The Earth

Here on our farm, my husband and I have chosen wood as our sole source of heat. Our house is kept warm and cozy by the wood stove in the living room. In an average heating season the stove consumes three cords of mixed hardwoods, all from our land.

Fortunately, we have about 30 acres of forest, so there’s never a shortage of firewood. Now, you don’t need to own 30 acres of woods to be self-sufficient in firewood. In most regions of the United States a woodlot of three acres is adequate. If available land is limited, firewood can be grown along roads, streams, edges of fields, stone fences, property lines or surrounding the house, as a windbreak or privacy screen. A small woodlot that is well planned and properly maintained is far more productive (per acre) than a large one that is neglected.

The mental attitude with which you approach the woodlot will determine how much firewood you can get from it. Many wood burners unconsciously see themselves as “hunters and gatherers” rather than producers of firewood. As a result, they cruise through the woods, chainsaw in hand, hunting only for their most-favored species (say, oak) and gathering everything they can find of burnable size in those species.

To get into the mindset of being a producer of firewood, I think it’s helpful to conceive of the forest as an “energy orchard”. Generally speaking, the principles and practices of managing a fruit orchard apply to the woodlot, whether you’re planting a new one or improving an existing stand of trees. Your goal is to produce a continuous supply of trees that is self-sustaining far into the future. To do this, you need to assure that the amount of new growth each year is at least equal to the amount harvested as fuel. This means, first and foremost, that you need to know about – and care about – the ecology of the forest. The ideal “energy orchard” consists of a wide variety of trees of all sizes and ages. It contains seedlings of many species just beginning to grow, as well as mature trees ready for cutting. There should be an even distribution of trees in varying stages of growth, so that the harvest can be continuous year in and year out.

In addition to having a variety of trees of differing ages, the plot should include a mixed planting of species with different rates of growth (see chart #l). This will provide a measure of insurance against an attack of insects and diseases that could wipe out an entire forest if planted to a single species. The spacing between trees should be sufficient to give access to sunlight, but not so spread out that space is under-utilized, or that “wolf” trees – with widespread, dense foliage – prevent other trees from developing.

Careful planning and decision-making are especially crucial in woodlot management. In starting a new woodlot or improving an existing one a key decision is the selection of trees to be planted. You want diversity, so choosing is more complicated. Be sure to plant at least five or six different species, even if one or two kinds predominate. Some things you’ll want to take into consideration are the burn characteristics of the different woods, fast vs. slow growing species, and species which are tolerant of crowding.

Burn Characteristics. In general deciduous trees are classed as “hardwood” while conifers are “softwood”. But some so-called hardwoods are softer and lighter than some softwood. Wood burners favor the denser hardwoods, which burn slow and hot, and produce lots of long-lasting red coals. In our area locust and red oak are highly prized for this. We keep a separate pile of “overnighters” (large diameter), which are put in the stove at bedtime. The next morning we need only to add more logs to the coals – no need to use kindling.

But firewood in all sizes and density has its special uses. Pine, poplar and dogwood are great for heating the house fast after the stove has been left untended too long. I find that it’s a good practice to burn slow and fast-burning wood together. Some of the densest wood burns well only when supported by the flames of the softer woods. (See Chart #2). For a quantitative measure of the different woods, it is good to compare their output of heat in BTU’s. As Chart #3 shows, hardwoods produce almost equal amounts of heat on a weight basis, but vary more widely in BTU/cord, which is measured by volume (one cord is 4 feet high, 4 feet wide, 8 feet long). Obviously, beech and red oak weigh more than the others and thus have the highest BTU’s per cord.

Fast vs. Slow Growing. You’ll want to plant both fast and slow growing trees, not only for diversity’s sake, but in order to maximize the value of total firewood harvest. In general the faster growing trees have more air space between the cells, are lighter in weight and will have a shorter burn-time. The slower growing species are denser and heavier, so they burn more slowly and produce better coals. There are exceptions to the rule, however. Note that in Chart #1, Rock Elm is a fast grower with a very high heat value. But the BTU/cord measure can be misleading, if the goal is to produce the most firewood (in BTU’s) from a given area. As Chart #3 indicates, the fast growing Hybrid Poplar has a much lower value in BTU/cord, but because it produces three to five times as many cords each year as the others, its BTU/acre per year figure is the highest by far.

Planting. Choose the location of the woodlot carefully. If you have the room, plant in blocks or wide strips, to encourage a slightly crowded condition. As the trees reach upward for the light, they produce more usable wood, faster. A good way to start is to plant 1200 trees per acre and periodically thin out the trees to increase the growth. The thinning can be used for firewood. Leave some trees to grow to maturity in 10 to 20 years.

Land that is too steep or rocky to be farmed can be excellent for firewood production. When locating the woodlot keep in mind the need for access at harvest time and avoid low, wet areas. As a bonus, a woodlot will provide excellent erosion control in the area planted and can increase the aesthetic appeal of the land.

Weeding. The competition for available nutrients, moisture and sunlight is as fierce in the woodlot as in the garden. So, in order to give every advantage to the trees you intend to harvest, remove defective, deformed and undesirable trees. Although diversity is important, it may become necessary to keep at a minimum or even eliminate certain species. Sassafras and Ailanthus are the most unwanted trees in our woods. They are extremely prolific, grow fast, and crowd out everything else. We root Ailanthus out on sight, but it’s a never-ending battle, since they sprout from runners.

Hedgerows and Coppices. The handsdown winner when it comes to BTU production per acre/year is the combination of methods invented and developed in Europe over centuries of practice. When a mature tree is felled, its massive roots do not die. Many hardwood species will produce sprouts from the trunk (see Chart #4). Since there is such an extensive existing root system, the growth rate is several times faster than a planted tree.

Managing sprouts is called coppicing. A coppice is literally, a sprout forest. If left to nature, a cutover area would soon become a thicket of brush, rather than useable firewood. In coppicing, no more than two sprouts are allowed to grow, forcing all of the energy of the roots into them.

In order to promote quick growth, the stumps – or stools as they are called – must receive lots of sunshine. This observation led Europeans to plant in hedgerows rather than in a block. Hedgerows are always less than 50 feet wide, to permit ample sunshine to reach the innermost trees. They are often planted as windbreaks between open fields and located along roads, banks of streams, stone fences, property lines, and surrounding a house as a privacy screen or windbreak.

The stools must be carefully prepared to foster strouting by making a smooth cut, on a slant, across the entire stump. The stump should be cut one-foot off the ground with no jagged surface, thus discouraging the stump from collecting water and rotting. Harvest should only be in late fall or winter to promote rapid regrowth. If done in spring, as the sap is rising, the tree will bleed heavily and lose much of its energy.

In the woodlot it is advisable to wait until the tree is almost fully mature before cutting. While in the hedgerow it is best to harvest the firewood before the trunk reaches five inches DBH (Diameter, Breast High). Beyond this size, trees start to produce seeds, and divert their energy from sucker growth to seed production.

Being able to grow your own firewood is challenging and rewarding, but most of all there is a sense of security knowing that you have control over your own fuel supply.

Chart #1:
Heat Equivalent (BTU/Cord)
Growth Rate Species Very High High Medium Low
Slow Apple X
Slow Beech X
Slow Birch X
Slow Hemlock X
Slow Hickory X
Slow Hornbeam X
Slow Oak X
Slow Walnut, Black X
Medium Ash, White, Black X
Medium Basswood X
Medium Butternut X
Medium Dogwood X
Medium Cherry, Black X
Medium Fir, Balsam X
Medium Locust X
Medium Maple
Medium Sugar, Red X
Medium Spruce, Red X
Fast Ash, Green X
Fast Elm, Rock X
Fast Maple, Silver X
Fast Pine X
Fast Poplar X
Fast Sycamore X
Fast Tuliptree X
Fast Willow X

Chart #2:
Apple Very dense hardwood considered among the best as firewood. Excellent coaling qualities for cooking and long-lasting fires.
Ash White ash is an excellent firewood with higher BTU value per cord than black or green ash. Grows well on poor soil. Black ash also does well on wet soil.
Beech Very slow grower and difficult to split. Very susceptible to disease.
Birch Excellent wood, high in BTUs. Some birch can be used in hedgerows because it has a tendency to sucker. Gray birch is suitable for wet soil.
Cherry, Wild Black Suckers freely and grows quickly, excellent for coppices. Burns with colorful flames.
Conifers Not good heat producer. Best used for fast fires or when mixed with other wood. Excellent for kindling. Watch out for flying sparks when used in open fire.
Dogwood Good firewood, high in BTU’s. Excellent in hedgerows and regenerates easily when a stump is left. Low growing tree.
Elm Rock elm is high in BTU’s and a slow burner. Does best in a mixed fire. Easy to transplant and quick to be established.
Hornbeam Very slow grower. Hard, tough, heavy wood, has dulled many saws and axes. Great as a heat producer.
Locust Black locust makes excellent firewood, more BTU’s than oak. Excellent hedgerows and coppices.
Maple Sugar maple is the best heat producer. Red maple grows well on poor soil and in damp places. Silver maple sends up suckers, is good in hedgerows, works fine for coppicing, but is susceptible to decay.
Oak Excellent firewood, great in BTU’s. Hardy, strong-wooded, long-lived and relatively free of serious insect and fungus troubles.
Popular, Hybrid Among the fastest growing wood for firewood. Regenerates very well from stumps. Grows over a wide area from 20 degrees below zero to northern Georgia. Can burn green when hot fire is maintained. Good tree to grow for reforestation of old fields, cutover areas, strip mines and worn out soil. Long-lived, grows five to eight feet per year. Harvest firewood four to five years from planting.
Sycamore Grows well in most of the country. Rapid grower. Sprouts from roots. Moderate BTU’s, but good quality wood.
Tuliptree One of the tallest of native trees. Fast growing, resprouts well. Grows well in most of the country except northern most regions. Fair quality wood with low BTU’s.

Chart #3:
Species Heat Value BTU/lb Heat Value BTU/cord* Growth Rate** Cord/Acre per Year BTU per Acre/Year Years to Harvest
Ash 8500 25,800,000 Medium 0.75 19,400,000 8-10
Beech 8600 28,900,000 Slow 0.50 14,450,000 10-15
Red Maple 8200 22,300,000 Medium 0.75 16,700,000 8-10
Red Oak 8300 27,200,000 Slow 0.50 13,700,000 10-15
Hybrid Poplar 8600 18,500,000 Fast 2.50 46,200,000 4-5

Chart #4:
Ash, Green Hickory Sycamore
Birch Locust Tuliptree
Cherry, Wild Black Maple, Silver Willow
Dogwood Oak
Elm Poplar

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