How often to water alpine sea holly in California
In July on the north-central coast, established alpine sea holly in loam needs a deep watering about every 9 days: about 1.5 gallons each time for a plant 2 feet across, about 1.1 gallons a week. Alpine sea holly is an upright perennial about 3 feet tall with heart-shaped, glossy dark green leaves at its base. In summer, cone-like flower heads sit inside a ruff of vivid blue, spiny bracts on blue stems, and pollinators visit them. It needs full sun and fairly dry, well-drained, poor to moderately fertile soil, with no winter wet.
How often to water alpine sea holly, 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: established roots fill the top 1 foot of soil, and you water again when that soil has dried halfway. Loam soil holds about 1.5 inches of water per foot. Water the whole area the plant covers, and skip a watering after a good soaking rain.
How to tell it needs water
- Soil dry 3 inches down beside the clump during summer bloom means alpine sea holly can take a deep drink
- Flower stems drooping in a long, hot dry spell can indicate thirst
- Basal leaves yellowing and the crown softening point to wet soil and root rot
- White powder on leaves points to powdery mildew rather than water
How to water it
- Water deeply but rarely, at the base of the clump
- Soak several inches down, then let the soil dry well
- Plant in full sun in fairly dry, well-drained, lean soil
- Avoid rich soil and heavy clay that stays wet
- Leave the seed heads standing over winter
Through the seasons
Water a new plant regularly until it settles. After that, it has good drought resistance and needs only occasional deep water in dry summers. It flowers in summer, and the spiny seed heads stand through winter, when wet soil is the greatest risk. On the north-central coast, WUCOLS rates alpine sea holly moderate water. WUCOLS marks it as not suited to South Inland, and has not evaluated it for the Central Valley, the south coast, the high desert or the low desert.
In pots
Alpine sea holly can grow in a deep pot with a gritty, free-draining mix. Water when the top two inches are dry, then let all excess drain away. In summer heat, a pot may need water every few days. Never leave it in a saucer of water. Keep the pot in full sun. In winter, water very little, and move the pot out of steady rain if the mix stays soggy.
- A year
- no figure
- Reference
- Sacramento climate table
- Counts
- Plant need, before sprinkler losses
WUCOLS lists Alpine Sea Holly as not evaluated for the Central Valley zone, so no monthly figure is computed here.
Monthly water need by climate zone
Alpine Sea Holly: gallons per square foot per month, by WUCOLS climate zone
| Month | N. Coast | C. Valley | S. Coast | S. Inland | Hi Desert | Lo Desert |
|---|---|---|---|---|---|---|
| Jan | 0.37 | – | – | – | – | – |
| Feb | 0.53 | – | – | – | – | – |
| Mar | 0.87 | – | – | – | – | – |
| Apr | 1.18 | – | – | – | – | – |
| May | 1.46 | – | – | – | – | – |
| Jun | 1.61 | – | – | – | – | – |
| Jul | 1.61 | – | – | – | – | – |
| Aug | 1.49 | – | – | – | – | – |
| Sep | 1.24 | – | – | – | – | – |
| Oct | 0.87 | – | – | – | – | – |
| Nov | 0.47 | – | – | – | – | – |
| Dec | 0.31 | – | – | – | – | – |
| Year | 12 | – | – | – | – | – |
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 16
Rated not evaluated in the Central Valley, like alpine sea holly. Plants that drink alike can share one valve and one schedule.
Lilyleaf LadybellsAdenophora liliifolianot rated, Central Valleyno Central Valley rating
ArnicaArnica montananot rated, Central Valleyno Central Valley rating
Frilly BergeniaBergenia ciliatanot rated, Central Valleyno Central Valley rating
Cabbage on a StickBrighamia insignisnot rated, Central Valleyno Central Valley rating
Basket PlantCallisia fragransnot rated, Central Valleyno Central Valley rating
Forest SedgeCarex sylvaticanot rated, Central Valleyno Central Valley rating
Umbrella DracaenaDianella ensifolianot rated, Central Valleyno Central Valley rating
Rusty FoxgloveDigitalis ferrugineanot rated, Central Valleyno Central Valley rating
Big-Flowered FoxgloveDigitalis grandifloranot rated, Central Valleyno Central Valley rating
Woolly FoxgloveDigitalis lanatanot rated, Central Valleyno Central Valley rating
Sunset FoxgloveDigitalis obscuranot rated, Central Valleyno Central Valley rating
Male FernDryopteris filix-masnot rated, Central Valleyno Central Valley rating
Purple SpurgeEuphorbia dulcisnot rated, Central Valleyno Central Valley rating
Queen of the MeadowFilipendula ulmarianot rated, Central Valleyno Central Valley rating
DropwortFilipendula vulgaris (Filipendula hexapetala)not rated, Central Valleyno Central Valley rating
GentianGentiana scabra procumbensnot rated, Central Valleyno Central Valley ratingTurn this into minutes on your water days
Every city page has a calculator that takes alpine sea holly, 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 water does alpine sea holly need per day?
In July on the north-central coast, established alpine sea holly needs about 0.2 gallons a day for a plant 2 feet across and about 0.7 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 alpine sea holly change across California?
Yes. WUCOLS rates alpine sea holly separately for each of the six California climate zones: moderate water in the North-Central Coastal zone, not evaluated in the Central Valley zone, not evaluated in the South Coastal zone, not suited to this region 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.
Does alpine sea holly like poor soil?
Yes, it grows best in poor to moderately fertile, fairly dry soil. Skip compost and fertilizer. Drainage matters most.
Why did my sea holly rot?
Wet soil, especially in winter, rots its roots. Plant it in well-drained soil in full sun. Water less.
Should I cut back sea holly after flowering?
You can, but the seed heads are attractive and usually left over winter. Cut them in spring. Water sparingly while it rests.
Does alpine sea holly attract pollinators?
Yes, bees and other pollinators visit its flowers. It suits gravel and wildlife gardens. It also makes a good cut flower.
What pests bother alpine sea holly?
Slugs and snails can damage young growth. Powdery mildew may appear. Root rot follows wet soil.
More plant watering guides
Sources
- WUCOLS IV plant water use classification for Eryngium alpinum, 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