Weekly vegetable update July 1, 2026

Authors: Natalie Hoidal & Marissa Schuh

After a hot start to the week, we are settling into temperatures that are a little more typical for July. Heat waves can slow down our vegetable crops in a few ways, see a rundown in the article “How vegetables respond to heat.”  In general, when we have hot days, and especially hot nights, there is reduced fruit set in vine crops and tomatoes, as well as a slow down in tomato ripening. 

Mid to late June is one of our favorite times of year. The big push to get everything planted is winding down (though succession planting continues), and we’re seeing the shift from just harvesting spring greens into early summer crops like carrots, beets, summer squash, etc. This is also when things start to get “interesting” in the field. We’ve had calls this week about hail damage, herbicide drift, disease, insects, some potential ozone damage, miscalibrated fertigation, and some nutrient deficiencies. Thankfully, at this time in the season there’s still plenty of time to make adjustments and fix problems. So, take some time now to look for problems or weird things going on in your fields and don’t hesitate to reach out for help.

Crop Updates

Brassicas: This week is a perfect example of why it’s so so hard to grow broccoli and cauliflower in the spring in Minnesota. These crops need cool weather to trigger head formation, which we get from Minnesota’s cool spring nights. Once head formation begins, heat can cause the heads to flower, often before they are the size we want them to be. The rapid shift from moderate spring temperatures to high summer heat is happening just as these crops are reaching maturity, which can ruin an entire crop. We expect to see a lot of bolting this week if it hasn’t happened already. What are the solutions? Choosing bolt resistant varieties can help, but many growers have simply shifted to fall maturing Brassicas, or to choosing Brassicas that are meant to be sold when they start flowering like sprouting broccoli and cauliflower (sprouting broccoli is a spectrum and can include broccolini, rapini, broccoli raab, etc). 

Peas: The earliest successions of peas are winding down. Last week saw a bumper crop of late spring planted peas, but we don’t expect them to fare well through this heat wave. 

Peppers: Bacterial spot is being spotted in peppers throughout the state. This disease is known to be seedborne, but can also show up again if you’ve had it on your farm in the last few years (pathogen can survive in crop residue and on surfaces).  Pepper tends to be a disease with few pest problems (instead, it struggles with nutrition and weather), so if you are seeing spots on leaves, this is the one we see most often. Leaves will spots, they often start looking diffuse, but in older plants, the disease appears as brown to black spots with yellow haloes, which get larger and coalesce, at this point the centers will turn tan and sometimes fall out. Sometimes this disease will infect the fruit, but more often reduces yields via plant stress.

Bacterial spot will cause numerous, diffuse spots on peppers leaves. These will eventually dry out and the leaf will look ratty. Photo: Dan Egel, Purdue University.

If you are seeing this in limited plants, remove those plants to get rid of disease reservoirs. If removal isn’t feasible, stay out of your field when it is wet, and work in those areas last, then clean clothes, shoes, and tools.  There are a few products that can slow down the disease (including a couple of OMRI listed ones), see the Midwest Vegetable Production Guide for information.

Tomatoes: Tomato harvests are picking up in high tunnels in southern MN, and we expect to see field grown tomatoes ripening in a couple of weeks. Tomato nutrition, particularly in high tunnels, is so complicated, and to be honest, we are still learning alongside you all. There is some consensus among Extension folks that high tunnel tomatoes really benefit from some continued feeding, with around 5 lbs per acre of nitrogen per week as they begin flowering and fruiting, but actually doing this in practice is tricky, and over-applying nitrogen causes its own problems (including groundwater contamination, aphid problems, and lower yields). If you’re struggling to fine-tune your tomato fertility program, don’t hesitate to reach out with questions. 

Vine crops: Heat waves are generally not great for vine crops, as heat interferes with flowering and fruiting, and can also make the bees needed for pollination less active. However, the heat might actually be a good thing for winter squash plantings with angular leaf spot or cucumber beetles (which we’ve seen a lot of). Warm weather + plenty of rain = fast growth. While humidity generally favors plant disease spread, vigorous growth can help plants push through insect feeding damage and some diseases. 

Strawberries: Strawberries have slowed down quite a bit in the southern part of the state. It’s time to renovate your plantings to keep them productive next year. Here’s a short video walking you through renovation step by step: mowing, fertilizing, and dealing with weeds, and here’s a webpage if you prefer to read about it. Do not renovate new plantings - let anything that was planted this year continue to grow for the rest of the summer. 

Sweet corn: We had a chat with Charlie Rohwer, a vegetable researcher in Waseca, about what he’s seeing in sweet corn. He has trials on early planted sweet corn this year, which have had some issues with variable emergence and poor pollination (the second is likely linked to the first, as ears were not in sync when they needed pollination). He also has noticed some varieties are prone to tillering, or making small side stems. These side stems rarely produce harvestable ears, and can cause issues for some mechanical harvesters. If you have varieties with lots of tillers, try a different one, reduce place spacing, or you might be alright just living with it.