The vast majority of bulbs that are native to the western United States come from a Mediterranean climate, where winters are cool and wet, but with only occasional severe frosts, and summers are completely dry. Other such climates are (obviously) the countries that surround the Mediterranean, the west coast of Chile, western Australia and the western portion of the Cape Province of South Africa.
Bulbs from all these regions exhibit the same growth patterns. As the winter rains commence in autumn they come into growth, producing leaves that persist throughout the winter, then blooming in late winter through spring, going dormant in the warm, dry summers, such as the lovely Triteleia hendersonii seen here to the left. When you grow these species from seed, you must sow the seed in autumn. Such seed requires cool temperatures to germinate, something that seems to surprise most people, familiar with growing tomatoes or annuals for their gardens. But seeds know what they are doing, they have built-in mechanisms that tell them when they should germinate, and if they sprouted in the warming temperatures of spring, the rains in these regions would soon stop and that would be the end of it for them.
There are, of course, exceptions to these generalizations, for all these regions have mountain ranges where the climate is different. Alpine bulbs from Mediterranean climates come into growth as the snow melts in spring. They grow extremely rapidly, and will bloom and set seed by midsummer, then go dormant in late summer, dropping their seeds to lie under the snow and germinate in early spring.
I only grow a few of the alpine species, for these really need a long cold period to do well, and I can't provide these conditions. I have been successful with a few, such as Calochortus gunnisoni (seen here to the left), but it is unusual, and I can't fuss with them enough to be successful.
Here are the main requirements of most California native bulbs:
** They need a cool, wet winter with little frost. They can withstand a few degrees of frost, but not freezing of the bulb itself. The soil should be well-drained. Bulbs need to be planted by November, since they will naturally start to sprout at the time the rains would normally commence in the region they come from (October to November in California).
** Most species do better if they are planted fairly deep for their size. Most are fairly small bulbs, 1.5-2cm in diameter, but they should be planted about 5-7cm deep. Even 10cm is not too deep.
** They must be kept TOTALLY dry in summer, or they will rot. The alpine species can take some summer water if temperatures are cool and the soil is extremely well drained.
** They are only suitable for gardens if these requirements can be met. They can be grown in gardens that have summer rainfall if they are lifted and kept in dry storage for the summer as soon as they go dormant. All species are very successful in containers, which can be stored in a warm, dry place during the summer.
** Rodents love these bulbs, so they must be protected from gophers and mice.
California native bulbs are well worth growing, and worth any trouble to keep them in your garden. They range from the lovely starry flowers of Brodiaea, Triteleia and Dichelostemma, to the true lilies and the lily relatives, such as Fritillaria and Erythronium and the enchanting genus Calochortus. The lovely Lewisia rediviva is seen here to the right, a sort of honorary bulb, for it is certainly not a bulb but behaves like one, going dormant in the hot dry summers of the west.
