Spring-flowering bulbs are a unique group of pollinator-friendly flowers that have been a staple of ornamental gardening in Europe and the U.S. for many years. These fall-planted, flowering plants are low-care additions to our landscapes, and they light up the spring garden before many other plants wake up and come into flower, providing essential early season nectar for bees.
Necessities for Successful Spring-Flowering Bulbs
Spring-flowering bulbs depend on two climatic factors to do well in our landscapes:
- Cold winter temperatures — sufficient hours below 40° F (Seek out low chill or pre-chilled bulbs for Zones 9 & 10).
- Good winter and spring moisture to bring them back into active growth and flowering.
After blooming, spring-flowering bulbs have already adapted to hot, dry summer conditions by going summer dormant (shedding their foliage by early summer or earlier) and resting underground as a "sleeping" bulb.
Other Maintenance For Long Term Success
When fall-planted bulbs receive sufficient moisture and cold temperatures over the winter and during early spring months, there is little else we need to do to keep them happy. They only need nutrients and space to grow.
- Feed the soil where bulbs are growing with organic and natural fertilizers in mid-spring.
- Divide bulb clumps that are blooming sparsely. Dig them up in the fall and pull apart tightly clustered bulbs; then re-plant after enriching their soil.
How Much Moisture is Enough?
Much attention has been directed toward drought conditions this summer in California and the Pacific Northwest. And gardeners want to know if spring-blooming bulbs are good waterwise (xeric or drought resistant) plants for drier growing conditions. The answer depends on where you are in the U.S. For many parts of the country that get 30" or more of precipitation annually, bulbs generally will not need any additional irrigation, unless winter snow cover is thin and spring conditions are unusually dry.
In the Western U.S. where there isn't as much rain and snow (20-25" or less), most bulbs will need some supplemental irrigation.
- In higher elevation areas where winter/early spring snows leave the soil moist, bulbs will only need extra water if conditions are unusually dry.
- Where snow coverage is unpredictable.and spring rains erratic, it is essential that beds where bulbs are planted be watered every week to two weeks to keep the soil moist to a depth of 6-12".
Mulching is an essential technique for growing bulbs in drier climates. A nice 1-2" deep blanket of coarse compost, composted bark, or other non-gravel material applied in late fall will conserve soil moisture and enrich the soil as it decomposes.
Fall Bulb Varieties That Tolerate Drier Conditions
For landscapes that have limited water available for irrigation, the spring flowering bulbs listed below, along with any of the Starflowers (Ipheon), are the most tolerant of dry soil. In areas that get 15-20" or less of annual precipitation, even these more xeric bulbs will need supplemental spring watering of 2" or more per month once the soil thaws.
- Grape Hyacinth
- Ornamental Onions (Allium)
- Cammas Lily
Camassia quamash bulbs like it moist during the spring (planted in low spots or moist areas) and bone dry over the summer. It is an excellent xeric species for the Pacific Northwest where it is native.
- Dwarf Iris
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