Fall is here, and it's not too late to get fall bulbs into the ground. In our climate, you'll want to plant bulbs by Nov 30 at the latest. A true bulb is defined as a compact package of fleshy scales with a small basal plate and a shoot that emerges deep within the bulb.  Scales are modified leaves and contain necessary food to sustain the bulb during its dormancy and early growth. They may be loose and open like a lily or tight and compact like a hyacinth. If cut in half horizontally, the scales are visible as rings. During the growing season, new bulblike organs called bulblets or offsets form from bulbs next to or around the scales at the bottom of the bulb.

Tulips, daffodils, hyacinths, amaryllis, ornamental onion, snowdrops and lilies are all true bulbs.  Plants that grow from bulblike organs are corms, tubers, rhizomes, and tuberous roots.

Some bulbs reproduce by a process called annual replacement.  In tulips or ornamental onions, the old bulb dies (mother bulb) after flowering and is replaced by new bulbs of varying sizes.  If conditions are right, the largest of these will flower the following season. Others bloom in subsequent years. In offsets, the mother bulb grows for two-three years and new bulbs, offsets, are produced alongside the mother bulb and can be removed and planted elsewhere.

Choosing a healthy bulb requires attention to appearance, size and timing. Choose ones that are large, heavy for their size, firm, free of bruises, soft spots, molds, or cuts. Big bulbs like tulips and hyacinth produce larger flowers on taller thicker stems. The largest roots will give you more flowers. If patience is your virtue, purchase smaller ones, which are less costly, and wait a year or two while they mature if planting in the ground.

Each species of bulbs has their own characteristics, heft and feel. Many bulbs are labeled "top size" which means they are the largest commercially available in size. Most bulbs are measured in centimeters (tulips are measured about four 1/2 inches around). When you want top size hybrid bulbs for a smaller setting that is fine. When you want large number of bulbs for naturalizing in a landscape, buy smaller sizes.

Outdoor containers also expand our need for visual beauty and increase our spatial ability.  The creative urge accentuates when contemplating the selection of an outdoor container. For best bulb displays, be aware of the following characteristics. Size: choose large deep containers to accommodate your bulbs at the proper planting depth with room to grow. Porosity: containers made of insulating materials; paint clay pots with breathable latex sealant and place thin-walled containers within insulated, decorative ceramic pots to reduce deposited mineral salts. Drainage:  To avoid fungal disease, choose those with drain holes or drill them yourself. 

The following steps will ensure optimum fertility and soil quality when planting bulbs in a landscape setting.  Turn over the soil by breaking any clods removing rocks, roots or debris.  Cultivate 12-16 inches deep.  Next rake layers of organic compost to cover each bed 2-3 inches.  Work the compost into the bed's soil with a shovel until evenly mixed.

Add 4 inches of compost to soil and mix thoroughly.  The ideal soil pH for most bulbs is 6.0-6.5.  Soils in Stanislaus County average between 7 and 8, so it is helpful to fertilize with a bulb fertilizer to get them off to a good start. The major nutrients plants need are nitrogen, (N) for chlorophyll for the leaves and stems; phosphorous (P) for root development, and potassium (K) or potash for the plant's general vigor.  Although bulbs do not require immediate fertilization afterplanting, it's a good time to add it so you don't forget later.  Fertilize spring bulbs each fall.  Spring flowering bulbs do not benefit from fertilizer during or after blooming. Some experts contend that an all-purpose fertilizer on summer flowering bulbs, when their foliage appears and blooming and then once monthly until the plants are in full bloom, is needed. High nitrogen fertilizer applied immediately after planting may promote fungal diseases. Some bulbs, belladonna lilies and autumn crocus, bloom after foliage has died.  Fertilize them while their foliage is green, not while blooming.  

Note the planting depth for the bulb species. To be safe, bulbs should be planted 5-8 inches deep measuring from their base. Add 10-10-5 fertilizer and cover with 2 inches of soil. Turn the pointed end of the bulb up and roots and plate down. Plant in its hole. It is fine to plant some bulbs close together like tulips. If you want them to multiply, leave space at least two or three times the bulbs' width. Some need more room like allium bulbs at 13 inches apart. When planting several large bulbs close together, dig one large hole. Backfill over each bulb with amended soil to the proper planting depth. For large areas, it is best to amend the soil when it is prepared for planting.

Check your final planting arrangement after all bulbs have been planted. Relocate bulbs to fill any space or skipped spots. Finally fill the hole with soil gently pressing it over each bulb to ensure good soil contact and eliminate any air pockets. 

One cannot forget watering after all this work. Natural rains may suffice for late autumn through spring. After that period, watch the temperature projections and adjust accordingly. Regular watering is required during active growth, usually weekly, dependent on rain showers.  For most species, the soil should remain evenly damp or moist. As a dry spell occurs, water overhead evenly. Place plastic cups around plantings to gauge the amount to apply.  Test cups should have filled with an inch of water. Dig down about 6 inches with a hand trowel to see if water has penetrated that far.

Work compost into the soil around plantings every year to improve soil structure. Mulching around bulbs helps regulate soil temperature, retains moisture, and hinders weeds. Use organic mulches such as wood chips, fine ground bark, compost, or cocoa hulls. Apply before bulb sprouts appear. Dump and rake mulch, keeping it 4-6 inches from trunks or stems. 

Planting singular bulbs is ideal for planting small areas or for as many as thirty bulbs. This allows for a rippling drift in a naturalized garden or for bulb accents in borders. Whether you desire a formal, informal or naturalized garden, mixed plantings are recommended.

For a formal bed, use the same layering technique as used for containers. Excavate the planting hole and plant layers of bulbs. Having plotted your schematic, mark the patterns to be used. Plant the first layer of bulbs, space evenly changing colors between areas, cover the second layer of bulbs until the final top layer.

Landscape plantings usually have bulbs set in trenches for large areas. Dig a trench 3-4 inches deeper than the desired planting depth. Apply granular fertilizer, backfill with a layer of soil 3-4 inches. Cover and water.

Voila! Naturalized plantings are stunning, colorful and uniquely creative. They reflect who we are.  Whether container gardening, using formal beds or landscape planting, we await the glorious outcome! 

Martha J. Martin has been a UC Cooperative Extension Master Gardener in Stanislaus County since 2020.

Photos by Anne Schellman, Program Coordinator.

References

Black and Decker Outdoor Home Landscaping with Bulbs 2002, multiple contributors

Ortho's All About Bulbs, multiple contributors 1999

Bulbs for All Seasons, Firefly Books, Pierre Gingras 2001

Sunset Bulbs, multiple contributors, 1st ed. 1998