In addition to getting questions about how to treat hemlock trees for hemlock woolly adelgid, we are frequently asked how best to plant or transplant young hemlocks. Therefore, this January, HRI reached out to western North Carolina nursery owners asking them to share what they know about planting hemlocks. They provided a wealth of information that was synthesized to create a short hemlock care guide to hand out during workshops. Bruce Appeldoorn, who specializes in the propagation of conifers, wrote this thorough guide on how to transplant and care for young hemlocks. Mr. Appeldoorn’s guide covers everything from the best site to plant a hemlock to how to care for it after planting. A one-page handout created by HRI summarizing the information below can be found here.
(Note: The photos on this page are from our 2019 volunteer days helping the USDA Forest Service Southern Research Station install hemlock restoration study plots. The sharing of the information below does not signify an endorsement of any services or products.)
TRANSPLANTING YOUNG HEMLOCK SEEDLINGS
By Bruce Appeldoorn
The excitement has been building for months—it’s finally time to plant out the young trees! When transplanting trees into the landscape, the important thing to concentrate on is the success rate. Chances are that lots of effort went into producing the quality seedlings themselves, but the essence of the task now is to ensure their successful long-term survival in the wild. Attention to detail is essential in the planting process. The transplanting and immediate aftercare phases are those that entail the highest risk for losses. Here are a few hints gleaned from working with hemlocks for over 45 years.
The Nature of the Beast
While we would all like to believe that one can just quick dibble a hole with a tool, drop in a seedling, press firmly with the foot to settle the seedling, and move on to the next hole, this approach won’t work with hemlocks. With pines, perhaps yes, with hemlocks definitely not. Hemlocks are a more delicate type of tree that grows more slowly and requires additional care and attention. Rest assured that your extra efforts will be well rewarded.
While both Canadian and Carolina hemlocks are shade tolerant plants, they actually seem to prefer a site with a good bit of sunshine. Growth will be faster if the trees are given more light and thus the trees will attain larger sizes sooner. However, when planting on sites at lower elevations (particularly Piedmont locations) or further south, locations that offer the benefit of afternoon shade are to be preferred. Cooler nighttime temperatures are definitely beneficial to hemlocks. Sites that are hot, sunny and dry are best avoided for hemlocks when trying to keep success rates high.
Hemlocks also benefit from well-drained soils with ample moisture. Native hemlocks are often seen in riparian sites, but are more rarely encountered on dry ridge-top locations. To succeed in site selection, observe hemlocks in the local natural landscape and try to mimic the sites on which they prefer to grow.
Trees for reforestation are normally planted out with 4’ spacing between trees, with the plan being to later thin this stand to trees that are 8’ apart. When desiring a more natural pattern to the stand, try to avoid planting in long rows. Plants set on triangles to each other will be sufficient. Individual young seedlings might need to be marked with a flag or stake to make them more noticeable to caregivers.
While hemlocks will often tolerate a heavy clay soil, they thrive in something closer to a loam or even a sandy-loam soil. Real topsoil is a scarce commodity in the Carolinas and the southeast in general. You will likely need to slightly alter the soil structure to improve planting conditions for best results.
Unless the site is rich in soil humus, it is best when possible to incorporate some rotting organic matter into the hole when planting the seedlings. Organic matter helps hold soil moisture in the area around young tree roots, preventing the fragile systems from drying out between rains. You get your only chance to add organic matter at planting time. Often it is not possible to carry humus into remote sites, but it is usually possible to scavenge some older leaf litter, “duff” or “forest floor” from nearby. This is added to the backfill mix, blending it well with the native soil before planting the seedling. In addition to organic matter, a starter fertilizer is recommended. A starter fertilizer containing a beneficial mycorrhizal/bacterial culture can give a young plant a real boost. This culture in essence causes the tree’s root surface area to expand greatly, enhancing its ability to absorb nutrients and moisture.
Preparation of the Transplant
Young hemlocks may be supplied as containerized plants with their entire root systems intact, or as “bare-root” with roots that have been severed during the digging process from a bed or native soil. Installers will have higher success rates using containerized hemlocks. Ideally, plants to be installed should be thoroughly watered about 48 hours in advance of transplanting (fully hydrated yet dry enough to be easily worked with).
Bare–root seedlings can also be used, but are more delicate and require more experience by the installer; these are best first transplanted into a container for a few more years of growing so that they can develop a more robust root system before hitting the woods. For small batches of freshly dug seedlings, carefully try to avoid losing any more clinging soil than necessary with bare-root stock; if it must be removed, do so by gently washing it off beforehand (in most cases this is probably the standard procedure). Bare-root seedlings (without soil attached) should be soaked overnight in a bucket of water before planting—do not submerge the tops. Care must be taken with bare-root trees to see that the exposed roots do not dry out in the sun—it really just takes a few minutes to cause damage. They are normally moved to the field carefully wrapped in moist burlap to keep them damp. They are kept in the shade at the planting site before installation occurs.
Transplant only high-quality seedlings. Runts can be discarded or left at the nursery for an additional year of growing. Seedlings that are less than robust will likely not survive the rigors of transplanting. Keep your success rates high by using only quality stock.
The Planting Routine
Plants are transported to the installation site with care. Significant damage can occur during the transport phase, so make sure the load is tightly packed and cannot shift in transit. Often a 4-wheel drive vehicle will be required for the final part of the journey and bouncing will occur. The load should be covered with a breathable tarp prior to the trip to the installation site.
At the installation site, individual containerized plants should have their root systems “ruffled” so that they no longer are in the smooth shape of the container. You don’t have to remove any soil, but some may fall off during the de-potting procedure, which is done at the hole. Plant a container plant about 1-2” higher than the surrounding soil. Mound backfill soil up to the height of the container plant’s soil and create a moat around the seedling so that water will be held within the moat while draining downward toward the roots.
When used in the field, bare-root seedlings are also planted slightly high so that its root collar at the base of the young trunk is above the level of the native soil. Additional attention is required to ensure that the root system is properly spread out within the hole before adding the soil. A watering moat is also constructed for bare-root plants. Timely application of water is critical. The use of bare-root seedlings in field plantings will result in higher plant losses, perhaps 50% or more.
When installing any conifers, the sound advice is to “plant high, dig wide.” Planting seedlings too deeply in the surrounding soil is a sure recipe for failure. Always make sure the root collar at the base of the young trunk is slightly above the level of the native ground. The old adage “dig a $10 hole for a $1 tree” is still true today. The hole at a minimum should be as wide as the spade (wider for larger plants, of course), but not deeper than the roots are long (or the height of the container). Excessively long or damaged roots are pruned shorter, but with hemlocks don’t take off any more roots than necessary.
The crowns of any existing weeds should be skimmed away with the point of a shovel before the hole is dug—remove weeds from a 24” diameter circle where a 12” wide hole will be dug. The soil is then removed from the hole with the shovel, neatly placed by the side of the hole, chopped up, amended, and gently nudged around the seedling’s roots, which are spread so that they go down and out. Any rocks coming out of the soil are best utilized on the downhill edge of the hole to help keep the soil from washing away. It’s best to level and gently firm up the bottom of the hole with the foot before inserting the plant, correcting the hole depth so that the plant will sit slightly high above the surrounding soil, and thus ensuring that the plant will not settle too deeply into the hole. After making sure the seedling is standing straight, the soil is firmed up around the seedling, but not violently so—just press firmly, no stomping. The goal is to remove any air pockets in the soil. “Finesse and patience, rather than power or speed, are required when dealing with the young.”
Mulching is very beneficial in controlling weed competition and in retaining soil moisture. A 2-3” layer of bark chips, rotting leaves, pine needles, grass stems (without seed heads), etc. works best. Avoid mounding the mulch up around the trunk of the young tree as it may invite insects to attack the trunk—mulch the ground, not the tree. This mulch material can also usually be scavenged from on-site sources, but bagged mulch can be convenient at times.
“A tree is never planted until it has been watered” is perhaps the oldest garden adage of all. Trees need water to survive; hemlocks are even more particular than most. Roots of young hemlocks are fine and thin and can dry out quickly. There is absolutely no substitute for watering upon installation. It is inviting to temp fate and install when rain is imminent, but if it fails to come promptly and in sufficient quantities, the seedlings will surely be lost unless water is supplied. The initial watering should re-establish proper soil contact with the root system as well as water the plant.
The next goal is to supply the equivalent of 1” of rainfall per week for the first month, then you can ease off a bit but the task is on the installer. One must be prepared to supply water to the trees for the first year and one half if rainfall is insufficient, again you’d like about 1” per week. Proper periodic monitoring is necessary to insure this step is completed. Foliage should remain turgid; flagging foliage is usually a sign of too little water. Too much or too frequent watering will kill plants as well, so check to make sure the soil is dry before applying more water needlessly. “Insert a finger into the hole down to the first knuckle, if you feel the soil to be moist, it is not time to water yet.”
In addition to checking soil moisture levels, aftercare requires monitoring the seedlings for storm damage, animal predation, insect attacks, and more. To keep the stand growing strongly, remove any limbs or brush that has accumulated among the young trees. Plants that are not growing straight might need to be staked with a straight piece of bamboo or nearby stiff branch that suits the purpose. It’s always best to stake the tree opposite from the side of the bend and tie the tree to the stake rather than to simply prop up the tree, which tends to be just a temporary fix (good only until the next strong wind). Ties should not be left in place more than one growing season before being removed or adjusted.
Plants may be fertilized during the growing season, waiting until all danger of frost has passed before application. Fertilizer applications should end by the Fourth of July. Hemlocks have shown a liking for timed release, sulfur coated urea fertilizers. These would be applied once only per year, and only in the establishment years. Fertilizers are expensive and their application should be thoughtfully considered.
Problems with animal browse might include pruning by deer, bear and the like, but more serious situations would be those involving wild hogs or beaver. Deer, beaver, rabbits and other rodents are indiscriminate pruners; hogs and armadillos are destructive indiscriminate rototillers that uproot entire plants. Hemlocks are not particularly attractive to these animals, but if damage is noted, the trees might have to be promptly protected inside of some sort of wire cage structure. Try to keep the solution simple yet effective. Nursery supply houses do carry tube-like devices for protecting young seedlings; netting and stiff plastic devices that surround the trunks are available as well for slightly older trees. All of these are rarely needed but should be employed if the damage exceeds a determined allowable threshold.
Weeds are the tree’s worst competitors, vying for the same available light, water, space and food that should belong to your hemlocks. Perennial weeds and particularly vines can quickly smother or strangle new plantings. Kudzu, bittersweet, wild grape, poison ivy, greenbriar, wisteria and other vines must be immediately eradicated when found to avoid losing seedlings. Physical removal should always precede chemical control measures.
Insects should rarely be a problem if the stand is being managed with insecticides for adelgid (aphid) control, but learn to recognize and keep on the lookout for mites and scales, which make their living by feeding on conifers—these two will usually not be affected by adelgid control measures.
Aftermath and Afterthoughts
Some seedlings will be lost—some death is inevitable and you will not achieve a 100% successful take, ever. The emphasis over time should be to reduce losses as much as possible and to get better results each and every year. Experience counts and experience takes time to acquire!
Be patient and be merciful to yourself—you are important too. The woods can be a dangerous place to work; use care and protect your body. Always carry drinking water. Wear stout shoes and long pants for protection—the work is physical and it’s no place for sandals.
Know that you are doing a very important job and that mankind has been doing this activity for well over 8,000 years. Revel in the joy of the activity! You are indeed re-greening your world, rescuing a threatened species, cooling the environment, providing needed shelter for birds and animals, and helping to save the planet. Thank you!
Additional advice available at:
Appeldoorn Landscape Nursery
1251 Jonestown Road
Bostic, North Carolina 28018