Issue: Decem1er 15, 2001

Lawn soil amendments?

I have a small front yard (30'x 50'). It faces south. For the last year it has been used as a parking lot. I would like to rototill in some leaves from my mulberry tree and some pecan shells. Would this be a good type of mulch? I plan on planting grass next spring.

When planting grass, it is a good idea to work organic matter into the soil. These materials, leaves and pecan shells, will help to loosen the soil to help the lawn. The "parking lot" has compacted the soil creating a need for the soil to be de-compacted. The pecan shells will be slow to decompose and will maintain a porous soil allowing water to permeate the soil. The leaves will decompose rapidly if kept moist (even in the winter). The humus formed by the leaves will serve as sponges and hold the water in the soil as well as helping keep the soil loose and aerated. Other organic materials may also be added to improve the characteristics of the soil and enhance grass development. However, I do have a concern regarding your plans to rototill. Is the tree in the vicinity of this lawn area? Tree roots will extend beyond the ends of the branches and may be damaged by the work you do in preparing the soil for the lawn. There is a term "critical root radius" which defines the zone in which there should be no rototilling or trenching (any activity that injures the roots). This is calculated by measuring the diameter of the tree trunk in inches at chest height (about 4 feet above the ground), multiplying by 1.5, and reporting the results (critical root radius) in feet. So, a 4-inch diameter trunk has a critical root radius of 6 feet. Within six feet of the trunk, do not damage the tree's roots. It is important that you do reduce the compaction of the soil by rototilling or digging, but avoid the critical root radius.

Poinsettias in darker room?

Is it necessary to leave my poinsettia in a south window throughout the holidays, or can I move it into a relatively dark dining room to use it as a centerpiece?

It is okay to move it to use as a centerpiece. If it remains for too long (a week or so), the green leaves and red bracts will begin to fall. Another consideration is the room's temperature. The plant will be injured more rapidly if the room is quite warm. Lower temperatures will reduce respiration and transpiration rates (the rate at which stored foods and water are lost). The best idea is keep the room cool (not cold) and return the plant to the brighter location as soon as possible.

Also, remember to water the plant while it is the centerpiece. As usual with houseplants, if you have a container under the pot to protect the table and table cloth, place some gravel or a piece of brick in the bottom of the container to keep the pot holding the poinsettia from sitting in water after watering.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

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