Planting Grass Under New Trees

The No. 3 issue of the K-State Horticultural Newsletter sent out on January 20,2015 talked about research done at the John C. Pair Horticultural Center.
Jason Griffin, William Reid, and Dale Bremer conducted a study to investigate the inhibition of growth of transplanted, seedling trees when lawn grasses were allowed to grow up to the trunk.

There were five treatments, including three with different species of grass. All treatments were applied to Eastern redbud seedlings as well as to pecan seedlings. All trees were fertilized and watered during the growing season. At the end of two years, trees were measured and harvested. There were no differences in any measure between the mulched treatment and the bare soil treatment for either tree species. All measures showed significant growth increases if lawn grasses were controlled around the tree.

Results include the following:
1. Caliper: Caliper measures 6 inches above the soil surface were twice as large for plots without grass than for those with either fescue or bluegrass, but only 50% larger when compared to the bermudagrass plots.
2. Top growth weight: Redbuds showed a 300% weight advantage for plots with grasses controlled than those without. Pecans showed a significant 200% increase.
3. Leaf area and leaf weight: Leaf areas were 200% larger in plots without grass competition and leaf weight showed a 300% increase. Ward Upham, the author of the Newsletter said. “The obvious conclusion from this study is that grasses must be controlled under a newly transplanted tree to get the best possible growth”. Though there were no differences in growth whether mulch was used or not, you may still wish to mulch for aesthetic reasons or to help control weed growth. How far from the trunk should the grasses be
controlled? Try a minimum of 3 feet. (Ward Upham)

Some Products To Help

Control Grass under trees with; Over the Top, or HY Grass Killer. You can also carefully spray KillZall under trees as long as you avoid getting it on the leaves. Don’t forget Spreader Sticker!

Kill and Prevent weeds with KillZall Extended Control, again avoiding the leaves. Kills grass and prevents germination of new weeds and grasses for up to 3 months.

Prevent weeds and grasses up to 4 months after you have controlled the weeds with HY Turf and Ornamental, apply to bare soil or on top of mulch and water in.

Increase Tree Vigor

ALWAYS use Root Stimulator when planting Trees to get good establishment. Make at least 3 applications 10 to 14 days apart.

Feed newly planted trees with a super slow release fertilizer such as Start-nGrow.
After establishment, feed 2 or 3 times every year with Tree and Shrub Food. Don’t forget that late Fall application!