Nursery Notes: Seedlings will require frost protection soon
Note: EPA representatives are currently visiting area nurseries checking for pesticide compliance and employee training with WPS (worker protection standards).
I get a few calls each spring about using antitranspirants (Vapor Gard, Wilt Pruf) to protect small seedlings (2 inches tall) in the row from late frosts. I have heard of a few successes and a few failures.
I suspect the antitranspirants may not have helped at all. The producer may have credited the antitranspirants when maybe the temperature at the soil may not have gotten low enough to cause injury.
Dr. Ken Tilt, nursery specialist at Auburn, recalls that while he was Tennessee’s Nursery Specialist, he too heard of accounts when the antitranspirant was not effective, sometimes effective and occasionally even harmful. Success or failure could be affected by the species, plant size, actual temperature at the soil line, humidity and wind.
I asked Dr. Stephen Garton, current UT Extension Nursery Specialist, about this in 2003. He responded by saying, “This is not a simple thing but on the whole I agree that frost protection of tender plant structures with antitranspirants is not effective and therefore not recommended. Like every other generality there will be exceptions and there are probably people who have tried such treatments on one or two species in specific situations who are convinced that the antitranspirant was beneficial. In the absence of good scientific information, we cannot endorse such practices.”
The tried-and-true methods of protecting seedlings from frosts are some sort of covers. I have seen the white, UV stable, spun-bonded polypropylene field covers and row covers used with satisfaction. It offers a few degrees of protection. It can be used repeatedly and stored for several years.
I like the large pieces that cover one-tenth of an acre or so. Wind is the enemy of large pieces, however. This may be the best overall method, if large pieces of a thicker cloth are used and plans are made to secure the edges.
The second best method may be burlap strips cut 18 inches wide and supported by twine 5 inches above the soil, supported by wooden stakes driven into the center of the rows every 20 feet or so, leaving 6 inches of the stake exposed. The edges are tacked down with 16 penny nails, every 3 feet, or so, to prevent the wind from carrying it away.
This protection is applied in March before emergence of the seedlings and removed in May when all chances of frost are gone. The burlap and fabric has sufficient light penetration for normal plant growth. Carpet backing might work well, since it contains some nylon.
I have also seen winter wheat drilled into the row middles offer some frost protection, as well as offer some wind protection to the first year buds and possibly reduce the number of scions blown off the stumps.
Forrest-Keeling Nursery in Missouri uses this method. The wheat is later mowed or sprayed with Envoy, Fusilade or Vantage.