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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Growing 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.

Delphiniums originate in mountainous 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.

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Contents

• Delphinium Plant Facts & Growing Tips
• Frequently-Asked Questions
  • How do I know if I can grow delphiniums where I live?
  • Do delphiniums require any special care?
  • Should I fertilize my delphiniums?
  • Can I grow delphiniums in containers?
  • What is the best way to start new delphinium plants?
  • How can I get a full-season of blooms from delphiniums?
  • My garden is windy. Is there a way to grow delphiniums without the wind breaking them?

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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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Related: 10 Flower Growing Secrets & Common Mistakes

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. This could be bamboo stakes with twine loosely secured around the plants, or peony cages placed on tall supports.

Also, 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?

We’ve been told for years to routinely add fertilizers as if it’s a given that plants need them and without any consideration for how excess fertilizer harms the earth.

I always recommending getting your soil tested to have a basic understanding of what it offers and what may be deficient.

Your garden will not be the same as mine. In my case, I just top dress my garden beds with homemade compost and topped with fine wood mulch, and that is all I do in terms of supplemental nutrition.

Assuming your soil actual needs it, 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.

I never use commercial pesticides or fertilizers because I want to keep things eco-friendly and know I can grow food anywhere in my yard without worrying about any product side effects.

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 to ensure the soil and plant do not freeze. This means moving it to a protected location during the winter. This post on over-wintering fig trees outlines the steps.

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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 outdoors as nature does it, 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?

Delphiniums are known to produce second blooms. The theory is that if you cut back first blooms as soon as they have finished, the plant can direct all of its energy into new growth.

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 two approaches. First, choose delphiniums that have traits that withstand wind. 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.

For the long-term, see if you can add wind breaks like evergreen trees or shrubs or a structure like a shed that physically block the prevailing winds from your delphiniums.

~Melissa the Empress of Dirt ♛