Last month I received the following question from a person who recently purchased some land in Virginia’s Shenandoah Valley:  “I have just purchased 32 acres of land near Staunton, Virginia that has been used for cattle grazing for years and is mostly short grasses. Once upon a time the land was wooded. I would like to return some of the land to forest on a portion of the property. Do you know of any state, federal or private conservation organization that might donate trees for re-establishment of woods, to provide shelter for the deer, squirrels, foxes and woodpeckers that live in that area? I can't afford to do it on my own.”

This landowner can certainly convert some of his open fields to forest, but the process is a little more complicated than simply planting a lot of trees on an old field.  Establishing forests on old pasture can be successful if you know what species to plant and is a great use for land no longer in agricultural production and marginally productive farmland.  Sources of technical and cost-share assistance are also available and will be discussed at the end of this article. 

Important decisions for any landowner considering the conversion of pasture to forest include the type of trees desired (pine, hardwood, or both) and how the landowner wishes to use the forest once it’s established, for example: timber income, wildlife habitat, hunting, bird watching, and aesthetics.  Throughout the following discussion it is important to remember we are discussing conversion of a long-established open field to forest.  The process of planting or regenerating trees on a recently cutover forest area is a different process.  On recently harvested hardwood sites, hardwood trees quickly regenerate from stump sprouts, dormant seeds, and seed from neighboring uncut forest stands.  On recently harvested pine forests, pines are generally planted after burning or chopping slash (branches and tops) and chemical control of hardwood competition.

Many landowners want to establish hardwood forests on old fields and for good reasons.  Hardwoods provide food and habitat to numerous animal species.  Hardwoods are beautiful throughout the year, especially in fall during color change.  And hardwoods tend to grow in mixed stands, that is, multiple species in an area versus pine stands which most often grow in pure (one species) stands.  From a wildlife standpoint, both pines and hardwoods are important, with pines providing thermal cover in the winter and hardwoods providing nesting habitat and food in the form of berries and nuts.  But whether a pine or hardwood stand is desired, converting an old pasture to forest in a reasonable period of time involves planting trees.

To better understand how to successfully convert a pasture to forest, a quick review of land use history in the south may reveal some important lessons.  The landowner from Staunton is probably correct that their fields were once forested.  But it may have been a long time ago indeed.  Humans have long used agents of disturbance, notably fire and cutting, to control the growth of forests for agriculture, hunting, and ease of travel.  As early as the 1500 and 1600’s, explorers such as DeSoto and John Smith noted that large expanses of the Shenandoah Valley and other valleys of the mid-Atlantic and southern U.S. were maintained in open fields for agriculture by Native Americans through the use of fire.  What is important to note is that these open field conditions were maintained through human management - specifically, through the use of fire as an agent of “disturbance.”  Regular use of fire controlled undesirable vegetation and allowed humans to manage and use land for their daily needs.  During the 1700’s and 1800’s, millions of acres of southern forests were cleared to build a growing nation.  Wood was used for fuel, buildings, furniture, railroad ties, poles and pilings, and to make way for agricultural fields.  After the Civil War and through the Depression of the 1930’s, a significant amount of southern agricultural land was abandoned and much of this abandoned land reverted back into forest.  Today, 60 percent of Virginia and many other southern states are forested, up from a low of 25-40 percent forested around 1900.  The important question to ask is – how did we get so much forest land?  Was it all planted on these abandoned agricultural fields?  In fact, only a small fraction of this land was planted.

When left fallow, nature automatically converts open fields and disturbed areas to forest.  And while it may seem counterintuitive, one of the best ways to establish a hardwood forest on old pasture is to plant pine.  A careful observer and reader of the land will understand why.  A drive along Interstate 81 in Virginia’s Shenandoah Valley reveals numerous old agricultural fields that have been left fallow for many years and are in various stages of reverting back to forest land.  After some time, if left alone, field crops are naturally replaced by grasses, shrubs, and other "pioneer" species such as eastern red-cedar, Virginia pine, and black locust.  Pioneer species are well suited for the relatively harsh conditions, e.g., dry, intense sunlight, and eroded soils, of open fields.  Because pioneer species are well suited to harsh open-field conditions, they quickly establish in areas disturbed by man (recently abandoned agricultural fields, road cuts, building sites, harvested areas) and by nature (volcanoes, hurricanes, tornadoes, and fire).  Over time, if the land is not further disturbed, pioneer species are gradually replaced by pines and then by hardwoods such as poplar, hickory, oak, and maple.

Foresters use the term "succession" to describe the process of old fields developing from open conditions of grasses into shrubs and pioneer tree species, and eventually to hardwood forests.  Rather than waiting for the process to occur gradually, landowners living in the mid-Atlantic and southern U.S. who would like to reestablish forests on old fields should seek to mimic and nudge the successional process along.  This is most easily done by skipping the naturally occurring grass and shrub pioneer stages and planting quick-growing pines.  Many southern pines, notably loblolly pine, are well suited to withstand the harsh conditions of open fields and offer income opportunities as well.  In addition, blue jays and squirrels seek young pine forests to bury their seed, forget where some of their seed is stashed, and some of these seeds germinate into hardwood tree seedlings.  Over time, this results in a mixed pine/hardwood stand that will eventually result in a hardwood stand.  Personal experience and that of other landowners reveals that naturally grown hardwoods in pine stands generally fare better, i.e., have better survival rates and quicker growth, than planted hardwoods in an open field.  To supplement the work of blue jays and squirrels, landowners can conduct their own "enrichment plantings" after the pine stand is established by cutting gaps in the pine stand and planting these gaps with hardwood seedlings. 

In addition to mimicking natural succession, the added advantage of going with pine over hardwood when reestablishing an old field is cost.  Hardwood trees are very expensive to establish, averaging upward of $2-3/tree (seedling, tree shelter, weed mat, oak stake, herbicide control, and labor) - or well over $600 per acre if planted on a 15' x 15' spacing (200 trees/acre).  Also, most hardwood species are very site sensitive.  That is, each species’ requirements for soil nutrients, light, and moisture are very specific and must be matched to the site appropriate site.  Costs for establishing pine on an old-field site are significantly less, running about $0.30 to $0.50 per tree or $100 to $125 per acre for trees (planted on a 10’ x 10’ spacing), site preparation, and labor.  Pines are more forgiving and tolerate a wider range of site conditions.  If income from timber is a goal, pines generally provide income much more quickly than hardwoods.  Again, pine stands can be managed with the goal of encouraging hardwoods and is a good way to reestablish an agricultural field into forest.

While planting hardwoods is an expensive proposition, it is appropriate on some sites and should be focused on areas where the chance for survival is greatest.  Specifically, hardwood plantings should be focused on wetter bottomland sites adjacent to streams and other water bodies.  Not only are these sites best suited to high quality hardwoods, but cost-share monies are available for establishing hardwoods adjacent to streams (see below).  Another good place to plant fruit and nut-bearing hardwoods is at field-forest edges.  Tree species at field edges provide excellent food sources for wildlife and include: fruits such as persimmon, pear, apple, crabapple, and nut-bearing species such as sawtooth oak, and hickory.

The demand for both hardwood and pine seedlings is very high in the mid-Atlantic and southeastern U.S., testament to the importance of forestry to the region's economy and environment.  A great online source for tree seedlings is the Virginia Department of Forestry online seedling catalog at www.dof.state.va.us.  At this site you will find hundreds of different trees for sale.  Significant discounts are given for large quantity sales.  You should also check with your state forestry agency for the appropriate species for your site, availability, and cost of locally grown seedlings from public and private sources.  Winter is the best time to place your order as early spring is tree-planting time and many nurseries sell out of popular tree species early in the season.