Who doesn’t love the glowing reds, yellows, oranges and all the other colors that make autumn so beautiful? Did you ever wonder what the mechanism is, or how to get more of that beauty in your yard?
Growing conditions throughout the season affect fall color, as does current weather. Fall leaf colors are due to plant pigments in leaves. Colors such as orange and yellow, which we see in the fall, are actually present in the leaf all summer. However, those colors are masked by the presence of chlorophyll, the substance responsible for green color in plants during the summer. Chlorophyll allows the plant to use sunlight and carbon dioxide from the air to produce carbohydrates (sugars and starch).
Trees continually replenish their supply of chlorophyll during the growing season. As the days grow shorter and (usually) temperatures cooler, the trees use chlorophyll faster than they can replace it. The green color fades as the level of chlorophyll decreases, allowing the other colored pigments to show through. Plants that are under stress — from conditions such as prolonged dry spells — often will display early fall color, because they are unable to produce as much chlorophyll.
So, that’s how plants make their beautiful fall colors. Ideally, for the best colors, you need normal amounts of rain during the summer and dryer fall conditions.
Trees, being the biggest plants, are the most noticeable in the fall. Certain colors are characteristic of particular species:
- Oaks — red, brown or russet;
- Hickories — golden bronze;
- Aspen and yellow poplar — golden yellow;
- Dogwood — purplish red;
- Beech — light tan;
- Sourwood and black tupelo — crimson.
The color of maple leaves differ by species:
- Our native red maple — brilliant scarlet;
- Sugar maple — orange-red.
Some leaves of some species, such as the elms, simply shrivel up and fall, exhibiting little color other than drab brown.
Many shrubs have spectacular fall color as well. One is aronia, also known as chokeberry. There are two species, aronia arbutifolia, with red fruit, and Aronia melanocarpa, with black fruit. Both get from 6 to 10 feet tall, but there are many smaller cultivars — “Low Scape Mound” is a particularly nice one, getting to about 3 feet by 3 feet. Beautiful white flowers in spring, and attractive berries that are edible but taste awful, make this a great addition to any yard. It likes full sun and moist soil and turns a brilliant red to orange in the fall. This is a great replacement for the highly-invasive burning bush.
Another superb shrub for fall color is the oak-leaf hydrangea, hydrangea quercifolia. A wonderful four-season shrub, it turns a gorgeous deep maroon-purple in the fall. With large hydrangea flowers, peeling bark in winter and nice foliage, it deserves a spot in your garden. It prefers part shade and moist soil, and a good mulch. There are many varieties going from 3 to 12 feet tall.
We’ve discussed fall perennials before, with asters and goldenrods being my favorites, but one that is overlooked and is spectacular is threadleaf bluestar, or amsonia hubrichtii. It has lovely lavender-blue flowers in spring and delicate foliage in the summer that turns a beautiful yellow in fall. The extremely fine-textured foliage contrasts well with coarse-textured plants, such as Joe Pye weed. Threadleaf bluestar is very adaptable and easy to grow. It tolerates moist sandy to heavy clay soils, and tolerates drought once established, while it can take a little bit of shade.
With all these choices, why not bring more color into your yard, before the quiet of winter?