It seems like we need all the help we can get when it comes to getting a new tree established in the landscape. The hurdles for small trees can include: heat stress, wind, poor soil, drought, insects and disease and even transplanting stress. With this in mind, planting a tree comes with a responsibility to do all we can to insure its survival.

A new study recently completed from K-State's John C. Pair Horticultural Center now offers yet another good tip for those who intend to plant a tree in the coming year.

The researchers conducted a study to investigate the inhibition of growth of transplanted seedling trees when lawn grasses were allowed to grow up to the trunk. In each study, a different type of grass was allowed to grow below the new tree.

The study included trees with bare soil maintained with herbicide, trees with 3 inches of mulch and trees with tall fescue, bermudagrass and Kentucky bluegrass growing up to the trunk. The trees were also fertilized and watered as required (similar to what a homeowner is expected to do.)

The results of the study were not unexpected, but did provide valuable insight into how turf and trees can compete for the same resources.

There is often a misconception that tree roots grow deeper than where the turf roots reside. This is not the case. The large majority of tree roots reside within the top 12 inches of soil. This means that where trees and turf grow together, competition will exist for the same water and nutrients.

The research revealed that the trees that were maintained with either bare soil or mulch did significantly better than trees that were competing with turf. The tree caliper (width of tree trunk, not circumference) that measured 6-inches at the base of the tree, were twice as large for plots without grass than for those with either fescue or bluegrass under the tree.

The top growth of the maintained Redbud trees showed a 300 percent weight advantage over the plots with grasses. The leaf area and weight were 200-300 percent larger in the plots without the grass competition.

Keep grass away

The conclusion from the study is obvious. Grasses and weeds must be controlled under a newly transplanted tree to get the best possible growth.

Mulch should also be applied to help moderate soil temperature changes and moisture loss. The distance the grass and weeds should be kept away may vary, but 3 feet of a grass-free and weed-free area around a new tree is a good place to start.

It has also been determined that mulch should not directly touch the tree trunk itself. This can invite disease causing organisms. It is best to leave a few inches of space between the mulch and the trunk of the tree.

-- Jason Graves, Horticulture Extension Agent, K-State Research and Extension Central Kansas District, can be reached at 309-5850 or by email at jlgraves@ksu.edu