Siberian Squill: Blue Harbingers of Spring

Siberian squill (Scilla siberica) is one of the first spring-flowering bulbs to bloom in spring.  Its deep blue flowers are a sure sign that spring has arrived.  In central Iowa, Siberian squill typically blooms in early to mid-April.  Flowering normally lasts for 10 to 14 days.
Siberian squill is a member of the asparagus (Asparagaceae) family.  It is native to southwestern Russia, the Caucasus, and Turkey.
Mature plants consist of 3 to 4 strap-like leaves that are approximately 6 inches long and ½ inch wide.  One or more flower stalks are produced in the center of each leaf cluster.  Flower stalks are topped with 1 to 3, nodding, bell-like, deep blue flowers.  The flowers have a pleasant flagrance and are attractive to various types of bees.  (On the other hand, deer, rabbits, and other herbivores seldom browse on Siberian squill as the plants contain toxic alkaloids.)  Small, oval seed capsules form after flowering.  The capsules are initially green.  At maturity, the capsules turn purple, split open, and release their seeds onto the ground.  Siberian squill spreads or naturalizes by seeds and bulb offsets.  Siberian squill bulbs are small (up to 8 to 10 centimeters in circumference) and enclosed within a purple, paper-like covering.
Siberian squill is a tough, easy to grow, low maintenance plant.  It can be grown in full sun to partial shade.  Plants require a well-drained soil as crown rot can be a problem in wet, poorly drained sites.  Siberian squill is extremely cold hardy.  Snow or freezing temperatures in late winter/early spring have little effect on plants.
Siberian squill is established by planting bulbs in fall.  Suitable planting sites include rock gardens, the fronts of beds and borders, in groups with other early spring-flowering bulbs (such as crocuses, snowdrops, and early daffodils), and in masses under trees and shrubs.  Plant bulbs 3 to 4 inches deep and 2 to 3 inches apart.  Plant in masses of 100 or more bulbs for the greatest visual impact.  A small number of Siberian squill cultivars are available.  Plants and flowers of 'Spring Beauty' are slightly larger than the species.  'Alba' has pure white flowers.
Siberian squill spreads easily by seed and bulb offsets.  Because of concerns that Siberian squill can be invasive, locations at the edges of natural woodland areas would be inappropriate planting sites.  If these plants establish in areas they are not wanted, they can be managed in several ways. Plants can be mowed during or just after flowering to reduce seed production.  Dig bulbs when they emerge in spring and remove them from the area.  Plants can be smothered under a layer of black plastic for at least one summer or treated with a non-selective herbicide.  Keep in mind that utilizing a non-selective herbicide and smothering with plastic will kill all plants in the area.  Always follow all label directions when applying any herbicide.  A combination of these management techniques would be most effective as plants are difficult to eradicate once established.

A hillside of Siberian Squill
A hillside of Siberian Squill on the Iowa State University campus.
A hillside of Siberian Squill
Siberian squill along a path on the ISU campus.

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