Every spring, beautiful flowering bulbs emerge from the ground to brighten the landscape. People see the beauty of these flowers and want to grow them in their own yards. A wide variety of bulbs grow well in Georgia. Most are grown for their flowers and some for their foliage. They are grown as pot plants, in shrub borders, naturalistic plantings and in mass displays. The best time to plant the bulbs is in the fall. Spring and early summer flowering bulbs must be planted in the fall to develop a strong root system and satisfy the cold requirements. In Georgia, spring-flowering bulbs can be planted from October through late December in most areas.
The term "bulb" is used to refer to true bulbs and other bulb-like structures, such as corms, tubers, tuberous roots and stems, and rhizomes. The main function of these modified plant parts is to store food for the plant's survival during adverse weather conditions. The differences among these structures are important, since each is handled differently with respect to culture, propagation and care. A bulb is a specialized underground organ consisting of a short, fleshy, usually vertical stem axis (basal plate) bearing at the top a growing point or a flower bud enclosed by thick, fleshy scales. Daffodils and tulips are examples of true bugs. A corm is the swollen base of a stem axis enclosed by dry, scale-like leaves and has nodes and internodes. Examples include crocus and gladiolus. A tuber is a modified stem structure that develops on underground stems. Caladiums are tubers and so are potatoes. Sweet potatoes and dahlias are examples of tuberous roots, thickened underground roots. These structures have the same external and internal structure as normal roots. A rhizome is a specialized stem structure in which the main stem of the plant grows horizontally at or just below the soil surface. Iris and canna lilies are classified as rhizomes.
Most spring-flowering bulbs prefer light shade to full sunshine. The majority of bulbous plants are actually less particular about soil than many other cultivated plants. Most, however, prefer a moist, well-drained medium sandy loam that does not remain wet and sticky after heavy rain or dry out too quickly. Good drainage is essential. For soils with poor drainage or if the soil is too sandy or is heavy clay, use a soil amendment. Peat moss, bark, rotted sawdust, compost, perlite, vermiculite, coarse sand and many other materials have been used successfully. In the absence of a soil test, add 1 to 2 pounds of 5-10-10, 10-10-10, or 8-8-8 fertilizer per 100 square feet of bed space. Organic fertilizers such as bonemeal are often recommended for bulbs, but they are probably no better than inorganic sources used at the proper rates. Always buy from a reputable dealer. Bulbs should be firm and have unblemished skin, and avoid bulbs that are soft or look molded or discolored.
Planting depth and spacing are very important to the success of bulbs. A general rule of thumb for planting depth (from top to bulb to soil surface) is two to three times the greatest diameter for bulbs 2 inches or more in diameter and three to four times the greatest diameter for smaller bulbs. Spacing will vary from 1 to 2 inches to as much as several feet. When spacing bulbs, consider not only how much space each plant needs, but also how frequently it will be dug and divided. Also, consider the landscape effect. Avoid spotty or line-out arrangements. It is sometimes suggested that bulbs be broadcast over the area to be planted in order to achieve a naturalistic look; this is unadvisable, however, because dropping or throwing the bulbs may bruise or injure them. Plant the bulbs upright (rhizomes and tuberous roots are usually planted on their sides), and press the soil firmly around them. Water the beds thoroughly to help settle the soil.
Timothy Daly is the agricultural and natural resources extension Aagent with Gwinnett County Extension office. He can be contacted at 678-377-4010 or firstname.lastname@example.org.