Planting Southern Pines: A Guide to Species Selection and Planting Techniques

Mississippi landowners have made a strong commitment to tree planting in recent years. Additional interest has been spurred by the Conservation Reserve Program that offers financial incentives to encourage tree planting on marginal cropland.

As more landowners become involved with tree planting, they learn that proper species selection and careful handling and care of seedlings are vitally important in the success of their reforestation investments. Use this bulletin as a guide for selecting the proper species and in handling seedlings throughout all phases of tree planting.

Selecting a Proper Species

Species selection is the critical first step in tree planting. Maximum growth and yield in the plantation are possible only if you select the right species for the particular planting site and geographic location (Table 1). Planting the wrong species on a site results in poor survival, poor growth, and low product yield. Geographic location limits species choice. For example, slash pines planted in northern Mississippi suffer from branch and stem breakage when glazed ice forms on needles.

Species selection also influences products produced. Longleaf pine may be preferred if high quality sawlogs and poles are the product objective. If maximum fiber yield is required, loblolly or slash pine could be favored.

Loblolly pine is usually planted, with limited acreages of shortleaf pine, slash pine, and longleaf pine planted on appropriate sites.

Table 1. Species-Site Selection Guide

Pine tip moth can be a problem in young stands, damaging terminal shoot growth. However, control is practical only in unusual cases. Older trees are not seriously damaged by this pest. Pine bark beetles cause excessive damage to weak, overcrowded, slow-growing stands of loblolly pine. Good management practices that promote vigorous stand growth greatly reduce pine bark beetle hazards.

The Livingston Parish loblolly source is commonly available and has good growth and resistance to fusiform rust. It is well suited for planting on high hazard fusiform rust sites in the Coastal Plain and on other loblolly pine sites. This variety can be planted throughout most of the Coastal Plain. However, ice glaze damage restricts plantings to the southern two-thirds of the state.

Ice glaze damage may be a problem in loblolly pine stands in the northern limits of the state, particularly in heavily thinned, open stands. Light, frequent thinnings minimize ice glaze damage.

Slash pine is sometimes planted in the Lower Coastal Plain for pulp, sawlog, and pole productions. Stands tend to stagnate if not thinned early to maintain adequate crown development. If thinnings are delayed until trees are 25 to 30 years old, little response will be gained from the thinning.

Bark beetles attack slash pine, particularly during extended dry spells, after stem damage from lightning strikes, and after logging operations. Other insect pests, such as pine tip moth, cause only minor damage in most cases.

Slash pine is very susceptible to fusiform rust. Trees that develop galls in the main stem are prone to breakage and early mortality. The fungus Fomes annosus can invade recently thinned slash pine and loblolly pine stands. The fungus attacks the tree's root system, ultimately killing the tree. Thinnings made during the summer lessen the chance of disease. Use chemical controls during thinning operations in high-risk areas.

With the advent of statewide fire control and because of its inability to tolerate weed competitions, the longleaf pine has largely been replaced in its native range by slash and loblolly pine and native hardwoods. (Periodic fires once kept competing vegetation to a point where the more fire-resistant longleaf was easily established and flourished.) The often prolonged grass stage in which long-leaf seedlings may remain for 3 to 8 years is a period in which no height growth occurs. The delay in onset of height growth allows competing vegetation to occupy the site at the expense of the longleaf seedlings. Once out of the grass stage, longleaf grows rapidly, producing trees with straight, clear trunks that are highly valued for lumber, poles, and piling.

Research shows that the grass stage is shortened and successful regeneration is possible by using high quality seedlings developed in breeding programs, proper planting techniques, and adequate site preparation with herbaceous weed control during the first growing season. Longleaf is a good choice for dry and intermediate sites where fusiform rust is a hazard to successful establishment and growth of loblolly and slash pine.

Longleaf pine is less susceptible than other southern pines to bark beetles and other insect pests. Fusiform rust is not a serious problem in longleaf stands. However, in some areas, seedlings are susceptible to brown spot needle blight fungus. When brown spot infestations are severe and prolonged, seedling death occurs. Use chemical treatments and prescribed burning to control brown spot.

Littleleaf disease is the most serious problem with shortleaf pine management. Trees in stands established on fine-textured soils that periodically are excessively wet and then dry begin showing stunted, yellowing needles when their age exceeds 30 years. Damage is caused by a fungus pathogen that feeds on tree roots, reducing water and nutrient uptake. Diameter growth is greatly reduced, and mortality is very high. Control is impractical. The recommended treatment is to salvage the trees before they die or before they are attacked by bark beetle, and then to replant loblolly pine.

Species selection in Mississippi is normally an easy task since loblolly pine is preferred on most sites. However, landowners in the Lower Coastal Plain are faced with several alternatives and must compare several species to determine which is best for their site. The most common problem is deciding between slash pine and loblolly pine. Slash has historically been favored in the Coastal Plain, not only for pulp and timber production, but as a source of resin and turpentine, along with longleaf pine. However, loblolly pine plantings have greatly increased in the region, and many landowners and foresters are unsure as to the merits of loblolly versus slash pine.

The following comparisons should help make the slash-loblolly pine selection in the Coastal Plain clearer. As with any tree, it is critical to match the species to the site. Soil properties and drainage are often used to decide between planting slash or loblolly pine on a particular site. General soils-site conditions and species preference are summarized in Table 3.

Other generalizations have been made to compare loblolly and slash pine in the Coastal Plain:

• Slash pine is usually preferred on wet poorly drained flatwoods sites; loblolly is favored on moist to better-drained soils.
• Loblolly is favored on good sites where hardwood competition is a problem because slash pine is less tolerant of hardwood competition.
• Slash pine grows better than loblolly pine on poorly drained sites where phosphorus is limited (determined by soil test) if the site is not fertilized.
• Although both slash and loblolly become infected with fusiform rust, slash pine grows better than loblolly pine if the site is not fertilized.
• On well-drained sites with moderate incidence of fusiform rust, improved seedlings of loblolly and slash pine perform about the same.
• Longleaf pine and slash pine are suited for resin and turpentine production. A slash pine variety is available for "high gum" production that produces up to 50 percent higher gum yields than nursery-run slash pine.
• Loblolly pine is more susceptible to attack from Southern pine beetle than slash pine.

* Adapted from Fisher (1981).
** Spodic horizon refers to a spodosol common in "flatwoods" areas. These soils are characterized by a surface of a light-gray to white sand over a darker sandy loam subsoil. A fragipan may be present that restricts root growth and limits downward movement of water.
*** Phosphorus may be required for establishment of loblolly pine on very poorly drained soils.
**** Use longleaf only on the better drained soils in these groups.

Coastal Plain planting sites -- Fusiform rust is often severe in the Lower Coastal Plain areas. Seedlings from improved strains of loblolly pine exhibiting good growth and resistance to fusiform rust are preferred. Livingston Parish loblolly pine seedlings are a proven rust-resistant source suitable for planting throughout the Lower Coastal Plain.

Ordering Seedlings

Once you select your species, order your seedlings from the nursery. Plan ahead to allow for adequate site preparation and to insure availability of seedlings. Most state and private nurseries begin taking seedling orders in mid-summer. Place orders early so that you have enough seedlings to meet your planting needs.

Several decisions must be made before ordering seedlings, such as how many seedlings you need and when they should be delivered. Information in the preceding sections will help you select the right species for your planting sites.

To determine the number of seedlings to order, consider several points:

1. How many acres are you going to plant? Determine acreage by actual field measurement, or estimate from maps, aerial photos, or other records.
2. What spacing will you use? Most pine plantations are established with 600 to 700 seedlings per acre. More or fewer seedlings may be planted based on the landowner's objectives. A minimum of 600 seedlings per acre may be required for participation in many federal assistance programs. In some cases the forest industry has planted seedlings at densities of up to 1,000 seedlings per acre to maximize fiber production in short rotations for use in their pulp mills. However, most landowners will get better returns by planting 600 to 700 trees per acre and managing for multiple products, such as pulpwood, chip-n-saw, sawtimber, and poles.

   Seedlings are planted at different spacings to achieve the desired density. A general trend is toward wider spacing between rows for better stand access for fire control, thinning, and harvesting equipment. Compare various spacings by using Table 4.

   Determine the number of seedlings required for any spacing by using this formula:

   Multiply desired spacing in feet and divide that product into the number of square feet per acre.

   For example, how many seedlings would be required to plant one acre at a spacing of 6 by 12 feet?

   6 feet by 12 feet = 72 square feet
   43,560 square feet per acre/
   72 square feet per seedling =
   605 seedlings per acre.

3. Make an allowance for cull seedlings. Cull seedlings are seedlings that are too small or too large to plant and those that died or were damaged before planting. Identifying cull seedlings is covered in detail in a later section. When ordering, allow for a 10-percent cull factor (i.e., seedlings that you will discard and not plant). Deduct these from the total number of seedlings ordered. In effect, you will be ordering 10 percent more seedlings than you calculated you needed for planting. This also helps to account for any shortage in the number of seedlings actually packaged.

   If you order seedlings to plant 35 acres at 7 by 10 spacing and allow for a 10-percent cull factor, you need to order 24,000 seedlings.

   7 by 10 spacing = 622 seedlings per acre (See Table 4.)
   35 acres by 622 seedlings per acre = 21,770 seedlings
   10 cull factor: 21,770 x .10 = 2,177 seedlings
   23,947 rounded to the next highest 1,000 = 24,000 seedlings to be ordered

Early planting before cold weather can kill seedlings if they have not hardened off while still in the nursery beds. Hardening-off is a physiological process where seedlings become acclimated to colder temperatures by reaching a stage of dormancy where active growth is temporarily suspended. Some nurseries use chilling hours (temperatures between 33 °F and 40 °F) as an indication of dormancy. Chilling hours are monitored in the nursery, and seedlings are lifted after 200 or more chilling hours have accumulated. This allows seedlings to be planted immediately or stored for no more than two or three days. When 400 chilling hours have accumulated, seedlings reach peak dormancy and can be cold-stored for up to 8 weeks. When you order seedlings, ask how the nursery determines that seedlings are properly hardened-off and are ready to lift.

If large acreages are to be planted or delays expected, arrange with the nursery to split shipments of seedlings to allow you to store and handle a minimum number of seedlings at a time.

Proper storage conditions must be provided before planting to maintain seedling quality. It is always best to plant seedlings as soon as possible. Do not store nondormant seedlings lifted early or late in the planting season; plant them immediately. Plant longleaf pine seedlings within one week after lifting from the nursery. These seedlings are extremely perishable and should be planted immediately if possible.

When you accept delivery of your seedlings from the nursery, you should be sure that they are protected from direct sun, high temperatures, and freezing temperatures. If you pick up your seedlings from the nursery or distribution point, provide cool shaded conditions for transportation of the seedlings. Arrange to pick up seedlings in late afternoon and schedule long-distance hauling at night to prevent heat buildup from the sun. If an open truck or trailer is used, a tarp can shade the seedlings, but be sure to allow for ventilation under the tarp and around the seedlings to prevent heat buildup.

To prevent water loss from open-end bales, avoid exposing the bales to wind during transport. Avoid stacking bales or bags of seedlings over two high without providing space between packages for air circulation and support to prevent crushing.

Cold-storage facilities offer the best conditions to store pine seedlings. Dormant seedlings packaged in bales, bags, and boxes can be kept for 8 to 12 weeks in cold storage at temperatures of 33 °F to 36 °F and high relative humidity. If seedlings are packaged in bags, relative humidity is less important. Baled seedlings may require periodic watering to prevent drying during long storage periods. Always allow excess water to drain from the bales to prevent damage from decay. Damage from lack of water drainage is evidenced by discolored roots and a sour smell when bales are opened. Seedlings in K-P bags and boxes and seedlings with clay-coated roots do not require watering if the packages have been unopened and undamaged. (Roots coated with kaolin clay are white.)

To prevent seedlings from drying out, store them at a relative humidity of 85 to 95 percent. If the relative humidity inside the storage chamber falls below 80 percent, spray water on the walls and floor to increase humidity. Do not stack bales, bags, or boxes over two high, and always allow for adequate air circulation around all containers. This also prevents damage from crushing.

Most landowners do not have access to cold-storage facilities; therefore, when seedlings cannot be planted immediately, landowners must rely on shed storage where temperatures cannot be controlled, but where seedlings can be protected from wind and temperature extremes. Baled seedlings can be stored for up to 8 weeks when watered every 2 to 3 days, draining excess water from the bales.

Seedlings in bags and unopened boxes trap heat generated from respiration. This heat buildup within the package damages the seedlings. If storage temperatures exceed 40 °F to 50 °F for several days, the vigor of seedlings in bags is reduced. Because of the potential damage from overheating, do not store seedlings packaged in bags or boxes for more than 4 weeks without cold storage.

Warm air temperatures may limit safe shed storage time. Allowing storage temperatures to reach 80 °F causes mold to develop on the seedling roots, initiating decay. Mold may be detected by the presence of fungal hyphae (spider-web-like strands around the seedling roots) and a musty smell when the packages are opened.

If seedlings freeze, let them completely thaw before attempting to separate and plant. Immersing the frozen seedlings in cool water for short periods helps to speed thawing. (Do not soak for more than an hour.) Freeze-damaged root systems will appear limp and discolored, and root tips will easily slough off in handling. Discard seedlings that have suffered freeze damage. Longleaf pine seedlings are likely to be killed if frozen.

You can store seedlings by removing them from their packages and heeling them into shaded shallow trenches. Cover roots with moist soil and water frequently. Lift seedlings before active root growth begins. Look for expanding white root tips as a sign of active root growth. Seedlings are easily damaged when removed from the trenches as roots are stripped off.

Seedlings can also be selected for planting on particular sites. For example, short, stout seedlings with dense fibrous root systems would perform better than taller seedlings with long root systems on sites with shallow, droughty soils. Taller seedlings with well-developed root systems are preferred over shorter seedlings on sites where herbaceous competition is uncontrolled and will quickly overtop the seedlings.

Grade the seedlings in a cool, high humidity area protected from sun and wind before they are taken to the field and given to the planters. As seedlings are removed from their packages, dip them in water, clay, or one of the synthetic gel root dips to reduce drying of the roots. (Check with forestry and farm chemical dealers for gel dips.) Seedlings with roots coated with kaolin clay can stand brief periods of exposure with minimal damage to roots. After grading, promptly repackage seedlings in their original containers with sufficient moisture, or place them in buckets or tubs with water to keep them from drying out while being transported to the field. Do not allow seedlings to sit in water for more than one hour. Allowing planters to grade during planting slows work and can result in cull seedlings being planted.

One or two people can handle grading and any necessary root pruning. Graders should know the grading standards presented in Table 5 and be aware that stem length is less important than stem root-collar diameter and root system development. Seedlings with thick sturdy stems 6 to 12 inches long and well-developed root systems with 5 or more lateral roots have the best initial survival and growth.

An optimum root system is 6 to 8 inches long with at least 5 to 7 or more strong first order lateral roots that are at least 3 inches long. Use seedlings with root systems 5 to 6 inches long with good lateral root development to plant sites with restricted rooting zones or high water tables. Otherwise, cull all seedlings with root systems less than 5 to 6 inches long and those with less than 3 strong lateral roots. If root systems are more than 8 inches long, the seedlings are difficult to plant correctly without special care and supervision during the planting operation.

Do not allow planting crew members to prune roots during the planting operation. This results in the roots being stripped off and leads to poor survival. Prune roots with scissors, shears, a hatchet, or machete. Make a single clean cut, removing as little of the roots as necessary. When root pruning is necessary, keep the pruned root system in balance with the top. Prune roots to no less than 8 inches in length for seedlings with tops of 8 to 12 inches.

* Adapted from Wakely (1954) and May (1986).
** Grade sand pine to shortleaf pine standards.

Seedling quality deteriorates quickly with careless field storage and handling. Always provide a shaded storage area. A tarp can be erected as a canopy above the seedlings to keep off direct sun. Be sure there is ample ventilation to prevent heat buildup in the packages. Temperatures exceeding 50 °F inside the packages quickly reduce the quality of the seedlings.

Do not lay a tarp directly over the seedlings during the day as temperatures inside seedling packages can quickly exceed 50 °F on sunny days, even when air temperatures are moderate. Cover seedlings left overnight in the field with a tarp to protect against freezing damage. Repair any tears or holes to the packages with duct tape. Repackage the seedlings as necessary. If seedlings are to be graded at the field site, be sure to do so in a cool shaded spot protected from wind and sun.

When giving seedlings to the planters, open and empty only one package at a time. Make sure that planters carry seedlings in bags or buckets. Never allow seedlings to be hand carried with roots exposed while planting. Have water and clay or synthetic gel dips available to keep seedling roots moist. Do not leave seedling roots in water for more than one hour, but repackage them in their original packages.

Depending on the site, both hand and machine planting are efficient and reliable planting options. Large open tracts are more easily planted by machine; smaller or irregularly shaped tracts, sites with minimal site preparation, and rocky sites are more easily planted by hand.

Show planters the correct depth to plant seedlings. The depth will vary with soil-site conditions, but plant seedlings no deeper than the length of the dibble bar or planting foot on the machine. Shallow planting results in early seedling mortality, particularly during early spring and summer droughts. On many "old field" sites where the soil contains a dense traffic pan or hardpan near the surface, subsoiling breaks up the pan to permit deeper planting. Slash, loblolly, and shortleaf pine can be planted up to 2 to 3 inches above the root collar, provided the planting hole is deep enough to avoid root deformation. Improper planting, resulting in J-rooting or L-rooting, slows early seedling growth. In wet soils with a high water table, plant only to 1 inch above the root collar.

Longleaf pine requires special care in planting and great attention to planting depth. Plant longleaf seedlings so the bud is not buried or the root collar exposed. The large tap root and lateral root system of high quality longleaf seedlings require larger and deeper planting holes than other pines. Hand planters should use the large KBC dibble rather than the narrow OST dibble. Machine planting is preferred when possible.

Regardless of planting method, plant seedlings at the correct spacing and depth so that the roots are not deformed and the soil is firmly packed around the roots. This eliminates air pockets. Have a written contract that details all planting specifications, including transport and handling of seedlings, planting dates, packing, and conditions when planting is to be suspended (site too wet or dry, freezing weather, or summer-like conditions). The contract should provide for inspections during planting to insure that quality standards are met before payment is made. This is especially important when planting with assistance of cost-share programs.

Have a supervisor at the site to insure that planting proceeds smoothly and properly. The supervisor should watch for poor practices, such as planters' stripping off roots to make planting of large seedlings easier, slow planters' discarding seedlings to "catch up" with the faster planters, shallow planting, loose packing, and carrying seedlings in hand during planting.

To insure correct spacing, frequently check distances of planted seedlings within and between rows. Proper packing is necessary to eliminate air pockets around the roots. Check by grasping several needles at the tip of the seedling between thumb and forefinger and gently try to pull the seedling from the soil. The needles should break if the seedling is firmly packed. A shovel can be used to dig around seedlings to check for "J-rooting."

Show your planting crew the correct dibble planting technique:

1. Insert the dibble straight down into the soil to full depth of the blade and pull back on the handle to open the planting slit. (DO NOT rock the dibble back and forth, as this causes soil in the planting slit to be compacted, hindering root growth.)
2. Remove the dibble and push the seedling roots deep into the planting slit. Pull the seedling back up to the correct planting depth (1 to 3 inches above the roots to fall straight inside the planting slit). DO NOT twist or spin the seedling into the planting slit or leave the roots "J-rooted."
3. Place the dibble several inches in front of the seedling and push the blade halfway in the soil. Twist and push the handle forward to close the top of the slit to hold the seedling in place.
4. Push down to the full depth of the blade and pull back on the handle, closing the bottom of the planting slit, and then push forward to close the top, eliminating air pockets around the roots.
5. Remove the dibble, and close and firm up the opening with your heel.

Seedlings are planted with machines using two systems: a manual system, where the seedling is placed into the trench by hand, or an automated system, where seedlings are placed in "fingers" that then place the seedling into the planting trench.

Frequently check planting performance to insure proper planting, particularly when soil type, texture, moisture, or amount of harvest debris changes on the site. Maintain proper adjustment by carefully checking planting performance under actual site conditions. Adjust packing wheels to close completely the planting trench from top to bottom. Be sure seedlings are planted straight and at the proper depth. Follow the planter and use a shovel to open the planting trench to judge root placement. "L-rooting" is a common problem with machine planting. Adjust the planter to open the trench to maximum depth and make sure the seedlings are placed at the proper depth and released quickly so the roots are not dragged along the trench.

The best planting conditions are when temperatures are between 35 °F and 60 °F with relative humidity greater than 40 percent and wind speeds less than 10 mph. When air temperatures are in the 70's and low 80's with low humidity (less than 40 percent) and wind speeds of 10 mph or greater, plant cautiously, as seedlings can quickly dry out after planting. If the situation allows, delay planting until conditions improve, or plant in the afternoon hours when seedlings will be exposed to less environmental stress. If planting must continue under these conditions, have planters carry fewer seedlings in the field and take more care to prevent them from drying out. Do not plant in freezing weather or summer-like conditions when temperatures are below 32 °F or above 85 °F.

Seedlings are best stored in their containers where they are protected from root damage and drying out. Protect them from freezing, as the root plugs can easily freeze. The limited soil volume of the container makes the seedlings susceptible to drying out in sunny and windy conditions. Store in partial shade, and water frequently to maintain adequate moisture throughout storage and planting.

Container-grown seedlings may be machine or hand planted, but whichever method is used, it is critical that the planting hole be deep enough so that the top of the root plug can be completely covered with soil. If the top of the root plug is not covered with soil, it will rapidly dry out, and the seedling will die. (This also reduces first heaving of fall-planted seedlings.) Take special care when planting container-grown longleaf pine seedlings. If planted too deep, the bud is covered; if planted too shallow, the root plug is exposed, which rapidly dries out the rooting media.

Stocking represents the number and distribution of living seedlings over the plantation. This information is used to determine whether replanting a portion or the entire stand is necessary. A systematic sampling system is the best way to sample stocking. The number of live trees is counted in fixed-area plots, usually circular plots. These plots are uniformly spaced across the plantation. Plots of 1/50 acre to 1/100 acre in size are convenient. Larger plots are time- and labor-consuming, while the larger number of plots smaller than 1/100 acre required to give an accurate estimate may be prohibitive.

You need 40 to 60 plots to get accurate estimates of first year stocking, regardless of plantation size. Orient sample plots on lines that cross the planting rows throughout the entire plantation.

Avoid interplanting the skips within rows. Newly planted seedlings do not compete favorably with established 1-year-old seedlings. Interplants seldom add to the volume production at harvest, and the added investment for the seedlings and planting cost will not be recovered. If you attempt interplanting, plant no closer than 20 feet to an established seedling. Interplanting may be required in stands established under federal incentive programs to meet minimum stocking requirements. If so, spot herbicide treatments for weed control around the interplants may aid their survival and growth.

Ezell, A.W. 1987. "Hand vs. Machine Planting." Forest Farmer, 47(1).

Fisher, R.F. 1981. "Soils Interpretations for Silviculture on the Southeastern Coastal Plain," Proceedings of the First Biennial Southern Silvicultural Research Conference. USDA For. Ser. GTR SO-34.

Jefferies, K.F. 1982. "Operational Guidelines for Handling Seedlings," Proceedings: 1982 Southern Nursery Conference. USDA For. Serv., R8-TP 4.

Lantz, C.W. 1987. "Which Southern Pine Species Is Best For Your Site?" Forest Farmer, 47(1).

Lantz, C.W., and J.F. Kraus. 1987. A Guide to Southern Pine Seed Sources. USDA For. Ser., GTR SE-43.

May, J.T. 1986. "Seedling Quality, Grading, Culling, and Counting," Southern Pine Nursery Handbook. USDA For. Ser., Southern Region Cooperative Forestry Publ.

May, J.T. 1986. "Packing, Storage, and Shipping," Southern Pine Nursery Handbook. USDA For. Ser. Southern Region Cooperative Forestry Publ.

South, D.B. and J.G. Mexal. 1984. Growing the "Best" Seedling for Reforestation Success. Forestry Dept. Series No. 12. Alabama Agricultural Experiment Station, Auburn University.

Wakely, P.C. 1954. Planting the Southern Pines. USDA For. Ser. Agri. Monograph 18. 233p.

Xydias, G.K., R.D. Sage, J.D. Hodges, and D.M. Moehring. 1983. "Establishment, Survival, and Tending of Slash Pine," The Managed Slash Pine Ecosystem. School of Forest Resources and Conservation, Univ. Florida. Gainesville, FL.

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Publication 1776
Extension Service of Mississippi State University, cooperating with U.S. Department of Agriculture. Published in furtherance of Acts of Congress, May 8 and June 30, 1914. Ronald A. Brown, Director