How often to water giant scilla in California
In July in the Central Valley, established giant scilla needs about 0.2 gallons a week for a plant 2 feet across. Giant scilla is a bulb from the western Mediterranean that forms a low rosette of strap-shaped leaves in fall. In spring, round-topped heads packed with tiny, deep blue-violet, star-shaped flowers rise on short stems and last for weeks. Bulbs multiply slowly into clumps. It is poisonous if eaten, and it prefers a dry summer rest.
How often to water giant scilla, month by month
Type your city above and the days between waterings and the gallons appear here, worked out from your city's climate table. Or read the figures by climate zone further down.
How this is worked out: the plant’s WUCOLS rating times your city’s climate for the month, over the area the plant covers. Skip a watering after a good soaking rain.
How to tell it needs water
- Soil dry 3 inches down beside the leaves in early spring means giant scilla could use water to bloom well
- Leaves yellowing after bloom on a dry site is the normal start of summer dormancy
- Soft, rotting bulbs in a wet summer bed point to too much water
- Flower heads coming up small after a dry spring can follow too little moisture
How to water it
- Water in spring if rain falls short, since it needs moisture to bloom well
- Let it go dry in summer while dormant
- Plant in full sun to part shade in lean, gritty, well-drained soil
- Leave clumps undisturbed to multiply
- Keep children and pets from eating the bulbs
Through the seasons
New leaves emerge after the first fall rain. Keep the soil lightly moist in winter and spring if rain is short, since it needs spring moisture to bloom well. After flowering it goes dormant if kept dry, which it prefers, though with steady water it can stay nearly evergreen. WUCOLS rates giant scilla very low water on the north-central coast, in the Central Valley and in South Inland. The south coast carries a low water rating. WUCOLS has not evaluated it for the high desert or the low desert.
In pots
Giant scilla grows well in a wide pot, where its blue flower heads show at eye level. Use a lean, gritty, well-drained mix. After fall growth starts, water when the top couple of inches dry. In spring, keep the mix lightly moist through bloom. After flowering, let the leaves fade and keep the pot dry through summer. Never let the bulbs sit in water.
- A year
- 1.71 gal per sq ft
- Reference
- Sacramento climate table
- Counts
- Plant need, before sprinkler losses
Monthly water need by climate zone
Giant Scilla: gallons per square foot per month, by WUCOLS climate zone
| Month | N. Coast | C. Valley | S. Coast | S. Inland | Hi Desert | Lo Desert |
|---|---|---|---|---|---|---|
| Jan | 0.04 | 0.04 | 0.31 | 0.08 | – | – |
| Feb | 0.05 | 0.07 | 0.32 | 0.09 | – | – |
| Mar | 0.09 | 0.11 | 0.46 | 0.13 | – | – |
| Apr | 0.12 | 0.15 | 0.56 | 0.16 | – | – |
| May | 0.15 | 0.21 | 0.64 | 0.2 | – | – |
| Jun | 0.16 | 0.25 | 0.69 | 0.23 | – | – |
| Jul | 0.16 | 0.27 | 0.79 | 0.25 | – | – |
| Aug | 0.15 | 0.24 | 0.74 | 0.23 | – | – |
| Sep | 0.12 | 0.18 | 0.6 | 0.19 | – | – |
| Oct | 0.09 | 0.12 | 0.46 | 0.13 | – | – |
| Nov | 0.05 | 0.06 | 0.33 | 0.09 | – | – |
| Dec | 0.03 | 0.03 | 0.26 | 0.07 | – | – |
| Year | 1.2 | 1.71 | 6.2 | 1.84 | – | – |
How this is worked out: the WUCOLS water rating for each zone times that zone’s climate for the month. A dash means WUCOLS does not rate the plant there. The figures are what the plant uses, before sprinkler losses.
Plants with the same water needs 2
Rated very low water in the Central Valley, like giant scilla. Plants that drink alike can share one valve and one schedule.
Turn this into minutes on your water days
Every city page has a calculator that takes giant scilla, your sprinkler type and the month, and gives the minutes per water day for that supplier's schedule. Or put it in a zone of the personal watering plan and get all twelve months printed.
Questions people ask
How much should I water giant scilla in summer?
In July, established giant scilla needs about 0.2 gallons in the Central Valley, 0.6 gallons on the south coast and 0.2 gallons in the South Inland zone each week, for a plant 2 feet across. Water deeply and let the top of the soil dry before the next watering. Skip a watering after a soaking rain.
How much water does giant scilla need per day?
In July in the Central Valley, established giant scilla needs about 0.0 gallons a day for a plant 2 feet across and about 0.1 gallons a day for a plant 4 feet across. Give it in deep waterings spread days apart rather than a little every day, so the whole root zone gets wet.
Does watering for giant scilla change across California?
Yes. WUCOLS rates giant scilla separately for each of the six California climate zones: very low water in the North-Central Coastal zone, very low water in the Central Valley zone, low water in the South Coastal zone, very low water in the South Inland zone, not evaluated in the High and Intermediate Desert zone, not evaluated in the Low Desert zone. The monthly table above shows how the same rating translates into different gallon amounts as reference evapotranspiration changes.
When does giant scilla bloom?
It blooms in spring, with dense heads of blue-violet flowers lasting several weeks. Spring moisture helps it bloom well. Leaves follow from fall.
Should I water giant scilla in summer?
It prefers a dry summer dormancy. Summer water is not needed and can rot bulbs in poor drainage. Resume when fall rains start.
Is giant scilla poisonous?
Yes, it is considered poisonous if eaten. Keep children and pets away from the bulbs. Wear gloves when dividing.
Does giant scilla spread?
Bulbs multiply slowly into clumps. Leave them undisturbed for a bigger show. Divide when crowded.
What soil does giant scilla need?
It wants lean, gritty, well-drained soil in sun to part shade. Rich, wet soil is a risk. Raised beds help.
More plant watering guides
Sources
- WUCOLS IV plant water use classification for Scilla peruviana (Scilla hughii), the University of California survey California agencies use for landscape plan reviewRead August 23, 2026 on wucols.ucdavis.edu
- Model Water Efficient Landscape Ordinance, adopted text and appendices, effective 2025-01-02 · monthly reference evapotranspiration per city, Appendix CRead August 23, 2026 on water.ca.gov/-/media/DWR-Website/Web-Pages/Programs/Water-Use-And-Efficiency/MWELO-Rulemaking/Final-MWELO-Text-and-Appendices_20250103.pdf
- UC Statewide IPM Program, irrigation scheduling using evapotranspirationRead September 30, 2026 on ipm.ucanr.edu/PMG/GARDEN/ENVIRON/evap.html
- Shaw and Pittenger, Landscape Irrigation System Evaluation and Management, UC Cooperative Extension, 2009Read September 30, 2026 on ucanr.edu/sites/default/files/2013-02/160836.pdf
- Pittenger, Water Management in Gardens and Landscapes, UC Riverside, 2017Read September 30, 2026 on ucanr.edu/sites/default/files/2017-03/258022.pdf