More Than Sun, Soil & Rain: Plant Growth

It takes more than just sun, soil and rain to grow healthy trees, shrubs and turf. Landscape contractors should be aware that their work plays an integral part not only in making sure plants look good when they are installed, but that they remain attractive during their growth.

Before planting anything, proper research must be done in order to ensure the species of plant is appropriate for the climate and soil, suggested Bonnie Appleton, associate professor of horticulture at Virginia Tech University, Virginia Beach. Appleton, an expert in trees and ornamentals, said she has seen too many specifications for design plans that used trees in places they did not environmentally belong, setting the contractor up for a long term problem.

“A lot of architects aren’t local and don’t know the area,” she remarked. “If they don’t know the microenvironment, they may not know the drainage patterns of the site or that there could be an existing plant or structure inhibiting light from the tree on their plans.”

“If you have the wrong plant in the wrong location, it’s not going to be successful,” Appleton warned.

Another component of the research is the survey of quality nursery stock. Plants should be scrutinized to ensure they have received proper pruning and are disease-free, Appleton said.

Next is getting the tree in the ground, and Appleton drew upon her experience to relay that the biggest mistake after planting a tree is to neglect properly watering it. “During the first year, it has to be watered on a weekly basis,” she said. There also must be proper mulching to guard against weed and turf growth, she added.

With a fine consistency of mulch, contractors should put no more under the tree or ornamental than 2 inches deep. For a coarser quality of mulch, no more than 4 inches should be applied to keep away weed growth, she suggested.

“The weeds and turf compete with the newly planted tree for limited soil moisture and nutrients,” Appleton explained. Using too much mulch will cause the mulch to behave like potting soil and stimulate growth of weeds, she added.

Appleton is not a proponent of growth regulators and said they are not necessary if the right plant is planted in the right area, “Frequently, they are used because someone has the wrong thing growing somewhere in the first place,” she commented.

Jeff Iles, assistant professor of horticulture, Iowa State University, Ames, Iowa, agreed that contractors can save time and trouble by making proper selection when installing plants. He suggested that a plant list be made as a reference to be consulted before planting.

“Putting plants in the right place can save a lot of problems,” Iles said, noting that a tree could become diseased if it is planted in the wrong climate. A common mistake he pointed out in the Midwest is to plant a pin oak in soil other than the acidic soil it likes. “Oaks also are great for landscaping, but must be placed in full sun, and lindens, too, want partial or full sunlight,” he added.

“The bald cypress does well in wet areas and would do well in such locations as a golf course or cemetery, and some variations of the flowering crabapple tree are very disease resistant,” he pointed out.

Planting a tree that has droppings is not a good idea near a public access area. Maple trees are staples and popular for their fall color but probably not a good choice if looking to plant a tree near a parking lot.

PROPER PRUNING. Proper pruning of a young tree promotes good branch spacing and is necessary when wanting to achieve a full, healthy tree as it ages, according to Iles. “Only prune pines to establish a leader branch, then let them go,” he said.

When pruning a young tree, Iles recommended finding the central leader branch, narrowing it down to the main branch and removing branches that are crossing or rubbing against each other. Some trees have branch angles that are narrow and weak at the branch to main-stem union. Remove the entire branch when encountering one of these narrow branch angles. After removal, the tree can cope with the wound while still young and removal of the branch is less noticeable than in an older tree, he commented.

But, one of the worst things to do is take away the young, lower branches. Remove them in subsequent years, but not in the early years, Iles warned, because the lower branches can set up problems for the tree such as spindley, weak branches susceptible to breakage.

Older trees need very little pruning and have reached a balance that makes the task unnecessary, Iles explained. Prune older trees only when needed, removing only those branches that might pose a threat to people or property or are rubbing, crossing, injured and decayed, he recommended.

“Tree topping is wrong. It should be outlawed,” Iles said, warning that it hurts the tree and invites decay entry into the tree, while regrowth from topping results in very weak limbs that break off easily.

Iles said in dry climates, pines and spruces do well and pines do not require a lot of pruning maintenance.

When selecting the proper tree, the region and climate must be taken into consideration.

“People in general tend to look at the size and flower color but don’t look at other features,” he remarked.

Choices also must be made when deciding to plant shrubs. Oftentimes, contractors don’t consider the heights to which various shrubs can grow and the maintenance involved in keeping them attractive, Iles said.

Shrubs, like trees, have to be pruned, and the lilac bush is one example where its spring flower will last longer if the shrub is pruned and thinned out properly to allow light penetration, he commented. “Not all shrubs are sun-loving, and research should be done to make sure the type of shrub planted is appropriate to the region,” Iles added.

GROWTH MAINTENANCE. Fertilization requirements vary based on the tree, but Iles recommends only fertilizing trees that suffer from nutrient deficiencies. “Most problems are not a result of a lack of fertilizer but more often are due to over or under watering, destructive pruning, construction injuries or injuries from people,” he pointed out.

Iles said he is not a proponent of growth regulators and added that if a plant grows too quickly, its form may not look as favorable. “Genetic growth rates are built in,” he added, “and it is not a good idea to tamper with them.

“I think the best thing we can do is give a plant what is needs,” Iles said.

Tom Watchke, professor of turfgrass science at Penn State University, University Park, said growth regulators often are used along roadsides by the department of transportation to decelerate growth and lessen the frequency of mowing.

Some landscape managers also use regulators in the spring, when a growth spurt occurs, to maintain their mowing schedules, Watchke said. Depending on the product, regulators can decrease mowing 50 percent for up to four to five weeks, but, regulators also take away a plant’s ability to recover if it is injured, he added. “Turf has a great propensity for healing itself and for quick recovery, which is a good defense,” he said.

“The contractor needs to determine the turf’s traffic before applying any growth regulator,” said Charles Mancino, associate professor of agronomy at Penn State. “It is essential to allow the turf to keep growing in order for it to fill in its damaged areas,” he said.

“When there is a lot of environmental stress, you wouldn’t want to hold the turf back in any way,” Mancino explained. A drawback in using a decelerator, is that some applications can result in a toxic effect, leaving the grass discolored, he added.

“The best way to control pests is to have a healthy, strong-standing turf, and fertilizer contributes to that,” he said.

Proper turf fertilization, consisting of an appropriate balance of potassium, nitrogen and phosphorus, can reduce the recurrence of diseases and result in a healthier turf stand, Mancino explained. The amount of fertilizer needed depends on the soil type and the rate contractors want the turf to become established. The higher the sand content of the soil, the higher the fertilitizer requirements, he said, explaining that sandy soil loses nutrients quicker and does not retain water as long as clay and silt soils.

“(Having sandy soil) doesn’t change the turf, but you have to work harder at managing the needs of the turf,” Mancino remarked.

Turf needs to be regularly fertilized, particularly if it is newly seeded turf. Establishing turf at a quicker rate is accomplished by giving any type of soil higher amounts of nutrients.

If the turf receives too little fertilizer, it can succomb to such diseases as dollar spot, and if the turf has too much fertilizer, it can suffer weak turf growth, producing very young plant tissue that can become susceptible to many types of stresses, weeds and forms of diseases, Mancino said.

When plants are young, their phosphorus needs are the highest, he said. Tips for fertilizing are to make sure the application of the fertilizer is in proper amounts or it could cause grass burns, and that fertilizer application is at the proper time.

“You want to match the nutrient application with the primary growth period of the turf,” Mancino explained.

Turf seeds also should be of a type that is appropriate to the region and climate, he suggested. It is a good idea to contact a local seed distributor or university extension specialist to find out what species do best in an area, he added.

When seeding, landscape contractors should prepare the area with an adequate depth of topsoil. Mancino recommended that 3 to 4 inches of topsoil at a minimum should be laid and, ideally, there should be 6 inches of soil. One mistake contractors commonly make is laying only 1to 2 inches of topsoil, which can result in a turf that starts out looking attractive, but soon runs out of soil, leading to problems such as disease and drought stress, he said.

Paul Rieke, professor of turf management at Michigan State University, East Lansing, said the basics of good turf require having quality soil consisting of the proper mixture of sand, silt and clay, a good site with adequate sunlight, and proper soil drainage. Loosely compacted soil is favorable because it retains water and nutrients better, whereas overly compacted soil can be too hard to prepare for seed beds and can make grass difficult to grow, he explained.

“The more limiting the sunlight, the less probablilty of success in seeding,” Rieke said.

Soil also must be free of substances that may be harmful to plantings of turf, such as residuals from former agricultural sites. In a larger area, there also should be good air movement. He explained that restricted air movement can enhance turf diseases such as brown patch and shaded areas can make turf more sensitive to disesases such as powdery mildew.