How to Grow Crocus

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The crocus (Crocus sativus) is a small purple-colored flower that is also known as autumn or saffron crocus. Its lavender flower has a red filament at its center, and this is the source of the spice many home chefs know as saffron.

The perennial flowers are autumn bloomers, unlike spring-blooming Dutch and giant crocuses, and they are native to the Mediterranean. They look very similar to springtime crocus flowers and don't grow much taller than 5 inches. Like their spring-blooming cousins, saffron crocuses don't require much effort to grow.

Why is the saffron spice so expensive? Each flower produces only three small orange-red saffron filaments, and it takes a considerable amount of flowers to harvest a very small usable amount, which is why the price point of saffron is so high. Because of this small availability, there's even a ton of fake saffron on the market. That said, home gardeners can easily grow enough flowers to harvest usable amounts of the spice for their culinary endeavors.

Saffron crocus is relatively cold hardy (down to -10 degrees Fahrenheit). It requires little upkeep once plants are established in your yard or garden. The drought-tolerant plants are great for those looking for a showy, hands-off flower that blooms in autumn.

Best Uses for Crocus

Crocus is best planted straight in the ground wherever you want to enjoy a view of pretty flower clusters in the fall. You can also plant it in containers, but a swath of spread-out crocus flowers in a garden is really something beautiful to see. You can plant crocuses for their aesthetic benefit or grow them in order to harvest the filaments to flavor all sorts of dishes.

That said, don't expect to get a truckload of saffron threads. It takes thousands of flowers to produce a single pound of saffron. Still, you can harvest a few threads for the occasional fancy dish. Most recipes call for only a pinch of saffron anyway, since too much can be overwhelming.

If you plan to harvest saffron from these flowers, be aware that each flower only produces three saffron threads. So, you'll need to plant multiple crocus corms in order to get a usable harvest. The petals of the saffron crocus flowers are also very fragrant and can be used to make homemade potpourri.

Each year, the plants will multiply, leaving you with more and more flowers to enjoy. That means more saffron for the taking and a showy display in your yard or garden. Once established, autumn crocus plants don't require much upkeep aside from dividing them to prevent overcrowding, which can limit the dazzling autumn display.

How to Grow Crocus

  • Common Name: Crocus or saffron crocus
  • Botanical Name: Crocus sativus
  • When to Plant: In the late summer or early fall, usually sometime in September. You can also plant in the spring.
  • USDA Zones: 6-9
  • Sun Exposure: Full sun or partial shade
  • Soil Type: Sandy, well-drained soil
  • When it's in Trouble: Over the years, if flowers begin to reduce in numbers, the problem is usually overcrowding. Yellowing is typically a sign of disease or pest activity.
  • When it's Thriving: Healthy purple flowers with grassy-green foliage pop up in the fall and multiply over time.

Starting Crocus from Corms

You don't actually plant crocus from crocus bulbs but from corms, which are bulby plant stems. When it comes to spacing, plant corms about 4 inches apart and at a depth of 4 inches. Flowers usually come up after six to eight weeks, though sometimes, they only appear the following year after planting. Typically, the flowers stick around for about three weeks, and the grasslike foliage holds on for up to 12 weeks depending on your climate.

Ideally, you should plant crocus corms in a spot with well-drained soil that receives plenty of sunlight. However, the plants can handle a bit of shade. Don't bury the corms in an area where the soil is moist all summer long. The corms will be dormant throughout the summertime months, so pick a spot that's mostly dry during that time.

Once the plants wither away for the winter, it's tough to discern that they were even there. If you're worried about accidentally digging up the corms during spring gardening, you may want to mark the spot where they're planted. Unlike other plants and flowers, there's no need to prune or remove crocus foliage at the end of the growing season. The foliage will die back and provide nutrients for next year's flowers.

In What Zone Does Crocus Grow Best?

Saffron crocus grows best in USDA hardiness zones 6 to 9. You can grow the perennial in these zones without having to worry about the corms surviving the winter. You'll need to dig up the corms in colder zones to protect them from harsh winters and store them indoors before planting them outdoors again in the spring.

Some people in zone 5 might be able to get away with leaving corms in the ground throughout the winter as long as soil temperatures don't go below -10 degrees Fahrenheit. However, if you choose to do this, it's a gamble that may not pay off. You can increase your chances of success by heavily mulching around your crocus plants to help insulate the soil. Don't forget to remove the mulch in the spring once your last frost date has passed.

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When Should You Plant Crocus?

Most companies that sell crocus corms will ship them at the right time for your zone and encourage you to plant them as soon as you receive them. It depends on your USDA growing zone, but planting usually occurs in August or September about six to eight weeks before your first frost date. You can also plant the corms in spring after the last frost but know that they won't flower until the fall.

Soil, Sunlight and Water Recommendations for Crocus

Crocus plants prefer a lot of sun but will still grow in partial shade. Soil needs to drain well, and high-moisture areas should be avoided. Pick a spot with dry, sandy soil for best results.

Crocus plants are drought tolerant and don't usually require any specialized care, including watering. In fact, it's best if the planting area is relatively dry throughout the summer while the corms are dormant. Excess water during the dormancy period can lead to root rot and disease. In the fall when the flowers bloom, you can hold off on watering if your area gets at least 1 1/2 inches of rain per week.

How to Propagate Crocus

Crocus multiplies every year. However, after about four to six years, perennial crocus can become overcrowded. You can divide and replant the corms in any year. Do this as soon as the blooms and foliage begin to fade at the tail-end of the fall. Unsure of when to divide crocus? It's also OK to wait a few years. When flower numbers begin to stagnate or decrease, it's definitely a sign that it's time to divide the corms.

To divide corms, wait until the flowers and foliage die back. Dig up the corms and rinse away any dirt. You'll be able to spot the cormels, which crop up at the base of the mother corm. These small pieces eventually separate from the central corm and become offshoot plants. Remove these. They're usually easy to pull off with your fingers. Once you're done taking these off the main corm, replant them. Don't forget to keep crocus spacing guidelines in mind.

How to Winterize Crocus

You can grow crocus in places colder than zone 6, but you'll need to do a bit of extra work to keep your plants alive. To preserve the corms for the next season, dig them up and bring them inside for the winter. You can do this after the first frost in the fall but do it before the ground is completely frozen and unworkable.

To keep the corms dormant until next year, put them in a large container or bucket and fill it with sand. Keep the bucket in a cool, dry location like a pantry or a very dry basement. In the spring, plant the corms after your last frost date. If locating and digging up the corms seems like an annoying task to undertake every year, you can make it a bit easier by planting the corms inside containers or buckets that you plant deeply in the ground. In zones 6 and higher, you don't need to worry about winterizing saffron crocus.

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How to Harvest Crocus

You can grow saffron crocus in order to harvest the earthy-tasting threads that emanate from the center of each flower. To gather the saffron pieces, wait until the flowers bloom. The threads need to be harvested right away. Harvest at midday when the cup-shaped flowers are fully open as they close at night and on gloomy days.

Gently pluck the red-orange threads from the flowers and bring them inside. Spread them onto a baking sheet and leave them to dry at room temperature. You'll know they're dry enough because they'll crumble easily when touched. You can keep the dried threads in an airtight container for up to two years.

Common Pests and Other Problems for Crocus

Small rodents can be a problem for plants with corms. If you've had issues with voles or mice in the past, apply a barrier like wire mesh before planting the corms. They're the most likely culprit if you're noticing saffron crocus damage. Bunnies and other animals are notorious for munching on the tender green growth of all kinds of crocus plants, including saffron crocus. They also eat and displace corms. Squirrels sometimes disturb dormant corms when burying and uprooting food. Deep plantings may deter rodents, but it's not a guarantee.

While insect pests aren't a huge problem for saffron crocus, they can still appear and cause issues. Mites, for instance, can enter the plants via nicks and scratches in the corms and leave behind a plant with stunted, yellowed leaves. A miticide can help combat them. Thrips can also cause foliage damage. They cause yellow and white spotting, but the damage isn't usually fatal. A quick application of neem oil is usually enough to mitigate the problem.

Common Diseases for Crocus

Saffron crocus is susceptible to fungal diseases and root rot if planted in a wet area, especially if conditions are very moist during the blooming period. Some examples of fungal diseases that affect saffron crocus include Aspergillus and Rhizopus. Planting in soil with good drainage is the best way to prevent these kinds of diseases. You can also prevent the problem by spraying corms with fungicide before planting.

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Steph is a freelance writer with over 10 years of gardening experience. She has taught gardening workshops, once created a communal gardening space from scratch, and never tires of sharing her passion for digging in the dirt. She also firmly believes that you can never have too many houseplants.

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