Crocus Planting Tips: Learn When To Plant Crocus Bulbs
By: Bonnie L. Grant, Certified Urban Agriculturist
Any plant that can bloom through snow is a true winner. Crocuses are the first bright surprise in early spring, painting the landscape in jewel tones. Read on for important crocus planting tips.
When to Plant Crocus
Why does it matter when you plant your bulbs and corms? It would seem that as long as they get in the ground they will grow when it is time, but actually bulbs, tubers, and corms require certain conditions to break dormancy. The plant will not emerge if it doesn’t get this combination of correct conditions. The best way to achieve this is to plant them just before they will experience those circumstances.
Since crocus is considered a spring bloomer, you need to plant corms in late summer to early fall. Crocus requires a minimum of 15 weeks of chilling to break dormancy. The chilling period gives the corm the clue that it is not time to grow up through the soil. This prevents early tender shoots from getting zapped by freezing temperatures.
The process is called vernalization, and most plants undergo some form of it during the cold season; however, some plants don’t even need it to sprout. Planting times for crocus differ from other species. Ideally, the best time to plant a crocus corm is 6 to 8 weeks before the first expected frost. This allows the corm to develop a root system before going dormant.
Crocus Bulb Growing
Interestingly, most plants not only need vernalization but also increased photo hours to sprout. Crocus corms will not bloom if the photo period is not long enough to provide solar energy. Therefore, planting times for crocus must include this factor in addition to the chilling period.
It is not uncommon to see crocus arise from the snow, but without the right amount of sunlight, the plant will fail to bloom. The 15 weeks of chilling will usually take you into March, which is when daylight hours are increasing and ambient temperatures start to warm. All this signals “bloom” to the plant and points to the best time to plant a crocus.
Crocus Planting Tips
Satisfying the chilling and photo-period requirements are important for crocus bulb growing but so is the actual planting. Choose a sunny location with well-draining soil for crocus bulb growing. This is important to prevent the corms from sitting in a bog and rotting.
If the soil has too much clay, amend it with bark, leaf litter, or compost. Sandy soils will require some organic amendment to enhance nutrient content. Select corms that are healthy and free of disease, mold, or damage.
Dig trenches 5 inches (13 cm.) deep and plant corms with the flat side down and 1 to 2 inches (2.5 to 5 cm.) apart. Cover with the soil and wait until spring!
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Crocus are native to a wide area from Central/Eastern Europe to the Middle East, North Africa and Asia. They have found a welcome home here in North America where different species are compatible in almost all areas of the continent. Crocuses bloom from very early spring through to March and April, and the lovely fall crocus flowers in August and September.
Snow Crocus: Early Blooming Crocus
The earliest Crocus to bloom are the Crocus chrysanthus or Snow Crocus. With narrow, almost grass-like leaves that appear after the blooms, and just 3-4 inches tall, they are perfect to plant in nooks and crannies or where they can poke up through low groundcovers. Because they bloom so early, they can be planted above and amongst other later blooming bulbs. Originally gold or yellow colored, they have been bred in a full array of colors. Plant them in tight groups where they will be noticed in the early spring garden.
Large-Flowered Dutch Crocus Bulbs
Next in the crocus parade is the Dutch or Giant Crocus (Crocus vernus, C. flavus). Taller, at a stately 4-6 inches, they are ideal for naturalizing in lawns. Be sure not to mow until the crocus leaves have faded, about 6 weeks, and organic lawn care only! Coming along about two weeks after the Snow Crocus, their larger flowers are available in a full array of colorful solids and beautiful patterns.
Striking Saffron Crocus
One of my favorite crocuses is the fall blooming Crocus sativus or saffron crocus. Lavender petaled, with three striking deep-red stigmas per flower, these stigmas are the source of the color and flavor we know as saffron. Bulbs usually arrive in early fall and you can plant them right away. They will begin to grow immediately and put on a display that fall. In zones 6-10, when conditions are right, they will naturalize and treat you to a fall show every year.
Saffron is known as the world’s most expensive spice, lending its color and flavor most famously to Spanish paella, risottos and many other drinks and dishes. It takes 225,000 stigmas to make one pound of saffron. At three stigmas per flower, that’s a lot of flowers! Each flower must be carefully hand harvested. You can harvest your own saffron simply, and as a little goes a long way. A dozen or so flowers can keep you in saffron for quite a few dishes. Harvest your saffron on a sunny day, mid-morning, when your flowers are in full bloom. Pluck the stigmas with your fingers or tweezers and then gently dry them on a paper towel in a warm place. Store in an airtight container in a cool, dark place. The next time your recipe calls for saffron, you’ll enjoy your simple harvest. Read our article about Growing Saffron Crocus.
There are many other crocus species, with a wide variety of colors and cold tolerances. Crocus seiberi ‘Spring Beauty’ is a showstopper with its deep wine stripes cloaking lovely lavender petals. No wonder our humble Crocus is the world’s most popular bulb!
Step 1: Plant bulbs as soon as possible after receiving them.
Step 2: Decide on a planting style:
A: Plant crocus bulbs close together to form a cluster, this technique creates a full showy colorful display. Space 12 bulbs per square foot.
B: For a more natural look, plant crocus bulbs speckled throughout a garden, or under trees.
C: Plant in a container with well-draining soil.
Step 3: To plant, dig a hole 2-4” deep for each bulb. Plant bulb pointy side up. If the crocus bulbs are being planted in poor soil conditions, add a layer of organic compost, bone meal or Yum Yum Mix around the crocus bulbs. Back-fill with soil and water thoroughly to remove air pockets.
Harvest your Saffron by removing the stigmas and drying them on a paper towel. Each bloom produces three stigmas.
How to Grow Crocuses at Home
There are more than 80 different species of crocus, but the most popular are the spring flowering crocus known to gardeners as the Dutch hybrids Crocus vernus, explains Dimitrov. "They like open ground, but they can do well in the light shade under deciduous trees and shrubs," he says. "Crocus requires well-drained soil that dries out in the summer, [and they're] not fussy about the Ph." The spring showstoppers do best in USDA hardiness zones three to eight. They are considered to be wildflowers by some, and very easy to grow.
If you'd like to add some crocus flowers to your garden, Roethling says it's easiest to do it by planting bulb-like corms. "The cost of most crocus [corms] are so low that it wouldn't be worth the waiting period to get a seed to actually perform to its fullest," she says. "And, the more you buy, the price breakdown gets less." Since she thinks the spring blooms make the biggest impact when planted in large groupings, she advises gardeners to plant 100 corms (as opposed to 10).
CROCUS PLANTING GUIDE
Crocuses might be small flowers, but they carry a powerful message: spring is around the corner! Blooming in yellow, white, purple, lilac and even orange, these hardy little fellows are a delightful start to the flower bulb season.
Blooms in late winter/early spring
Full sun or partial shade
- WIDTH & DEPTH
When your DutchGrown crocuses arrive and you can’t plant them immediately, it’s important to store them correctly: unpack them right away and put them in a dry place with plenty of air circulation, where the temperature is between 40 and 70 degrees Fahrenheit.
Garden & Container Planting
Like all flower bulbs, crocuses need a cold period to develop their roots and get ready for spring. So once you feel fall’s first chill in the air, it’s time to get planting. If you live in hardiness zone 9 or higher, the soil won’t get cold enough for the root-developing process to happen, but you might consider forcing.
Crocuses are tough cookies that are easy to grow, but one thing they hate is getting their feet wet: a crocus bulb that is ‘bathing’ in water will rot in no time. So avoid soggy soil at all cost – this means places where you can still see puddles 5-6 hours after a rainstorm. Another thing you can do is to upgrade potentially soggy soil by adding organic material such as peat, bark or manure. When it comes to planting bulbs in containers, the mantra is exactly the same: drainage-drainage-drainage. Get a pot or box with at least some drainage holes at the bottom.
Crocuses need the sun to grow, but though they adore basking in its glory all day, they can also do very well in places with dappled shade or scattered sunlight.
Crocuses will need to be planted deep enough that they won’t be affected by temperature variations above ground, either too warm or too cold. Unfortunately containers can’t protect bulbs as well as mother earth can, so when you live in hardiness zones 3-7 it might be better to let your containers spend the winter indoors, in a cool, dark, well-aired spot that won’t get warmer than 60 degrees Fahrenheit, like an unheated basement or garage.
The standard method for calculating the ideal depth is to dig a hole three times as deep as the bulb is high, and place the bulb at the bottom with its pointy end up. Since crocuses grow less well when they have to fight for nutrients with their fellow bulbs, it’s best to plant them 3” apart.
To help the bulbs settle and grow roots quickly, it’s important to water them well after planting, but after that you won’t have to water them again. Now all you have to do is wait patiently for winter to do its magic underground, and spring to surprise you with the rewards of your work.
During blooming season, you generally don’t have to water your crocuses, but you can water them when there hasn’t been any rain for 3-5 days.
After crocuses have finished blooming, don’t cut the foliage straight away: through photosynthesis the leaves will create nutrients that the bulb will be needing for its next growing season. After a few weeks the foliage will automatically yellow and die back, and then you can remove it. Now the bulb will be going dormant, and won’t need any watering until next spring.
How to plant crocuses in your garden:
- Wait until the soil is 60 degrees Fahrenheit or colder. In the North this will be in September or October, in the South in October or November.
- Pick a spot in your garden that has well-draining soil and gets full sun or partial shade.
- Plant the crocus bulbs about 2-3” deep and 3” apart, placing them in the ground with their pointy ends up.
- Water well once and wait for spring
- After the crocuses have bloomed don’t cut off the foliage. Leave it until it’s completely withered and yellow, then remove.
How to plant crocuses in containers:
- Wait until it’s cold outside, with a soil temperature of 60 degrees Fahrenheit or lower. In the North this will be in September or October, in the South in October or November.
- Pick a spot in your garden that gets full sun or partial shade.
- Find a well-draining container and fill it with loose soil, making sure water won’t gather and stay at the bottom.
- Plant the crocus bulbs about 2-3” deep and 3” apart, placing them in the soil with their pointy ends up. Since containers often have limited space, you can also experiment with placing the bulbs closer together, but make sure they never touch.
- Water well once and wait for spring, or, when you live in hardiness zone 3-7, water well and bring the containers indoors, letting them spend the winter in a cool spot like an unheated garage or basement.
- After the crocuses have bloomed don’t cut off the foliage. Leave it until it’s completely withered and yellow, then remove.
Special 'Flower Bulbs'
Even though we’ve been talking about bulbs when referring to how to plant crocuses, they actually grow from a tuber called a corm. True bulbs are like onions: layers of skin and an embryo of the plant it will eventually turn into. Corms on the other hand are like batteries: solid masses of food with a plate on the bottom and eyes or buds on top. Plant the corms with the buds facing upwards. During growth the corm is consumed by the plant itself, which also creates new corms for next season, making crocuses naturalizing flowers.
Hyacinth (Hyacinthus orientalis), also referred to as common hyacinth and Dutch hyacinth, are hardy flowering bulbs that display blooms in white, blue, purple, red, yellow, and varieties of pink. Hyacinths thrive in full sun, prefer well-drained sandy loam soil and grow to a height of 6 to 15 inches, according to the Purdue University Cooperative Extension Service. Bloom time for hyacinth bulbs is during the spring season.
- Flowering bulbs in Arizona provide gardeners with a reliable source of color and interest the root systems of bulbs act as food storage centers for the plants, allowing them to exist in dry conditions, such as the arid desert climate of Arizona, according to the Arizona Cooperative Extension.
- Hyacinths thrive in full sun, prefer well-drained sandy loam soil and grow to a height of 6 to 15 inches, according to the Purdue University Cooperative Extension Service.
How to Transplant Crocus Bulbs
Crocus grows from a bulb-like structure known as a corm. These spring-blooming perennials are one of the first flowers of the season, according to Clemson University extension. The crocus survives and flowers for many years in the flower garden. Eventually the bed becomes crowded, so the corms must be dug, divided then transplanted into new beds. You may also need to dig and transplant the corms to a new bed as your landscape design changes. When possible, transplant your crocus bulbs in fall about six weeks before the first expected frost.
Loosen the soil around the crocus with a handheld cultivating fork. Slide a trowel under the corms and lift them from the soil.
- Crocus grows from a bulb-like structure known as a corm.
- Eventually the bed becomes crowded, so the corms must be dug, divided then transplanted into new beds.
Brush the excess soil off the corms and inspect them. Twist apart any that are connected. Dispose of any that have open wounds, appear shriveled or have soft spots indicating rot.
Spread a 2-inch layer of compost over a well-draining, full-sun garden bed. Apply a slow-release balanced fertilizer to the bed at the rate recommended on the label, then work both the compost and fertilizer into the top 6 inches of the soil.
Plant the crocus so that the top of each corm is 3 inches beneath the soil surface. Space the crocus 3 inches apart in clusters of five to seven corms.
- Brush the excess soil off the corms and inspect them.
- Plant the crocus so that the top of each corm is 3 inches beneath the soil surface.
Water the bed thoroughly after transplanting, wetting the soil to a 6-inch depth. Cover the bed in 2- to 3-inches of straw mulch, which preserves moisture and prevents frost damage over the winter months.
Mark the location of the corms in spring so you can easily find them at transplanting time.
If you must transplant crocus in spring, wait until the foliage dies back completely on its own, usually within six weeks after blooming completes.