- Author: susanne von rosenberg
Planting Bulbs for Spring Flowers
by Susanne von Rosenberg, UC Master Gardener of Napa County
It's September, and it's obvious that the days are getting shorter and autumn is on the way. One of the most pleasurable activities in a fall garden is planting spring-flowering bulbs. Spring-flowering bulbs add color to a late winter and spring garden, and the right kinds of bulbs will naturalize and reward your efforts for many years.
While we commonly refer to them all as bulbs, these spring-flowering marvels are actually five different types: true bulbs (such as daffodils and tulips), rhizomes (such as bearded iris), corms (freesias and gladiolas are common examples), tubers (cannas and anemones) and tuberous roots (like day lilies and ranunculus).
You see the most common types, including daffodils, tulips, irises, day lilies, calla lilies, dahlias and gladiolas, in many local gardens. Tulips are the most difficult to grow locally because our winters do not provide enough chill, and because gophers adore tulip bulbs. If you want tulips in your landscape, the best approach is to think of them as annuals that you will need to replant every year. Grow them in pots or put them in protective cages if you plant them in the ground. Most other types of bulbs will regrow every year, provided they get the basic care they need.
First, plant them correctly. The best method will depend greatly on the bulb type. True bulbs should be planted at a depth of two to three times their diameter. Bearded iris rhizomes, on the other hand, should be planted with the top of the rhizome at or just below the soil surface.
If you buy bulbs at a nursery, ask the staff about proper care and planting instructions for the types you're buying. If you buy mail order, the delivery should be accompanied by planting instructions.
In our area, bulbs should be planted in October or November, when the soil temperature has dropped below 60°F. All bulbs do best in welldrained soil and should be watered well after planting. If our rainy season starts at the normal time, you won't need to do any additional watering. If rain is delayed or below normal, water the bulbs to give them about the same amount of water and with the same frequency as they would get in a normal year.
Most bulbs need full sun, but some, such as calla lilies, prefer partial shade. You can plant the earlier spring-flowering bulbs under deciduous trees; they will have finished blooming by the time the trees leaf out fully and cast too much shade.
To keep your bulbs performing well year after year, let the foliage die back naturally after bloom. Those produce food that is stored in the bulb to nourish next year's flowers. Also give them a light application of phosphate-heavy fertilizer (such as bone meal) every year. After three or four years, many types of bulbs become crowded and need to be divided. You can tell that it's time to divide them when you see a lot of leaves growing in a crowded area, but you get fewer flowers than in previous years.
Many bulbs native to the Cape Province of South Africa, which also has a Mediterranean climate, will do well here and naturalize easily. Try spraxia (also known as wand flower or harlequin flower), ixia or babiana. Another interesting variety to consider is rain lily, a Mexican native (Zephyranthes) that looks a bit like a crocus and comes in many colors.
You can also plant native bulbs this fall. One advantage of natives is that they bloom when native insects need them. They are also adapted to our climate and do not require any special soil preparation.
There are more than 200 species of native California bulbs, corms and rhizomes. Some examples include Coast iris, blue-eyed grass (a very small native iris), snake lily, camas bulbs and fritillaria. The Calflora website (www.calflora.org) lists 23 native species.
If you buy native bulbs, make sure they are ethically sourced, not collected from the wild but propagated by the nursery that sells them. Because native bulbs are likely to be more expensive, it's particularly important to be well-informed about the growing conditions they require.
For example, camas bulbs prefer soil that is very moist in the spring and then dries out, conditions typical of seasonal wetlands and the edges of creeks. Give them a home in an area of your garden that is soggy during the wet season, but then dries out. They have a long flowering period (typically April through June).
Camas bulbs were used as a food source by native American tribes and are very appealing to gophers. They are one of the few native bulbs that need gopher protection. California native bulbs are a worthy addition to a native garden and also make great potted plants.
Next workshop: “Stinking Roses and Edible Alliums: Grow These Essentials for Your Kitchen” on Saturday, October 12, from 9:30 to 11:30 a.m., at the University of California Cooperative Extension, 1710 Soscol Avenue, Napa. For more details and online registration go to http://napamg.ucanr.edu or call 707-253-4221.
The UC Master Gardeners are volunteers who provide UC research-based information on home gardening and answer your questions. To find out more about upcoming programs or to ask a garden question, visit the Master Gardener website (http://napamg.ucanr.edu) or call (707) 253-4221 between 9 a.m. and noon on Mondays, Wednesdays or Fridays.
Order your spring-blooming bulbs now to have the best selection. The bulb growers will ship your bulbs in time for proper planting in our area. Local nurseries also stock bulbs to coincide with the best planting time for our area.
Select the largest bulbs available; mature bulbs produce more flowers. Choose heavy, dense bulbs with no decay or mold. Pre-packaged bulbs frequently cost less, but they are likely to produce smaller blooms.
Plant your bulbs in the fall when temperatures remain consistently cool and the soil temperature has cooled to below 60 degrees. If you plant too early, when the soil is still warm, you are likely to end up with lots of top growth and fewer flowers.
If your bulbs arrive before you are ready to plant, open the packages to give the bulbs good air circulation. Store them in a cool, dark, dry place.
Despite what your grandmother may have told you, it is not necessary to pre-chill bulbs in our area. Tests done by Sunset Magazine and the U.C. Master Gardeners showed that there was little difference in the performance of pre-chilled and non-chilled bulbs.
Choose a location for spring-flowering bulbs that receives at least five to six hours of sunlight. You can even plant under deciduous trees as the trees generally do not leaf out until after the bulbs have bloomed.
It is critical to plant bulbs where the soil drains well. Bulbs hate to have “wet feet” and will let you know by rotting instead of blooming.
Plant all bulbs with the pointy end up and the root scars down. Follow directions on planting depth for that type of bulb. The general rule is to plant most types of bulbs three times as deep as the bulb is wide.
Bulbs need water while they are actively growing. Even though you cannot see them after planting, remember to irrigate until winter rains begin.
Soil preparation depends on whether you are planting for repeat bloom. Bulbs contain all of the nutrients they need for the coming season’s growth and bloom. But if you want bulbs to repeat in successive seasons, amend your soil with compost and other nutrients. Do not put fertilizer in the planting hole as bulbs are susceptible to root burn. Instead, dig bulb fertilizer into the soil under the root zone or broadcast fertilizer over the beds after planting.
For repeat blooming, leave the bulbs in the soil after flowering and allow the leaves to turn brown so that the bulbs build back their reserves for the following season. Daffodils, native iris, muscari and scilla are the most reliable repeat bloomers in our area.
I have a love affair with tulips but have finally admitted that they do not repeat well in my garden. I also have very active gopher and rodent populations, and they consider tulip bulbs a culinary delight.
My solution is to treat my tulips as annuals. I grow them in strategically placed two-foot diameter pots that I also use for summer annuals. When the annuals are giving up the ghost in fall, I remove them from the pots and plant tulips in the same soil. There is no need to enrich the soil at this point as the bulbs contain all of the nourishment they need for a single season. When the tulips have finished their spectacular demonstration, I remove the bulbs, renew the soil in the pots, add compost and fertilizer and plant flowering annuals. This way, I have an almost continuous display of blooms in the same pots with minimal effort.
Because the critters do not seem to like daffodils, I have had success in naturalizing daffodils for repeat bloom in several locations in my garden. Daffodils do not require the cooler winter temperatures that tulips demand so are much better suited for repeat blooming in the Napa Valley.
Whether you choose to naturalize daffodils in your yard, grow tulips as annuals in pots or experiment with varieties of bulbs you have never tried, now is the time to plan your spring bulb garden. A small amount of effort this fall should provide you with a magical floral display next spring.
Workshop: Napa County Master Gardeners will present a workshop on “Planting Spring Bulbs” on Saturday, September 14, from 9:30 a.m. to 11:30 a.m., at University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Plant bulbs now for a colorful display in early spring and find hidden beauty in your garden. Learn about different kinds of bulbs, how to plant them and what they need to thrive. Online registration (credit card only) Mail in registration (cash or check only).
Garden Tour: Napa County Master Gardeners will host a self-guided garden tour, “Down the Garden Path,” on Sunday, September 22, from 10 a.m. to 4 p.m. Visit seven unique gardens in and around downtown Napa, all maintained by Master Gardeners. Tickets: $25 advance/$30 day of event. For more information and to purchase tickets, visit http://ucanr.edu/ucmgnapa or call 707-253-4147. Find us on Facebook under UC Master Gardeners of Napa County.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. Napa County Master Gardeners ( http://ucanr.org/ucmgnapa/) are available to answer gardening questions in person or by phone, Monday, Wednesday and Friday, 9 a.m. to Noon, at the U. C. Cooperative Extension office, 1710 Soscol Avenue, Suite 4, Napa, 707-253-4143, or from outside City of Napa toll-free at 877-279-3065. Or e-mail your garden questions by following the guidelines on our web site. Click on Napa, then on Have Garden Questions?