Does winter solstice affect plants?

All these trees -- crape myrtle, ornamental cherry and valley oak -- will grow leaves again this spring, determining the sunlight and shade that any plants underneath receive.

Observation is key when planting in winter



Happy winter solstice!

Saturday, Dec. 21, is the first day of winter as well as the shortest day of the year. That also means Friday and Saturday are the longest nights with the most hours of darkness.

We people can cope with the extra darkness by turning on lights.

But how does the winter solstice affect plants?

Most of the plants we grow cope with winter darkness and short days just fine. The change of season (as well as temperature) prompts deciduous species to drop their leaves and go dormant until spring.

In some plants, winter’s shorter days and longer nights trigger blooming. That includes poinsettias, chrysanthemums, camellias and Christmas cactus. (That’s also why those plants are such popular holiday gifts.)

From Sunday on, the days get longer and nights shorter. But a sunny day in winter is not the same as one in summer due to the angle of the sun.

During winter months in Sacramento, the sun stays lower on the horizon and doesn’t generate the same warmth if shining directly overhead. That angle casts longer shadows, too, shading some plants that usually receive more sun.

On the other hand, plants that are usually shaded under deciduous trees get more sun in winter because those trees have dropped their leaves.

When planting (or planning to plant) in winter, take into consideration the differences in sun and shade in your garden. Blooming spring bulbs, for example, do just fine under dormant leafless trees, but can’t cope with the constant shade of evergreens. Likewise, that sunny spot under a naked maple won’t be sunny in summer.

Due to the changing sun angle, azaleas and other shrubs that appreciate afternoon shade may get it in winter but not in summer when they need it most.

Let this solstice be a reminder: Observation of sun and shade can be a key to garden success.