MSU Extension Vegetables

Weather

We had a series of freeze and frost events over the weekend and today, May 13. The Thumb and Bay stayed relatively warm on Saturday, May 9, with temperatures from 27 to 34 degrees Fahrenheit. However, our region was hit harder than the rest of the state last night, May 12-13. The lowest temperatures across the region were as follows: Fairgrove (23.9), Flint (28.1), Frankenmuth (25.9), Freeland (25.9), Ithaca (27.0), Kinde (24.7), Lapeer (23.5), Linwood (25.9), Munger (26.9), Pigeon (24.6), Romeo (26.6) and Verona (25.4).

In the next few days, we should have higher temperatures and some rain.

I have gotten damage reports from last night’s/this morning’s deep freeze.

So much of freeze damage depends on air drainage (low spots being colder), wind and moisture. Reports from fruit country this week have shown that high moisture levels in irrigated grape and blueberry have enhanced freeze damage by filling plant tissues with water, which then froze. However, unirrigated grapes and blueberries lacked this moisture and experienced less damage. This effect of drier tissues surviving is known as “supercooling” and it has also been recorded in cabbages. There appears to be a balance between irrigating for soil warming and potentially increasing plant damage by the water uptake in some crops. The rain on Sunday likely allowed young plants to gulp some water, which them froze inside them last night.

You can find more detailed weather information for your area by visiting the Enviroweather station closest to you:

• Emmet (under construction)
• Fairgrove
• Flint
• Frankenmuth
• Freeland
• Kinde
• Lapeer
• Linwood
• Munger
• Pigeon
• Romeo
• Sandusky
• Verona

Vegetable crops

Nematode samples coming to the Michigan State University Plant & Pest Diagnostics Laboratory and Marisol Quintanilla’s lab are coming back with very low numbers of all plant-pest nematodes. They are hypothesizing that the predominately wet season in 2019 suppressed their reproduction by creating a soil environment that was starved of oxygen from being too wet. So, one good thing may have come from that wet year!

Asparagus that were emerged are now melted. They tend to take longer to resprout after a freeze than they do after a mowing, but it can help recovery by cutting these out.

Rhubarb seems to have toughed it out.

Seeded root crops are in various stages of emergence. The ones with young cotyledons and true leaves could have been killed, but it is hard to say. Some plantings may bolt. Peas, beets and carrots are quite cold tolerant, but could be killed off at very low temperatures.

Transplanted crops were perhaps at the biggest risk of freeze damage. Temperatures under plastic low tunnels and in unheated high tunnels probably got low enough to damage plants. Those that made it are going to do well going forward. Growers who were holding transplants are now sprinting to get them in with warmer and wetter forecasted in the days ahead.

Bolting

Periodic freezes and a prolonged period of cool temperatures in the spring will give biennial crops and winter/spring annual vegetable crops an accumulation of several hours in their vernalization range that could add to previous weeks where nights got below 50 F as well. This may fully or partially vernalize some plantings of older, larger or earlier-maturing varieties of sweet onion, leeks, Brassica and celeriac/celery transplants to the point where they bolt later this spring and summer. The direct-seeded crops most at threat are beets, chard, spinach, lettuces, radishes and turnips because of their ability to vernalize as seed with short vernalizing times of one to four weeks for most of them.

Seeded carrots, parsnips, storage onions and fall-transplanted shallots are not as likely to bolt from spring temperatures because of their larger juvenile plant size requirement and longer vernalizing times. Fall-planted hardneck garlic routinely bolts and should be expected.

Great Lakes Vegetable Producer’s Network

MSU Extension is participating in a live, weekly roundtable discussion during the growing season for commercial vegetable producers in the Great Lakes and Midwest region. Join us! We broadcast live via Zoom at 12:30 p.m. ET/11:30 a.m. CT every Wednesday from the first week of May to the first week of September. You must register to be a part of the live audience. If you have a pressing vegetable production issue that you would like discussed, simply email it, along with your phone number, to greatlakesvegwg@gmail.com.

On-tap for next week, May 20 – The white thread: Early season weed management.

Please contact me at phill406@msu.edu or 616-901-7513 with questions, concerns, or to schedule a farm visit. You can also send plant materials to MSU Plant & Pest Diagnostics.