- 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.
An Iris Primer, by Iris Craig
My mother loved flowers: she named me Iris. Having a flower name has affected my life and perhaps led me to be a Master Gardener.
When I purchased my house 40 years ago, friends arrived with iris rhizomes for my garden. Not sure how to plant them, I asked for advice from my friend, Alice, who inherited an iris garden from her mother. Some of those gifts—often neglected, rarely transplanted—still bloom today. Abandoned houses sometimes have iris blooming long after the owners have left.
Iris is the largest genus in the Iridacadae family. Iris have thrived in the wild for thousands of years and figure in cultures throughout the world. In Greek mythology, Iris is the rainbow goddess who brings messages from humanity to the gods. In Roman mythology, she walks the rainbow to the heavens carrying messages to the gods.
Egyptian and Indian cultures used iris rhizomes for healing and for making perfume. Orris root, made from the rhizomes of bearded iris, was burned to create scents pleasing to the gods. Dried iris rhizomes were an industry in Florence in the 19th Century, and the flower became the emblem of Florence.
Iris represents the renewal of life. Clovis I of France chose the fleur-de-lis for his emblem in the sixth century. The fleur-de-lis continues today as the emblem of New Orleans and the state flower of Tennessee.
There are about 280 species of iris. Moors brought iris to the Alhambra in Spain. When Columbus set sail for America, Holland had already developed many new species. Some American iris came across the Atlantic with early settlers and date back to the 1600s.
Twenty-eight native species are found today in North America. The three main natives are Blue Flag, Louisiana and Pacific Coast iris. This last is native to California and Washington State. All attract pollinators and are a colorful addition to your garden.
The Siberian bearded iris, with more than 200 species and a multitude of colors, is the one often found in Napa Valley gardens/ These non-natives can be divided into two main groups: bulbs and rhizomes.
Rhizomatous iris grow horizontally close to the surface with underground stems that supply food for the plants. The common bearded Siberian and Japanese iris grow from rhizomes that are planted in the summer. Bulbous iris, among the most reliable, are repeat bloomers in our area. These include Dutch iris and the dwarf reticulated iris, both of which are best planted in October with other bulbs.
When iris have been in the ground for a couple of years and have fewer blooms, it is time to divide and replant. Rhizomatous iris do well when divided every three to five years. Here's how:
With clean garden shears, cut back the leaves by one third. Next, lift out the entire clump with a shovel or pitchfork. Using a sharp knife dipped in 10 percent bleach solution after each cut, separate the rhizomes.
My friend Alice called the main, larger rhizome with last season's bloom stem at one end the ‘mother.' The smaller rhizomes attached to her are her children and, thus, the pieces to be broken off and transplanted. The ‘mother' rhizome is discarded. The new healthy (children) transplants are firm, with roots, and a fan of five or more leaves.
Check the new rhizomes for soft-rot, a bacterium (erwinia carotovora). Victimized iris have wilted leaves, and the rhizome emits a foul odor. It occurs when the plants are over-watered. If rot is evident, while digging up the plant, cut off the affected areas with a clean knife, expose the healthy rhizome to the sun, and wash with an anti-bacterial soap. Do not put the leaves and diseased rhizome in your compost.
Next, check for the iris borer (Macronoctua onusta). This moth lays eggs on the leaves of old iris leaves and debris. In midsummer, the caterpillars chew through the leaves, find their way down to the rhizome and begin eating it, causing soft rot and possibly death. The best way to prevent damage by this pest and others is to water lightly and keep the garden free of debris and weeds.
Water and excessive moisture are the source of soft-rot. Iris do well when planted in the heat, during the dry weather of summer. In Napa Valley, plant late July through September to minimize rot. Choose a sunny, well-drained area in the yard. A few varieties found on the edge of ponds can manage moisture; however, most iris cannot.
Plant groups of the same variety 18 to 20 inches apart. Dig a hole five inches deep. Place a mound of dirt in the center. Set the young, healthy rhizomes on the top of the mound with the roots hanging down the sides. Cover the roots but leave the top of the rhizome exposed to the sun. If planted too deep, iris may not bloom and could rot.
Master Gardeners are volunteers who help the University of California reach the gardening public with home gardening information. U. C. Master Gardeners of Napa County ( http://ucanr.edu/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? Find us on Facebook under UC Master Gardeners of Napa County.