Our fall weather is very warm compared with other planting zones. In many other areas, spring-blooming bulbs are planted when temperatures have dropped to near freezing and the fall rains have soaked the soil.
We need to chill spring-blooming bulbs for several weeks starting in September in order to replicate cooler conditions. Buy or order spring-blooming bulbs soon so that the pre-chilled bulbs can be in the ground before Thanksgiving. If ordering online, let the shipper know your planting zones (Zones 8 and 9 in the Valley; Zone 7 in the foothills) and that you’ll be refrigerating the bulbs.
Local nurseries stock bulbs that are well-suited to our climate. Garden centers are a good place to buy generic bulbs in bulk. Pre-chilled bulbs produce bigger, longer-lasting flowers that should bloom in spring. (That’s why many bulbs planted in previous years bloom out of season here; our warm autumn soil temperatures trick them into blooming in fall or mid-winter.)
When choosing bulbs at the nursery or garden center, look for large, firm bulbs (give them a gentle squeeze) with no green sprouts at the tip. Place the bulbs into paper bags or thick plastic bags with a few holes punched in the sides (bulbs need a little air), label the bags and keep them in the vegetable drawer of the refrigerator.
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Tulips and hyacinths need more chill hours than daffodils, narcissus, snowdrops or snowflakes (leucojum) and grape hyacinths (muscari). Tulips and hyacinths are more heat-sensitive than other types and often rebloom for only one or two successive springs in our climate. Planting tulips and hyacinths a little deeper than normal in other areas will give them more soil cover to insulate them from our intense summer heat. The general rule for planting bulbs is to plant them at twice the depth of the length of the bulb. A 3-inch-long tulip or daffodil bulb should be planted at least 6 inches deep in most climate zones. Try planting your tulips and hyacinths about 8 inches deep for a few more years of rebloom.
If we’re lucky this year, we’ll get enough rain this fall to soak and soften the soil. If the drought continues, it’s going to be difficult to dig into hard-baked planting beds. Consider planting bulbs in containers in sterilized potting soil this year. Bulbs have very shallow roots and can be packed into fairly small pots as long as the bulbs don’t touch one another. Layering bulbs in pots with the largest (tulips, daffodils, large narcissus) on the bottom, medium-size bulbs (smaller narcissus) in the middle and the smallest (crocus, jonquils) on the top can provide a flower exhibition throughout the spring months.
When planting your bulbs, sprinkle a tablespoon of “bulb food” or bone meal into the bottom of the planting hole. Sprinkle another tablespoon or two over the leaf tips as they poke through the soil surface in spring and again when the flowers have finished blooming.