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Trees: From heat to garden

Fronk shares insight into Juniata Valley trees

A familiar sight and smell have returned to the Juniata Valley. Depending on the weather next spring, it will be here until almost April. I’m writing about chimney smoke. Many Pennsylvanians rely on wood to heat their homes through the winter months. It is not uncommon to see homes with stacks of cut logs, piles of whole logs, pyramids of board ends, stockpiles of pellets–I could go on and on. Did you know that Pennsylvania has a $19 billion per year forest products industry according to the Department of Conservation and Natural Resources? Every county in our state has a timber-related business. As a horticulture educator with the Penn State Extension, I am interested in the trees that we see every day.

About 90 percent of all trees in Pennsylvania are hardwoods. Hardwood trees lose their leaves each fall and their wood is generally hard and dense, though there are some exceptions. The most important and common hardwood trees in Pennsylvania include maple, cherry, oak, poplar, beech, hickory and ash. The remaining 10 percent are softwoods. These trees are usually referred to as evergreens or conifers. It is fun to try to identify trees while in the woods hunting or at a park. But it’s challenging this time of year because there are no leaves on most of our trees. It’s possible to identify trees by their bark, twigs and even odor. The Extension office has books and literature available if you’d like to learn more about tree identification.

As far as firewood goes, hardwoods are the economical choice for most heat per volume. Softwoods have a higher heat value, but you need more of it. Also, hardwoods are less likely to result in creosote build-up. The moisture of the wood is very important. A fellow Extension associate and Penn State forestry professor Michael Jacobsen details that firewood is best when it has 20 percent or less moisture content, which requires a year or more of drying under a roof and off the ground. Additionally, green or wet wood can have moisture content of 50 percent or more, depending on the type of tree. Burning wet wood is a bad idea because the moisture must be driven out before combustion can occur.

A by-product of hardwood trees to gardeners are the leaves they drop each autumn. If you allow the leaves to stay on your lawn, they may be too deep and can kill the grass. An option may be to mow them back onto the yard. You can set your mower to mulch them, or mow over them several times so you can still see grass underneath. This ensures the leaves are finely shredded and will not stunt your grass. Putting some of those leaves in your garden has been proven to increase productivity. A study from Rutgers showed that adding six inches of uncomposted leaves each fall and incorporating it in the spring increased organic matter, fertility and moisture holding ability.

Another use is to pile leaves as insulation for sensitive plants. A mulch of leaves around plants such as lavender and rosemary will help shield them from cold snaps. Edible plants like strawberries and asparagus will also benefit from a protective layer. However, you must remember to remove this layer of insulation in the spring. There are some leaves that are better left out of your garden. Large amounts of walnut leaves may be detrimental because they contain a natural plant growth inhibitor, juglone. Also, poisonous plants such as poison ivy, poison oak and poison sumac, and blighted or diseased plants should not be used as mulch or insulation in the garden. Oak leaves have long been believed to lower acidity, but using oak leaves in the way described above should not alter your soil pH. If you are unsure, you can always get a soil test kit at the Extension office.

When you burn wood for heat, you end up with wood ash. This can be a useful soil amendment if used correctly. In fertilizer terms, average wood ash has an analysis of 0-1-3 (N-P-K). It is a good source of calcium and other micronutrients. Wood ash will work best in a garden that is already slightly acidic. If your garden soil is at the optimum soil pH of 6.5, using wood ash is not a good option. A soil test kit will assist you in determining soil pH and calcium levels of your current soil.

Thank you for reading and I hope you enjoyed learning about some of the uses of Pennsylvania hardwood trees. Feel free to email me at lxf339@psu.edu or call the Extension office at (717) 436-7744 with questions.