Mother’s Day and Memorial Day are rightly seen as the beginning of the planting season, if the thousands of hanging flower baskets that suddenly appear on decks and porches and in decorative pots are any measure. These baskets often contain some of my favorite flowers: pansies, snapdragons, violas and petunias.
They are vigorous growers but often break gardeners’ hearts because they can become unattractive — leggy and stringy with few flowers or one sad bloom at the end of a long, seemingly naked stem.
There is a simple way to keep the four plants named above in abundant bloom throughout the summer. The solution — an understanding of a bit of basic botany. Examine the stems of any of the four mentioned plants and you will see two or more leaves in an arrangement — alternate, opposite, or whorled — near or at the base of the stem. This is a node. Clusters of leaves along the stem are more nodes and the space between each of them is called, obviously, an internode.
Every stem has an apical or terminal bud at its very end. An apical bud governs the growth activity of that stem. It releases a hormone that prevents axillary buds (found at the axils in nodes) from growing or causes them to grow slowly. This growth-governing action allows the plant to grow taller to reach more light or causes a hanging basket to become stringy.
But once the stem (with its apical bud, hormones, nodes, internodes and potential stems and leaves at the axils) has produced a flower, that stem wants to produce seed. For the lover of summertime hanging flower baskets, it is time for a botanical hormone intervention. Cut that long stringy stem back to just above a leaf node that is close to the base of the plant. When the stem containing the growth-governing apical tip is removed, the hormone signal now affects the axillary buds which begin to grow vigorously.
This act of removing the terminal bud by cutting just above one of the nodes alerts the growth hormones to get in gear and produce more shoots, each of which is an exact copy of the main stem and equipped with the power to produce more nodes, internodes and flowers.
In gardening terms, removing the terminal bud is known as “pinching back” and the plant’s resultant more compact, bushy growth is called “stooling out” (which I think is an unfortunate description).
Violas (or petunias, snapdragons or pansies) are lovely when regularly pinched back to produce compact and colorful fullness. To support this vigorous growth, it is generally recommended to feed the plants with a liquid fertilizer at one half or one-quarter strength at every watering.