Seedling Care

Seedling Care

The process of moving a planted tree from one growing site to another (transplanting) can result in a lot of shock to the tree. Your job is to keep this shock to an absolute minimum, in order for the tree to stand an excellent chance of survival. Seedlings are living organisms. When not in their natural environment, they are extremely vulnerable to physical damage and stress caused by poor care. Exposure to high temperatures, low humidity, or rough handling physically damages the seedling, or alters physiological processes.

Overwintered (frozen) seedlings become physiologically active (ie. respiration) at +4 degrees Celcius. Once active, the seedling begins to use up stored reserves of food and water. The higher the temperature, the faster the food and water is used up. These are the same reserves that the seedling needs to produce roots and to establish itself when planted. In a planting situation, the longer a seedling sits in a warm box or a planting bag, the less chance it has to establish itself and to grow. Therefore, seedlings must be protected from high temperatures at all times.

All physiological processes in the seedling require water. To prevent desiccation (drying out), seedlings must remain moist. The seedling's root system is especially sensitive to drying out because the roots have no protective covering like the needles have. In closed boxes, the humidity level is high. However, in open boxes and in planting bags, the moisture levels can become critically low, especially as temperatures and winds increase. Exposing the roots of a bare-root seedling to direct sunlight and temperatures of +20 degrees Celcius for as little as 20 or 30 seconds will kill the fine root hairs that absorb water and nutrients.With both bare-root and container seedlings it is important that moisture levels are kept high in the boxes and especially in your planting bags. Spring trees have been frozen during the winter, and should be stored in closed boxes. Summer trees have been "hot-lifted" and are growing upon delivery. Summer trees should always be stored standing up in boxes, with the tops open.

All plants and their parts react to mechanical disturbances. Dropping boxes of trees, shaking, and pulling seedlings all cause internal physical damage. Root systems in particular are very susceptible. Minimize exposure to the sun, wind, and high temperatures. Seedlings should never be in planting bags for more than one hour. Peat moss or sponges in bags should always be kept moist. Always bag out before taking a break or coming back to the cache. Trees must be packed standing up in your planting bags. Do not over-fill planting bags, so that loose trees or bundles can fall out onto the ground. Do not remove plastic bundle wrappers from more than one bundle at a time (check with your foreman for particular details on each contract). If frozen stock is discovered, let thaw gradually in the shade in open boxes – never lay frozen bundles out in direct sunlight.

A seedling's root must be planted in mineral or humus soil – soil that "sticks" when squeezed between your fingers. Moss, twigs, rotten wood (red rot), grass sod or duff are not adequate growth mediums. These materials dry up too quickly. Wet sphagnum moss areas can be planted, as long as they do not include standing water. If the shovel hole fills with water immediately as the hole is opened, the ground is probably too wet to plant (ask foreman for special techniques for planting in swamps, sphagnum, etc.).

The screef (an area for the seedling which has been cleared of debris) must be large enough and deep enough to remove competing vegetation and root mats from around the tree, and expose an area of mineral soil. A scalp is similar to a screef, but not as comprehensive – living vegetation, debris, etc. is cleared, but roots, etc. may not be removed down to mineral soil. Check with foreman on each individual contract to determine minimum required screef/scalp size. Many contracts nowadays use FH or LFH planting methods, whereby screefing is minimized. The initials LFH stand for litter, fungus, and humus, the layers on the surface of the ground. On many contracts since about 1995, it has become common for planters to be allowed to plant the seedlings through certain of these layers, rather than removing them.

Spot selection – don't plant in depressions (water and frost can collect and damage seedlings). In site-prepped ground (ie. ripper plough, disc trenching, or mounding, never plant in the bottom of the trench – always try to hit as high up the side as possible while still maintaining that the roots are in mineral soil.

Summary of Some General Stock-Handling Rules

  • While transferring boxes of trees from a truck to the main cache, boxes should be passed and not thrown. Special attention should be focused on NOT dropping the boxes.
  • When loading a pick-up or ATV with boxes for transportation, make sure the boxes are firmly packed and if piling more than two layers, use racks (ie. plywood, slats, or sticks) to keep the weight evenly distributed.
  • Never stack boxes more than four high and keep enough space between boxes for adequate air circulation. Cover boxes with an elevated large silvicool tarp.
  • Boxes of trees should always be stored in a shaded area (preferably forest), and covered with a reflective tarp.
  • Field caches should be in the shade, ie. timber, north slope, near streams, patches of snow, and make sure there is good air circulation.
  • The inside of the box must never be allowed to warm up.
  • Trees must be transferred directly from your box to your planting bags.
  • Bare-root stock may need the roots dipped in a mixture of water and peat moss (slurry) before loading them into your bags.
  • Insert bags must always be sealed with the exception of your feeder bag (drawbag).
  • Moisture must always be kept in the bottom of your bags, in the form of wet moss, peat moss, or sponge(s). The roots of all trees must be kept damp at all times, and under all weather conditions. A dry tree is a dead tree.
  • Never leave trees in your planting bags for any length of time, ie. overnight or during breaks.
  • Always bag out before quitting or put your trees back into the box.
  • Don't leave boxes of trees in a pickup, especially in warm weather.
  • Boxes must be covered with a reflective tarp at all times.
  • Boxes must be put back in the main cache on days off, etc. Individual caches should only hold about a half day's supply of trees.

The Nursery Lift

Spring planting stock is used in most reforestation programs. Seedlings are lifted in late fall when the stock is fully dormant. They are immediately sorted, packaged, and placed in cold storage until required the following spring. Bareroot stocktypes need special handling as the exposed roots are sensitive to drying.

Seedlings of acceptable quality are wrapped in small bundles and packed into boxes where humidity soon reaches 100%. Boxes are usually freezer-stored in cold-storage facilities (reefers) at a constant controlled temperature of -1 to -2 degrees Celcius. Freezing reduces respiration, maintains dormancy, and inhibits the formation of disease molds.

Summer planting stock is lifted in June, July, and August. Although its top growth is partially dormant, summer planting stock is still very physiologically active. Roots are particularly active and vulnerable to damage. The essence of “hot-lifting” and the subsequent planting is speed: lifting, packaging, shipping, and planting must be completed within a few days. Special care is essential so that active roots are not exposed to drying conditions or subjected to physical damage between the nursery and the site.

Seedling Treatment

Planting operations must take the thawing schedules of different stock types into account. Before delivery, the tops and roots must be carefully and evenly thawed: about nineteen days for container stock, and about five days for bareroot. Thawing too quickly damages tissues.

Encountering frozen bundles of seedlings is one of the most frustrating things for a planter to deal with. See your foreman for more advice. The best thing in general is to get the foreman to mix and match boxes to try to provide you with full boxes of seedlings that have no frozen trees, then to leave the boxes with frozen bundles open in the shade to gradually complete the thawing process. Mind you, this isn’t much good when the entire reefer is full of frozen trees, which happens occasionally and may mean a day or two off work.

When seedlings are moved from the controlled environment of the reefer to transport vehicles with less controllable temperatures, strict attention must be paid to box temperatures. Increased temperatures increase respiration which increases temperatures.

How to Minimize Temperature Fluctuations

  • Maintain temperature at 1-4 degrees Celcius for spring planting stock, or 6-14 degrees Celcius for summer planting stock
  • Use the right type of vehicle; reefers for long distances, covered vans with good ventilation for shorter trips
  • Be sure the truck bed is insulated from the exhaust system
  • Check box temperatures to ensure seedlings are not overheating
  • Ensure there is air flow around all sides of the boxes on longer trips. For short trips, cover the boxes securely with reflective tarps, keeping the white side up
  • Avoid transporting in the heat of mid-day
  • Park in the shade.

How to Minimize Water Loss

  • Stand seedlings up in the boxes and water to keep the roots moist and reduce temperatures
  • Replace or repair punctured boxes to prevent moisture loss, inspect for seedling damage, and flushing

Improper handling injures seedlings, and this injury is repaired only at the expense of the seedling's vigor. Handle boxes carefully. Bouncing boxes around in the back of a pickup, ATV, or trailer causes physical damage, shock, and stress. Be sure boxes are firmly packed and use properly spaced racks. Do not drop, throw, or crush boxes together. The boxes may not break, but fine seedling roots will. Note: at Folklore, we keep several dozen pieces of wooden "one by three" slats in the back of all the FIST's (Forest Industry Seedling Transport?) and canopy trucks, to use between layers of boxes to keep them spaced out, and more importantly, to keep the boxes in better shape after being transported over bumpy roads. This incidentally makes it easier to move the boxes around on the quads afterwards.

At the planting site, short-term storage must be good if seedling vigor is to be maintained. Portable reefers provide a properly controlled but costly environment. In many situations, local innovation and initiative must be used to ensure that satisfactory alternative storage is developed.

How To Provide Proper On-Site Storage

  • Don't leave boxes of trees in the back of the truck in warm weather
  • Select a field cache in the shade (timber, north slope, near streams, patches of snow) where there is good air circulation
  • Provide shelter by stringing a tarp or tent fly over the cache; allow indirect light for active seedlings
  • Never stack boxes more than four high
  • Keep enough space between boxes for adequate air circulation
  • Check that temperatures for spring planting stock do not exceed 10 degrees Celcius
  • Reflective tarps may be used to cover the boxes for short periods (1-2 hours) until proper storage is prepared

Planters are the last people to handle trees. If everyone else in the lift-to-plant sequence has done a good job, the seedlings will arrive at the site in good condition. As was done for on-site storage, planters should not expose seedlings to temperature fluctuations and moisture losses.

How to Load Bags and Carry Trees

  • Check that planting bags are in good condition; holed or torn bags allow air to dry roots
  • Maintain moist conditions around the root by placing moist absorbent material in the bags
  • Handle and unwrap bundles carefully. Do not wrench them apart. In plug stocktypes, avoid loosening the rooting medium
  • Use reflective bag liner (a "silvi-cool" insert) to protect trees during carrying
  • Limit the number of trees carried during hot weather
  • Close the box after loading and use reflective tarps to protect the remaining trees in the box for an hour or two
  • Never store more than half a day's supply of seedlings outside the on-site storage area
  • Bareroot stocktypes require special attention. Before planting, dip seedling roots in warm water for no more than one minute. Separate bareroot trees by shaking the roots loose in the bag. Be careful not to damage the stem with the bundling string
  • Work with one tree at a time
  • During breaks, place planting bags in the shade.

Stock Types

The vast majority of trees planted in the interior of BC and Northern Alberta are either pine or spruce trees, with a smaller amount of fir and other species. These species may be grown as either bare-root or plug (container) seedlings. In BC, the classification system for bare-root trees is as follows:

  • 1+0: A one year old (usually a small tree with a small root system)
  • 2+0: A two year old (usually average size with roots up to 25cm long). Spruce root systems are fuller and have more small hair roots than pine.
  • 1.5+1.5: A three year old (can be a very large tree with very long roots). These trees take special care when planting
  • 1P+1: A two year old plug transplant. Root systems are compact

Plugs are grown in containers for one to two years and are measured by the size of the container. The three digit number system is broken down into the first digit which indicates the width of the plug, and the last two digits which indicate plug length.

  • 211: Width 2cm, length 11cm
  • 313: Width 3cm, length 13cm
  • 410: Width 4cm, length 10cm (good in rocky ground)
  • 415: Width 4cm, length 15cm (a sturdy tree, but heavy)
  • 512: Width 5cm, length 12cm (a bigger, sturdier, heavier tree)
  • 615: Width 6cm, length 15cm (a very large tree…)