How to prepare delphinium plants for winter

It’s like a miracle that my first delphinium survived its first winter in Alaska.

I bought them at Home Depot, planted them, and then sat back and happily watched the spikes pop up in beautiful shades of purple and blue against my red house.

When September arrived, the delphiniums died back, bringing with it increasingly chilly nights.

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And then… I just left them there. Tall, rough and brown, without any mulch to speak of.

Unless you count snow.

Yet they returned the following spring. I had to cut off the dead stalks to allow the new green growth to grow unabated.

The next winter, I made sure to cut back the stalks before the snow fell. I also made a few more preparations to make sure my beautiful plants could easily put out new shoots next spring.

If you’re wondering how to prepare your delphiniums for winter, this guide will tell you everything you need to know.

Here’s what I’ll cover:

Delphinium vs. Larkspur

Before preparing your plants for winter, it’s a good idea to make sure you know what’s in your garden.

Delphiniums are often confused with their close relatives, the larkspurs. And for good reason: The two look almost identical.

But true larkspur is an annual that isn’t going to survive the winter no matter what you do, while delphiniums are short-lived perennials that can become overheated.

However, Larkspur is easy to grow, so don’t lose hope if you are growing Larkspur!

Some of the most common perennial delphinium species include Delphinium elatum, D. grandiflorum and D. chelianthum.

In addition to the difference between annual and perennial status, larkspurs (Consolida spp.) tend to have more delicate flowers with more spaced separate blooms.

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Delphinium blooms, on the other hand, are often more densely clustered.

Yet perennial delphiniums are sometimes referred to with the common name “larkspur,” so I don’t blame you if you’re confused.

When and how to cut dry stalks

To keep your garden looking neat during the growing season, feel free to deadhead. Cut flower stalks down to where the leaves begin when all flowers have faded.

This will encourage the development of side shoots, possibly giving you a second round of color before fall.

Make sure you don’t cut off the leaf petioles until all the leaves are starting to turn yellow and brown.

When those leaves are nice and dead, you can cut the stalks back to about an inch or two above soil level.

The area around the stalk is bark mulch, but I’ll add straw in a couple of weeks. Photo by Laura Melchor.

As shown in the photo above, you may still see the smaller side shoots recover until the first frost, and that’s okay. They will soon die back.

When spring comes, new shoots will sprout from the top of the old stems to add color to your flower beds.

clean debris

Winter cleaning is just as important as spring cleaning—especially when it comes to gardening.

In the area where your delphiniums are growing, remove any debris left behind by your dazzling columns of blue and purple beauties.

Remove the remaining weeds as well.

Cleaning up my flower garden before I tuck my delphiniums into their winter dormancy is extra important this year because my garden suffered a massive aphid infestation.

Whenever I cut aphid-infested stalks this summer, I took them to a fire pit to burn.

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Many species of aphid eggs, unfortunately, are quite cold hardy. You can’t even count on a bitterly cold zone 3 winter to kill them off and prevent them from returning next spring.

By cleaning your garden, you make it harder for aphids, along with other pests and diseases, to come back in full force when the weather warms up again.

water your plants

Just because the plant stops blooming and starts to die back doesn’t mean you should stop watering it. The roots are, after all, very much alive and will need moisture until the ground freezes.

If it rains about once or twice a week, don’t worry about adding water. But if you’re stuck in a drought situation, be sure to give your plants about an inch of water every week.

Stop watering them once the air temperature starts to drop further below 40 degrees.

During warm periods between colds, if you don’t have melting snow or rain, go ahead and give the plants some water.

Keeping plants hydrated in the fall and during any period when air temperatures are above freezing will help ensure a spectacular return of their beauty.

add mulch for winter warmth

The next thing you want to do is mulch the stalk and root zone to help the plant stay warm and hydrated during the winter.

While delphiniums are cold hardy to USDA zone 3, where temperatures can drop down to -30°F, they need a little help to make sure they survive cold and frosty winters.

In mid to late fall, pick up some organic mulch from your local gardening store. I love buying straw bales from my local animal supply store, and this is another excellent option.

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Sometimes I also use a mixture of straw and hay, and until recently, I admit I didn’t quite understand the difference between the two.

Here’s a quick analysis:

Straw is the dried stem of cereal crops. It is what is left after harvesting the grains that grow on it. These are literally just hollow stalks. Hay is an uncut, dried grain and hay, which means that hay has a lot of seeds that can find their way into your garden soil and grow into weeds if they are viable.

You can also use wood chips, shredded leaves, and even evergreen branches such as those left over after you removed your Christmas tree – make sure you remove these in the spring as they can affect the pH of the soil. Can change as they break down.

Mulch provides protection from severe cold, especially if a layer of snow falls on top of it. Mulch helps the soil move and warm up under changing temperatures and unpredictable spells of rain and snow.

You can learn more about winter mulching in this guide.

safely tucked away for the winter

With your delphiniums ready for colder times, you will be able to relax and enjoy the hibernation period in comfort.

When spring arrives again, you and your delphiniums can be re-energized and ready for a wonderful spring and summer.

Have you ever overwintered these lovely flowers? If you have any additional tips or questions, drop me a line in the comments below.

And further check out these articles on growing delphiniums in your garden:

Photo Laura Melkor © Ask the Experts, LLC. All rights reserved. See our TOS for more details. Uncredited photos: Shutterstock.