Common Crocus

Common Crocus, Dutch Crocus, Dutch Crows, Species Crocuses

Crocus flowers lead the way for other spring bloomers to follow. They bloom bright and early, bringing much needed color after a long winter. These small-but-mighty plants with their colorful blooms and sweet fragrance lure hungry bees out of their hives. Crocus plants will multiply and come back year after year, bringing more blooms with them each time

I. Appearance and Characteristics 

Crocus display the general characteristics of family Iridaceae, which include basal cauline (arising from the aerial stem) leaves that sheath the stem base, hermaphrodite flowers that are relatively large and showy, the perianth petaloid with 2 whorls of 3 tepals each and septal nectaries. The flowers have 3 stamens and a gynoecium of 3 united carpels and an inferior ovary, 3 locules and axile placentation with fruit that is a loculicidal capsule.

Crocus is an acaulescent (lacking a visible lower stem above ground) diminutive seasonal cormous (growing from corms) herbaceous perennial geophytic genus. The corms are symmetrical and globose or oblate (round in shape with flatted tops and bottoms), and are covered with tunic leaves that are fibrous, membranous or coriaceous (leathery). The corms produce fibrous roots, and contractile roots which adjust the corms depth in the soil, which maybe pulled as deep as 20 centimeters (8 in) into the soil.The roots appear randomly from the lower part of the corm, but in a few species, from a basal ridge.

  • Leaves

Plants produce several basal linear bifacial green leaves that arise from the corms. These are axially (upper surface facing axis) flat or channeled with pale median stripes, while the opposite (abaxial) surface is strongly keeled, with two grooves on either side. The leaves have a distinctive shape in cross-section, being boat-shaped with two lateral arms with margins recurved inwardly towards the central ridged keel, forming the sides of the “boat”. The keel may be square or rectangular, but is lacking in C. carpetanus. The pale central stripe is caused by parenchymatous cells which lack chloroplasts and may contain air spaces. The leaves are from 5 to 30 millimeters (3⁄16 to 1+3⁄16 in) wide and 10 to 118 centimeters (4 to 46 in) long. The leaf-like bracts are membranous, while the smaller bracteoles are either membranous or absent. The leaf bases are surrounded by up to 5 membranous sheaths called cataphylls, a specialized leaf. The bases of the cataphylls form the corm tunic, and their number varies from 3 to 6, and enclose the true leaves (euphylls), bracts, bracteoles and flowering stalk.

  • Flowers

The number of peduncles (flower stems) vary from one to several and remain underground, emerging only at the fruiting stage, bearing flowers that are solitary or several, so that a true scape is absent. The flowers are pedicellate (attached to the peduncle by a short subterranean pedicel stalk). The pedicel is sometimes subtended (below pedicel) by a membranous, sheathing prophyll (leaf-like structure).

The showy, salver to cup-shaped, single or clustered actinomorphic flowers taper off into a narrow tube; the flowers emerge from the ground, and can be white, yellow, lilac to dark purple, or variegated in cultivars. The flower tube is long, cylindrical and slender, expanding apically. The floral tube is long and narrow with 6 lobes in 2 whorls. The perianth is 3+3 (3 sepals+3 petals) and gamophyllous (with fused segments). The tepal whorls are similar, equal or subequal with a smaller inner whorl, and cupped to outspread. The bracts are membranous, but the inner ones are sometimes lacking.

The 3 stamens are erect and linear and inserted in the throat of the perianth tube, with anthers shorter than the filaments. Pollen grains are in aperture (apertures absent) but sometimes spiraperturate (spiral shaped). Each flower has a single style which is exerted (projecting beyond the corolla tube) and slender distally with three to many branches. The branches are highly variable, being short or long, and simple, bifurcate (dividing in two) or multifid and sometimes distally flattened. The inferior ovary has 3 carpels with axile placentation. It remains underground, and as the seeds ripen, the pedicel (stem of the flower) grows longer – so the fruit is above the soil surface.

  • Fruit and seed

The fruit is a small membranous capsule, ellipsoid or oblong-ellipsoid in shape and the many seeds are globose to ellipsoid. The seed surface is highly variable, including papillate (covered in small protuberances), digitiform (finger-like) and other epidermal cell types. In some species the seeds are arillate, with fleshy appendages. Crocus seeds have both inner and outer integuments and in some species the outer epidermis may display long papillae. Embryo-sac development is Polygonum type. Dehiscence (splitting of the capsule to release the seed) is of the loculicidal type in which it splits through the wall of the locules leaving the septa that separate them intact.

  • Distribution and habitat

Crocuses are distributed from the Mediterranean, from the Iberian peninsula and North Africa, through central and southern Europe, the islands of the Aegean, the Middle East and across central and southwest Asia to Xinjiang in western China, but most species are restricted to Turkey and Asia Minor and the Balkans, with the Balkan Peninsula having the largest number of species (at least 31), forming the centre of diversity, however they are widely introduced. The distribution of species is described over five contiguous areas from west to east (see map).

Habitats range from sea level to as high as subalpine altitudes, and in a wide range of habitats from woodlands to meadows and deserts, often on stony mountain slopes with good drainage. The majority of species are native to areas with cold winters and hot summers with little rain, and active growth is typically from fall to mid-spring. The natural habitats of crocus species are threatened by human activities, including urbanization, industrialization, and other land disturbances and recreational uses. They are negatively impacted by uncontrolled gathering and heavy grazing by livestock.

II. How to Grow and Care

Light

Crocus can grow in full sun or partial shade.

Temperature and Humidity

Crocuses are hardy perennials that can be grown down to zone 3. Summers above zone 8 are too hot and winters too mild to grow them. By the time the weather turns humid, crocuses have entered their summer dormancy so they are not affected by humid weather.

Soil and Water

Crocus bulbs grow best in well-drained and even slightly dry soil. Poor drainage and soggy soil is problematic. If you have clay soil, add soil amendments. Mix sand, peat moss, and well-aged compost with a neutral pH into the soil at planting time.

Crocuses usually don’t need watering, as their growth period is during a time of sufficient natural precipitation in the late winter and early spring.

Fertilizing

Generally, crocuses don’t need a lot of fertilizer but they benefit from a balanced complete fertilizer after planting (never added to the planting hole but scattered afterwards), then again in the spring as soon as their sprouts emerge, and a third time after the bloom when they die back.

Planting Instructions

  • Plant crocus corms 3 to 4 inches deep (with the pointy end up). After planting, water well.
  • Plant bulbs in groups or clusters rather than spacing them in a single line along a walkway or border. Single flowers get lost in the landscape. Plant a few inches apart, and plant in groups of 10 or more.
  • Consider planting crocuses in lawns and meadows where they can form carpets, or mass them in the front of flower beds along the edge.
  • Plant taller spring-flowering bulbs and shrubs behind the early bulbs for color contrast.

Pruning

After the crocus blooms, allow the foliage to remain in the garden or lawn until it turns completely yellow. During this time foliage produces nutrients that sustain the bulb for the next growing season. Delay mowing a lawn embedded with crocus until the plant’s foliage turns fully yellow. In some areas, this means delaying the first lawn mowing until mid- to late June.

Potting and Repotting Crocus

Crocuses are not suitable for growing in containers. The corms need consistently cold winter temperatures to develop good root systems and grow foliage and flowers in the spring. In containers, unlike in garden soil, they are exposed to temperature fluctuations and cycles of freezing and thawing, regardless of the size of the container.

Propagation

Crocuses are best propagated by division when they are getting too crowded. This can be done every three to four years, or as needed. As crocuses die back after their bloom, mark the location so you know where to dig them in the fall. Using a shovel, dig up the corms, which may range in size from large to tiny offsets. All of the corms can be planted except bruised, dead, and diseased corms, which should be discarded. Transplant the corms in a new location as described above.

Pests and Diseases

Squirrels and chipmunks are the biggest danger to crocuses; these critters are ready to dig in as soon as you have planted your crocuses. One option is to plant a lot of crocuses to beat their appetite. You can also plant the crocuses as late as possible in the fall, just before the ground freezes, to decrease the chance of critters digging up the corms. Another option is to cover the planting area with fine chicken wire or hardware cloth after planting and remove it in the spring when the crocuses start to sprout

III. Uses and Benefits 

The corms of crocuses have been used as foodstuffs in Syria. The carotenoids found in the styles of Crocus species, particularly C. sativus have been shown to inhibit cancer cell proliferation, and have led to interest in potential pharmaceutical applications.

Common Crocus Details

Common name Common Crocus, Dutch Crocus, Dutch Crows, Species Crocuses
Botanical name Crocus
Plant type Bulb
Hardiness zone 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, 7a, 7b, 8a, 8b
Growth rate Fast
Height 0 ft. 2 in. - 0 ft. 6 in.
Width 0 ft. 2 in. - 0 ft. 6 in.
Sunlight Full sun (6 or more hours of direct sunlight a day)
Soil condition High Organic Matter
Flower color Gold/Yellow
Leaf color Gray/Silver