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Weekly vegetable update 8/19/2021

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

The summer of 2021 continues to be hot, dry, and generally exhausting; 50% of the state is now under extreme drought conditions. Despite these challenges, we are in peak summer production and growers are now consistently harvesting melons, tomatoes, peppers, and other late summer veggies.

Crop updates 

  • Cucurbits: Cucurbits are the stars of the show this week. Melons are ripening, and winter squash harvest is beginning already! This is the time of year when raccoons can do a lot of damage in a melon field, so keep an eye out for damage and signs of critters.
  • Tomatoes: There seems to be more blossom end rot than usual this year. This is to be expected given the drought, and the fact that many farmers are struggling to keep up with watering. Keep notes about varieties that seem particularly susceptible, and remove any tomatoes with symptoms as soon as you see them so that your plants can focus on growing healthy fruit. 
  • Potatoes: Most of the potatoes being harvested now are still for fresh market, but we're reaching storage potato harvest season. Last year we saw quite a bit of soft rot, so make sure you're harvesting as gently as possible and carefully sorting bruised potatoes.
  • Onions: While many growers have been harvesting fresh market onions for a while, harvest for wholesale markets and storage onions is starting to ramp up. If you plan to store your onions, read about proper curing and storage here. 
  • Garlic: This is a good time to start thinking about buying your garlic seed for fall planting. Sustainable Farming Association has a directory of local garlic sellers who have tested negative for Garlic Bloat Nematode. Now that your garlic has cured, sort through it and look for bulbs infected with Aster Yellows. Farmers around the state are seeing AY in their garlic. If you suspect you have it, you can still eat your infected garlic, but do not save and re-plant it. More about garlic aster yellows. 
Garlic wrapper discoloration after AY infection. Photos: UMN Extension

  • Beans -While dry beans are not exactly a "vegetable" (or maybe they are? "Vegetable" is a cultural designation, not a botanical one), I write about them here because every year I see more and more vegetable farmers growing heirloom dry beans. They are a great option for crop rotation, winter sales, and they are also just beautiful and fun to grow. Irrigation can be cut off when around 80% of the pods have begun to yellow, and beans can be harvested when the majority of pods are yellow. If you wait to long to harvest (especially with a combine), the likelihood of shattering increases. Read more about dry bean harvest in NDSU's dry bean guide.  
Beans ready to harvest. Photo: Jordan Wente
  • Peppers: Peppers are reaching peak production, generally with very few problems. I'm seeing a lot of sunburnt peppers - make sure you're rouging these out, as sun spots can be more susceptible to secondary infections.
  • Cole crops: Alternaria is showing up around the state in the form of head rot, even in plants that have fairly minor foliar symptoms. If you think you're seeing Alternaria in your broccoli, please let me know! I have funds to send broccoli samples from around the state to the disease clinic to screen for Alternaria, and to help us confirm which species is / are causing the majority of the damage in Minnesota. Read on below for a more in-depth look at some of the symptoms we're seeing in broccoli harvested in August.
  • Sweet corn: Corn earworm trap counts were up last week in Blue Earth (Faribault County), above the threshold of 5 moths / trap / night. They remained low at other trapping locations including Rosemount, Lamberton, and Crookston. More farmers are having issues with deer, birds, and raccoons.

Vegetable weather report

The US drought monitor was updated this morning, and 50% of Minnesota is now under extreme drought conditions; 88% is under severe drought, and 99% is under moderate drought. Most of the state is expected to see some rain this weekend, and in some cases this might become severe weather. There may also be some light scattered showers mid-next week. The forecast maps are showing predictions of one inch or so in Southeast Minnesota, closer to 2 inches in Western MN, and possibly even 3 inches in the far Northwest corner. Heavy rains following drought conditions are one example of a situation where we really see the benefits of investing in cover crops, strips of perennial vegetation to absorb water, and other soil health investments. 

Temperatures will cool down after the Friday night weather event, and we can expect to see highs in the mid 80's (southern MN) / 70's (northern MN), and nighttime temperatures dropping into the 50s and 60s (southern MN) / 40's (southern MN).

7 day weather forecast,

Problems in the field and things to anticipate this week

Broccoli problems

Brown bead vs. Alternaria: We're seeing both brown bead and Alternaria in broccoli heads lately. While they share some similarities (brown beads on the head), they have some significant distinguishing characteristics. Broccoli 504 in the photos below has Alternaria. Notice that the brown beads are concentrated together, and the brown spot extends down each bead and into the stem. It is worth discarding infected heads, even if the spots are quite small, as the disease can worsen in storage and can lead to very smelly unmarketable broccoli. 
Brown bead on the other hand tends to be more dispersed throughout the head (Broccoli 601 below). It starts as yellowing of unopened beads / buds (different from flowering yellow buds / bolting). The yellowing buds eventually become dry and brown, and sometimes become necrotic. Broccoli heads with brown bead tend to be prone to secondary infections, so it's important to scout your broccoli regularly so that you don't mistake the secondary infection for the main problem. Brown bead is most common in the warmest parts of the summer, and is a bit like blossom end rot in that it can result from a lack of calcium reaching the buds. Uneven watering can exacerbate the problem. We are seeing varietal differences in our summer broccoli trial; we'll post more thorough results this fall. Brown bead is most influenced by heat in the week or so before harvest, and so planting regular successions is another strategy to avoid it. While broccoli with brown bead is technically fine to eat, keep in mind that shelf life will be reduced, and these heads are more prone to secondary infection.
  • Broccoli photos from 2021 summer trials. Photos: Charlie Rohwer

Hollow stem: We're seeing a fair amount of hollow stem in our broccoli trials. While not terribly problematic in and of itself, hollow stem makes broccoli more susceptible to secondary pathogens, and it may not be attractive to some buyers. Wide plant spacing and over-fertilizing are correlated with hollow stem. You may read online that this is caused by a boron deficiency, but this is usually not the primary factor. Additionally, most Minnesota soils have sufficient boron levels, and growers should be careful to avoid adding too much boron, as it can be toxic to some crops. More info about hollow stem.

Hollow stem in broccoli. Photo: Charlie Rohwer

Time to prepare for winter greens

Growers who plan to grow winter crops in tunnels such as spinach and other cold hardy greens should start to plan now for high tunnel turnover. Ideally, this would include a soil test so that you can make amendments in the time between pulling your current summer crop, and planting the next one. Johnnys has an excellent chart showing when you should plant various crops relative to the "Persephone period" when daylengths drop below 10 hours per day, and plants basically go dormant. I also want to draw peoples attention to yesterday's Vegetable Beet podcast, which was all about leafy greens. The hosts had a very helpful discussion about varieties that may help you choose what to grow. 

Spinach in February in an unheated tunnel

Educational opportunities

Field day!  

Learn how seed saving farmers make selections to improve or maintain crop varieties, and how working with seed companies and universities can strengthen your farm operation. Topics and demonstrations will include regionally specific seed saving techniques, useful tools for both small-scale and wholesale seed growers, and more to be determined. See how regionally adapted seed varieties are bred by and for organic farmers. Hosted by Organic Seed Alliance and Greg Reynolds of Riverbend Farm, in collaboration with Koby Jeshkeit-Hagen of Seed Sages, and Dr. Julie Dawson of the University of Wisconsin-Madison.

This field day is being offered free of charge, though pre-registration is required. Please sign up at

Questions? Email, or call/txt 248-404-7616.

Podcast: The Vegetable Beet: join us during your lunch break on Wednesdays for a 30 minute discussion about vegetables. Next week's topic will be about wildlife management for vegetable growers.

Technical assistance: 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, and you can submit questions and requests for diagnostic help here

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