By Brent McGhie, Butte County Master Gardener, February 5, 2016.
Not all of these plants are technically bulbs. Both gardeners and plant companies alike tend to group true bulbs along with corms, rhizomes and tubers under the general heading of “bulbs.” A true bulb consists of layers of fleshy leaves, like an onion. Amaryllis, Chalochortus and lilies are true bulbs.
Corms are shaped like bulbs, but are solid (not layered) inside. Crocosmia, gladiolus and Liatris grow from corms.
A tuber is actually a fleshy underground stem and its “eyes” are buds from which new plants can develop. A potato is the most familiar example of a tuber. Tuberous begonias grow from tubers (other begonias form rhizomes) and dahlias develop from tuber-like roots. Rhizomes are actually underground stems. Cannas, callas and tuberose are summer-blooming plants that produce rhizomes.
Bulbs need well-drained soil and will often rot if planted in soggy soil. When planting a bulb, loosen the soil past root depth and then amend it with compost or other organic material before placing the bulb in its hole. Commercial fertilizers formulated specifically for bulbs are also available and are normally worked into the soil beneath the bulb at planting time. There may be some individual variation, but generally most true bulbs, corms and tubers should be planted about three times as deep as they are wide. Rhizomes should be planted just under the soil surface, while tuberous roots (e.g. dahlias) should be covered by three or four inches of soil.
Like most plants, bulbs benefit from regular watering during the growing season. Once they have flowered, the spent blooms can be deadheaded, but don't cut back any green leaves. The plants need these leaves to photosynthesize and to replenish the food lost by the bulb during growth and flowering. Once the leaves have browned off, they can be removed. Over time, most bulbs will multiply and become naturalized. To avoid overcrowding and encourage plentiful blooms, it is a good idea to divide the clumps of bulbs every two or three years.
It's too late this year to plant other summer-blooming bulbs, but if you want to plan for next year, Allium, Anemone and Watsonia can be planted this fall. There are also several native bulbs that should be planted in the fall. Species of Brodiaea, Sisyrinchium (blue-eyed grass) and Triteleia (Ithuriel's spear) all bloom from late spring to early summer. Soaproot (Chlorogalum) blooms appear from May to August. If you do buy native bulbs, be certain you buy from reputable dealers who propagate their bulbs rather than collecting them from the wild. This will help ensure these beautiful wildflowers will be available for others to see for generations to come.
By Carolyn Faulkner, Butte County Master Gardener, October 18, 2013
For many gardeners, fall brings with it the excitement of selecting and planting spring-flowering bulbs.
The term “bulb” is commonly used to describe a wide range of plants that have underground structures in which they store their nutrient reserves. These reserves allow bulbs to survive and bloom from year to year, if conditions are right. Knowing the differences among the five bulb types can help you determine when and where to plant them.
Of the five bulb types, the most common are the true bulbs. The best example of a true bulb is the onion. The rings you see when you slice an onion in half are actually leaves modified to hold food for the bulb when it is dormant. Garlic too is a true bulb. Common flowering true bulbs include tulips, daffodils, hyacinths, amaryllis, lilies, and Dutch iris.
The third type of bulb is the rhizome. These have elongated underground stems which sometimes emerge above the soil surface. Some of these stems are thick, while others are the thickness of a blade of grass, but all produce leaf growth from the top, and roots that emerge from the underside. Examples of rhizomatous bulbs are bearded iris, cannas and calla lilies. The cattail is a rhizome. Unfortunately Bermuda grass and mint are also rhizomes, and their small underground stems allow them to spread easily and become invasive.
The fourth type of bulb is the tuber. Tubers are also underground stems, but not the base of the stem as in a corm. Tubers have multiple “eyes” (buds) and most of them prefer filtered sun. The potato and yam are tubers. Begonias, cyclamen and anemones are all examples of flowering tubers.
The fifth type of bulb is the tuberous root. These are roots that form around a central stem. The sweet potato is a tuberous root which is where it differs from the yam. Some examples of flowering plants that have tuberous roots are dahlias, agapanthus and day lilies.
The depth that each bulb is planted varies according to the type: some (like rhizomatous bearded iris) can be planted just below the surface, while others (like tulips) require deep planting of up to eight inches. Because bulb depth varies so widely, it is important to check sources before planting, but the general rule of thumb for plantingspring bulbsis toplant two to three times as deep as the bulbis tall.
Bulbs to plant in the fall for late winter and spring blooms include tulips, daffodils, crocuses, Dutch iris, and many types of lilies. Bulbs to plant in the late winter and early spring for summer flowers include dahlia, canna, begonia, and gladiolus. Light fertilizer can be applied just as the bulbs begin to grow.
Most bulbs like full sun, but there are some exceptions, such as hyacinthoides (bluebells) and many daffodils, which bloom in early spring before trees leaf out.
Most bulbs are perennials, and many do well in containers. Most bulbs prefer well-drained soil, but exceptions include the Summer Snowflake (Leucojum), Camassia quamash, and Lilium lancifolium (the orange tiger lily), cattail and (of course) the Water Lily, all of which like damp, even soggy, conditions.
Once bulbs have bloomed, do not cut back their leaves until they have turned yellow and are obviously dead. The bulbs require these leaves to manufacture carbohydrates and store energy for the next year, through photosynthesis. However, the flower stalks can be cut back to where the foliage begins. It is important to apply a complete fertilizer after bloom in the spring, spreading around the base of the leaves, and to continue minimal watering. Once leaves have been removed the bulb can be dug up and stored in a dark dry cool place or simply left in the ground. Be careful not to over-water. Unless your bulbs are among the water-tolerating exceptions, too much water will cause the bulbs to mildew or rot.
A helpful chart for bulb planting can be found at http://ucanr.edu/sites/sacmg/Sacramento_Bulb_Planting_Schedule/. Keep in mind, however, that our Butte County winters tend to be colder than those in Sacramento./span>