Row Covers Recommended for Weekend Freeze (1/07/10)

— Written By Barclay Poling
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berry mg
Vol 11, No. 3
Jan. 07, 2010 (7  pm update)

Dear Growers and Agents,

1. Row Covers applied today at Clayton (southeast of Raleigh, NC) in anticipation of weekend freeze:  We were able to take advantage of milder weather today and minimal winds to apply  row covers at Clayton in anticipation of colder temperatures this weekend (Jan 9-10) and into next Monday. Early Monday morning (Jan 11) we are expecting a low of 17 F in the canopy and 19 F at weather shelter height (temperatures will not be too much different on Saturday morning or Sunday). Our plants look very well right now, and the covers should help to keep the canopy from sustaining any real damage (burning) from the colder temperatures expected this weekend and into Monday.

2. Cover removal next Wednesday (Jan 13) at Clayton:  To keep plants as cold hardy as possible,  the covers will be pulled back off the beds in the mid-week, when nightly lows at Clayton will be back in a safe range (mid-20s by mid-week and then in the 30s by the weekend) and should stay that way for the next week or more. As I have mentioned before, at Clayton (transition area between piedmont and coastal plain), we do not use covers in winter except for freeze episodes like the one we’re expecting this  weekend when there is a  threat of temperatures possibly dropping into the mid-teens. The reason the covers will probably come off in the mid-week next week is thatwe like to keep our plants as hardy as possible in January, and row covers definitely “push” the plants out of dormancy quite a bit sooner than uncovered plants. Also, it should be dry in the mid-week (never handle the covers when wet).

3. Dormancy:  It is hard to say when dormancy will be broken this year, but with uncovered Chandler plants we do not see dormancy being broken  at Clayton until between mid-February and the 1st of March at Clayton (seasonally dependent). You know when dormancy has been broken when  you see new leaves breaking in the center of the plant from the crown area. Dormancy can be broken earlier by leaving the row covers on through the month of January and then into the first 2-3 weeks of February, and you can also achieve an earlier harvest by as much as 10 days. But, you are also obligated to do about 2 more weeks of frost and freeze protection!

4. Row covers stay on all winter in mountains:  How row covers are used in the winter season depends a great deal on your growing region. In the state’s coldest region, the mountains, row covers are necessary for protection all winter. The covers help protect  the plants from cold extremes in the mountains where it is not uncommon to drop below 10 F (like this weekend), and they also reduce plant desiccation (drying out) in winter. Even with temperatures heading down this weekend into the single digits in places like Fletcher, NC (near Asheville), the strawberry crop in this area will do fine provided there is a nice 1.5 ounce (per square yard) cover on top, or a good snow cover. I  realize there is a nice snow cover in many areas of the mountains at this time, and  more snow is on the way tomorrow. The snow on top of the covers is a real bonus! Generally,  mountain growers  leave covers on through the end of February, or early March (they are applied in early to mid-Dec). The covers are pulled back from the rows and left rolled up in the field through most of March, and then will be used again for frost protection during spring bloom.

5. Northern piedmont of NC:  this region of the state is shifting more and more to overwinter row cover usage similar to the mountains. But, in the northern piedmont the lighter weight 1.0 or 1.2 oz row cover is preferred to the 1.5 oz cover because of concerns with more shading with the 1.5 oz cover. Cover removal is done in late winter, and hopefully before the popcorn blossom stage. I believe it is a mistake to leave the row covers on until bloom.

6. Lower piedmont and sandhills:  these regions don’t get quite as cold in the winter as the northern piedmont, and my experience with Chandler is that an overwinter cover is not needed for this variety (except ‘possibly’ for cold events like this weekend). For Camarosa, I am much more defensive in my winter row cover strategy. And, Camarosa should be covered through all the piedmont and  sandhills before this weekend (tomorrow). If you are a piedmont or sandhills grower with a limited inventory of row covers, then use them  on Camarosa, not Chandler.

7. What about Chandler? I would apply row covers to all Chandler fields in the piedmont and Sandhills this weekend – if they are available. And, I would use them in transition coastal plain/piedmont areas (like Clayton). I still do not think they are essential for crown protection with the current weather forecast. If the forecast is wrong and temperatures drop into the  low teens and single digits, then we’re protected! If you are growing Chandler in the piedmont or sandhills, and don’t have covers, I still think you’ll be ok. But, the covers could help  to reduce your labor bill for “cleaning up”  dead foliage later this winter, and they may offer  crown protection if temperatures do go lower than expected now.

Well, as one Virginia grower friend of mine said to me this afternoon, “It looks like row covers are getting a real good work out in the Carolinas this winter.”  He’s absolutely right! If you are a producer in the sandhills,  piedmont, or mountains, I definitely recommend them for this weekend. If you need some supplier names, please check out the NC Strawberry Growers Assn. website:  http://www.ncstrawberry.org/  and go right to GROWERS, then FROST PROTECTION, then FROST/PROTECTION RESOURCE LIST, and also take a look at the article on Row Cover Hold Down Bags (and suppliers of hold downs).

Barclay

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—————————————————
Dr. E. Barclay Poling
Professor and Extension Specialist (Small Fruits)
Dept. of Horticultural Science
Campus Box 7609
NC State University
Raleigh, NC 27695-7609
919-515-1195
919-515-2505 fax
919-418-9687 cell
email:  barclay_poling@ncsu.edu

Posted on Jan 7, 2010
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