How often to water devil's trumpet in California
In July on the north-central coast, established devil's trumpet in loam needs a deep soak only about once a month or less: about 1.5 gallons each time for a plant 2 feet across. Devil's trumpet is a sprawling, shrub-like perennial in the nightshade family, often grown as an annual. It reaches 3 to 4 feet tall and wide. Huge upward-facing trumpets in white or violet open in the late afternoon from midsummer to frost and fade by the next midday. It likes rich, well-drained soil and full sun to part shade, and every part of it is highly toxic.
How often to water devil's trumpet, 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 2 to 3 inches down around the base signals that devil's trumpet needs a soak, especially during bloom
- Large downy leaves wilting into the evening can indicate a dry root zone in summer heat
- Flower buds stalling or dropping in a hot, dry spell can accompany thirst
- Yellowing leaves and a soft stem base over soggy soil can indicate overwatering or poor drainage
- Fine webbing, sticky leaves or white specks point to spider mites, mealybugs or whiteflies rather than water stress
How to water it
- Water at the base of the plant with drip or a watering can, keeping the downy leaves dry
- Moisten the soil about 8 inches deep, then let the top couple of inches dry before the next watering
- Plant in rich, well-drained soil in full sun or part shade, spacing plants about 3 feet apart
- Stake or support the sprawling stems so they stay off damp ground
- Remove spent flowers before the spiny pods ripen to limit self-sown seedlings
Through the seasons
Keep new plants evenly moist until they root in. Established plants take deeper watering through summer, when they flower from midsummer until frost. In mild areas the plant can persist as a perennial, while frost ends it elsewhere. Its seeds can lie dormant in the soil for years. WUCOLS rates devil's trumpet very low water on the north-central coast and moderate water on the south coast. WUCOLS has not evaluated it for the Central Valley, South Inland, the high desert or the low desert. Winter rain covers resting plants on the coast.
In pots
Devil's trumpet grows well in a large container on a patio, where its evening flowers are easy to enjoy. Use a rich, well-drained mix and a pot with drainage holes. Check the mix an inch or two down every few days in summer heat and water when it is dry. Water until excess drains, then empty the saucer. Keep the pot out of reach of children and pets, since all parts are highly toxic. In fall, cut it back and overwinter it indoors in a sunny window, watering sparingly.
- A year
- no figure
- Reference
- Sacramento climate table
- Counts
- Plant need, before sprinkler losses
WUCOLS lists Devil's Trumpet as not evaluated for the Central Valley zone, so no monthly figure is computed here.
Monthly water need by climate zone
Devil's Trumpet: 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 | – | 0.78 | – | – | – |
| Feb | 0.05 | – | 0.81 | – | – | – |
| Mar | 0.09 | – | 1.15 | – | – | – |
| Apr | 0.12 | – | 1.4 | – | – | – |
| May | 0.15 | – | 1.61 | – | – | – |
| Jun | 0.16 | – | 1.74 | – | – | – |
| Jul | 0.16 | – | 1.98 | – | – | – |
| Aug | 0.15 | – | 1.86 | – | – | – |
| Sep | 0.12 | – | 1.49 | – | – | – |
| Oct | 0.09 | – | 1.15 | – | – | – |
| Nov | 0.05 | – | 0.84 | – | – | – |
| Dec | 0.03 | – | 0.65 | – | – | – |
| Year | 1.2 | – | 15.5 | – | – | – |
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 devil's trumpet. 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
Alpine Sea HollyEryngium alpinumnot 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 ratingTurn this into minutes on your water days
Every city page has a calculator that takes devil's trumpet, 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 devil's trumpet need per day?
In July on the north-central coast, established devil's trumpet 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 devil's trumpet change across California?
Yes. WUCOLS rates devil's trumpet separately for each of the six California climate zones: very low water in the North-Central Coastal zone, not evaluated in the Central Valley zone, moderate water in the South Coastal zone, not evaluated 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.
Is devil's trumpet poisonous?
Yes. All parts are highly toxic if eaten, including the seeds, and it is a danger to children, cats, dogs and horses. Plant it out of reach of children and pets, and wash your hands after handling it.
Is devil's trumpet the same as angel's trumpet?
Not quite. Datura flowers like these face upward, while the related Brugmansia, also called angel's trumpet, has hanging flowers. Check the flower direction to tell them apart.
When do devil's trumpet flowers open?
Each flower unfurls in the late afternoon or evening from a cigar-shaped bud and fades by the next midday. Cloudy days can open them earlier. Blooming runs from midsummer to the first frost.
Will devil's trumpet come back from seed?
Yes. It self-sows if flowers are not removed, and its seeds can stay dormant in the soil for many years. Deadhead to prevent seedlings, especially where children or pets play.
Can you overwater devil's trumpet?
Yes. It prefers moist but well-drained soil, and soggy ground can harm the stem base and roots. Let the top couple of inches dry between waterings.
More plant watering guides
Sources
- WUCOLS IV plant water use classification for Datura metel (fastuosa), 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