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When to plant crocuses in Idaho Falls: 14 September – 14 November

In Idaho Falls, crocus: plant from 14 September to about 14 November.

Bulbs are best planted early in the window: late-planted bulbs may flower later or less well. Late planting works only while the soil can be dug. Mulch after planting.

The date is about two weeks before the average daily temperature here falls below 0 °C (ten years of weather): an estimate, not the day the ground freezes, and a cold spell can freeze it earlier. Sources: Iowa State University Extension, Wisconsin Horticulture Extension, UNH Extension, RHS, how the ground freezes (NRC Canada, CBD-26).

Crocus in Idaho Falls: soil, season and weather

Nights then average below 0 °C in November–March; the coldest, January, averages -9.4 °C.

Planting14 September – 14 November
First autumn frost14 October
Coldest nightsJanuary, -9.4 °C
Soil back at 1 °C in spring7 March
Daylight12:36 on 14 September
Daylight at the winter solstice8:57

The same dates in Idaho Falls hold for Garlic, Tulip, Daffodil and Hyacinth.

Crocus in Idaho Falls: depth, winter cold, pests and pets

Plant Dutch crocuses (Crocus vernus) about 12 cm deep and 9 cm apart; smaller species go 7–10 cm deep (RHS).

In Idaho Falls the average daily temperature stays at 10 °C or lower for about 29 weeks a year (our estimate from ten years of monthly weather). For this bulb Wisconsin Horticulture Extension gives a cold period of 15–17 weeks at about 2–10 °C. The winter here gives that in the ground, so the bulbs need no pre-chilling.

Crocuses multiply on their own (they naturalise); in a lawn, hold off mowing until their leaves die back (RHS).

Birds, squirrels and rodents damage crocuses; planting under metal mesh may reduce losses (RHS). Spring crocus gives dogs and cats vomiting and diarrhoea; do not confuse it with autumn crocus (Colchicum), which is very toxic (Pet Poison Helpline).

Sources: RHS, Wisconsin Horticulture Extension, Pet Poison Helpline.

Crocus in nearby cities

Around Idaho Falls, Helena is 11 days earlier and Boise 13 days later.

CityDistanceDateDifference
Salt Lake City305 km26 September – 23 December12 days later
Boise336 km27 September – end of December13 days later
Helena345 km3 September – 5 November11 days earlier
Billings377 km14 September – 23 Novembersame day
Missoula406 km6 September – 12 November8 days earlier
Elko425 km13 September – 15 November1 day earlier

Where to buy crocus for planting in Idaho Falls

Planting stock goes into the ground from 14 September to about 14 November; buy it before that. Within 15 km of Idaho Falls OpenStreetMap lists 4 garden centres, 3 farm-supply shops, 2 plant nurseries, 2 markets and 1 farm shop (collected 28 October 2026).

Places: © OpenStreetMap contributors, ODbL.

Questions

When to plant crocuses in Idaho Falls?

In Idaho Falls, crocus: plant from 14 September to about 14 November. Bulbs are best planted early in the window: late-planted bulbs may flower later or less well. Late planting works only while the soil can be dug. Mulch after planting.

When is the last spring frost in Idaho Falls?

Last spring frost around 11 May, first autumn frost around 14 October.

Other crops in Idaho Falls, with their dates