How to Plant, Grow and Care For Delphinium Flowers

Delphiniums in bloom are the quintessential sign of summer. These cottage flowers have adorned paintings, bouquets, and garden beds for centuries. Their tall perennial flowers in soft colors of stunning blue, cheery pink, or delicate white are unmistakable.

The tall perennial spires of gorgeous color add height to any garden, creating a backdrop when planted in the back. There are dwarf varieties that can be grown in pots or containers to plant in the front where they can be appreciated from a closer distance. Thankfully, there are several varieties you can choose from for either application.

Though there are a few common mistakes gardeners make with delphiniums, they are fairly easy to care for. If you are considering adding these pretty plants to your garden, continue reading and find out how to plant, grow, and care for delphiniums so you can enjoy these glorious garden flowers for years.

Plant History

Delphinium were actually named by ancient Greeks. The name comes from the root Delphi which means “dolphin.” It was thought that the flower bud before it opens resembles the long nose of a dolphin. After a quick Google image search, I can confirm this (it was past delphinium blooming season when I wrote this article).

Delphinium is part of the Ranunculaceae, or buttercup, family. There are more than 2000 species of plants that are included in the ranunculaceae family. Other familiar perennials in the buttercup family include columbine, hellebore, clematis, and anemone.

Cultivation

There are more than 300 species of delphiniums in existence. The most common species of garden perennials are elatum, grandiflorum, and belladonna. It is important to decide which species of delphinium will suit your needs in the garden.

Delphinium elatum is what I think comes to mind for most of us when we think of delphiniums. They are varieties with tall spikes of flowers that reach up to 6 feet in height.

Delphinium grandiflorum is a delphinium species that is native to China and Russia. If your preconceived notion of delphinium is the long spikes of flowers, you may not immediately classify this species as delphinium. Until you look closer at their distinctive delphinium-shaped flowers. These varieties are much shorter than elatum. They feature fine, almost ferny foliage, and small clusters of delphinium flowers.

Delphinium belladonna is a hybrid of grandiflorum and elatum delphinium (and sometimes other species). They have tall spikes of flowers that delphinium elatum features. But the flowers are looser in the stalk and have more branching stems, like grandiflora delphiniums. Belladonna delphiniums are said to be more heat tolerant than other species.

There are many other species of delphiniums, but these are the three main ones that make up most delphiniums planted by gardeners.

Propagation

There are many ways to obtain a delphinium plant for your garden. They can be purchased at nurseries, planted by seed, divided, or have cuttings taken. Let’s look further into each of these methods.

Purchase

The easiest way to obtain a delphinium plant is to go to your local garden center or nursery and purchase one. I recommend a specialized local nursery that shows the exact variety so you know exactly what you are going to get.

Some of the larger chain stores may only have ‘delphinium sp‘ on the tag so you do not know the variety. Since there are so many height and color variations in delphiniums, it is nice to know the exact variety you are getting so you will plant it in the right spot.

You can purchase delphiniums at any time during the growing season. You can plant them at any time up to two weeks before the ground in your area freezes. This gives the plant time to establish roots before winter sleep.

Seeds

Delphiniums are actually quite easy to start from seed. This is a great way to save money. Some varieties will even bloom the first year they are grown from seed.

You can purchase seeds from the garden center or online. Make sure if you are purchasing them online you buy them from a reputable seed company. There are many fake seeds floating around the internet. 

You can also harvest the seeds from a delphinium plant. You will have to be aware of the variety. Some delphinium varieties are sterile, and some will not come true from seed. This means you will not get the big fancy delphinium that is growing. You will end up with just a plain purple variety.

Start your delphinium seeds about eight weeks before the last frost date in your area. You can do a quick online search to find the approximate date in your specific area.

Steps to Propagate Delphinium by Seeds

Once you have the seed, a great way to achieve higher germination rates is a process called cold stratification. The best way to do this is to simply pop the seeds into the refrigerator for a week or two prior to planting them.

Next, take your seeds and a seed tray. You can purchase a seed tray, or you can use what you have on hand. Berry containers work great. Whatever you decide to use, make sure you poke drainage holes in the bottom that are large enough for excess water to drain out.

Fill the seed tray with a seed starting mix. You can use potting soil, but for delphiniums, I do recommend a sterile seed starting mix since they are prone to damping off which is caused by a fungus in the soil.

Evenly water the seed starting mix. It shouldn’t be soggy or dripping wet. Now place the delphinium seeds onto the dampened soil. Cover the seeds with about ⅛” of the soil. Now place a dome cover over the seeds. Place the containers in a room-temperature area. Check on them regularly. Spray with water if they are drying out.

In about 14-28 the seedlings will emerge. Once they start to emerge, remove the cover and place them in a sunny window or under a grow light. Keep them watered. If they are too spindly and reaching for the light, it is a sign they need more light. Lower the height of the grow lights or find a sunnier window.

Hardening Off

Once the danger of frost has passed in your area it is time to harden off your new seedlings. Don’t skip this step. New seedlings that have been grown indoors have never experienced weather. If you plant them straight into your garden beds they will die.

Start by placing the new plants outside in a shady area. Leave them for a couple of hours then bring them in. Slowly leave them out longer, and then start adding time in the sun.

Start with a couple of hours in the sun and gradually work their way up. After about a week they will be hardy and ready to be planted in your garden.

Cuttings

You can take cuttings from a delphinium plant in order to start a new one growing. This is done in early spring just as the delphinium is starting to grow.

When you look at a newly growing delphinium plant you will notice the main clump of plant, but if you look closer you will see some smaller offshoots.

These make great cuttings. Take a clean sharp knife or pair of clippers. You will want to take the cutting from below the soil line. You will see the stem below the soil line is white.

Now take that cutting and trim off most of the leaves. We want the energy to go into root production at this time, it will grow new leaves. Now plant the cutting into some evenly moist potting soil. Keep the cutting in a shady spot and keep it watered until it starts growing roots and is ready to be planted.

Division

Dividing delphiniums is best done in the early spring. Start by digging up your delphinium. Do not dig it right at the base of the plant, dig it wider than the plant so as to not disturb its roots too much. Now you can split off chunks of the delphinium. I generally use the rule of thirds in gardening. You can take ⅔ of the plant and leave ⅓ of the original.

Replant the new delphinium as soon as possible. If you are moving it into a new location in your garden, pre dig the holes before dividing the plant.

Or if you are sharing it with a friend or neighbor, put it in a container with soil and compost until it can be transplanted. Add compost back into the hole with the delphinium. Water all parts of the plant really well.

This can also be done in the fall. Do not disturb delphiniums when they are in bloom or about to bloom. It is also better to divide plants on a cool and cloudy day.

Planting

Choose a good spot to plant your delphinium (read ahead to the how-to-grow section to find that ideal location). Dig a hole double the height and width of the container you are planting.

Fill the bottom of the hole with compost, aged manure, worm castings, or sea soil. Then place the delphinium in the center of the hole. Line up the crown of the plant with the soil line and fill it in with a mixture of compost and the existing soil. Water it well and keep it watered until it starts establishing roots.

How to Grow

Delphiniums are a fairly easy garden perennial to grow. If they are planted in their correct conditions they will bloom beautifully and create quite a show in your garden. Here are what your delphiniums need to make them grow optimally in your garden.

Light

Delphiniums are full-sun perennial flowers. This means 6-8 hours of direct sunlight. A bit of dappled shade for the strong heat of the afternoon will help them from shriveling too quickly. Especially if you are in a warmer zone. Delphiniums do not like too much heat, they are cool-season flowers.

If your delphiniums are not getting enough sun you will know right away. The blooms and stems will be spindly and leggy. There will be few blooms, and they will have a hard time standing upright.

There will also be an increased chance of diseases like powdery mildew and crown rot. slugs and snails will also feast on the weakened plants.

It is important to remember that a garden is a living being. So planting your delphinium in a sunny spot does not necessarily guarantee it will always be sunny. In 10 years things grow and evolve.

So a once sunny patch of the garden may now be shaded by a large tree that grew up. If your delphiniums are failing, really consider how much sunlight they are actually getting. You may have to move your delphiniums to a new sunny spot in the garden.

Soil

Delphiniums require excellent well-draining soil that is rich in organic matter. Delphinium will struggle in soils that are lacking nutrients and/or soils that are heavy and full of clay.

To achieve this blend you will need to first assess your soil. I know the type of soil in my area. Where I am from our soil is heavy clay soil. You may already have an idea of what kind of soil you are working with in your area. I am constantly amending soil with coconut coir or peat to make the soil looser.

You can do a quick test on your soil. Simply grab a handful of your garden soil and squeeze it. If the handful of soil squeezes into a tight ball and when you release it, it stays the shape of that ball, you have clay soil. The soil should crumble back to no shape after you release it.

If it does stay a ball, this is where you’ll need to amend with lots of grit. Coconut coir or peat works great. I know it seems adding sand would work, but if you have clay soil and add sand you will end up with concrete.

Now add compost, aged manure, worm castings, or sea soil. This will also help loosen the soil and will add all the nutrients to the soil that your delphinium will need to grow over the season. You can also mulch your delphiniums to help retain moisture and keep the soil loose.

Water

Delphiniums do require frequent and consistent water. But they do not tolerate being left in standing water or soggy soil. This is why it is important to get the soil type right first. If the soil is light it will be able to drain excess water away while absorbing enough water for the delphiniums to thrive.

Make sure to water during dry periods. Delphinium will shrivel and turn brown if they are not getting enough water. Delphiniums that are overwatered will have soft yellowing leaves. They are also more prone to crown and root rot and powdery mildew.

Watering at the base of the plant if possible is best. I use a drip hose snaked through my garden rather than an overhead sprinkler. Overhead watering that leaves foliage wet will make your delphiniums more prone to powdery mildew, and crown rot.

Climate and Temperature

Delphiniums are cool-season flowers. They can be grown in zones 3-7. There are varieties that can be grown up to Zone 8. Belladonna species of delphinium are more heat tolerant than other species

If you live in a zone higher than 8, consider annual larkspur flowers instead (Consolida).

Fertilizer

I don’t tend to fertilize my perennials. Instead, I will top-dress my garden with compost. Ideally, I like to add compost in the late fall, after I’ve cut everything down.

I compost right over the leaves and then the snow will fall on it and melt. This way all the compost nutrients can seep into the soil in the spring. But if you didn’t get around to it in the fall, composting in the early spring works fine too.

In the spring I will sometimes water my perennial bed with compost tea or a sea-derived fertilizer. These are natural products filled with nutrients that will boost your garden.

Maintenance

Delphiniums require some maintenance to keep them looking great. First, choose a location that offers them some protection from wind and storms if possible. Perhaps along a fence line, or in a garden that has some trees for wind protection.

The first thing to do with delphiniums in early spring is to cage them. You can get hoops, like peony cages, that are tall and the delphiniums can grow into them. You can also stake them later in the season, but I find this tedious and it can be difficult. It is better to get them caged early.

Once the flower has bloomed you can cut back the entire plant. You may get a second flush of flowers late in the season.

Varieties

This is the fun part. There are so many varieties of delphiniums to choose from that will suit your needs in the garden. Here are a few of my favorites.

‘Cobalt Dreams’

‘Cobalt Dreams’ is a classic flowering blue perennial. This variety reaches up to 6 feet tall. The semi double flowers are an intense cobalt blue. The center eye, which is called a bee, is fluffy and white. The blue flowers with the white center really stand out, making this variety great for planting in the background of gardens.

‘Delphina Light Blue White Bee’

This is a dwarf variety of delphinium. It features ruffled light lavender flowers and a white bee. It only grows 1 1/2′ tall. This variety can be planted in mixed garden beds and borders. It would also look great grown in a container.

‘Magic Fountain White’

This is a medium-height delphinium. It reaches up to 3 feet tall. What is so different about this variety is the color. It is white, with a black center/bee. This one would look great planted along a garden path to brighten it up in the dark.

‘Summer Nights’

‘Summer Nights’ is a dwarf variety. It only reaches 1′ tall. It doesn’t have the tall spikes of flowers that are often associated with delphinium. Instead, it has clusters of flowers on low ferny foliage. ‘Summer Nights’ is an intense blue color. This variety would look great planted in a cottage or meadow-style garden.

Companion Plants

Delphiniums pair really well with other perennials. They are a great building block to creating a beautiful garden scape. Here are a few perennials that pair wonderfully with delphinium.

Peony

Peonies and delphiniums are a classic combination. Depending on the varieties of both your peony and delphinium, the sun exposure, and your zone, they may bloom at the same time. If not they will bloom in slight succession. Either way, they look great together.

Peonies have lovely foliage that looks great at the base of the delphinium. They may bloom before, in which case you will have gorgeous large peony blossoms in full bloom with lacy delphinium foliage in the background. Then the peonies will fade and the delphiniums will start blooming their darling spikes of delphiniums.

Shasta Daisy

Shasta daisy, not to be confused with its naughty counterpart the weedy oxeye daisy, is a perfect delphinium companion. They bloom at similar times.

The sunny mounds of happy daisies sit beneath the feet of tall varieties of delphinium. Or they can be interspersed with shorter bushier varieties of delphinium. The white and yellow daisies are a perfect neutral accent to show off the intense blue and purple delphinium blooms.

Roses

Delphinium and roses make a perfect cottage garden pair. They bloom at the same time and you can really play with color combinations. Try a dark red rose next to an intense dark indigo-blue delphinium. Or place a fluffy pink rose near a sky-blue delphinium. Or yellow roses with blue delphiniums for a sunny display. The possibilities with these two plants are endless!

Yarrow

Another companion plan for delphinium is yarrow, which is a great cottage garden flower. It can be aggressive and is not for everyone. But in a wildflower, or meadow-style garden, it creates an explosion of blooms. The fine ferny texture of yarrow with their rounded flower heads in vibrant reds and pinks is the perfect contrast to the tall spikes of delphiniums.

Foxglove

Foxgloves and delphiniums are great together because they are similar.  They both create tall spires of flowers. But the shape of those flowers is different and adds an extra layer to the garden. The star-shaped delphinium flowers next to the bell-shaped flowers of foxglove flowers contrast beautifully.

Pests and Diseases

As with most flowers, delphiniums come with a few insects that can cause damage to the plant. There are also a few diseases you need to watch out for. However, there is very little chance of these if you properly care for your plants, especially when it comes to watering techniques.

Aphids

Aphids are a common pest to have on garden plants. If there are aphids present it is usually a sign the plant is not in good health to begin with. Aphids prey on the weak. So after you deal with the infestation take a look at the affected delphinium’s growing conditions and see if there is an area they are lacking in (light, water, soil).

To deal with aphids, never underestimate the power of a good blast with the hose. Spray the aphids off, or get in there and squish them.

They are small greenish transparent bugs. You will find them along the stems and undersides of the leaves. They will suck nutrients from the delphinium and can delay or destroy the blooms.

If a good spray with the hose isn’t enough, or if you are concerned about snapping or bending the stalks (if they are about to bloom, or in bloom) with the hose. Use insecticidal soap weekly, or as directed on the label. This should clear up the problem. Next, work on correcting the growing conditions so they stay away.

Slugs and Snails

Leaves with holes eaten through them might be a slug or snail problem. I find this particular problem near the base of the plant where it can be damp.

There are many methods of dealing with snails. Eggshell or diatomaceous earth (available at garden centers) barriers around the base of the delphiniums will deter them. This will need to be reapplied after heavy rains.

Bowls of beer work as well. The slugs will go to the bowls and you can dispose of them. You will have to check often. I use slug bait pellets from the garden center. I toss some in the garden beds and they seem to disappear.

Powdery Mildew

Powdery mildew is a fungus that can affect a variety of plants, delphinium included. Powdery mildew appears as a silt-like white powder on the leaves of delphiniums. You can wipe the powder off with your fingers. This mildew will stunt and possibly prevent your delphiniums from blooming to their fullest.

Prevention is the best way to avoid powdery mildew. Avoid watering the foliage of your delphinium. I use a drip hose snaked through the garden and water the soil directly. If you are watering overhead, water in the morning.

If you water in the evening the plants will sit with water on their leaves all night before the sun comes up to dry them. This leaves them prone to developing mildew.

Another thing to consider for prevention is spacing. Have your delphiniums spaced out enough to allow adequate airflow through their stems. If the bottoms of the plants are yellow and wet it is a breeding ground for all sorts of fungus, including powdery mildew.

If you already have powdery mildew, spray the leaves with a fungicide that is formulated for powdery mildew (it will specify on the label). In the fall make sure to dispose of all the affected leaf litter so it doesn’t reinfect your plants the following year.

Crown Rot

Crown rot is caused by bacteria in the soil. The crown of the plant is where the soil meets the stem. When delphiniums are affected by the bacteria the lower leaves will turn yellow and then the crown of the plant will turn to mush and die.

There is not much treatment for crown rot. It can be prevented by not planting in wet areas of the garden. Also, avoid overhead watering that wets the entire foliage of the plant. Also, Spacing plants to allow adequate airflow will help.

Cut down and dispose of all infected plants. Do not replant delphiniums in the same spot or they will also become infected.

Frequently Asked Questions