Carrie Barre-LiBaire's Gardening Column

Down to Earth Gardening

A majority of the questions I get asked are about trees, and lately they have been specifically about maple trees. You may have noticed that some maples start changing color in August or earlier, and some have yet to change color. This difference is a clue to what’s going on with a maple tree. A perfectly healthy maple tree will not change color until after the first frost or late fall. If your maple has already turned you may have what is characterized as “maple decline”.

Maple decline is not a single disease, but a combination of factors that lead to early death. Some of these factors include soil type, site of planting and genetic disposition of the tree. If one or more of these factors is not favorable it puts permanent stress on the tree that contributes to the tree’s decline.

Three major types of maples are the Sugar, Red and Norway. Sugar maples do not like crowded conditions or compact soil. This means this is not the tree to plant in the space between the road and the sidewalk; that’s a death sentence. Sugar maples should be planted out in the open where they have plenty of room to grow. Red maples prefer slightly acidic soils and will develop chlorosis (splotchy yellowing of the leaves) from magnesium deficiency if planted in alkaline soil (pH above 6.7). Norway maples are more tolerant of space and soil conditions, but frost cracks on the trunk are pretty common, and they seem to be prone to developing stem girdling roots. Stem girdling roots occur when the trees roots circle the tree instead of spreading out from the tree. So you can see that site selection and soil are the first defense against maple decline.

As I’ve mentioned, one of the first clues of maple decline is earlier and earlier fall leaf change. Another indicator is a cluster of branches near the top of the tree that appear dead or leaves in that area drop significantly earlier than the rest of the tree. Dieback that starts at the top of the tree is usually a bad sign no matter what type of tree you have. Now, the maple may limp along like this for many years, but in the final stage of decline you will see rotting fungi on the tree, usually at the base or root collar.

So what can you do in the meantime? In the spring prune out dead branches, aerate the soil and fertilize. You should also start thinking about what kind of tree you want to replace the declining one. Some of the new maple hybrids or crosses are showing good potential in various settings. I planted an ‘Autumn Blaze’™, which is a cross between a sugar and a red maple, a year ago last spring and it is doing very well. When you do your research and take into consideration the site, soil and genetics it will ensure you have a tree that lasts a lifetime.

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