Planting Trees

April 16, 2007 at 5:31 am Leave a comment

This page includes information and links about planting trees in Minnesota woodlands.

Planning

Tree planting costs money and is hard work. Good planning is essential. Talk to a local professional forester about species selection, spacing, season and method of regeneration, equipment and contracting options, and other considerations.

planting_hands

Flickr photo by Tim Redpath. Click for original.

Planning for regeneration should begin well before harvesting the site. Thinking ahead may create opportunities for natural regeneration, which can be less costly and every bit as effective planting trees.

Planting stock

Planting seedlings, either bare-root or container-grown stock, is the most reliable way to regenerate a stand, especially for conifers. Bare-root seedlings are the most common. They frequently are designated as 1-0, 2-0 or 2-1 stock, with the first number referring to how many years they were grown in the original nursery seedbed and the second to how many years they were grown in a transplant bed.

Transplants (seedlings that spent a year in a transplant bed) generally have a larger root system and stem diameter than seedlings that were not transplanted. Transplants are recommended for regenerating slow-growing conifer species such as spruce and fir, and for harsh planting sites where survival is likely to be a problem.

Seedling costs vary by tree age, species, and quantity ordered. Transplants survive very well, but are expensive and therefore are not widely used. One- or two-year-old seedlings are less expensive than transplants and are recommended for most hardwood and conifer plantings.

Two kinds of seedlings can be purchased: Bare root and containerized.

Bareroot red pine seedlings. Click for a better view. Containerized white pine seedlings.  Click for a better view.

Bare root and containerized seedlings.
Click either image for a better view.

Bare root seedlings are grown in open air nursery beds. When removed for planting, they are bundled without soil.

Containerized seedlings usually are grown in a greenhouse in containers between 1 and 2 inches in diameter. Some biodegradable containers may be planted in the ground with the seedling in them. Others must be removed from the seedling before it is planted. Container-grown stock can be very useful for dry planting sites or for planting late in the growing season.

Cuttings

Cuttings provide another alternative for artificially regenerating certain tree species. These usually are 8- to 12-inch lengths of tree stems about 1/4- to 3/4-inch in diameter (longer cuttings may be used on drier sites). They are cut during the dormant season from the previous year’s growth of vigorous seedlings or stump sprouts. Cuttings usually have no visible roots, but when buried vertically with just an inch of the stem protruding above ground, they will form roots. Rooted cuttings also may be available for purchase.

Cuttings produce an exact genetic replica of the parent tree. They commonly are used to regenerate poplars, but also can be used to regenerate willow and green ash. Cuttings grow best where the soil remains moist throughout the growing season.

Direct Seeding

Fruit (seed) ready for direct seeding. Photo by Brian Lockhart, USDA Forest Service. Click for original.

Photo by Brian Lockhart. Click for original.

Direct seeding is the process of sowing or planting seeds. In Minnesota, direct seeding is most often used to regenerate heavy-seeded hardwoods such as black walnut, oaks, and hickory. It is also used in some cases to regenerate jack pine or black spruce. In the right situations, direct seeding can be relatively inexpensive and can produce prolific regeneration.

Spacing

When designing a plantation, you need to determine an appropriate spacing between trees. Consider the crown width of trees when they reach a useful size. For example, when growing trees for timber, allocate space so individual trees are just beginning to crowd each other when the trees are large enough to support a commercial thinning. A professional forester can help you determine the correct spacing depending on the species and purpose for the plantation.

The following table shows the number of trees needed per acre for various spacings. To calculate the number of trees per acre for other spacings, multiply the planned spacing (in feet) within rows by the spacing (in feet) between rows and divide that number into 43,560. For example, if trees are to be spaced 8 feet apart within rows and rows are to be 10 feet apart, you would plant 545 trees per acre:

43,560 =  545 TREES PER ACRE
8×10

Number of trees per acre at different spacings:

Spacing (ft) Trees per acre
4×4 2,722
5×5 1,742
6×6 1,210
7×7 890
8×8 680
9×9 538
10×10 436
11×11 368
12×12 303

Site Preparation

Site preparation often is necessary prior to planting. Its purposes usually are to expose mineral soil and set back competing vegetation. While site preparation can be done with hand tools, this method usually is expensive and vegetation that is cut down may resprout. There are herbicides available for site preparation that may be very effective and economical in some situations. You also can use mechanical methods such as disking, scalping, or trenching. If you use mechanical methods, be careful not to destroy the nutrient-rich organic layer near the soil surface. Often a combination of mechanical and chemical methods is most effective. In some circumstances controlled burning can be used to remove debris from sites and temporarily reduce vegetative competition.

Handling seedlings

The Minnesota Department of Natural Resources packages its nursery trees in a plastic bag inside a wax-lined cardboard box. It recommends the following handling procedures:

  1. Protect the box of seedlings from direct sunlight and heat.
  2. Plant the seedlings as soon as possible. Seedlings should not be stored for more than three to five days and then only at temperatures of 35° to 45 F.
  3. Once you open the package, plant the seedlings immediately. Exposure of tree roots to hot sunlight and drying winds for three to five minutes may be fatal.
  4. While planting, keep the seedling roots moist, but do not immerse them in water for more than an hour.
  5. If you need to postpone planting for more than three to five days after receiving the trees, remove the seedlings from the container and heel them in a trench.
Heeling in seedlings for temporary storage

Heeling in seedlings for temporary storage

To heel-in trees, dig a V-shaped trench in a cool, shady location, deep enough so the earth will cover the entire root system and part of the lower stem. Open the boxes, spread the trees along the sloping side of the trench in two or three layers, pack soil around the roots, and water as necessary to keep the roots moist. Store trees in this manner only as long as they remain dormant.

An even better storage method is to place the seedlings in a refrigerator set at 40 F or slightly cooler.  It is absolutely essential that seedlings be planted before new growth starts to emerge. The sooner you plant the trees after they arrive from the nursery, the better the survival will be.

Planting
The best time to plant is in the spring as soon as the frost is out of the ground. At this time the soil is moist, the climate is somewhat mild, and normally there is ample rainfall. If necessary, container-grown seedlings can be planted later in the growing season. Fall planting usually is less successful because frost heaving may occur, especially on fine-textured or wet soils, and growth regulators in the tree may become imbalanced, leading to top dieback.

Be sure to take good care of seedlings before you plant them. They should be dormant when you receive them (i.e., the buds should not be elongating or flushed). Do not let the roots dry out or freeze.This will likely kill the trees, but since the crown will appear alive (conifers will remain green) for a period of time, you may not realize it. To minimize risk of tree roots drying during shipment, ask nurseries to ship by the swiftest transportation available. If you transport the trees yourself, protect them from wind and sun during transit.

General tree planting guidelines

You may plant trees by hand or machine. Regardless of the method, follow these rules:

  1. Plant the tree at the same depth that it grew in the nursery
  2. Plant the tree in a vertical, upright position to avoid a crooked stem.
  3. Place the roots in the planting hole in a normal position without twisting or bending.
  4. Carefully firm the soil around the roots to eliminate air pockets.
  5. Plant only when soil moisture is adequate to ensure survival.

Hand planting

Photo by Brian Lockhart. Click for original.

Photo by Brian Lockhart. Click for original.

There are two general methods of hand planting. One of these is the hole method. Dig a hole with a shovel, mattock, or grub hoe. It should be large enough to accommodate the tree roots without bending. Place the tree in the hole, distribute the roots evenly, and pack the soil firmly around the roots, covering the root collar. This method usually results in a high rate of survival, but it is slow and is not practical for planting large numbers of trees.

The slit or bar method is preferred when a large number of trees are being planted because it is faster. Insert a spade, planting bar, hoedad or similar tool into the soil and move it back and forth to form a V-shaped slit. Insert the tree seedling into the slit so it will be buried to the root collar or to the same depth the tree was growing in the nursery. (If you err at all, plant slightly too deep rather than too shallow.) Remove the planting bar and reinsert it about three inches behind the seedling. Pull the bar back to firm soil around the roots, then push forward on the bar to seal the top of the planting hole. Push soil into the second slit and press down firmly with your boot to seal the slit. Using this method, you can plant 1,000 to 3,000 seedlings per day, depending on your experience and the condition of the planting site.

This website illustrates proper hand-planting technique.

Tree planting machines
There are many designs for tree-planting machines, but generally they have a coulter that breaks through the soil surface, a V-shaped blade that opens a trench into which the operator places seedlings, and packing wheels that firm the soil around the seedlings. Some newer planting machines have spray attachments for applying herbicides for grass and weed control.

Tree-planting machines work best where terrain is fairly level and the site has been cleared of stumps and logging debris. If you use a tree-planting machine, protect seedlings from the wind and sun so the roots do not dry out. Place seedlings erect in the planting trench at the proper depth and pack the soil firmly around the roots. A three-person crew using a tree-planting machine can plant about 10,000 trees in an eight-hour day.

Protecting planted seedlings from damage

To you, newly planted seedlings are a future forest. To hungry deer, they’re a welcome meal on a cold winter day.

Deer herds in our area are far, far above historic norms. Deer love to browse seedlings, and unless you protect the seedlings well, deer will wipe them all out in the first winter after you plant them. There are a few common strategies to reduce deer browse damage:

Budcapping. The main problem with deer browse isdamage to the terminal leader (the tallest central stem). Stapling an index card over the terminal bud may deter some deer. I’ve heard other landowners talk about using different materials in place of paper once the deer get used to the paper. Other readers may want to suggest other materials?

Click for a better view.

Deer repellents : There are a variety of deer repellent products out there. Some are made from hot chili peppers, some from rotten eggs, some from blood meal (image), and maybe some others. You should be able to find these at garden supply centers.

Again, these have varying rates of effectiveness. But they do seem to work, at least for a while, in most cases. If you care to read more, here are links to two studies of different deer repellent products: Comparison and to a Walnut Council Deer Repellent Study (Illinois).

Fencing: While very effective, this approach quickly gets cost-prohibitive for large areas.

You can read more about reducing deer damage in this 2003 Forest Tree Notes article by Mike Demchik.

Competing vegetation: If you can keep the deer off of your seedlings, you’ll still need to control competing vegetation, especially in old field situations. There are many different ways to approach this, including use of herbicides, mechanical soil disruption (like discing), and more.

This will need to be an ongoing effort–planted seedlings will need several years of vegetation control in order to overtop and outcompete the weeds. You can learn more about controlling competing vegetation in your tree plantings in an Extension publication called Vegetation Management in Forestry and Agroforestry.

Read one family forest owner’s tree planting story on our discussion board.

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News and information of interest to Minnesota woodland owners. Sister site to MyMinnesotaWoods.org.

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