The Signs of Fall and Autumn

Time to Cover Plants

• In autumn, the sun travels lower and lower across the southern sky in the Northern Hemisphere, resulting in the shorter days due to the Earth shifting its tilt away from the sun. As the sun’s angle changes, shadows cast from trees and buildings become longer than during summer. If shadows shroud sun-loving plants in shade part of the day, these plants become susceptible to nighttime freeze, meaning it’s the time of year to cover cold-sensitive plants to extend their growing season. Autumn’s fading light also cues warm-season grasses to begin the dormancy shutdown for winter survival.

Harvest Fall Crops

• Picking pumpkins (Cucurbita maxima) and harvesting fall crops of celery (Apium graveolens) and kohlrabi (Brassica oleracea) signal autumn has arrived. Nuts like pecans (Carya illinoinensis), hardy in U.S. Department of Agriculture zones 5 through 9, and walnuts (Juglans regia), which grow in USDA zones 3 through 7, are also ripe and dropping from trees. Squirrels scurry around scooping up the nuts and running off to hide them for winter storage. Fall is also the time for picking apples (Malus domestica), which are hardy in USDA zones 3 through 8, and making them into apple butter or hot cider.

Enjoy Fall Flowers

• Fall color usually brings to mind images of brilliant tree leaves, but some flowers also bloom in fall. Garden chrysanthemum (Dendranthema x grandiflora), hardy in USDA zones 8 through 10, puts on a display of color in fall, and autumn crocus (Colchicum autumnale), which grows in USDA zones 4 to 8, is just waking up from its summer dormancy to put out purple, star-shaped blooms on 10-inch stalks.

Fall Color and Cleanup

• Foliage of trees and shrubs bursting into golden yellow, brilliant orange and wine red is a hallmark signal of fall. Shorter day length and cooler temperatures cue this change in leaf color. And it's not just the leaves of trees, such as the maples (Acer spp.) that occupy USDA hardiness zones 3 through 9, that change color. Edible plants like blueberry (Vaccinium spp.), which thrives in USDA zones 5 through 10, and the ornamental shrub red-twig dogwood (Cornus spp.), hardy in USDA zones 2 through 9, also put on displays of colorful fall foliage. Afterward, the leaves of many of these trees and shrubs fall to the ground signaling another sign of autumn, the fall yard cleanup.