Tropical Flowers

How To Plant and Grow Annual Delphinium

Delphiniums’ spectacular spikes of colorful blooms provide summer gardens with an unmatched height and beauty. Although different colors are available, blue and purple tones are the most popular. In bloom, they produce florets that can be single, semi-double, or double.

Delphiniums need a lot of care and the appropriate environment to grow. They favor summers that are pleasant, chilly, and low in humidity. Place them in a location with sufficient soil drainage and moisture. Thankfully, less picky hybrid strains are currently being produced.

Annual Delphinium: Overview

The Ranunculaceae family contains the genus Delphinium. Delphiniums come in a wide range of heights from miniature hybrids to 6-foot-tall beauties—so they can be planted in the front, center, or back of a perennial border. There are more than 300 delphinium species. Although the blue delphinium is the most popular, it also has stunning violet, pink, white, red, and purple hues. They are well-liked in both cutting gardens and cottage gardening.

Most delphiniums are annuals that only live for two or three years in the garden. Certain types will bloom all summer if the plants are routinely pruned back. Other hybrids bloom in the early to mid-summer and, if the old flower stem is removed, will produce a second flower display in the late summer or early fall.

See Also:

Understanding that delphiniums will thrive if you match their unique requirements is crucial. Summers that are cool and damp are preferred by delphinium; hot, dry weather and unexpected wind or rain, which can knock them down, are not good for them.

How to Grow Annual Delphinium

The drama of delphinium blossoms is unmatched. They generate over two-meter-tall flower spikes in the months of June and July. Although they also come in mauve, pink, white, and even red, their beautiful sapphire blue blossoms probably set them apart from other species. Depending on the type, delphinium blossoms can be single or double.

Bringing height and color to displays, delphiniums are a mainstay of cottage gardens and herbaceous borders. They pair well with roses, peonies, and other vertical flowers like lupins and verbascum. Bees adore the blossoms, which also look gorgeous in a vase.

Since ancient times, delphiniums, which belong to the Ranunculaceae family of plants, have been cultivated in the UK. Due to the opening flower’s shape and the Greek word delphinos, which means dolphin, the delphinium got its name. Larkspur, their common name, is a holdover from the Tudor era. Although there are also annual and biennial kinds of delphiniums, perennials are the most common. The most widely cultivated and tallest variety of delphiniums, with spikes of single or double flowers rising to a height of 2 meters, belongs to the Elatum Group. Belladonna delphiniums have solitary flowers, a looser growth habit, and are shorter.

Grow delphiniums in full sun, in wet but well-drained soil. If your soil is heavy and you want to grow delphiniums, improve drainage by adding grit to the planting hole. Stake newly growing shoots as soon as they emerge in the spring to keep slugs away. Use a high potash fertilizer to feed once every week. Cut stems back after flowering to promote a second flush of blossoms. Use well-rotted manure or leaf mold as a fall mulch.

How to Care for Annual Delphiniums

Because annual delphiniums are hungry plants, they require regular feeding. Once the first shoots show, fertilize with a liquid fertilizer every two weeks to promote vigorous growth.

The optimum time to stake taller kinds is in the spring, with canes or a frame that allows plants to climb through. Make sure plants don’t dry out in hot weather because delphiniums do best in cooler climates and with slightly wet soil in the summer.

Cutting back delphinium flower spikes as soon as they have faded might enable plants to produce a few flowers in late August or September despite their very brief flowering season.

Reducing a delphinium:

Cut all flower stems to the ground as soon as the flower spikes begin to appear scruffy, leaving any side shoots that are forming and the remaining foliage at the base.

Well-water the plant.

Cut the plant back to the ground in the fall once it has stopped flowering. Plants can be divided annually in the spring to maintain healthy flowering.


When fresh plants are 3 inches tall, they should be divided into 2 to 3 healthy shoots for the most extraordinary flowering. The best shoots from established plants can be reduced to 5 to 7. After flowering, trim the main stalk down to the level of the smaller side branches, which will later blossom with somewhat smaller flowers. Just after flowering, trim the stalks to the ground to promote a second, lesser bloom in late summer or early autumn. After it wilts in the fall, cut the entire plant down to the ground.


A must-have is humus-rich, well-drained soil that is ideally slightly alkaline. Although mulch helps keep the soil moist, it can induce stem rot if it is placed too closely to them. The success or failure of fussy delphiniums is greatly influenced by the quality of the soil.

Amendments & fertilizer

Every two or three weeks, use a balanced, slow-release liquid fertilizer. Avoid fertilizers with a lot of nitrogen. Composted manure spread in the fall aids in the supplemental feeding these heavy feeders.

How to Propagate Annual Delphiniums

Delphiniums can be grown from seeds. There are many choices, or you may try saving your own from February to June, or in September or October, plant delphinium seeds. Keep seeds at a temperature of around 50° to 60°F and sow them in miniature pots or seed trays.

Taking cuttings from the plant’s base (basal cuttings) in the spring is the best way to multiply delphiniums. To take delphinium basal cuttings:

Take a sharp knife and cut a shoot just below the soil’s surface in the spring as the new shoots emerge. Take a shoot or two from each plant.

Put the cutting right away into a plastic bag to prevent moisture from escaping.

Remove some of the cutting’s top foliage, but leave a few for the roots to eat.

Each clipping is potted up in a little container with perlite and multipurpose compost.

Water the leaves and cover with a polythene bag to retain the moisture, or mist them frequently to prevent drying out

Maintain inside a greenhouse or on a sunny windowsill.

Growing Annual Delphiniums: Problem-Solving

Protect young delphiniums from slugs and snails as soon as the new shoots sprout in the spring since they will eat their fresh, green growth. Use a biological control, organic slug pellets, or a garlic drench (which is only effective against slugs).

Keep the soil surrounding delphiniums moist because it can be sensitive to powdery mildew in dry weather.

Rust, which results in pustules on the rust-colored foliage, can also harm them. As you see any damaged leaves, remove them and clean up any fallen leaves in the fall.

Remove rust

A bacterial illness is known as delphinium black blotch results in noticeable black spots on leaves. It can harm the plant’s overall health and is more prevalent in humid summers. The only cure to stop the disease from spreading is to eliminate the infected plants.

Advice on buying delphiniums

Keep in mind that delphiniums can grow to be enormous, tall plants; therefore, determine the variety’s potential size.

The greatest place for delphiniums to thrive is in the sun, so make sure your garden is set up in the appropriate way.

Annual Delphiniums are available from specialized merchants at nurseries, garden centers, and online. To purchase delphiniums cheaply, keep an eye out for little plug plants in the spring.

Look for wholesome, emerald-green foliage that is free of insects or disease

Types of Annual Delphiniums

The groupings D. elatum, D. belladonna, D. grandiflorum, and hybrid contain the most widely grown delphiniums.

  • Elatum Group: From early to midsummer, this clump-forming perennial produces a profusion of solitary, semi-double, or double flowers. Stalls typically 5 to 6 feet tall are covered in flowers that measure up to 2-1/2 inches across. Because they require substantial attention, growing this type is not a good idea for novice gardeners.
  • Belladonna Group: This erect perennial produces branched flower spikes with single or double flowers that range in size from 1-1/2 to 2-1/2 inches. Belladonnas grow 3 to 4 feet tall and are typically hybrid hybrids of D. elatum and D. cheilanthum.
  • Grandiflorum Group: This variety of delphinium, also known as the Chinese or Siberian delphinium, has a compact, bushy habit and grows 1 to 2 feet tall. Grandiflorums often have a stronger heat tolerance than other delphinium species and bloom mid-summer with blue or white flowers.
  • The well-known cultivars “Black Knight,” “Galahad,” “King Arthur,” “Blue Jay,” and “Blue Bird” are examples of Pacific hybrids, which are referred to as “Pacific Giants” and can grow to heights of 4-6 feet.
  • New Zealand Hybrids: The medium-sized New Zealand hybrids include well-known varieties like “Pagan Purples,” “Dasante Blue,” and the New Millennium series.


The colorful, spiky blooms on a tall, occasionally towering stem of annual delphinium flowers enhance the beauty of the summer garden. There are many different colors of delphiniums. When hearing that delphiniums are challenging to grow, many gardeners hesitate to plant them.

Regular fertilizer is necessary for delphinium maintenance throughout the flowering season and spring when the plant starts to grow. Use a basic granular fertilizer or well-composted organic material, such as rotting cow manure. Leaf yellowing or stunted development are frequent signs that the plant needs additional fertilizer. Another element of delphinium care that the gardener must get correct for the spectacular blooms to occur is sun exposure. The delphinium plants like gentle morning sun because they are picky about large temperature variations. Provide afternoon shade, mainly if the plants are grown in hotter climates.


Are delphiniums poisonous?

Yes, delphiniums are extremely toxic. Ingesting seeds or seedlings can result in vomiting, jerking muscles, paralysis, and even death. This is mostly a problem for grazing animals like sheep, horses, and cattle, but it is also a warning for gardeners with young children.

Where to grow annual delphiniums?

Grow delphiniums in full sun, in wet but well-drained soil for maximum results. Due to their height, delphiniums grow best at the back of a sunny border. Avoid windy areas as the wind may cause the plants to topple.

How to plant annual delphiniums?

The optimum times to plant a delphinium are in the spring or the fall when the soil is warm and moist. To provide nutrients, dig a planting hole and fill it with compost or well-rotted manure. Winter rain makes delphiniums difficult to grow, so add grit to heavy soils to improve drainage. Place your delphinium where it was growing in the pot and gently firm the soil before planting. Finally, water the plants.