The best reason to divide plants is to prevent overcrowding. Many potted plants and perennials need occasional thinning to prevent crowding of the root systems.
Signs of Overcrowding
- Roots protruding from the pot's drainage hole.
- Plants look crowded or top-heavy.
- Plants wilt soon after watering because its roots have filled the pot. Soil is unable to hold water due to lack of space.
- Lower leaves turn yellow and die.
- Centers of old plants die out.
- Growth in the center of the plant starts to slow or die.
- Clumps of growth occur on the outside ring of the perennial.
- Plants may not bloom as often or as much as before.
Natural division makes flowers produced from bulbs (tulips, lilies, etc.) the simplest to propagate. They’ll form tiny bulbs on the sides of the original bulb after a year of growth. When the plant is dormant (after it flowers), lift it out of the ground, remove the tiny bulbs by hand and plant them individually. Replant the original bulb. New bulbs require at least one year to fully mature.
Another example of natural division is offsets or offshoots, which are stems coming from the base of a plant just under the ground. They often have roots of their own and can be removed from the parent plant and grown into new plants. Plants such as pandanus, sansevieria, and aloe are good examples. Snake plants, Boston ferns, cast-iron plants, African violets, philodendrons, and asparagus ferns are also good plants to divide. Each of these plants produces a cluster of stems at the base of the plant, making them easy to split up.
Dividing houseplants and perennials
The best time to divide houseplants is in the spring while they're beginning an active growth period. Before you begin the division or cutting, give the plant less water than usual to firm up the top growth. When you're ready to divide a houseplant, remove it carefully from the pot and cut the various sections apart with a sharp, sterile knife. Don’t use clippers as they crush fragile stems. Make sure there is a good root and top on each section. Work as quickly as possible to prevent the plants from drying out. Repot all divisions in fresh soil and water immediately.
Divide perennials the same way after they finish flowering. For example, plants that bloom in spring should be divided in early summer, and plants that bloom in summer should be divided in early fall.