When to plant tulips in Missoula: 6 September – 12 November

Tulip in Missoula: depth, winter cold, pests and pets

Plant tulips at a depth of two to three times the bulb’s height, at least twice the bulb’s width apart, pointed end up (RHS). Where winters are very cold, tulips benefit from deeper planting to protect them from frost penetrating the soil (RHS); here the average daily temperature drops below 0 °C in winter.

In Missoula the average daily temperature stays at 10 °C or lower for about 31 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.

Border tulips often fail to flower in their second year if left in the ground, so many gardeners grow them for one spring and plant fresh bulbs each autumn; Darwin hybrid and Kaufmanniana tulips reflower more reliably (RHS). Soils that stay wet in summer make reflowering difficult (RHS): in Missoula the three warmest months bring about 95 mm of rain together.

Grey squirrels often dig up tulip bulbs: lay chicken wire over the bed until the leaves appear, or plant daffodils among them, which squirrels avoid (RHS). Tulips are toxic to dogs, cats and horses, the bulb most of all (ASPCA).

Sources: RHS, Wisconsin Horticulture Extension, ASPCA.