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Methods Used to Propagate Bulbs
Propagate and Grow More Bulbs
Double your garden plants by using these easy methods for dividing, propagating, and planting new bulbs in containers, landscapes, and beds.
We’ll demonstrate four popular methods most gardeners use to propagate new bulbs:
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- How to Harvest and Plant Bulb Offsets
- How to Divide Rhizomes and Tuberous Roots
- How to Take Stem Cuttings from Bulbs
- How to Harvest and Plant Bulbils and Bulblets
Step-by-Step Instructions
True bulbs multiply by producing seed and miniature bulbs called offsets.
While each seed produces plants genetically different than the parent bulb—even from other seeds of the same parent—offsets are identical [see: Bulb Basics]. Find offsets growing along the edges of the parent’s platelike base.
For some hybrids, a parent bulb loses vigor and dies after a season or two. Growing their offsets is the only way to keep such bulbs flowering in your garden.
Review how to lift bulbs [see: Dividing Bulbs and Roots].
Then, harvest the offsets as you lift and cure your bulbs to increase their numbers. Gather a sharp knife, your cured bulbs, and follow these easy steps:
How to Harvest and Plant Bulb Offsets
After lifting, use a sharp knife to carefully cut and separate large offsets from the parent bulb. Avoid damaging the parent bulbs’ base.
Remove and discard any tiny offsets, unless you plan to take several years to grow them to mature, blooming size. Large offsets often bloom in their one season, while small offsets usually take two or three growing seasons to flower.
Also discard any cut or damaged bulbs, plus those with telltale signs of fungal decay. Bulbs sometimes become infected with mold, fungus, patches of white, powdery mildew, or soft, damp-rot blemishes.
Allow the bulbs and offsets to dry thoroughly in a sheltered, well-ventilated, shady spot with warm temperatures for 4–7 days. Plant them seasonally along with their lifted parent bulbs, either in the same garden spot or a new location.
Dividing Rhizomes and Tuberous Roots
Divide fleshy-rooted bulbous plants when colonies become crowded.
Lift and divide deciduous bulbs after flowering has finished and their foliage begins to wither. Divide evergreen bulbs in autumn or early spring when their growth slows, usually after blooming. Divide bearded iris from early to midsummer.
Gather a sharp, long-bladed garden knife, a shovel, a garden fork, gloves, and a tarp, then follow these easy steps:
How to Divide Rhizomes and Tuberous Roots
Using a shovel, vertically cut the soil around the bulb colony, about 6–8 in. (15–20 cm) out from the outermost stems.
Work with the shovel, outside the first cut. Remove soil up to the first cut with an angled cut. Repeat, working around the colony, opening a trench for access to the soil under the bulb colony.
Push hard and drive the shovel underneath the colony. Pry up, freeing and breaking the colony away from the soil beneath. Carefully lift it by the soil and set it onto a tarp.
Use a garden fork and the shovel to pry the roots of the colony apart. Work from side to side across the root ball. Separate the colony into two plants, each with its own intact rootball.
When necessary, carefully use a sharp garden knife to cut the roots and soil between the colony’s plants.
Cut away, remove, and discard the oldest, central plants of the original colony. Replant each divided root set at the spacing recommended for the particular bulb species.
Planting Stem Cuttings, Bulbils and Bulblets
Two other popular methods for propagating bulbs use stem cuttings or growing small offsets and bulbils to flowering size. Both are popular ways to increase the number of your plants.
Understanding and mastering these processes require time, patience, and practice.
To root dahlia and tuberous begonia cuttings, you’ll need loose, moist soil in a deep container and a sharp budding knife. To plant bulbils and bulblets, only a hand trowel is necessary.
Experiment with these advanced techniques by following these simple steps:
How to Take Stem Cuttings from Bulbs
Begin by planting tubers of dahlia or begonia in containers. Hold them at 65°F (18°C) until they send up shoots.
Shoots will emerge and begin to grow. Care for the planting until the shoots are 3–5 in. (75–125 mm) long. Use a sharp budding knife to carefully cut them from the stem of the parent bulb, making the cut at a 45° angle.
Root each cutting in sterile, damp potting soil or a very sandy mix of potting soil and sand. Cover the entire container top and sides with clear plastic to retain moisture. Avoid allowing any foliage to touch soil or the plastic covering. Put the cuttings in a protected spot with strong light out of direct sun, and keep them warmer than 55°F (12°C).
In 10–14 days, the cuttings will begin to root. After their roots are established, repot them into individual rearing containers.
Divide fleshy-rooted bulbous plants when colonies become crowded.
Lift and divide deciduous bulbs after flowering has finished and their foliage begins to wither. Divide evergreen bulbs in autumn or early spring when their growth slows, usually after blooming. Divide bearded iris from early to midsummer.
Gather a sharp, long-bladed garden knife, a shovel, a garden fork, gloves, and a tarp, then follow these easy steps:
How to Harvest and Plant Bubils and Bulblets
Harvest small bulbils by removing them from the leaf axils of some lilies and ornamental onions, or collect bulblets from lifted bulbs as shown above [see: How to Harvest and Plant Bulb Offsets].
Plant single bulbils or bulblets 1/2 in. (12 mm) deep in a bedding tray filled with moist potting soil.
Allow new plants to sprout and grow through their first season. Lift and store the young plants once their foliage yellows and withers. Replant the bulbs the following season, at a depth one-quarter as deep as for mature bulbs of their species. Repeat lifting, storage, and replanting. Most will bloom in their third year.