North Quabbin Forestry

Crop Tree Management and a Timber Marking Guide

Crop Tree Management focuses on promoting the growth of the more desirable trees by thinning around them. Crop trees can be timber crop trees, wildlife crop trees, and crop trees noted for their scenic beauty. Since many landowners find traditional even-aged forest management too severe and always want to see large trees on most of their property, Crop Tree Management is an attractive alternative.

I. Benefits of Crop Tree Management:

1. Can significantly accelerate the growth of timber crop trees. You can double the diameter growth of released crop trees. A crop tree harvest allows sunlight onto all sides of the crop tree and crop tree growth is maximized as the crop tree has more room to grow.

2. Maintain or improve wildlife habitat by retaining or developing more den trees/acre.

Increase wildlife habitat by encouraging the development of understory vegetation and increased production of mast bearing trees such as oak.

3. Maintain or improve scenic beauty by retaining trees that are unique in the forest due to size, shape, color of foliage, or unusual form.

II. Crop Tree Selection Criteria:

1. Timber Crop Trees:

A. Select dominant and codominant trees.

B. Favor desirable high value tree species (white pine, red oak, sugar maple, and cherry).

C. Should have at least one potential 16 foot sawlog in the main stem.

D. Crowns must be large and healthy relative to diameter with no sign of top dieback or insect or disease damage.

E. No epicormic branches in the lower 17 feet of the main stem. You want to produce at least one 16 foot sawlog. The extra foot is for trim.

F. Stem form must be reasonably straight and free from forks or severe sweep and crook in the lower 17 feet of the main stem.

G. Red oak responds well to release, while epicormic branching is not serious.

For white pine, the response to release depends primarily upon how strong the competition has been and how long the pine has been in a subordinate position. In general, pines less than 30 years old with at least 1/3 of their height in live crown will respond well, but response declines proportionally with increasing age and decreasing crown length.

2. Wildlife Crop Trees:

A. Trees at least 15 inches in diameter are preferred.

B. Any species is acceptable for den trees.

C. Favor mast producing species such as oak, hickory, and disease free beech which have large healthy crowns and are especially valuable to many wildlife species.

3. Scenic Crop Trees

A. These trees can be of any species. Favor trees that have a unique or distinctive form or are distinguished from other crop trees by their great size, attractive foliage, or unusual occurrence.

Red and sugar maples have brilliant fall foliage. White birch can be very attractive. Trees with unusual bark like shagbark hickory or attractive bark like disease free beech can be retained.

Large straight hemlock trees can be very distinctive. White pine can grow to exceptional size.

Old white oak with gnarly branches are rare and are exceptionally attractive.

Timber Marking Guide

 I. Using the Crown Touching Release Technique:

Remove all intermediate, codominant, and dominant trees that interfere with the crop trees (except another crop tree). Most crop trees will be released on all 4 sides and have at least a 5 foot release area around the perimeter of the crop tree crown. Try to pick crop trees about 25 feet apart and you should end up with enough crop trees/acre in most sawlog size forest stands.  Some crop trees may be spaced 15 feet apart, while other crop trees may be spaced 35 feet apart. Occasionally, two high value crop trees may be left close to each other and treated as a single crown. Try not to leave groups of more than 2 crop trees close to each other, otherwise the growth response will be small.   

II. Marking the Trees to be Cut:

 1. Before marking the timber, all boundary lines must be determined and marked (usually with red paint) Trees to be cut are marked (usually with blue paint) at chest height on both sides and at the stump  along North-South or East-West transects. This will aid the timber harvester as well as provide assurance that only marked trees were cut.

2. While retaining the Wildlife Crop Trees and Scenic Crop Trees, mark trees that are growing below the optimal rate of return and are interfering with the growth of the more valuable Timber Crop Trees:

A. Cull Trees:

  1. White Pine: multi-stemmed, poorly formed “wolf trees” and younger “cabbage pine” (caused by the white pine weevil which attacks the leading terminal shoot of white pine).

  2. Hardwoods: evidence of significant butt rot; large trunk cankers (nectria canker on birch, cobra canker on sugar maple, strumella canker on oak)

B. Low Vigor Trees:

  1. Overtopped suppressed trees.

  2. Poor crown density.

  3. Low live crown ratio.

  4. Large dead branches in crown.

  5. Roots may be sprung.

  6. Serious defects due to insects or disease.

  7. May be some epicormic branches which indicates stress.

  8. Old, over mature trees for site and species.

III. Save Trees That are Growing Well:

 A. High Vigor Trees:

  1. Dominant or codominant crown position in the forest canopy.

  2. Good leaf density for species; leaves dark green. Good live crown.

  3. Smooth bark (especially on white pine) is an indication of fast growth.

  4. No large dead branches in crown.

  5. Roots not sprung.

  6. Defects are minor; no epicormic branches.

  7. Trees of immature age; not overly large for site.

  8. In addition to vigor, good stem form is important as noted above.

IV. Estimating Volume of Trees to be Cut:

   The volume of marked trees is determined by measuring diameter at breast height (DBH) and measuring the merchantable height in the number of 16 foot sawlogs (or 8 foot 1/2 sawlogs). A scale stick is used to measure the DBH in inches and the height in number of 16 foot sawlogs.

The volume for each marked tree is looked up in a volume table which shows the amount of board feet for trees of a given diameter and height.

V. Conducting the Timber Sale.

  After marking all of the timber to be cut, a Forest Cutting Plan is prepared and Notices to Bid on Standing Timber are sent out to reputable timber harvesting companies. After the bid process, the contract is awarded and conditions of the timber sale are spelled out. The details of Forest Cutting Plans and Timber Sale Administration are explained here: https://northquabbinforestry.com/forest-cutting-plans/  .

In conclusion, Crop Tree Management may be the best choice for many landowners.