Although I live outside the native range of most Calochortus species, I
have found most of them unproblematic to grow in large, deep pots plunged
in sand, in unheated bulb frames. The only one I grow in the open garden is
C. uniflorus, which is native near this region. The other species found
near my home is C. subalpinus, but it is difficult to grow because it's
adapted to long winter dormancy under unthawing snow cover. C. tolmiei is
also reported to grow in the Coast Range across the valley from where I
live; it is easy to grow in the frame.
As Diana mentioned, much Calochortus seed germinates readily, especially
when obtained from Northwest Native Seeds (Ron Ratko). The seed retains its
viability for some years in dry storage. The only species I have failed to
obtain germination from is C. macrocarpus, a plant of the northern Great
Basin and semiarid steppe; others report the same trouble with it. Seeds
typically germinate in cool, moist conditions, and here that means bringing
them into a frost-free situation as soon as germination occurs.
Difficulties ensue, since the seedlings are vulnerable to damping off
(treated with a fungicide) and to aphids (treated with systemic granular
insecticide). If the seedlings can be kept growing into summer, some but
not all of them will form bulbs; in some species a certain proportion fails
to do this and is lost. Crowding may be the reason -- some plant species
release substances that kill off conspecific competitors within a certain
area. This and the damping off have taught me to plant the seeds sparsely
in large pots.
Many growers prefer to leave the seedling bulbs in the original pots for 2
years, since the bulbs are very small and some germination may be delayed
until the second year. If this is done, attention should be paid to
fertilizing the plants when in growth. Once potted on or planted out, they
should have a dry dormancy. Even those from "monsoon" rain areas of the
desert seem able to adapt to "Mediterranean" cycles, in my experience. I
repot them every other year and grow them in deep clay or plastic mesh
pots, plunged in sand in full sun. All the species I grow have survived
temperatures to at least 20 degrees F (minus 7 C).
Following are the species that have matured and flowered under this
treatment here: Cc. albus, amabilis, amoenus, apiculatus, argillosus,
barbatus, bruneaunis, catalinae, clavatus, coeruleus, concolor, coxii,
elegans, eurycarpus, excavatus, greenei, gunnisonii, howellii, invenustus,
leichtlinii, longebarbatus, luteus, lyallii, monophyllus, nudus, nuttallii,
obispoensis, palmeri, plummerae, pulchellus, simulans, splendens, superbus,
syntrophus, tolmiei, umpquaensis, uniflorus, venustus, vestae, weedii. I'm
also growing some others that have not yet flowered -- it can take 6 or 7
years from seed.
Many Calochortus species increase by bulbils formed on the stem near or
just below the surface. These start making root growth about now and
gradually pull themselves down in the soil as they mature. So when you're
cleaning up dried stems in summer, be sure not to throw away these little,
hard bulbils.
Some Calochortus species hybridize readily, particularly the Mariposa
section to which C. venustus belongs. I have a population of hybrids
between C. leichtlinii and, I think, C. superbus, for instance. Natural
hybrid swarms also occur.
The commercially available species include C. venustus in various colors
(being grown in Holland as cutflowers), C. luteus (offered as 'Golden
Orb'), C. superbus, C. splendens ('Violet Queen' or some such boring Dutch
bulb name), and C. uniflorus ('Cupido'). The Dutch method of growing this
genus is to store the bulbs at controlled temperature and humidity until
late fall, then plant them out very late so they won't break dormancy when
the weather is still too cold for them. SInce the fields are essentially
pure sand, planting can be done after frost.
Pests of mature plants include deer and rabbits, and rodents are known to
eat the bulbs. I haven't seen any Botrytis on the plants in the frame, but
for some reason there is little Botrytis there anyway. Bulbs that are in
moist soil during dormancy are likely to rot.
In the garden, it is best to place Calochortus among plants such as
clumping grasses and leafy low perennials and shrubs (e.g., Helianthemum)
that will support their tall, bare stems and give them some winter
protection. Short species such as C. uniflorus and C. tolmiei are suitable
for the rock garden. Some of the really tall species with big flowers, such
as C. plummerae and C. clavatus, are best appreciated if supported with a
natural stake such as a forked branch. However, C. macrocarpus, the tallest
of all, has a stout stem -- now if I could only get it growing!
Jane McGary
Northwestern Oregon, USA