Overview and Description:
Crocus flowers are one of the earliest blooms of spring. They are very adaptable and small enough to be tucked into flower beds, under trees or even in the lawn.
There are over 80 species of crocus, but most of the bulbs (actually corms) available are mixes of different species and varieties. There is only one qualification you need to be certain of when choosing your bulbs: are they spring or fall bloomers.
This article focuses on spring blooming crocus, but there are several, including Crocus speciosus, which bloom in the fall. [Crocus speciosus is the source of the spice saffron. In fact, crocus comes from the Greek word for saffron.]
Crocuses are low growing, clump forming perennial plants grown from corms. The are found growing in a range of conditions, from woodlands to coastal gardens to suburban lawns. Crocuses are in the Iris (Iridaceae) family.
Many of the commonly found spring blooming crocus are hybrids of Crocus vernus, Dutch crocus, with large, single flowers, or Crocus chrysanthus, which blooms a couple of weeks earlier and has smaller, but more profuse blooms. They are hardy and easy to naturalize plants that pop up very, very early in spring. Crocuses don't come in a large variety of colors, but they are bright enough to put on a good show. The hybrids tend to bloom a little later, and mixing them with other species of crocus will give you a longer period of bloom
- Leaves: Semi-erect thin, lance-shaped leaves look like blades of grass, with a center white stripe. They grow taller as the flowers fade.
- Flowers: The narrow, cup-shaped flowers have 6 tepals and can be shades of white, purple and yellow, depending on the variety.
Crocus, Dutch crocus, snow crocus
Full sun to partial shade. Crocuses do best in full sun, but since they bloom so early in the year, there are few leaves on the trees to shade them anyway. If the temperature heats up, crocus will fade quickly.
Crocus bulb hardiness will vary slightly depending on which type you are growing and exposure, but most crocuses are reliable within USDA Hardiness Zones 3- 8. They bloom and perennialize best where winters are cold. Crocus corms need a 12-15 week period of cold (35 to 45 degrees F.) temperatures, to set their blooms.
There is a bit of variability in the size of crocus plants, but none are more than 6 inches (h) x 3-4 inches (w).
Crocus flowers bloom very early in the season, either late winter or early spring, depending on your growing zone.
Crocuses look best when they appear natural. Large drifts waving throughout the garden, under trees or speckled throughout the lawn make a wonderful sight in early spring. The corms also do well in alpine and rock gardens and in containers. (See below) They look especially nice in hypertufa troughs.
To extend the bloom time, mix different species of crocus. You will probably need to look through one of the catalogs that specialize in bulbs, to find a good, reliable selection.
Crocus planted in a protected spot can bloom weeks earlier than those in open exposure, like a lawn. This is also a good way to extend their blooming period.
The flowers fade quickly in the heat. Planting them where other plants will fill in and hide their foliage will give the crocus a chance to store energy for the next season.
- Crocus chrysanthus 'Blue Pearl' - Pale blue with a yellow throat and white edges. Later blooming.
- Crocus chrysanthus 'Cream Beauty' - Buttery yellow petals with a bright orange stamen. Early to mid-season.
- Crocus chrysanthus 'Fuscotinctus' - Early blooming yellow flowers with purple streaks.
- Crocus vernus 'Pickwick' - White flowers webbed with lilac stripes. Later blooming.
Other Species Crocu
- Crocus flavus - Small yellow flowers in thick clumps. A good choice for temperate climates.
- Crocus leichtlinii - Small, clear white flowers. Good for areas with cold winters and hot, dry summers.
- Crocus tommasinianus 'Tommy Crocus' - A small, but very prolific purple flowering crocus.
Crocus Growing Tips:
Soil: Crocus plants prefer a neutral soil pH of 6.0 - 7.0. More important than soil pH is good drainage. As with most bulb-like plants, crocuses do not like to sit in wet soil, especially during the summer, when they are dormant.
Planting Crocus Bulbs: Spring blooming crocus are planted in the early fall. Plant them about 4 inches deep and 2-4 inches apart, pointed end up. It can sometimes be hard to tell which is the pointed end of a corm but don't worry too much. The plant will grow toward the light.
For a more natural look, you can toss the corms onto the planting space and plant them where they land. Even easier, dig a wide hole, toss them in and cover them over.
Adding some bulb food or bone meal will ensure they have all the nutrients they need to get started.
Crocus require very little maintenance. They like to be watered regularly in the spring and fall. If there is no snow cover, the corms will also need water throughout the winter. They go dormant during the summer and prefer a drier soil.
Fertilizer: Crocuses do not require a lot of fertilizer. They store their own energy in their corms, which is why it is essential that you do not cut back the leaves until they yellow on their own. However a light top dressing, in the fall, with bulb food or bone meal, is a good idea in poor soils.
Dividing Crocus: You don't need to divide your crocus plants. In fact, in many areas they will be somewhat short lived and you may need to replant every few years. However, if your crocuses do very well and start to multiply, they will eventually begin to bloom less. When that happens, you can lift and divide the corms when the foliage starts to die back and replant where you wish.
Pests & Problems:
Crocus are susceptible to viruses which can cause distortions, streaking, and buds that fail to open.
There is no cure for viral diseases. Dispose of the plants to prevent spreading the virus.
The biggest problem you will encounter is your corms being eaten. Chipmunks, deer, rabbits and squirrels will all eat the leaves and flowers. An assortment of rodents will also feed on the corms themselves. And other animals, like skunks, will dig them out of the ground while searching for insects.
There are deterrents that can be sprayed on the leaves, to prevent browsing. They also sell wire cages, to protect the corms. If you find your plants are constantly being harmed, avoid using bone meal, which can attract animals, and try interplanting your crocus with daffodils, which animals hate.
Planting Crocus in Containers
- Crocus make a cheerful container plant. They will still need a period of cold, but the corms can be packed into a container, for intense bloom.
- Select a wide, shallow container, at least 3-4 inches deep, with drainage holes.
- Add potting soil to about 1 inch from the container's rim and water it until damp.
- Set the corms onto the soil, close but not touching.
- Barely cover corms with soil.
- Water and let the excess drain.
- Move the container to a cool, dark location, like the basement or garage, for at least 12 weeks. Water when dry.
- When the plants start to sprout, move the container to a slightly warmer location with indirect light.
- Gradually move closer toward the light. Rotate the pot so the plants grow straight and sturdy.
- Once in bloom, they'll need plenty of direct sunlight and water when dry.
- Allow the plants to die naturally, then plant your corms outdoors. Forced corms don't usually rebloom well in containers.