When to Plant Crocus Bulbs

There’s nothing like waking up one late-winter day to a field of gorgeous crocus blooms in your own backyard.

But when, exactly, do you have to plant crocus bulbs, technically called corms, in order to see a bounty of flowers?

A vertical close up picture of purple crocus flowers with bright orange center on a soft focus background. To the center and bottom of the frame is green and white text.

Of the three most popular varieties – snow (Crocus chrysanthus), Dutch (C. vernus), and saffron (C. sativus) – two are vernal and one is autumnal, so planting times differ, and vary according to your USDA Hardiness Zone.

You can find out more about growing crocus in our complete guide, but in this article, we’ll be focusing on when to plant this hardy member of the iris family.

When to Plant Snow and Dutch Crocus Varieties

Both snow and Dutch varieties are hardy in USDA Hardiness Zones 3-8. These two varieties are vernal, which means they bloom in spring.

A close up of purple crocus flowers with orange centers growing in between autumn leaves on the ground fading to soft focus in the background.

But of course, the lowest extreme temperature in Zone 3 is very different than it is in Zone 8, and planting times need to be adjusted accordingly.

I live in Alaska, in Zone 4. Those of us living in states with cold winters stretching from Washington to Maine and down through Utah, Colorado, Kansas, and Ohio – in other words, gardeners in Zones 3-6 – need to plant crocus corms in September and October.

Those in warmer climates will generally aim to plant their corms closer to November.

A close up of a gardening trowel and some crocus bulbs surrounded by fall leaves set on the soil ready for planting.

In either case, the exact month for planting depends on one thing: the average date of the first hard frost in your area, when outside temperatures fall below 28°F for several hours at a stretch.

Count back six to eight weeks before your average first frost date and you’ll know when to plant your corms.

There’s a caveat, though: the soil must be 60°F or lower when you plant the bulbs. To make sure you plant at the right time, use a soil thermometer, like this one from Vee Gee Scientific that is available via Amazon.

Soil Thermometer, Available via Amazon

Not sure how to use a soil thermometer?

Read on.

How to Use a Soil Thermometer

Eight weeks before the average first frost date in your area, head out into the yard in the morning – the earlier, the better.

The soil’s more likely to be at its coldest, and that’s when you want to measure the temperature.

Stick the probe three to four inches deep in the soil where you plan to plant your corms.

A close up vertical picture of a soil thermometer placed in the earth with soil in the background.

Wait until the thermometer finishes reading. If the temperature is 61°F or higher, take the temperature again the following day and the day after, until you get a reading of 60°F or below.

Crocuses love the cold, so don’t worry if your soil is well below 60°F when you take the temperature.

Just get those corms into the ground as soon as possible so they can burrow down for the long, cold winter ahead and prepare for their spring debut.

A close up of purple crocus flowers pushing through the snow in light sunshine fading to soft focus in the background.

If you live in Zone 9, you can still grow crocuses, but you’ll have to chill the bulbs in the refrigerator for 12-15 weeks before planting.

Simply put your corms in a ventilated bag, like these available from Amazon, and store them in the coldest section of your refrigerator. This is typically at the very back of the bottom portion of the fridge.

In midwinter or early spring, depending on your zone, plant them in trenches three inches deep.

Crocus corms need chilling because as they are native to regions with cold winter temperatures, and they require a cold period in order to start pushing through the earth and flowering.

Plant Crocuses Together

Unlike other plants, crocuses don’t mind company. For bright clumps of blooms, plant them in groups of three to nine corms.

A close up of purple crocus flowers growing in the garden through a light dusting of snow on a soft focus background.

First, choose a sunny or partly shady area.

Then dig a trench three inches deep if you live in USDA Zones 6-8, or four inches deep for Zones 3-5, to provide extra insulation. Place the corms in the trench, flat side down and about two inches apart.

A close up of yellow crocus flowers growing in the bright sunshine in a snowy lawn with trees in soft focus in the background.

The opposite side of the bulb will have a small point and sometimes even new shoots beginning to form. This side should face upward.

Cover the corms with soil, give them a good watering, and start daydreaming about your springtime reward.

When to Plant Saffron Crocus

Are you impatient in your desire to see those brilliant crocus blooms in your yard?

If you live in Zones 6-10, you’re in luck. You can plant the saffron variety, C. sativus, mother of the precious saffron spice, in your yard in August for colder regions, or in September in the warmer zones in this range.

In this case, you want to plant the bulbs at least six weeks before the first frost.

A close up of a purple crocus flower and a pile of saffron set on a purple background.

Because saffron crocus corms are more heat-resistant than the vernal varieties and don’t need a chilling period, you don’t need to worry as much about soil temperature when you plant.

Saffron crocuses bloom in just two months, providing you with a burst of color before winter tightens its grip on the land.

Even if you live in Zones 5 and below, go ahead and plant saffron crocuses outdoors in a pot at the beginning of August.

Then bring the plant indoors before the first frost, and watch the blooms brighten up your living space within a few weeks.

Just make sure your indoor plant gets plenty of sunlight, or use a grow light during the day.

A close up of purple crocus flowers on a white wooden surface with a small jar of saffron and a brass pestle and mortar.

You can also harvest the long red stigmas of the saffron crocus and dry them for use in delicious recipes, like this one for cardamom saffron cookies from our sister site, Foodal.

There’s No Hocus-Pocus in a Crocus

Crocuses aren’t tricky. Plant them at the right time and you’ll see blooms come fall or spring, depending on the variety.

A close up of yellow crocus flowers growing through a blanket of snow in light sunshine with a soft focus background.

And every year thereafter, your plants will multiply with little help from you. They’re dependable, stouthearted little plants that can lift your spirits just when you need it.

Do you have any tips, questions, or comments about when to grow crocuses? Let us know in the comments below.

For more tips on propagating flowers in your garden check out these articles:

© Ask the Experts, LLC. ALL RIGHTS RESERVED. See our TOS for more details. Originally published on January 28, 2020. Last updated: February 20, 2020 at 17:59 pm. Product photo via Amazon. Uncredited photos: Shutterstock. With additional writing and editing by Clare Groom and Allison Sidhu.

About Laura Melchor

Laura Melchor grew up helping her mom in the garden in Montana, and as an adult she’s brought her cold-weather gardening skills with her to her home in Alaska. She’s especially proud of the flowerbeds she and her three-year-old son built with rocks dug up from their little Alaska homestead. As a freelance writer, she contributes to several websites and blogs across the web. Laura also writes novels and holds an MFA in writing from Vermont College of Fine Arts.

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