Landscape contractors, property owners, golf course superintendents and park managers plant trees for many reasons. Replacing removed trees, bolstering thinning stands and home construction plantings are just a few of the more common planting projects. After all, who could argue with new tree planting? I recall a blunt, somewhat humorous presentation by a forester who spent most of his days in the field. He certainly didn’t call the lecture room his home turf. His talk was short and sweet; it went something like, “Top trees? %$# No! Plant trees? %$# Yes!”
The only people that might not be delighted over new trees are the folks who have “new tree care” added to their already overly long list of daily duties. Yet, with a clear set of guidelines on what to do and when to do it, a frown can easily be turned upside down.
Now that it’s fall
Headed into winter, the need to care for newly-planted trees is great. There’s just no way to overemphasize the importance of starting out well, because correcting problematic trees is much more difficult than just giving them a little care before the snow flies and the daylight shortens. Young trees that have their essential needs met before the end of the year will establish quicker and have fewer problems in the future. There are many notions of early-life tree care floating around these days; just to put the false ones to rest and to emphasize the beneficial steps, I’ll categorize them simply as what to do and what not to do:
What to do
Soil test: Because a tree’s nutrient supply comes from the soil in and surrounding the tree root ball, it’s important to sample the soil to determine the existing level of the essential elements. The question often arises of where to sample; the obvious answer is where the roots are and will be. In fact, that’s the best initial division of subsamples — in the root ball, in the area from 6 inches outside the root mass to 3 to 4 feet, and from 4 to 10 feet away. The first will provide a good idea of initial supply, the second is what will be available in years two or three and the third in the years that follow. Naturally, these three zones of testing are estimates (as some trees simply grow roots faster than others), but it’s a good place to start. In addition to the various nutrients of phosphorous, potassium, secondary elements and the micronutrients, special attention should be paid to ones that have a reputation for being in short supply in the local area.
Testing for nitrogen is tricky, as even though it’s required by trees, it’s a mobile and changeable element, thus the testing results are reliable only in the short term. As well as nutrients, the pH, organic matter content, cation exchange capacity and sodium absorption ratio are key indicators of the need for future soil modification.
Remove grass and weeds around the trunk: Turfgrass, annual grassy and broadleaf weeds and other vegetation are undesirable companions for newly-planted trees for at least three reasons. First, they compete for water, light and nutrients with the tree. Second, these unwanted plants create a need to trim and mow closely to the trunk. (The bark of most newly-planted trees tends to be a little on the tender side.) Third, they’re downright ugly in most cases. Removing weeds and unwanted grasses preserves the available water and nutrients for the tree, helps protect the all-important water-conducting cambium and increases the aesthetic appeal of the landscape.
Watering: In the case of trees, the approach is to soak the soil thoroughly, then keep it moist, not soggy or dry. Even though it may require a little time, it’s well worth it to simply check for soil moisture before irrigation. A sophisticated soil moisture probe can be used, but actually, the same information can be determined with a piece of rebar or a long screwdriver. The technique is to push it in about 2 feet deep (that’s where 80 percent of the new roots will be) and pull it out, noting how much resistance there is to the insertion of the device. If it’s hard to push in with moderate force, the soil is probably too dry. If it slides in easily and makes a bit of a sloshing sound, it’s probably too wet. The strategy for new tree care is scheduling watering operations to avoid the extremes.
Group landscape elements by like kind: Trees and turf were not meant to be growing closely together; in a way, they’re a little like oil and vinegar in that they are both necessary to add flavor to a salad, but Mother Nature really doesn’t put them together herself. While the tree is still young, it’s wise to separate it from turfgrass plantings. This is best done by massing like plants together — masses of turf, masses of sunny/ shady perennials, masses of woody plants and masses of shade-adapted perennials under trees. For guidance on separation of turf and ornamentals, it’s best to consult a landscape designer/architect.
Mulch: The main objectives in proper mulching are to keep the soil moist, reduce weed competition and to replicate Mother Nature.
As such, 2- to 3-inch layers of wood chip mulch, applied 3 to 6 inches away from the trunk and extending as far into the landscape as the client will allow is the goal. Avoidance of rock or stone that adds heat to the planting, piling mulch on the trunk and excessive depth that acts as a thatch layer — sometimes preventing water penetration, sometimes keeping the soil too moist for extended periods of time — are tangible management techniques to eschew.
White PVC: Two reasons exist for the placement of white PVC columns around the trunks of newly-planted trees in the Northeast, Midwest and Mountain states. One reason is for rodent protection, as shrews, mice, rabbits, squirrels and even some waterfowl are pests of new trees. Another reason is the avoidance of sunscald or bark flaking during winter. Care should be taken to select loose-fitting, yet protective barriers to reflect warming winter sunlight (hence the white color), yet allow excessive heat to escape. The objective isn’t to keep the trunk warm, it’s to keep it stable and cold.
What not to do
In addition to too much water, too much mulch, placing turf next to trees and forgetting to soil test, an important practice to avoid is the installation of a tree surround or planter box, where a short set of decorative blocks or timbers are constructed to encircle the tree. The big problem with these is that they require added soil (usually 2 or 3 feet) to be placed inside the structure, so that groundcovers, vines and/or flowers can be planted inside. The added soil is the big issue here. Again, using Mother Nature as the guide, she doesn’t plant trees and then dump a bunch of soil on the roots to facilitate the growing of other plants. Sure, if some forbs sprout next to the sapling, they can intermingle their developing roots along with the shallow tree roots, with the tree’s roots eventually taking over and the forbs retreating to a location where the competition is less fierce. Otherwise, intentionally adding soil is a huge no-no.
What to possibly do
In some situations, early-life tree care technique falls into a “maybe…if needed” category. Three good examples follow:
Fertilize: As described above, soil testing is important to set a baseline of nutrient levels and characteristics for the health of a tree. If soils are deficient in any of these, then sure, add what’s needed according to recommendations in the soil test. For example, if the test results indicate low organic matter and cation exchange capacity, applying a thin, 0.5-inch scattering of compost over the roots will condition the soil for healthy tree growth. If turfgrass is present outside of the applied mulch, making several passes with a core cultivator beforehand will facilitate downward movement of the compost.
Staking: If new trees are planted in a windswept area, it may be beneficial to stake them to prevent wind throw. When doing so, it’s best to stake loosely to allow the tree to develop some supporting roots. Use a sturdy post and a material such as wide canvas strapping to create a snowshoe effect, softening the impact of the material as it wraps around the tree.
Pruning: In some cases, clients may request that the tree be “brought into balance” by pruning the top to match the root ball in the ground. Pruning is only recommended if broken branches or co-dominant leaders are present. If so, correcting these flaws will prevent future problems.