Bulb · Asparagaceae
Siberian Squill
Scilla siberica
Plant the bulbs once and a low sheet of deep blue bells rises again every spring.
Full sun
Every 7–14 days
USDA 2–8
3–6 in · 8–15 cm
Overview
Siberian squill opens some of the first flowers of the year, its deep blue, bell-shaped blooms nodding on slim stems in early spring just after the snowdrops. Each plant sits low to the ground, only 3 to 6 inches (8 to 15 cm) tall, so a planting reads as a close, ankle-high wash of blue rather than anything that rises to meet the eye. Massed under trees or along a path, the small nodding bells run together into an unbroken blue.
Below the flowers, the low foliage carries the plant through spring before it yellows and dies back. The bulbs beneath are extremely cold hardy, unbothered by winter lows of -40°F (-40°C), and they multiply into thicker and thicker clumps. Left to itself, squill fills in by seed and by offset bulbs until the blue spreads well past its first patch, into lawn and woodland, and it is treated as invasive in parts of the US.
For all the softness of those little bells, the plant is poisonous through and through, and the bulb hidden below is the most toxic part of all. Every piece of it carries the same danger, so it does not belong where pets graze or small children dig. Given the right spot, the low blue returns and deepens season after season.
Care
The short version: the bulbs go 2 to 3 inches deep in fall, into sun or part shade and well-drained soil, drinking in medium moisture as the blue bells rise in spring and then resting dry through summer, with deadheading to keep the low blue from spreading too far.
Light
The deep blue flowers color up most fully in full sun, though the plant carries on in partial sun or partial shade. Because those bells open before the trees leaf out, even a shaded summer spot pours light onto them while they bloom.
Water
Through spring, while the foliage is green and the bells are open, the plant takes medium moisture from the soil. Once the leaves yellow and fold down, the bulb rests underground and wants almost none, and standing water is what turns a firm bulb soft and rotten.
Soil
The bulb sits best in average, well-drained soil, indifferent to pH. Sharp drainage keeps the underground bulb firm, and that matters most across the dry summer months when it lies dormant.
Temperature
Underground, the bulb is remarkably tough, hardy through zones 2 to 8 and unharmed by lows of -40°F (-40°C). The blue bells rise in the cool of early spring, and the whole plant retreats to its bulb once the air warms past about 75°F (24°C).
Humidity
The air around the leaves and flowers can be as dry or damp as it likes, since humidity leaves the plant unmoved. What the bulb needs instead is soil that dries out during its summer rest.
Feeding
The bulb draws almost all it needs from average soil. A thin yearly topdressing of compost or a balanced bulb fertilizer worked over the surface in fall or early spring is plenty, and heavier feeding shows up nowhere in the plant.
Pruning
Nothing here calls for the shears. The green leaves should be left to yellow and collapse on their own after the bells fade, feeding the bulb below, and only the spent flower heads are snipped to hold back the heavy seeding.
Repotting
The bulbs sit quietly underground for years. The signs that it is time to dig are thinner bloom in a tight clump or a mass of bulbs shouldering up through the soil surface.
Size & spacing
Every plant stays small, a mound of foliage and bells just 3 to 6 inches (8 to 15 cm) tall and about as wide. The bulbs are tucked 2 to 3 inches deep in fall and spaced apart, so the separate tufts eventually close into one low sheet of blue.
When to plant
Squill keeps a tight early-spring calendar. The bulbs go in through fall, wait out the cold underground, and push up their nodding blue bells around April, close behind the snowdrops.
Northern hemisphere
Southern hemisphere
Typical months for a temperate climate: start earlier in warm zones, later where spring frosts linger.
- Plant: Plant bulbs in fall, 2-3 inches deep
- Harvest: Blooms in early spring (around April), shortly after snowdrops
Hardiness
USDA hardiness zones: 2–8
Temperature: down to -46°C
Troubleshooting
For all its ease, squill shows a few clear physical signs when something is off, and they trace to wet soil, one bulb pest, and its own spreading. Look closely at the bulbs, the foliage, and the edges of the patch, and match what you find below.
Soft, browning bulbs and a slumping crown
A firm bulb gone soft and a crown that slumps into the soil is crown and bulb rot, born of waterlogged ground rather than any sprayable disease. Squill cannot bear a wet seat, least of all while the bulb rests through summer. Dig one up and you will find soft, brown, foul-smelling tissue at the base, so discard every spongy bulb and move the rest to ground that drains sharply.
Fix:
- Remove and discard affected bulbs
- Improve drainage or move planting to a better-drained site
- Reduce watering, especially during dormancy
Hollowed bulbs and thin, failing shoots
A bulb that pushes up crooked or not at all often hides the work of the narcissus bulb fly. Its larva eats out the core and leaves a hollow shell packed with crumbly brown frass. Cut one open and a single fat, cream-colored maggot usually sits inside, so destroy every infested bulb and break up the soil to turn the pupae out.
Fix:
- Dig and destroy infested bulbs
- Cultivate soil to expose pupae
Blue flowers appearing well past the original patch
Fresh blue turning up in the lawn and at the wood's edge marks squill as an aggressive self-seeder that also throws offset bulbs. The little colonies knit outward year on year, and parts of the US label the plant invasive. Mow or deadhead the bells before seed forms, lift and thin the crowded clumps, and keep it back from wild ground.
Fix:
- Mow or deadhead while in bloom to remove seed heads before seed sets
- Dig and thin clumps before seeds mature
- Compost removed material at temperatures above 130 degrees F
Toxicity
Behind the delicate blue bells sits a genuinely poisonous plant. Every part holds cardiac glycosides, and the plump bulb underground carries the most, so eating any of it can bring drooling, vomiting, and cramping, and in quantity a dangerously slow or uneven heartbeat. Keep it away from pets, livestock, and children, and reach a vet or poison control at once if any is swallowed.
Toxic to
Cats · Dogs · Horses · Rabbits · Livestock · Birds · People
Cats Severe
A cat that bites into any part soon starts drooling and bringing it back up. The pale bulb holds the densest load of cardiac glycoside, so a full mouthful can throw the heartbeat into disarray, which is an emergency.
Dogs Severe
Dogs go for the bulb, digging it up and crunching into the most toxic part of the plant. Drooling, vomiting, and loose stool come first, and a slow or ragged heartbeat follows once a large amount is down.
Horses Severe
In a horse, the same cardiac glycosides bring on colic and leave the animal dull-eyed and unsteady on its legs. A big enough mouthful can throw the heartbeat off, a grave thing in a body that large.
Rabbits Toxic
For a rabbit, squill is no safe nibble. The bulb and the leaves alike churn the gut and, in any real amount, reach the heart, so the plant has to stay out of reach.
Livestock Toxic
Cattle, sheep, and goats can take poison from cropping the leaves or turning bulbs up out of the ground. The signs are drooling, a roiled gut, and a heartbeat gone irregular, so wall the patch off from pasture.
Birds Toxic
In birds the cardiac glycosides taint every part, down to the bulbs that backyard hens scratch loose. Keep poultry and pet birds well off the plantings.
People Caution
None of this plant is edible in any part. A swallowed piece brings mouth pain, nausea, vomiting, and cramping, and the bulb in quantity drags the heartbeat slow or crooked, so keep prying children away and call poison control if any goes down.
Keep bulbs and plants away from pets and children; wear gloves when handling, as sap can cause minor skin irritation in susceptible individuals.
Helpline numbers
United States
ASPCA Animal Poison Control: (888) 426-4435 (fee applies)
Poison Control: (800) 222-1222
Canada
Poison Centres: 1-844-764-7669
Varieties
There is not much variation to see here. Beyond the wild species, one named form turns up most, and a close look at size and color tells the two apart.
Spring Beauty
It wears the same form as the wild species but on a slightly larger frame, holds its bells for a longer spell, and colors up in a darker, more saturated blue.
Scilla siberica (species)
The wild species throws up 3 to 4 slender scapes, and from each hang 1 to 3 nodding, bell-shaped flowers of deep blue, their centers pricked with blue anthers.
Companions
Squill pairs best with the other earliest bulbs that bloom alongside it and naturalize the same way, building a layered carpet of late-winter and early-spring color.
Plant near
Galanthus (snowdrops): Both are very early spring bulbs that bloom in sequence and naturalize well together in drifts.
Crocus: Similar early-spring bulb that can be naturalized in lawns and beds alongside squill for layered bloom.
How to propagate
Making more squill is almost automatic, since the bulbs pile up on their own underground. A gardener can split those thickening clumps or set fresh bulbs, or simply let the ripe seed scatter.
Offsets & pupsEasy
Lift and separate dormant bulbs after foliage dies back · One growing season
The easiest increase is the crop of small offset bulbs the plant clusters around itself. Once the leaves have yellowed and the bulbs lie dormant, lift a packed clump and break the offsets away by hand. Tucked back into the soil, they take hold within one growing season.
Bulbs & cormsEasy
Plant bulbs 2-3 inches deep in fall · Blooms the following spring
A bag of dry bulbs is the simplest start of all. Press them 2 to 3 inches deep in fall, cover them over, and the blue bells appear the next spring. The bulbs are firm and extremely cold hardy, so even a savage winter leaves them sound.
SeedEasy
Self-sows in spring as seed matures · Several years to flowering size
Left alone, squill scatters ripe seed across the soil in spring as the pods split open. That loose seed is exactly what feeds its aggressive naturalizing. The seedlings creep toward flowering size over several years, making seed the slowest way to a blue patch.
Myths
Those pretty little blue bells make Siberian squill a harmless, pet-safe bulb.
The soft look is deceiving, since every part carries cardiac glycosides and the plant rates as a high-severity poison. Eating it brings vomiting, diarrhea, and a lowered heart rate, and a real dose can be fatal. Keep the bulbs and plants away from pets and children.
A bulb this small and low surely stays in the patch where it was set.
In fact the blue creeps outward fast, carried by self-sown seed and by offset bulbs from beds into lawns and woodlands. It is considered invasive in parts of the US, so cut the seed heads and keep it clear of wild ground.