First weekly vegetable update of 2022: 5/12/22

Author: Natalie Hoidal, UMN Extension educator, local foods and vegetable crops

After a long and cold spring, summer is finally approaching. Everything is delayed this year due to cold weather, stunted seedlings, and wet fields. Starting this week, I'll be sharing weekly vegetable updates to inform growers about what we're seeing across the state, and things to consider in the coming week. 

If you're seeing interesting things in your fields, need help identifying problems, or just want to share photos, we'd love to hear from you! Growers can reach out directly to me any time at hoida016@umn.edu, and you can submit questions and diagnostic help below.

Vegetable weather report

What a week! As the weather finally warmed up enough to start planting, we've experienced severe storms across the state. It's not yet clear how much damage growers have suffered from the storms this week, but at the very least, heavy rains have further delayed planting. We can expect hot, humid weather for the next couple of days, followed by a return to more typical cool spring weather in the high 50's to low 70's. While the wet spring meant delays for many growers, it also brought welcome relief to our dry soils. As of this week, we are no longer experiencing drought conditions in Minnesota! Soil moisture is lower than normal in the far Northeast and far Southwest corners of the state, but not low enough to be considered "drought" conditions. On the other hand, growers in the Red River Valley are experiencing flooding. Over the next week, forecasts show about an inch of rain in northwest Minnesota, with closer to half an inch or less in the southeast part of the state.

 

 

The DNR publishes summaries of annual normal temperatures from 1981-2010, which they use to estimate last spring frost dates (less than 10% risk of 32 degree weather). Most of the state is still in the danger zone, though 10 day forecasts show that frost is unlikely for most of the state. Click on the link to see frost dates for your area; while southern MN is about a week away from reaching this 10% risk threshold, northern MN is still a few weeks out. 

 

Soil temperatures are warming quickly across the state. The Minnesota Department of Agriculture publishes daily updated soil temperatures for major field crop growing regions of the state. Data is compiled from MDA managed stations in the Southern half of the state, and NDAWN managed stations in the northern half. As such, the data is presented slightly differently. The following tables provide a snapshot of soil temperatures across the state. For more detailed info, see https://app.gisdata.mn.gov/mda-soiltemp/

Soil temperatures from MDA stations, data collected to 6’’ depth

Station location	Nearest major town	Coldest soil temperature in the last 7 days (approx.)	Temperature on May 10, 2020 (approx).
Blue Earth	Albert Lea (Iowa border)	46 º F	55.5 º F
Russel	Marshall	45 º F	63 º F
Henderson	St. Peter / Belle Plaine	46 º F	60 º F
Hoffman	Alexandria	39 º F	49 º F

Soil temperatures from ND-managed stations in MN

Station location	Nearest major town	Average turf soil temp on May 10  (4’’)
Sabin	Fargo / Moorhead	52 º F
Mavie	Thief River Falls	44 º F
Fox	Roseau (Canada border)	45 º F

Crop updates 

Basically, everything is significantly delayed this year. If you're feeling behind, you are not alone!

• Cole crops: Due to delayed field prep, many farmers were planting their first outdoor successions of Brassicas this week. It's been fun to see so many of you trying new broccoli varieties based on our 2021 trials! The cabbage maggot forecast predicts that emergence will occur this week in the southern half of the state. If you use row cover, now is a good time to start getting it ready if it's not already out, at least for growers in the southern half of the state. 
  
• Sweet corn: We're getting really close to planting time! Check your variety for optimal soil temperatures; some varieties can handle 55 degree soil, and others prefer it to be a bit warmer. Many growers in Southern MN have already started transplanting. The seedcorn maggot forecast predicts emergence in the southern half of the state this week; read more about it here. 
• Lettuce: High tunnel lettuce is maturing nicely. I heard from quite a few of you who had rabits and gophers in high tunnels this spring. I checked in with a vertebrate pest specialist, who confirmed that our squirrel, gopher, rabbit, opossum, etc. neighbors are generally pretty hungry this year. With limited food options outdoors due to the delayed spring, your high tunnel lettuce looks very tasty. 

 

Photo: Audrey, Flickr

• Carrots and beets: I continue to see creative strategies to support carrot and beet germination. More and more growers are using row cover to maintain consistent soil moisture, and I heard from another person who uses silage tarps right up until the moment carrots are about to germinate. 
  
• Onions: Most growers didn't get their onions planted until the last few days or so, so there's not much to report yet.
  
• Garlic: Garlic is a bit delayed this year, but it's generally looking healthy. Early to mid May is the time for spring nitrogen applications; ideally do so soon, as late nitrogen applications can delay bulb formation. More info on garlic management. 
• Asparagus: Asparagus is a bit later than last year, but it's catching up quickly!
  
• Potatoes: Around this time last year I noted that potatoes were mostly planted. That does not seem to be the case this year, but there is still plenty of time to plant. I already heard my first report of Colorado Potato Beetle in a high tunnel, so get ready!
• Tomatoes and peppers: Tomatoes and peppers are all over the place; most of the tomatoes and peppers I've seen have been fairly stunted due to the cool spring, and in some cases due to potting soil issues. There is still a good chance they will catch up in the next few weeks. Many growers have been busy transplanting tomatoes in tunnels this week.
  

Problems in the field

Delayed rye cover crops

I've visited / heard from quite a few farmers whose rye cover crops are quite delayed this year. If you use herbicides, this is not a problem. Many organic growers wait until rye reaches anthesis (head formation / onset of flowering) to terminate it by mowing or crimping, because it's a lot less likely to re-sprout at that point. However, with delayed growth, it's going to take a bit longer for the rye to reach that point. Some options for termianting rye early include tarping to kill it via occultation / lack of sunlight (if you're on a small enough scale) and tilling. If you choose the tillage route, note that it may take a couple of passes. I asked a couple of colleagues who have more experience terminating rye than I do about this, and they recommended mowing and discing it, then tilling. 

A rye cover crop ~4 inches tall 5/9/22, photo by Natalie Hoidal

 

Greenhouse humidity

A cold, wet spring can lead to high greenhouse humidity. Plants aren't growing as quickly so it's easy to overwater, and evaporation was minimized by the cloudy cool weather. In general, I still see a lot of high tunnels and greenhouses that don't have adequate ventillation systems. Many farmers rely entirely on roll-up sides for ventillation, but tunnels should really have vents at the tops of the side-walls, and at least a couple of fans. As a result of the humid weather, disease conditions in tunnels have been great. The photos below show some common greenhouse diseases: gray mold (top) and bacterial spot (bottom). Read Marissa's article from last week to learn more about managing bacterial diseases in the greenhouse, and feel free to reach out for help with ID and management plans!

Gray mold in peppers, photo Natalie Hoidal

Bacterial spot on a pepper, photo by Natalie Hoidal

Get help

Do you have questions about issues you're seeing in the field, or would you like assistance with things like nutrient management plans, regulatory issues, etc? Growers can reach out directly to me any time at hoida016@umn.edu, and you can submit questions and diagnostic requests via this form.