Flowering bulbs are among the most popular and carefree plants for the home gardener. They are divided into two types: hardy or spring flowering bulbs such as tulips, crocus, daffodils and hyacinth that can withstand and need cold winters; and tender or summer flowering bulbs such as anemone, gladiolus and caladium that cannot survive cold temperatures and are planted after danger of frost is past for blooming in the summer. Planting times for each vary by the climate in the area where they will be planted.
Climate of Western Washington
The Pacific Northwest Coast ecoregion comprises most of Western Washington. This climate features high precipitation–from 60 to 240 inches–falling mostly as rainfall from November through April. The area is also known for mild winters and cool, foggy summers. Western Washington lies within the USDA Hardiness Zone 8. The Sunset climate zones offer more precise climate zone information for specific areas in Western Washington.
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Spring Flowering Bulbs
Spring flowering bulbs require at least 11 to 13 weeks of cold (below 45 degrees Fahrenheit) for their roots to develop. Although you can plant them earlier or later as long as the ground is not frozen, the ideal time to plant spring flowering bulbs in Western Washington is in November and December, according to the Washington State University Extension. According to the International Bulb Society, a good rule of thumb is to plant them six weeks before the ground freezes.
Summer Flowering Bulbs
Treat summer flowering bulbs the same way you would treat summer annuals, planting them after the threat of frost is past. Average last frost dates vary for Western Washington from March 25 for Vancouver, April 6 for Seattle, April 26 for Longview and April 30 for Olympia. Not all plants considered summer flowering bulbs are actually bulbs–some are tubers, corms or rhizomes. So they may look different and need to be positioned in the soil differently from the traditional onion-shaped bulbs, but essentially they are grown the same way. The best time for planting most summer bulbs is when the soil warms to about 60 degrees Fahrenheit. The exact planting time varies by the hardiness of the specific plant, so consult package directions. You can monitor soil temperature yourself, but a good resource for this information is the Washington Agricultural Weather Network at Washington State University.
Summer flowering bulbs need to be lifted and stored during the winter in zones where they cannot survive the winter. Western Washington has borderline climate for most summer flowering bulbs, so consult your local garden center to see if you may be able to winter them in the ground if they are well mulched and in a protected place.