous perennials, which flower during the height of summer, producing flower spikes that tower above the rest of the plant.
Some varieties can reach a maximum height of 2 feet, while others can range from 6 to 8 feet tall.
Delphinium Flowers
The flowers produced on a delphinium appear on a spike, above the foliage.
There are different forms of flowers, dictated by the type. You can get single-form, semi-double, and double delphinium flowers.
Single-form delphiniums produce flowers which feature five sepals. You’ll notice that the lower petals are covered in hair, also known as honey leaves.
Semi-double delphiniums have five sepals as single-forms do, but semi-double blooms also have eight more sepals.
Each flower has two parts, a larger, outer flower, and a smaller flower in the center, which is called the ‘bees’ or ‘eyes’ of the flower.
This particular part may be white, black, brown, or stripy, depending on the variety of the delphinium.
Double-form delphiniums don’t always have eyes, instead, they have more sepals.
Each bloom features five sepals, which resemble petals. These act as a pouch, and inside are the true petals.
Colors include a vivid blue, purple which can range from a very pale purple to a deep plum, pink, crimson, yellow, and white.
Delphinium Fruits
Delphinium produce seed pods which are classed as follicle fruit, and these split open only on one side to release lots of seeds, which will create new delphiniums.
Delphinium Leaves
Leaves form alternately on the plant, featuring long stalks, in a lovely deep green.
Depending on the type, these leaves will have a minimum of three palm-shaped lobes, though this may be as many as seven.
Delphinium Roots
Despite the lofty heights that delphinium flower spikes can grow to, the roots of the plant are shallow, which is one reason why you should stake them.
Delphiniums usually form from a crown, and roots emerge from this part of the plant, in two different types, the anchor, and the feeder.
As the name suggests, the anchor roots help hold the delphiniums securely in the soil, and they are the fleshier, more substantial of the two.
The feeder roots sit nearly on the surface of the soil, which are much younger than the anchor roots. Their job is to find the water and nutrients for the plant to live off.
Delphinium Types
There are several types to choose from when it comes to delphiniums, and each has their own qualities.
Belladonna Delphiniums
One of the most popular groups is those that belong to the Belladonna category. You’ll also see them categorized as Delphinium x belladonna, and they are hybrids formed from Delphinium cheilanthum and Delphinium elatum.
Typically, belladonna delphiniums reach a maximum of 4 feet tall, sometimes 3, spreading anywhere between a foot wide and 2.5 feet.
Delphiniums in this group are single or double flowering plants, usually in striking shades of blue or white, produced in early summer.
If you deadhead them early enough, they will produce a second flower spike in the later days of summer, or even fall, before the first frosts take hold.
Belladonna delphiniums are demanding in their care, but they are easy to grow.
Elatum Delphiniums
Elatum delphiniums encompass those that belong to D. elatum species, as you might guess. You’ll also see them referred to as the alpine delphinium, or the candle larkspur.
Elatum delphiniums can produce all three forms of flowers, usually from early summer onwards.
They also produce significantly more flowers than the belladonna type, but they don’t last as long. You’ll find them in shades of purple, blue, cream, white, and pink.
These are much taller than the belladonna group too, reaching up to 8 feet tall for a fantastic display, often spreading up to 3 feet, so they need plenty of space.
Because they get so tall, they also require staking, as strong winds will break the flower spikes well before they finish.
While they are known for producing taller varieties, there are much shorter cultivars to choose from if you don’t want your other plants being outdone.
Grandiflorum Delphiniums
Grandiflorum delphiniums create impressive displays, as you might guess from the name.
They are also suitable for much smaller gardens, as they will grow to a maximum height of 2 feet.
You might also know them as the Siberian or Chinese delphiniums, as that’s where these cultivars come from. As a result, they are perfect for rockeries, or gardens with sandy soil, thriving in freely-draining, dry soil.
Grandiflorum delphiniums produce spectacular blooms in white or blue, in a dispersed form.
Pacific Giants Delphiniums
These gorgeous types can grow to an impressive 6 feet tall, with flower spikes that produce single or double blooms.
They have a much wider range of colors than grandiflorum delphiniums, including pink, purple, white and blue, usually appearing in the height of summer.
You might also recognize some cultivars in this group, named after famous figures of legend, such as ‘King Arthur’ and ‘Galahad’.
New Zealand Hybrid Delphiniums
Those delphiniums which come from New Zealand, bred by Dowdeswell’s, thrive in warm climates when compared to Pacific hybrids.
Delphiniums You Should Grow at Least Once
It can be difficult to decide what varieties of delphinium you should start with, as there are hundreds of cultivars.
Here are some suggestions, all of which are striking, and will provide a plethora of color and architectural form into your own green space.
Delphinium ‘Bella Andes Lavender’
A much lighter purple than some varieties of delphinium produce, ‘Bella Andes Lavender’ is a belladonna delphinium which is fairly hardy.
It’s best planted in the middle of a border where it can soak up as much sun as possible, where the foliage will be a feature of its own.
From June, through until July, ‘Bella Andes Lavender’ will produce flower spikes that will reach a maximum height of 4 feet, which feature long-lasting flowers.
Like most delphiniums, ‘Bella Andes Lavender’ will require staking in order to support the flower spike.
Delphinium x ‘Benary’s Pacific Summer Skies’
Also known as candle larkspur, ‘Benary’s Pacific Summer Skies’ produces plenty of flowers, while also having the benefit of being resistant to diseases such as mildew.
This cultivar is best planted at the back of a border which is sunny.
It will reach a maximum height of 3 feet tall, flowering in a clear blue from June until July, though you may get an additional, more petite flower spike in September.
As long as the soil is well-draining, this candle larkspur will thrive in any type of soil.
Delphinium ‘Bolero’
A truly unusual form of delphinium, this cultivar is perfect for sunny patios, producing extraordinary blue to purple flowers, with white, almost green centers in a double form.
‘Bolero’ will reach a maximum height of 3 feet when it produces its flower spikes in May and June, slightly earlier than other varieties.
This cultivar, like most, needs full sunlight in order to bloom as much as possible, and well-draining soil to prevent root rot.
It’s also an extremely hardy variety, potentially surviving temperatures as low as -4°F or -20°C.
Delphinium ‘Blue Bird’
A Pacific Hybrid, ‘Blue Bird’ is suitable for the backs of borders where it can still get full sunlight.
This cultivar is usually grown as an annual or biennial, depending on where you live.
It can reach an impressive 6 feet tall, which means you’ll need to stake it firmly in order for it to thrive. Depending on the conditions it’s grown in, it can reach between 3 and 6 feet tall.
The flower spike produces fantastic deep blue flowers, with white eyes, and while they don’t last as long as other cultivars, the display they create is worth it.
Delphinium ‘Cinderella’
One of the most ornate-looking cultivars you can get, ‘Cinderella’ is nevertheless extremely resistant to disease and cold temperatures.
The flower spikes can reach anywhere from 3 to 5 feet tall, and they are much sturdier than some, producing incredible triple blooms in a light pink to white.
This triple form also means that they are a little more wind-resistant than others, but it’s still beneficial and good preventative protection to stake them properly.
Delphinium elatum ‘Holly Cookland Wilkins’
‘Holly Cookland Wilkins’ is a compact flowerer which will produce semi-double violet blooms, contrasting against the dark eyes.
In the right conditions, it will reach 5 feet tall, and it’s a more weather-resistant variety than some, able to withstand colder temperatures and stronger winds.
Delphinium ‘Faust’
If pale blue delphiniums aren’t really your thing, ‘Faust’ produces the most captivating, double-form true-blue flowers in June, July, or even as late as August or September. This is a favorite of many cottage gardeners.
This is a Delphinium elatum variety, and needs full sun in order to produce the best blooms it is capable of. In the right conditions, it can reach 6 feet tall, making it a perfect feature for any garden.
If you want a unique display, you can plant a group of them at the back of a border, where they will help protect each other from strong winds, but they will still need some support.
Delphinium ‘Foxhill Nina’
Winner of the Award of Garden Merit in 2008, this elatum variety produces large, pale pink to purple flowers with white central eyes.
When mature, ‘Foxhill Nina’ can reach up to 5 feet tall, making it perfect for breaking up the view of fences or walls in the height of summer.
It will happily grow in chalky, loamy, or even sandy soil, as long as it drains well, and the plant can soak up full sun.
Delphinium elatum ‘Constance Rivett’
‘Constance Rivett’ is sure to impress in any garden, featuring semi-double, brilliant white flowers, which contrast well against the dark, glossy leaves.
Place it somewhere sheltered and sunny to get the most out of this beautiful cultivar, but note that the flowers won’t last as long in hot climates which have a high level of humidity.
‘Constance Rivett’ will grow to 4 feet tall once it has matured, and this may take a couple of years.
Delphinium grandiflorum ‘Summer Nights’
If towering flower spikes aren’t something you want, or if you have a much smaller space that you’d like to fill with color, ‘Summer Nights’, a Delphinium grandiflorum cultivar part of the Summer series, is the perfect choice.
‘Summer Nights’ grows as a low bush, making it perfect for container gardens, or borders which need some injection of color at the front.
It will reach around 45cm tall, making it ideal for a mixed border full of other tall plants, rockeries, edging a border, or compact spaces.
Like any delphinium, ‘Summer Nights’ needs full sun and well-draining soil in order to thrive and produce the most flowers possible.
Growing Delphiniums and Plant Care
While delphiniums will come back after a season, they normally don’t last more than two or three years, making it worthwhile to collect their seeds, or buy more to resow them for continuous years of color.
Delphiniums are perfect for any informal planting style, and while they are easy to grow, they are harder to maintain.
Planting and Position
You need to plant delphiniums in full sun in order to get the best out of these lovely plants, but also somewhere away from exposed areas where strong winds can snap the stems in two.
To get the most flowers possible, plant them in soil which drains well, but still holds some moisture. If there’s not a lot of nutrition in the soil, it’s worth adding some mulch, and feeding the delphiniums during the flowering season.
Make sure to plant delphiniums in early spring, leaving at least 2 feet between each plant. For best results, make sure the crown of the plant is firmly in the soil to weigh it down and help anchor it.
Watering and Feeding
While delphiniums will largely take care of themselves, they do benefit from regular soakings during the summer months.
Make sure the water doesn’t sit around the plant for too long, so do this in the early morning before the sun reaches the plant, and when the sun does hit, it will burn off any leftover moisture once the plant has had its fill.
Delphiniums are hungry, demanding plants, so you should aim to feed them once planted, and then every time you water them during summer. Make sure not to get any fertilizer on the leaves, as this will burn them.
You can use an all-purpose fertilizer, or if you prefer, a fertilizer made from seaweed.
How to Stake Delphiniums
Delphiniums need to be staked. There’s no way around it. Without staking them, they will fall over and break, not just from strong winds, but also from the weight of the flowers themselves.
The easiest way to stake delphiniums is to get three large, strong bamboo stakes. Put the stakes firmly into the soil around the delphinium in a triangular shape, careful not to stab the roots.
Do this before the delphiniums require support. Use twine to link the stakes together and form a loose barrier, and the flower spikes should form in the middle.
By leaving some space between the stakes, and avoiding tying in the plant to the stakes, the delphinium flower spikes will be able to move with the wind, but the stakes will stop them breaking and falling over.
How to Deadhead Delphiniums
Once the flowers start to fade, or if you want to take cut flowers, use sharp, clean cutters to cut the flower spike off to the base of the plant in one simple step.
You can then cut the flower stem to your desired size, and either use it as a gift, or to bring some colors indoors. This can encourage a second round of blooms, too.
If you just want to get rid of spent flowers without cutting off the whole spike, use cutters to trim any lateral flowers which have faded.
Pests and Diseases to Watch Out For
Most delphiniums are fairly resistant to pests and disease, but there are some you should still keep a look-out for.
Powdery mildew is a big killer of delphiniums. You’ll find it growing on delphiniums which don’t have enough air flow around the plant, if there’s too many packed together, combined with high levels of humidity.
It doesn’t help that delphiniums do best in sheltered locations, which is where this fungus thrives. The best way to combat this is to water the plants at the base, and keep some room in between delphiniums and their neighboring plants.
Aphids, mites, and leaf miners will also affect the growth and health of delphiniums. To make sure they stay healthy as possible, keep an eye on your delphiniums, removing any dead or dying leaves, and dying flower heads.
