- 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.
By T. Eric Nightingale, UC Master Gardener of Napa County
It may surprise you but California has a good deal in common, environmentally speaking, with South Africa. Both have a variety of climate zones, many of which overlap. Many plants from South Africa will grow well in Napa Valley, especially with proper care.
You are doubtless already familiar with some South African plants. Red hot pokers (Kniphofia uvaria), with their spiked yellow and red blooms, are used frequently in Bay Area gardens. Two South African irises, Dietes bicolor and Dieties grandiflora, are present in what seems like two out of three shopping center parking lots. Even the popular bird of paradise, Strelitza reginae, is native to this region.
Many other less-common South African plants will also grow well in Napa. If you are curious about a new plant but unsure if it will grow well in your area, look into its native climate. While the Bay Area has many microclimates, we generally have a warm-summer Mediterranean climate.
This description comes from the Köppen climate-classification system used by many to identify climate zones around the world. You can find a color-coded map online showing areas with similar climates. If a plant comes from an area with the same color code as your garden, it should be a good choice for you. Compare the climate maps of California and South Africa and you will see many of the same colors.
We have native salvias here in California, but Africa also has some members of the genus. A personal favorite of mine is Salvia africana-lutea. It has a pleasant smell and small, dusty-green leaves. The flowers are rust-brown, giving rise to its common name: dune sage. That may not sound appealing, but the blooms and leaves create a color contrast that is attractive in the proper setting.
Another lovely plant in this genus is Salvia dolomitica, conveniently known as South African sage. Its silver-gray foliage makes a background to delicate purple flowers. The calyx—the leaf-like structure that holds the flower—starts out burgundy but turns pink with age. However, my favorite thing about Salvia dolomitica is its fragrance, an intoxicating blend of floral and herbal aromas befitting the plant's elegant appearance.
While some South African plants, such as Dietes, feel so at home here they need almost no help from us, others need a little extra care to remain healthy. Often, this means amending your garden soil to improve drainage or protecting the plant from frost. This is particularly true of plants in the Proteacea family. Leucospermum cordifolium is a shrub that grows large, colorful flowers with extended styles, often called “pincushions”.
A similar plant in the Protea family, the Leucodendron salignum,produces a flower that resembles a pine cone in shape, but in colors ranging from yellow to silver. These plants must have exceptional drainage or their roots will quickly rot. They are also sensitive to frost and can only take low-phosphorus fertilizer. Even though they require this special attention, they are drought tolerant once established. And oh, are the flowers worth the effort!
Many succulents are native to South Africa and will perform well in Napa Valley. Aloe brevifolia is a stubby-leaved, clumping plant that produces orange flowers in fall and winter. It is frost tolerant as well, which is not a common trait in a succulent. Delosperma cooperi, a personal favorite, is a vine-like plant that forms dense mats along the ground and over the edges of planters. It is very cold hardy and produces dozens of pink flowers. When the blooms appear in spring and fall, they will add thick swaths of color to your garden.
Some of the most striking South African plants are bulbs. Freesia, Crocosmia and Gladiolus are familiar, but there are many others. One of my personal favorites is Babiana rubrocyanea, whose flowers have vibrant purple petals with a bright red center. Equally as attractive is Sparaxis elegans, which produces a delicately-colored orange and maroon bloom.
These bulbs are interesting because they thrive in clay soil and are summer-deciduous. During the hot months they die back to the ground and require no water at all. In fact, more than a sprinkling of water in summer will likely cause them to rot. Come spring, however, their leaves return and the flowers burst forth in all their glory.
I encourage you to explore the many plants from South Africa. You just might find a perfect plant for your garden.
Next workshop: “Succulents Celebration!” on Saturday, July 20, from 9:30 a.m. to 11:30 a.m., at the University of California Cooperative Extension, 1710 Soscol Avenue, Napa. Learn why succulents have become the trendiest members of the plant kingdom. For more details & 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.