A source of both fascination and frustration for millions of gardeners across the world, Delphiniums are some of our most prized plants, despite their reputation for being a little high-maintenance. It’s no surprise that these lofty lovelies are known by some as the “Queen of the Border” with their diva-like demands, luxurious colours, abundant blooms, and mighty height. They really are the crowning glory of any garden.
So if you’re up for a challenge, why not have a go at growing your own Delphiniums? Learn all about them with our guide to the best varieties and how to grow them!
What are Delphiniums?
Delphinium is a large genus that contains over three hundred species of flowering perennial plants. Extensive breeding over the years has created many hundreds more hybrids and cultivars. Surprisingly, these intricate, ornate giants are members of the Ranunculaceae family, meaning they are closely related to the small and simple buttercup! Beloved for their statuesque height and showy, densely packed flowers, delphiniums are a firm favourite amongst gardeners and florists, despite them being somewhat tricky to please.
Delphiniums are endemic throughout the Northern hemisphere, particularly North America, although they can also be found growing at high altitudes in mountainous regions of Africa, and in some parts of Russia and Asia. They generally grow in large, wide-open areas such as prairies and meadows where there is plenty of fresh air circulating and they have lots of room to spread. Despite being classed as perennials, meaning they can endure cold winters to return and bloom year after year, delphiniums are relatively short-lived plants. Often, they will die back completely within five years.
But what delphiniums lack in longevity, they more than make up for in glamour and grandeur. Famed for their impressive flower spikes which teeter high above other border plants, delphiniums can often exceed six feet in height, although there are many smaller dwarf varieties which stand at a more modest two feet or less. Usually, the large, satin-textured flowers are arranged tightly, encircling the top of the stems to form conical racemes, and offering single, semi-double, or double flowers. In some species, the flowers are arranged in a more sporadic but nonetheless enchanting manner, with individual flowers dangling loosely from the stems. Delphiniums are known best for their quintessential cobalt, indigo, and violet-hued flowers, although they can also be found in shades of pink, cream, purple, and white. The centre of each flower is actually made up of several smaller petals, often in black, brown, or gold hues. This central part of the flower is often affectionately called the “bee” since they resemble little honey bees.
Flowering from early to late summer, the brightly coloured, wide open blooms are especially enticing to a huge variety of native bees, butterflies, moths, and wasps, meaning delphiniums are often grown in naturalistic wildlife, cottage, conservation, and informal style gardens.
What do Delphiniums Symbolise?
It’s easy to be impressed by these imposing plants, but beauty aside, Delphiniums hold deeper meanings for many. They are often used to symbolise cheerfulness and goodwill and are traditionally given as a gift to a friend who could perhaps do with some cheering up. Delphiniums are also used to bring about protection from negative energies.
Different coloured delphiniums can also be used to represent different meanings, too. Classic blue delphiniums are often used to symbolise dignity, grace, and remembrance of a lost loved one. Pink delphiniums can be used to symbolise new beginnings, new life, and births, as well as love and romance, whilst purple delphiniums can represent royalty or authority. White delphiniums can be used to signify innocence, purity, and spirituality, and are a common feature in weddings and christenings.
The History Of Delphiniums
The genus name delphinium originates from the ancient Greek word delphínion, meaning Dolphin. This is probably due to the vaguely cup-shaped flowers, which can be seen to resemble dolphins as they leap majestically from the water.
The majority of the Delphiniums we see today are not wild species but are the result of two centuries of extensive cultivation efforts to create an ever-expanding plethora of different colours, sizes, growth habits, and flower types. Before breeders began to experiment with delphiniums in the 19th Century, however, Native American communities were cultivating wild delphinium to create blue inks from their brightly coloured petals. Perhaps due to its reputation for offering protection against evil, Delphiniums have also been used to ward off scorpions and other deadly creatures. And despite modern science now recognising that all parts of the delphinium plant are toxic, many years ago they were a frequent feature in traditional herbal medicine. Delphiniums concoctions were used to aid sleep and lower blood pressure, although we now know that they can slow the heart rate and cause breathing difficulties!
Best Types of Delphinium to Grow
There are four distinct groups contained within the delphinium genus. Each group contains hundreds of cultivars and hybrids within it. Here’s a quick breakdown of each group and a few of the best varieties contained within them.
Elatum group delphiniums are some of the more reliable, robust varieties to grow. Also known as alpine delphiniums, they tend to be fairly cold-hardy and more adaptable to poor soils. Novice gardeners will probably have the most success with Elatum delphiniums. They offer a variety of single, semi-double, and double-flowered varieties, ranging from the quintessential delphinium blues to pinks, creams, and whites. Most mature Elatum varieties will reach around six feet tall.
Delphinium ‘Rosemary Brock’ is one of the smaller Elatum cultivars, with a maximum height of around 60 inches. It features densely packed spikes of dusky pink petals framing smaller golden petals in the centre. Its compact growth habit is favoured by gardeners with small spaces who don’t want to compromise on beauty.
Delphinium ‘Bruce’ are one of the more statuesque members of the Elatum group, reaching around two meters in height. They offer towering spiked inflorescences which range in colour from vivid violets to deep inky blues. With an average spread of around a meter, these giants need plenty of space in the garden.
Belladonna group delphiniums are far more modest in stature than some of their gargantuan cousins, rarely exceeding around four feet in height. They are available in both single or double-flowered varieties and mostly display a spectrum of blue hues. Belladonna varieties can tolerate more heat than other varieties, so are perfectly suited to gardens in a warm, southern climate.
Delphinium ‘Casablanca’ are an elegant belladonna variety with sparser flowerheads than other species, creating an altogether wilder, and more naturalistic aesthetic. Their large, creamy white flowers dangle delicately from exceptionally sturdy stems, so this is one of the few delphinium varieties which doesn’t always need staking.
The Delphinium ‘Piccolo’ is another delightful belladonna variety which is also prized for its sparser flowerheads, offering a much more whimsical visual appeal than some of its more formal cousins. Piccolo features almost bell-shaped, inky blue petals which frame smaller, central white petals, and has a maximum height of around a meter tall.
Grandiflorum group delphiniums originate from China and parts of Russia and are often known alternatively as Chinese or Siberian delphiniums. Members of the Grandiflorum group tend to be smaller and more compact than other delphiniums, so are well suited to being grown in containers and small gardens. These varieties rarely need staking because of their smaller size and sparser flower distribution. They also grow well in dry soil or rock gardens and have a relatively high heat tolerance. Grandiflorum varieties are often recommended for delphinium beginners as they are decidedly lower maintenance than some of the other varieties.
Delphinium ‘Blue Butterfly’ is a charming Grandiflorum variety which almost resembles a wildflower more than it does a formal ornamental. With a maximum height of just half a meter, it offers delicate cobalt blue blooms throughout summer, although it’s fairly short-lived, so you may want to treat it as an annual rather than a perennial.
Delphinium ‘Summer Nights’ offers delightful sprays of true-blue single flowers, with a satin-like petal texture. Each flower frames two golden stamens which protrude from the centre. Summer Nights has a bushy yet compact growth habit which is ideal for borders and pots alike.
Pacific Giant group delphiniums are, as the name suggests, some of the taller delphinium types. Although they are known for being somewhat high-maintenance and relatively short-lived, they are nonetheless impressive to grow and stunning to look at. They are often grown and treated as annuals, rather than perennials. Often exceeding six feet in height, they offer densely packed spikes of large, showy flowers in colours ranging from deep blue to bright pink to pure white.
Delphinium ‘Black Knight’ is prized for its rich, deep midnight-blue petals which frame smaller black and gold central petals. They have a maximum height of two and a half meters when grown in full sun positions.
Delphinium ‘King Arthur’ are another statuesque member of the pacific giant group, whose semi-double indigo petals encircle bright white centres. The contrasting colours of this cultivar mean they are sure to catch the attention of any visitors to your garden. King Arthur has a relatively compact spread of around 60 centimetres, so is a good choice for smaller spaces.
How to grow Delphinium from Seed
Selecting which variety of delphinium you want to grow is the easy part. Once you’ve chosen the right variety for you, it’s time to get started with the somewhat growing part. Most nurseries and garden centres offer a huge range of young delphinium plants to purchase, but it’s far more cost-effective (and arguably more fun!) to have a grow at growing them from seeds. Seeds can either be purchased or collected from existing delphinium plants in your garden. Delphiniums grown from seed tend not to flower until their second year, so you’ll need to be a little patient.
You can start the seeds indoors in late winter or early spring, usually around eight to ten weeks before the final frost is due. Delphinium seeds germinate best if they have been exposed to cold, so pop your seeds in the fridge for a week before sowing. Once chilled, soak the seeds overnight before sprinkling them thinly in seed trays filled with loose, fertile compost. Cover the seeds with another thin layer of compost or vermiculite, and cover the whole tray with a clear plastic bag or place it inside a propagator. Keep the soil lightly and evenly moist using a mister, but don’t let the soil become waterlogged.
Delphiniums are fairly quick to germinate, taking just a couple of weeks in optimum conditions. Once each seedling has at least two true leaves, you can place them into individual pots. They may need potting up a couple more times to accommodate their growth. Keep them indoors until the last frost, after which you can gently harden them off over the course of a couple of weeks. Once fully acclimatised to outdoor conditions, they can be transferred to their final growing position.
Caring for your Delphiniums
It may take a little trial and error to create just the right conditions for your delphiniums to flourish, but our growing guide will help you to master the art of growing delphiniums in no time!
Planting and Positioning
Young Delphiniums should be planted outside in spring after the last frost passes. Select a sheltered position which offers protection from strong winds, since delphiniums’ tall stems can snap easily. Growing them against a wall, fence, or trellis will give them extra support.
Delphiniums have fairly shallow roots so they needn’t be buried excessively deep, but they do need plenty of lateral space as they hate being overcrowded. They need plenty of air circulation in busy borders to prevent them from falling victim to powdery mildew or other diseases, so allow around two to three feet in every direction. Bury the rootball so that the crown lays flush with the soil and not below it. Burying them too deep will allow excess water to pool around the rootball and damage the root system.
Despite their great stature, delphiniums perform very well in pots, thanks to their modest root systems. Choose a wide, deep pot that is stable enough to support the mature height of a delphinium. Make sure there are plenty of drainage holes so water can flow through freely. Terracotta pots are ideal for delphinium because they are porous, permitting plenty of airflow to the roots.
Your Delphiniums will perform best in fertile soil, so wherever you choose to plant them, work a generous amount of humus-rich compost or other organic materials through the soil. This will also help to loosen heavy soils and improve drainage, protecting your delphinium’s shallow roots from rot. For added slow-release nutrients, you can spread a good layer of mulch across the border in early spring too. Delphiniums need a slightly alkaline pH level, so adding things like lime, eggshells, and bonemeal to the soil regularly will help to raise the pH level and keep yours happy.
To achieve the show-stopping blooms that Delphiniums are renowned for, you should plant them somewhere that gets at least six hours of full sun each day. They will cope in a dappled shade position but will flower much less abundantly.
Delphiniums like to be watered regularly, but not oversaturated. Always wait for the top couple of inches of soil to dry out between waterings. Aim to give established delphiniums around an inch of water per week. Make sure you water young delphiniums deeply to encourage strong root growth. Always water your delphiniums at ground level rather than above, since they are particularly prone to Fungal problems if the foliage gets wet.
Temperature and Humidity
Extreme heat is something that delphiniums won’t tolerate, so the cooler summers of northern climates are ideal for them. They also hate humidity, so don’t do well in very rainy climates, or if grown near to ponds or in wet areas of the garden. Delphiniums grown in hot and humid climates tend to have a shorter lifespan than those grown in cool, dry climates.
Delphiniums have a big appetite that befits their huge stature, so regular feeds are a must. Apply some all-purpose food just after planting, and continue with regular feeds all throughout the flowering season to promote strong, sturdy stems and bountiful blooms. Stunted growth, yellowing foliage and sparse flowers can all indicate that your delphinium is lacking in nutrients and needs a little boost.
As with most flowering perennials, regular deadheading and removing spent flower spikes is the best way to extend the blooming season and rejuvenate your delphiniums throughout the summer. Snip off any fading flowers periodically, and remove the whole stem once all of its flowers have faded and no new buds are waiting to open.
The stall stems of Delphiniums are hollow inside, meaning they often struggle to support the sheer weight of their heavily laden blooms. To prevent them from flopping over, you will need to stake your delphiniums in late spring as they begin to form buds. A garden cane attached to the stems with some twine will do the job.
Although hardy in most climates, your delphiniums will appreciate a little extra protection in winter. After they have completely finished flowering in late summer, you can snip their stems right back, leaving just six or so inches protruding from the ground. Be careful not to remove any new foliage emerging at ground level, as your delphiniums will use this new growth for photosynthesis, collecting and storing energy to see them through the winter. They may even produce a few small flowers on the remaining stems throughout autumn.
A thin layer of dry mulch made from straw or wood chips can be spread across the border to protect your delphiniums from extreme winter frosts in very cold climates, but only do this in moderation. Heavy mulch will trap too much moisture in the soil and cause the roots to rot. Potted delphiniums should be moved to a sheltered position in the garden to protect them over winter.
What does Delphinium Smell Like?
Most delphiniums have almost no fragrance at all. Those that do have some scent are described as having a weak, lightly musky aroma.
Are Delphiniums Toxic?
Delphiniums are highly toxic to both humans and animals. All parts of the Delphinium plant, and even the seeds, contain high amounts of diterpene alkaloids which can cause breathing difficulties, paralysis, and even death if ingested. Grow your delphiniums safely out of reach of inquisitive hands or paws!
Whilst they may not be for the faint of heart, it’s well worth having a go at growing your own delphiniums. Despite their somewhat dramatic temperament, few plants can compare with their equally dramatic floral displays and colossal heights. High-maintenance they may be, but they’re certainly worth the hassle!