Published: October 26, 2009 05:21 pm      

PLATEAU GARDENING: More transplant tips for woody landscape plants

By C. Rae Hozer / Chronicle contributor — While the primary job of roots is to bring water and nutrients from the soil into a plant, they have a very important secondary function. Roots anchor a plant. With all the weight and wind resistance of a big canopy (on both trees and larger shrubs), strong roots are necessary to hold the plant upright. Cutting away big anchor roots growing on one side of an existing tree to put a sidewalk, driveway or foundation for a house in place, may be a recipe for disaster. It is wiser to take a large, old tree down if its roots are in the path of such construction. Don’t risk the possibility of a tree with no support roots on one side falling over sometime in the future. 

Tree experts now advise making the planting hole for trees or shrubs 3 to 5 times as wide as a woody plant’s root ball to encourage good root development to all sides. Old time tree lore incorrectly assumed roots grew out from a trunk as far as the outer tips of above-ground branches. (This was referred to as the “drip line.”) Modern day arbor research has proved tree roots extend out to all sides far beyond the drip line. Think about that when selecting the right spot to put your new tree. Don’t site a tree which will be big at maturity within 15 feet of a vegetable plot or flower bed. If you do, tree roots will probably grow into the garden.  

Experts recommend you NOT fertilize newly transplanted trees (not at installation nor during two years after transplant) and shrubs (no fertilizer at installation and not during first year in new location). Reminder: Nitrogen fertilizer is not recommended for established trees and shrubs between August 1 and November 15 in Tennessee.

Organic soil amendments add tiny air pockets within soil that improve movement of air, water, dissolved soil minerals and nutrients. That is a good thing. It is okay to dig or till then add peat moss, compost or other amendments to a LARGE AREA in your landscape prior to planting trees and shrubs there or  making a bed or border for herbaceous perennials in that spot.

However, digging a planting hole just larger than the transplant’s root system and adding amendments to the backfill dirt is NOT recommended. Amending the soil in just the planting hole creates a difference in texture between surrounding native soil and the growing medium where the roots are. In that situation, transplant roots tend to stay within the hole circling around like roots of a houseplant growing in pot that is too small. Stunting root development in this manner hurts the entire plant above ground level and below. Another problem is that rain and water from irrigation tends to pool in a planting hole that has much “fluffier” soil than the natural soil surrounding it. Drainage is a problem. The effect is similar to placing plant roots inside a big bowl of water. Too much water and too little air encourages disease problems like root rot, which can kill a new transplant in a relatively short time.

Once a woody ornamental is in place, improper staking may weaken stem/trunk development. Woody plant stems grow stronger if they are allowed to sway in the wind. Research indicates staking should be avoided. If a tree or shrub is staked, have enough slack in the supporting lines to let the plant move a bit. Use stretchy straps rather than wires or rope that may cut into tender bark on young tree and shrub stems. Thin bark on transplant stems is also easily damaged by weed whackers or mower decks. Use a circle of mulch about 3 feet all around a transplant’s stem to keep weeds and grass from growing there.

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Plateau Gardening is written by Tennessee Master Gardeners about home landscapes and gardening in our state’s Upper Cumberland Region. Contact UT Extension Cumberland County, P.O. Box 483, Crossville, TN 38557 (phone 484-6743) for quick answers to specific questions, free publications, or to learn about becoming a Master Gardener. E-mail comments or yard and garden inquiries to Master Gardener Rae at mgardenerrae@frontiernet.net.