How to Grow Delphiniums

Love delphinium flowers with those tall stems and blue blooms? These delphinium care tips show how to grow and maintain these beautiful plants in your garden including tricks for growing them from seeds.

I also have tips for growing hollyhocks, peonies, lilacs, and lavender.

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Falling in Love with Delphiniums

I officially became a gardener the day I visited a local garden and saw a raised bed filled with tall, blue, gorgeous delphiniums. I just knew I wanted them in my yard (not yet a ‘garden’) and I would do whatever it took (organically speaking) to have them. They come in several colours—blues, purples, reds / pinks, yellow, white—but it was the blues that had me at hello.

Since then, my repertoire has expanded to include dozens of different flowering perennials suitable for a cottage-style garden.

Creating a Cottage Garden

This is part of a new series featuring the key plants in my garden that give it the casual, overflowing cottage style.

I provide growing tips, plant facts, and answer some frequently asked questions helpful for growing these beauties.

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How to Grow Delphiniums in Containers

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Know Your Plants

For delphiniums, they have a mountain history: originating in foothills in North America, and higher mountain regions in tropical Africa.

This is why they do best in climates with four seasons: the winter chilling period is essential to trigger new growth in the spring.

Here in southern Canada, they are a perfect fit. If you are in the southern United States it will be a struggle to keep them happy but any cold climate could work.

Related: 20 Perennials for Long-Lasting Blooms

Delphinium Plant Facts & Growing Tips

Family	Ranunculaceae
Genus	Delphinium (from the Latin word for ‘dolphin’)
Species	Approximately 300
Cultivars	Elatum hybrids, belladonnas, grandiflorums
Common name(s)	Larkspur The different genus Consolida (an annual) is also commonly called ‘larkspur’. Make sure you’re buying delphiniums!
Origin	Native to northern hemisphere and mountains in tropical Africa
Type	Perennial
Height	4-60″ tall | 10 cm to 2m tall
Spacing	18-24″ | 45-60 cm
Light	Sun or part sun
USDA Zones	3a to 8b (they may wilt in heat)
Flower times	Late spring, summer | deadhead for second blooms
Colours	Purple, blue, red, yellow, white
Soil	Moist, well-drained loamy soil is best; clay and sand should be amended
Fertilizer	16-16-16 kelp and seaweed extract (I do not use any in my garden but I see this recommended) This is the only example I could find on Amazon.
Pollination	Butterflies and bumble bees
Propagation	Seeds – like to be chilled in-ground before germinating Root division (cutting root ball) Herbaceous stem cuttings (in spring before flowering)
Toxicity	All parts are toxic to humans if ingested; skin irritant; poisonous to cattle
Trivia	The juice of Delphinium consolida can be mixed with alum to produce blue ink.

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Also:

• Plant Parenting by Leslie Halleck
• Plant Propagator’s Bible by Miranda Smith

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Frequently Asked Questions About Delphiniums

1How do I know if I can grow delphiniums where I live?

The best hint is to check if other (successful) gardeners are already growing them in your area without babying the plants. If they grow easily without special accommodations, that’s a good sign.

Before proceeding, check your growing zone. Delphiniums originate as mountainous plants and do best in a climate that provides a cold (near or below freezing) winter. This helps trigger seed germination and flowering in spring.

To find your growing zone, use the following sites:

• United States – USDA Plant Hardiness Zone Map
• Canada – Provincial Plant Hardiness Zone Maps

Generally speaking, delphiniums grow in zones 3a to 8b. However, each hybrid and cultivar is unique and may only be suitable for a narrower range of zones. I get emails from gardeners in the southern-ish United States who struggle to keep delphiniums happy when heat is constant even though they are in zone 8 or cooler. Also, always check plant tags before purchasing plants for recommended growing conditions.

A good, local garden nursery is a great resource for plant information. If they are growing and propagating the plants in your zone, be sure to ask for their best tips and plant recommendations.

2Do delphiniums require any special care?

The beauty of delphiniums is their tall stature and mass of blooms. I have the best luck when I grow delphiniums in a sheltered location (here in Ontario, Canada, zone 6b) where they are protected from strong winds. A strong wind won’t kill the plant but it can snap the flowers off, which defeats the purpose of growing them (unless you want accidentally-cut flowers).

Leggy delphiniums benefit from supports. I place bamboo posts a few inches from the plant base and attach twine, loosely around the plant in a few places. This way, if the wind pushes or pulls the plant, the twine prevents it from falling right over. Because the twine is loose, it does not damage the stems.

When selecting plants, look for nice, thick stems. There are many beautiful delphinium cultivars, but some of them have massive flowers on rather thin stalks and these can easily fold or collapse, killing off the flowers. Tragic, really.

3Should I fertilize my delphiniums?

Many advise to use a 16-16-16 kelp and seaweed extract fertilizer because delphiniums are heavy feeders. It is recommended to wait until the plant has established good roots before fertilizing.

That said, I do not use any commercial fertilizers in my garden. You may consider this over-the-top organic growing but here’s my thinking. I grow all sorts of food crops (veggies, fruits, nuts) as well as ornamental plants in containers and the ground. I want to be able to freely use my soil and container mixes without ever having to worry that there is something in there that is not safe for food crops (because it could be absorbed by the plant), or because it is considered hazardous in the soil (potentially harmful to microbes, insects, or other life in the garden). Going fertilizer-free (and pesticide/herbicide-free) removes much of this worry.

So, how do my delphiniums grow so nicely? I choose good plants, with strong, thick stalks. My sandy soil is constantly amended with compost from my food scraps and covered in organic mulch (usually wood chips). I also plant everything closely together to prevent weed growth and shade the roots, which keeps more moisture in.

4Can I grow delphiniums in containers?

Yes. You will need proper container mix made for flowering perennials. You may need to use fertilizer or replace most of the container mix each year to ensure the plant has the nutrients it needs to grow and bloom. And, you will need to ‘over-winter’ the container. This means moving it to a protected location during the winter. This post on over-wintering fig trees outlines the steps.

5What is the best way to start new delphinium plants?

If you want to propagate new plants from existing ones, the fastest way is to divide a large (mature) plant by digging it up and splitting/cutting the root ball in two (or more pieces).

Another method is to take ‘basal’ root cuttings in spring. This involves partially digging up the plant and taking a section of the roots for propagating in a container. There’s a specific window of time for this which I famously forget about each spring.

For germination by seed, in autumn, toss some seeds in your garden bed, cover them lightly with soil, mark the spot, and leave them to germinate in spring.

This article shares more info on propagating delphiniums. If you plan to grow from seeds indoor, see this tip for getting delphinium seeds to sprout faster.

6How can I get a full-season of blooms from delphiniums?

The trick is to cut them back after first flowering. When the late spring flowers have started to fade, trim most of the flower stalks down to the ground, leaving the surrounding growth. You should get a second set of flowers before fall frosts set in. You can read more about this method here.

7My garden is windy. Is there a way to grow delphiniums without the wind breaking them?

Yes. There are some dwarf varieties with nice thick stems and dense flower heads. Look for the Delphinium Blue Fountains Group. They are one of my top favorites with their gorgeous blue colors.

~Melissa the Empress of Dirt ♛