As the days shorten, and the weather becomes cooler, the grim prospect of winter is softened by the glories of fall. For a short time, our trees surrounded us in the brilliance of their goodbye to the season. As the nights become colder, the rich greens of summer make way for the golds, oranges and reds of fall, aided, in the words of the poet John Keats, by fall’s ‘close bosom-friend’, the ‘maturing sun’. But what if your garden has fallen behind, and instead of fall brilliance, you have just a few dreary browns, or soft greenish-yellows. What has gone wrong? If this sounds like you, or even if you just wonder what makes fall so brilliant, then join us in exploring the reasons why we have ‘good’ falls, and other that fall short, and why some trees glow brighter than others. We will explore these questions, and see what you can do to help your garden join the party.
Give Your Trees Their Brightest Fall Colors
- Grow Them in the Sun – it will bring out the reds and oranges
- Pray for Cold Nights – temperatures close to, but above, freezing make the strongest colors
- Cut Back on the Water – turn off the sprinklers and irrigation early. The wetter the fall, the poorer the color
- Choose the Right Plants – all trees are adapted to certain climates. If you plant a tree from the north further south, or vice-versa, you will not see the same coloring
- Skip the Lawn Food – trees in lawns will color best if you stop feeding in early summer – the food that makes your lawn green also keeps your trees that way
It Takes a little Sunshine to Make a Bright Fall
There are several factors that cause the leaves on certain trees to color in the fall, but sun is one of the most important ones. A big part of the reason why eastern North America is blessed with spectacular fall color is the weather. Fall there is usually filled with bright, sunny days, followed by cool nights. The bright sun keeps the leaves producing sugars, but the cold night stops their transport to the roots, and instead they are broken down into pigments called anthocyanins. As well, with the generally colder temperatures, the green pigment chlorophyll is destroyed, letting the color of the anthocyanins, and other masked pigments like yellow carotenes show through. It is the anthocyanins that give the brilliant reds. Mixed with carotenes they produce oranges. So if the days are instead cloudy, and the nights therefore warmer, fewer anthocyanins are made. The carotenes, which are yellow, are still revealed, and we see lots of yellow leaves, but not much else.
This happens on a grand scale if we have a cloudy, wet fall, and is something we can’t control. On a small scale, in your own garden, if your trees are shaded in fall they will not make any red pigments, and simply turn yellow, or even stay green until a frost destroys them. When you choose a place for a tree you are planting for fall color, place it so that it gets as much sun as possible, especially in fall. The south side of evergreens, for example, is not a suitable position. Luckily, with larger trees, after a few years they will grow taller, and their crowns will reach the sun, so even in a poor location, you will see a big improvement in the fall display after a few years.
How Quickly Does the Frost Arrive?
The beautiful Maiden-Hair tree, Gingko biloba, often stays green for a long time, even as the weather cools down. In the north, in some years, this tree develops very little fall color, because the early frost kill the leaves while they are still green. If you live in such an area, it is especially important to choose a selected form of this tree, not just a seedling. The Autumn Gold Gingko Tree is a special variety that develop its rich, butter-yellow tones early, and reliably.
This idea of growing selected forms of trees is always good one. Each plant in a group of seedlings is a little different from the others, and someone has taken the trouble to choose the one with the best features, often from among hundreds of others. Don’t pass up that wisdom to save a dollar or two – always pick the named variety over the seedling tree, it’s always the right choice. Another example would be with Red Maple (Acer rubrum). Although well-known for its fall color, varieties like ‘Red Sunset’, or ‘Autumn Flame’, are more brilliant, and more reliable, than seedling trees. So by choosing them, and not a seedling tree, you are guaranteeing brilliant colors every fall.
Poor Fall Color in Wet Weather
Sunlight, and temperatures close to freezing, are the main factors that affect the intensity of fall color. The third important factor is water. As a rule, wet weather gives reduced coloring, especially in those desirable red pigments. This is why the fall color on American trees planted in Europe is usually disappointing. The damp, cloudy weather across Britain and Europe pretty much guarantees that simple yellow will be the most prominent fall shade. Although there is nothing we can do about the weather, you can make sure you don’t add to it by continuing to water your trees into the fall. If you have irrigation, turn it off in early September – a little dryness will help the garden mature, and bring stronger color to your trees. You will also save water, but remember to give your evergreens a couple of soakings before freeze-up, as a protection against winter burn.
Fall Color in Warmer Regions
If you live in the warmer states, then the brilliant colors of New England are not going to happen for you. The warmer nights in fall will inhibit color development. While a Sugar Maple can still be a great shade tree in zone 8, if you want bright fall colors, choose something more suitable. The American Sweetgum, (Liquidambar styraciflua) grows wild throughout the southern states. This large tree has spectacular fall colors of gold, crimson and purple, and rich color develops well even in areas with very mild fall weather. The tree is very popular in Australia as one of the few that will color well in such a warm climate. If you live in a warmer place, and love the brilliance of fall, then this, and the gingko tree, are your number one choices.
Don’t Overfeed Your Trees
While we want to get the best growth from our trees, after the first few years, they don’t need much fertilizer. If your soil is of average fertility, and you use mulch, you won’t need fertilizer for your trees. In fact, by making them grow big green leaves, you reduce the brilliance of their color in fall. Especially with trees in lawns, a heavy program of lawn food will reduce the colors of your shade trees. Stop feeding in early summer, and never put high-nitrogen fertilizer down in fall. Your grass will be fine, and your trees will thank you.