Harvesting and Culturing Offsets

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Robert J. Dolezal

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As you’ve probably noticed, a ready, varied supply of fresh, healthy bulbs is available each year from garden centers and direct retailers. Many home gardeners prefer to plant new bulbs each year; some cultivars and climates demand that you do so. For those who prefer to grow new plants from their own bulbs – or propagate them – it’s relatively easy to harvest offsets and divide rhizomes and tubers to create fresh plants.

Divide your bulb plantings when they become crowded. The lily-of-the-Nile in this front yard started as single plants. In the span of just a few years’ time, they’ve formed crowded groups. The time has come to divide them if they’re to remain attractive.

Propagation also includes techniques that require greater patience and skill. Some lily plants, for instance, grow bulbils in the leaf axils – the point where the leaf joins the stem. Bulbils can be cultured to grow new individual plants. It’s also possible to create new plants of tuberous begonia and dahlia by taking stem cuttings of fresh shoots, rooting them, and allowing them to form bulbs.

Still another method frequently used is to grow new hybrid bulbs from seed. If a flower stalk remains on the bulb after its bloom fades, it will swell and form seed. Offspring grown from the seed are not the same as their parent, but a cross-hybrid of the original plant with pollen from another. Their growth habit, bloom color and form may differ greatly from either of the parent plants.

Harvesting and culturing bulb seed is somewhat more challenging than for other garden seeds, but with practice and experience it can be easily mastered. Try your hand at harvesting and culturing bulb seed by allowing the seedpods to fully develop and turn brown and brittle. Crack them open over a sheet of clean, white paper to release their tiny seeds. Label and store the seeds in individually sealed containers in the vegetable keeper of your refrigerator for 2 months. Then plant them in loose, rich, moist, sterile potting soil and raise them under glass at 62-75 degrees F. Uncover when they sprout, watering whenever the soil starts to dry. Then transplant them outdoors in spring, lift, and overwinter them indoors until they mature.

True bulbs multiply by producing miniature bulbs – or offsets – at their plate-like bases. Offsets are identical to their parent. In some hybrids, the parent bulb’s vigor wanes after a season or two; growing offsets to flower or planting anew is the only way to keep such varieties in your garden. Harvest offsets as you lift your bulbs to increase their numbers, taking the easy steps shown in the following pictures and described in their captions.

Culturing Bulbs - Step 1

After lifting the bulbs from the soil, carefully separate large offsets from the parent bulb, using a sharp knife if necessary to avoid damaging the bulbs’ base.

Culturing Bulbs - Step 2

Remove and discard any of the small bulblets, unless you plan to propagate them. (They’ll usually take between two or three growing seasons to flower.)

Culturing Bulbs - Step 3

Discard any cut or damaged bulbs, along with those that show telltale signs of fungal decay, such as a white, powdery coating or soft, damp blemishes.

Culturing Bulbs - Step 4

Allow the bulbs and offsets to dry thoroughly in a protected, well-ventilated, and shady spot with warm temperatures. Cure for 20-14 days. Store the bulbs under the light, humidity and temperature conditions each species requires.

Facts

Professional growers carefully develop new bulb varieties, called “hybrid cultivars,” by dusting pollen from the anther of one parent plant onto the stigma of another. The results are entirely new bulb cultivars.

Tips

If you harvest and store bulbs, in addition to making a note as to what type of bulb you’ve harvested, include what color and height the plant offers to help you remember for next year’s plantings.
When the day comes that there are too many offsets to replant, offer an exchange of your extras with a neighbor or friend who also has bulbs, corms, bulbils and divisions to share. You may find they have just the flower you’ve been looking for to complete the look of your plantings – and the same could be true for them.

Have a question about harvesting and culturing bulb seed? Come to The Garden Party and post it in the L2G Forums for our gardening experts and other knowledgeable home gardeners to answer.

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Proper care for lifted bulbs requires two steps: curing and storage. Curing ensures that your bulbs enter dormancy. Storage conditions depend on the specific bulb type. Learn the easy steps of how to cure and store bulb plants.
Dividing Tubers and Rhizomes
As gorgeous as a blooming flower bed of bulbous plants can be, dividing tubers and rhizomes is necessary when their multi-plant colonies become crowded. Learn the easy steps of how to divide bulb plants, and keep your garden beds healthy and beautiful.
Advanced Bulb Propagation Techniques
Off all the more involved bulb-propagation methods, the easiest specialized techniques to master are taking and propagating bulb cuttings, and rearing bulbils or bulblets to flowering size. Feeling confident in your propagation skills? Learn how to propagate bulbs beyond the usual lifting and dividing methods.

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