Grower Photos and Comments About Row Covers and Sprinkling (5:30pm, Wed., March 7, 2018)

— Written By Barclay Poling
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Fig. 1. Photo by John Gross, Sanford, NC – taken on Monday morning, March 5th. The Sanford area had a “pretty good frost” that morning. John had protected with row covers. However, in this one area he had a tear in the cover, and you could see a pretty heavy frost on the leaves of unprotected plants. The grower did suffer some frost losses in places where the row cover was in direct contact with blossoms beneath. At the bottom of this advisory you can see how Louisiana growers prevent blossom losses of this type by suspending the row covers with wire hoops. Louisiana growers use row covers differently from growers in NC, SC, and VA. They actually suspend them so that blossoms in contact with the cover don’t get killed. With a “good frost” it is possible to lose 5% or more of the blossoms that are in direct contact with the cover (see Figs. 4-5).

Fig. 2. John Gross, who took this photo of his Sweet Charlies today, said:  “there is a lot of green fruit and 4-6 new blossoms.”   Last week was when these Sweet Charlie plants were “covered up.”  A week ago (Feb 28), these same Sweet Charlie plants had 10-15 open blooms. It looks like bloom has already peaked with this variety!

Frost returning

The row covers went back on today at about 4 p.m. – expecting a “big frost” in the morning in Sanford. Sanford 3.7.18 Detailed Forecast

The Sweet Charlie plants shown in Figure 1  had almost 2 full days this week without covers being on. They were rolled back Tuesday morning (after the frost), to “open things up” and allow better air movement for pollination and fruit set. The grower saw a “few” bees, but not many were flying with these cool daytime temperatures. The grower thought it might have been worth it (uncovering for 2 days), but if he did not have a sprinkling system, it would NOT have been a good idea to remove the covers in the early week, as it also rained yesterday and last night. And, once a cover gets soaked, it cannot be quickly re-deployed in the event of another frost! They must be handled dry!

Rains complicates matters with row covers, but this grower had sprinkling as back-up plan for tonight — in the event covers were too wet to re-apply

I know this particular Sanford grower was quite concerned he may not be able to get his covers back on if they became soaked by rains on Tuesday and Wednesday night. However, rainfall accumulations weren’t too heavy (< 4/10ths) and high winds today helped to dry covers out. Had he not been able to get covers back on, he has sprinkler irrigation as back-up.

Sprinkling on a night with high dewpoints

In case he had been forced to sprinkle for frost protection tonight, my guess he would have been starting around 1 a.m. (see Sanford 3.7.18 Detailed Forecast). With dewpoints this high (27-28 F) you can pretty much rely on starting the sprinkling when you see first sign of “ice crystals” forming on lay flat hose, or in the rolled up row covers.

Sprinkling on a night with low dewpoints – stick with the 33 F wet bulb rule

I am noticing that for Thursday night/Friday morning, temperatures will be colder (see state map in Fig. 3), and air may be much drier! Dewpoints on Friday morning will be down in the low 20s in Sanford, but take a look at other parts of the state like Greensboro Greensboro

Note that Greensboro could see a minimum of 27 F and dewpoint of only 14 F on Friday morning! A grower using irrigation for frost protection in that central piedmont area would need to plan on starting sprinkling at about 6 p.m.! That’s right! Note that at 1800 (6 p.m.) the wet bulb is down to 32 F, and sunset is 6:20 p.m. So, that temperature will be dropping like a rock. There is no question about it, a row cover would be a lot easier to use, and should also be very effective.

Because conditions are so variable across North Carolina, and throughout our whole region, everyone needs to be keeping a close eye on the forecast for their immediate area:



Abingdon Ashland_VA Charlottesville Chesapeake-Ches
Culpeper Danville Dublin/New_Riv Emporia_VA
Farmville Fentress_Naval_A Fort_Belvoir/Da Fort_Eustis/Fel
Franklin/J_B_Ro Hillsville Hot_Springs/Ing Jonesville_AP
Langley_AFB Leesburg/Godfre Louisa-Louisa_C Lynchburg
Manassas_Muni(A Marion/Wythev Martinsville Mecklenburg/Bru
Melfa/Accomack Newport_News Norfolk_Hampton_ Norfolk_NAS
Norfolk_VA Oceana Orange_VA Petersburg_(AWO
Quantico Richlands_AP Richlands_VA Richmond
Richmond_Chester Roanoke Shannon_Arpt Stafford_AP_VA
Staunton-Shenan Suffolk-Suffolk Tappahannock_AP Virginia_Tech_A
Wakefield_AP Wallops_Island Warrenton_Fauqui Washington_Dulle
West_Point_VA Williamsburg_VA Winchester_Rgnl Wise/Lonesome_P

North Carolina


Ahoskie-Tri-Cou Albemarle_AP Andrews Asheboro
Asheville_Munic Beaufort-Michae Boone_NC Burlington-Burl
Cape_Hatteras_AG Chapel_Hill-Hor Charlotte Cherry_Point
Clinton_NC Concord_NC Currituck_NC Edenton-Northea
Elizabeth_City Elizabethtown_NC Erwin-Harnett_C Fayetteville_AP
Fort_Bragg/Simm Franklin/Macon_C Gastonia-Gaston Goldsboro_AFB
Goldsboro_NC Greensboro Greenville_AP_NC Hickory
Jacksonville Jacksonville_(A Jefferson_AP_NC Kenansville-Dup
Kill_Devil_Hills Kinston_AP Lexington-David Lincolnton_AP
Louisburg_NC Lumberton_AP_NC Mackall_AAF Manteo/Dare_Co
Maxton Mcalf_Bogue_Fiel Monroe_AP_NC Morganton-Morga
Mount_Airy-Moun New_Bern North_Wilkesbor Oxford_NC
Piney_Island_Bom Pope_AFB Raleigh-Durham Reidsville_AP
Roanoke_Rap_AP Roanoke_Rapids_R Rockingham_NC Rocky_Mount-Wils
Roxboro_AP Rutherfordton Salisbury-Rowan Sanford_NC
Shelby_AP_NC Smithfield_AP Southern_Pines Southport_NC
Statesville-Sta Tarboro_AP Wadesboro_AP Washington-Warr
Whiteville_NC Wilmington_AP_NC Winston-Salem

South Carolina


Aiken_AP Anderson_Co_Air Barnwell_AP Beaufort_Cnty_AP
Beaufort_SC Bennettsville_Je Camden_AP Charleston_Exec_
Charleston_Muni Cheraw_AP Chester_AP Clemson-Clemson
Columbia-Columb Columbia/McEnti Columbia_Metro Conway_AP
Darlington Florence_SC Georgetown_AP_SC Greenville_Donal
Greenville_Down Greenville-Spart Greenwood-Green Hartsville_AP
Hilton_Head_AP Kingstree_AP Lancaster-McWhir Laurens_AP
Manning_AP Marion_AP_SC Moncks_Corner_AP Mount_Pleasant_A
Myrtle_Beach Newberry_AP North_Myrtle_Be Orangeburg-Oran
Pickens_AP Rock_Hill Spartanburg_Down Summerville_AP
Sumter_AP Sumter_SC Walterboro_AP Winnsboro_AP



Albany_Municipa Alma/Bacon_Co Americus_AP Athens_Municipa
Atlanta/DeKalb Atlanta/Fulton Atlanta_Intl_Ar Atlanta_Paulding
Augusta/Bush_Fi Augusta_Daniel_F Bainbridge_GA Blakely_AP
Brunswick_GA Brunswick/Glync Canton_GA Carrollton_AP
Cartersville_AP Claxton_AP Columbus_GA Covington_GA_AP
Dalton-Dalton_M Douglas_Muni Dublin/WHBarron Fitzgerald_AP
Fort_Benning Ft_Stewart/Wrig Gainesville_AP_G Greensboro_GA
Homerville_AP Hunter_(AAF) Jesup_AP La_Grange
Lakeland Lawrenceville_AP Macon_AP Marietta
Marietta/Cobb Milledgeville_AP Moultrie_Muni_AP Newnan-Newnan_C
Peachtree_City Rome_GA Savannah Statesboro_GA
Swainsboro_AP Sylvania_AP_GA Thomaston_AP Thomasville_AP
Thomson_GA Tifton_AP Valdosta Valdosta/Moody
Vidalia Warner_Robins_A Washington_GA Washington_GA
Waycross_AP Winder_AP

Parting shot of Camarosa taken today in SANFORD NC (about 3 new blooms)

Fig. 3. Camarosa in Sanford today

Fig. 4.Row covers are suspended and not allowed to float on top of strawberry plants in Louisiana’s Tangipahoa Parish.

Fig. 5. The row cover you see in the photo can be pulled back over the crop to protect blooms from a possible frost event during picking season.