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Growing in the Desert Column

(List of Growing in the Desert columns)

Time to pay attention to winter-growing bulbs by Mark Dimmitt

Photos by Mark Dimmitt unless noted

(This article may only be reprinted with the author's permission.)

Whether or not bulbs are true succulents, people who collect succulent plants tend to be attracted to bulbs too. If you have a collection of winter-growing bulbs, you probably put the barren pots away at the end of spring, out of sight and sheltered from summer rains. September is the time to remember where you stashed them and prepare them for their coming growing season. It’s also time to order any new ones you want to try. Most winter bulbs are activated by cooling nights and soil moisture. They may not show above ground until late October or November, but the roots began to grow a month before you see green. The following task list applies to the great majority of winter bulbs:

1. If the bulbs have multiplied and become crowded, future flower spikes will be stunted. Unpot and divide the clusters, replanting the largest bulbs. Space them to allow two or three years of growth before they become crowded again.

2. Because cooling temperature is necessary to break dormancy, bulbs in clay pots or pots located in the shade will sprout before those in plastic pots in the sun. Plastic pots can be wrapped in aluminum foil or painted white with spray paint to keep them cooler. (You may notice that the bulbs on the south side of the pot will sprout last, and are often smaller than those on the north side. Many winter bulbs are marginally adapted to the desert’s warm winters.)

3. In late September or October when nights begin to drop into the 60s F, soak the pots once. Then keep the medium barely moist until you see green sprouts. Some bulbs such as Ferraria will sprout at much higher temperatures. Move the pots of sprouted plants into a sunny location if they aren’t there already. Full desert sun is a bit too much for most species, especially in spring. So most potted bulbs should be shielded from full afternoon sun. High temperatures can trigger premature dormancy. This is a major reason why those from the coolest habitats do not perform well here.

4. When growth is well under way, water and fertilize generously. Be prepared to cover the tender species on frosty nights. Most species will tolerate nights in the upper 20s in partial shade, while mid to low 20s will damage many if they’re exposed to the night sky. Some of the winter bulbs that do well in Tucson include:

  • Boophane species (Figure 1): Fan-shaped foliage tops large above-ground bulbs that are covered with papery layers, but have succulent interiors and fleshy roots. Hardy to at least the low 20s under a cover. Dull flowers appear in fall before leaves. (B. disticha is summer-active and bears red flowers.) petal margins, weirdly spotted on a greenish background, and deliciously fragrant. Hardy to the mid 20s.
  • Freesia: Very easy to grow. Bell-shaped flowers in several colors are lightly fragrant. Hardy to at least the low 20s.
  • Ipheion uniflorum: A tiny plant no taller than 6 inches. One-inch flowers in shades of blue are borne one at a time in spring. Seems to be completely hardy in Tucson.
  • Lachenalia (Cape hyacinth, Figure 3): Numerous species, some of which have attractively spotted foliage. Flowers range from inconspicuous to large and colorful.
  • Leucocoryne: Grasslike foliage and inch-wide star flowers of lavender to purple on tall stems; lightly fragrant. Likes lots of water; hardy to mid 20s.
  • Moraea polystachya: A small iris with two-inch bluish flowers over a two month period, usually in spring. Will sprout as early as August with good rains and be in flower by late September. Very easy to grow. In fact, it will volunteer freely in any watered site; keep it away from other bulb pots or you will soon have nothing but moraea. Other species have more beautiful flowers, but most are difficult to grow in the desert. Completely hardy in most of Tucson.
  • Ornithogalum dubium (Figure 4): Most species in this genus have white flowers with black eyes. But this one has bright orange flowers, or sometimes lemon yellow. Easy to grow; hardy to mid 20s under cover. Oxalis species
  • Rhodophiala bifida (hurricane lily, Figure 5): This bulb flowers in August while dormant after a heavy rain, hence the name. Leaves sprout in the fall and die in spring. Bulbs multiply freely, but never set seed. This species needs to be in the ground; for reasons I don’t understand, it rarely flowers in pots. Hardy to at least 20. There is also a pink-flowered form.
  • Sparaxis (Figure 6): These miniature irises bear several one-inch flowers in a wide range of bright color combinations. The flowering season is very short in the desert, only about a week for each bulb, spread over a two-week period. Hardy to mid 20s.


List of Growing in the Desert columns