Two Part Advisory: 1) What Just Happened This Morning? 2) What’s Ahead for Tomorrow Morning? (6:30pm, Sun., 3/29/15)
This advisory is now organized in two parts:
3 p.m. update on 3/29 – dealing with what just happened this morning
6:30 p.m. update on 3/29 – evaluating potential for frost on Monday morning
Note: In areas where skies may be clear tonight, and minimum temps of 35 or below are expected, BE SURE TO SET YOUR FROST ALARM!
Part 1. A mid-afternoon update on 3/29 – dealing with what just happened this morning
Across the region last night and this morning we experienced a classic black frost. Many piedmont locations were in the mid-20s, like Upper Piedmont Research Station in Reidsville (Fig. 1). Temperatures began to plummet even before sunset because of very dry air conditions.
Fig. 1. Reidsville had a low of about 25.7 at 6 a.m. A high was reached on Saturday of 42.6 F around 4 p.m., and then temperatures began to tumble in the very late afternoon. This rapid drop was associated with exceptionally dry air.
I have had a few reports from the field today, but would be very happy to hear from you! Thus far, I am not aware of any significant blossom or flower bud injury?
Grower in Concord, NC (4 p.m.)
“Just left the field and we appeared to have some decent cold damage from the event last night. We used our row covers and most held in place. Attached are images of what the buds look like currently, which is different than how it looked a day ago. We have many buds that are still a healthy yellow with green insides (there is a bisected picture attached), we have other buds that are brown but still have green/healthy insides, finally we have buds that are brown with brown (below) insides.
Fig. 2. Bloom killed in black frost, 3/29/15, Concord NC
Editor’s note – please let us know your minimum this morning, and what did Skybit forecast? What was the actual low? What weight row cover? Glad that most of the crop is ok.
VA Beach Feedback
I did receive this note from Tom Baker, VA Beach, a moment ago:
“I’ll go out a little later (3:30-4 p.m.) and take another look at blossoms that were in the few not-covered Camarosa rows as well as the not-covered Chandler rows (all rows had drip last night). Covert damage may not show up yet but overt damage should be evident. Will of course look at covered plants when we remove covers tomorrow.”
His questions earlier today were:
1. How long after a freeze event should one wait before an accurate evaluation of blossom damage is possible?
2. How long after a frost event should one wait before an accurate evaluation of blossom damage is possible?
3. How long after a frost and freeze event should one wait before an accurate evaluation of blossom damage is possible?
My reply: You can begin to evaluate open blossom, popcorn and flower buds within a few hours for damage. Instead of “bright yellow” centers you have what are often referred to as “black eyes.” This sort of injury can be observed by mid-morning following a radiation frost (white or black), frost/freeze, or windborne freeze. With a light frost, you may not see this more obvious damage (brown centers), but there can be partial injury to the flower that shows up later in the season as very bumpy looking fruit. Something that I believe everyone should be on the look-out for is possible damage to tight flower buds last night?
Fig. 4. Growers will want to check inside the flower buds for damage. In a freshly cut flower bud you will not likely see this kind of blackening so quickly after the cold event (this photo was taken of an emerged flower bud that had been injured during late winter, and my site visit was a few weeks following the event).
Crop damage report (5 p.m.) – Va Beach (an example where drip and no cover was unsuccessful)
I checked blossoms about 5 p.m. today.
Camarosas in two rows at Pungo that had no row covers and were dripped starting at 4 a.m. had about 40-50% blossom loss (flower eyes “brown,” not yet “black.” This is a disappointing surprise since air temp didn’t fall below 28.9 (WeatherUnderground), air was dry (dew point in single digits after 11 p.m.), and wind was mostly 5 to 10 mph and never less than 3.5.
Hindsight says perhaps drip should have been started earlier, but maybe wind negated effect of drip where there were no row covers?
A peek under row covers where drip was also used showed no damage to Camarosa or Chandler blossoms.
Drip ran in the entire field; no rows with “row cover and no drip.”
Tom & Anne Baker and Amanda McCann
Leaving covers on another day? Tom Baker, like many other seasoned growers in the region, know that after a cold event such as last night, it is a good idea to get prepared for a one, or possibly even a second “after-shock,” and the reason he is leaving his covers on today (Sunday), is due to the potential for a frost tomorrow morning.
Part 2. Evening update
Clayton – clouds moving in tonight and rains tomorrow morning
However, as of this evening, it would now appear that overcast skies and even rain tomorrow morning minimize chance of frost at Clayton. Here is the AccuWeather for Clayton as of 6 p.m.:
Rains in morning:
My evening SkyBit shows that the minimum expected in canopy tomorrow is now 35 (it was 34 this morning). There doesn’t appear to be much chance of frost.
Here is the follow-up SkyBit for Clayton:
Latest minimum temp map for NC (6 p.m., 3/29)
It would be helpful for you to click on the live link below to see what conditions will be like in your area tomorrow morning. For example, we know overcast skies and then rains are moving into much of the state tonight, but in areas on the map above where temperatures will be coldest tomorrow morning, it would not hurt to see if skies might be clear tomorrow morning, and if they are, a FROST might occur. In areas where skies may be clear tonight, and minimum temps of 35 or below are expected, BE SURE TO SET YOUR FROST ALARM!
An example, NEW BERN, NC
AWIS Detailed Hourly Forecast for Locations Across NC
Virginia: AWIS VA Mar 29 – Apr 5
Maryland: AWIS MD Mar 29-Apr 5
Please send photos and feedback on how things turned out from last night. Thanks
Good luck tonight!
Raleigh, NC 27695-7609
Sidney J. Harris, In: Reclaiming a Lost Heritage – Land-Grant & Other Higher Education Initiatives for the Twenty-first Century