Pine seedlings are commonly packaged in open-end bales, kraft-polyethylene line (K-P) bags, and wax-coated boxes. These packages protect seedling quality during transport and storage.
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 non-dormant 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 timberland owners do not have access to cold-storage facilities; therefore, when seedlings cannot be planted immediately, they 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.
Preparing Seedlings for Planting
Seedlings of various sizes and quality may be in your order. Some nurseries grade seedlings to a uniform size before packaging. Others attempt to produce a uniform seedling in the nursery bed to eliminate the added expense of hand grading after lifting. Grading before planting removes seedlings that are too large or too small to be planted. It also removes seedlings with roots and stems that are broken, crushed, have bark missing, roots or needles stripped off, stem swellings indicating fusiform rust, or that are otherwise damaged.
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. 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 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.
Seedling Care in the Field
When transporting seedlings to the planting site, take only as many as can be planted in a day. If time and logistics permit, arrange to have seedlings delivered twice a day to the planting site. Load and transport packages carefully to avoid damage to seedlings.
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.
