The fall time change just occurred and us humans are getting adjusted to shorter days, but did you know that the amount of daylight affects plant growth? While daylight savings was theoretically created for the farmer, plants really don’t care what number you assign to the time on the clock. They are concerned about how much light they receive.
Why should I care about daylight?
While we often see grass, shrubs, and other landscaping growing underneath trees and in the shade just fine, food-producing plants require sunlight. The sun is a key part in the photosynthesis process, which determines how much energy and growth a plant will have. Without sufficient sunlight, you will end up with leggy, light green plants that don’t produce much. These weaker plants will be more susceptible to disease and pest issues.
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How much is enough daylight?
As a general rule plants that we grow to eat their roots and leaves require a bit less sunlight and can be grown in shadier locations and the shoulder seasons of fall and spring. This includes plants like lettuce, kale, radishes, chard, spinach, potatoes, etc. Plants that we grow to eat their fruit require more daylight. Vegetables like tomatoes, peppers, eggplant and squash. Nearly all food-producing plants will go dormant when the daylight dips close to or below 10 hours, which means vegetable production in the winter is trickier no only because it is cold, but also because the days are short.
Note: Onions are in their own category and you can learn more about their sunlight needs here.
How do I know how much daylight I have?
Length of days and nights is determined by how far you are from the equator. You can use a simple website like this one to figure out what length of days you have currently. For example, here in upstate South Carolina in mid-November we are getting about 10 hours and 25 minutes of daylight each day. This means nearly all our plants are nearly dormant and we shouldn’t expect much growth until the days lengthen next year.
How does this affect my vegetable garden?
If you only garden in the summer, daylight isn’t much more of a concern than how much shade you have. However, if you want to grow in the other three seasons, being aware of your day lengths will enable you to grow more successfully. For example, if you would like to have a steady supply of kale all winter long (at least in milder climates), you will need to plant your transplants early enough to take advantage of longer days so that they can get established and grow to a good size before your daylight dips below 10 hours. Essentially you want a mature plant in the garden when entering the dark days of winter.
If you’d like to learn more about growing in the winter checkout Eliot Coleman’s book, The Winter Harvest Handbook.
Hope learning how daylight affects plant growth leads to a happy 4-season garden on your homestead.