Final Weekly Vegetable Update September 10, 2026

Authors: Natalie Hoidal, Marissa Schuh, & Cindy Tong

Updates are over, we’re still here! This will be our final update of the season. We know you still have a lot of farming to do this fall, but we generally find that there’s less to say in September as things start to wind down. It’s too late to make many management changes, and we start to shift our focus to winter programming. We’ll keep writing articles over the winter, we’re just shifting away from weekly crop by crop updates. 

Some other places you can find us this fall /winter/spring:

• Email us any time! (general vegetable hoida016@umn.edu, pest management mschuh@umn.edu)
• There are still field days this fall, including...
• Mechanical Weed Control Field Day - September 28th Delano, Minnesota (Wright County). A full day focused on selecting, assembling, running, and calibrating all sizes of tools and equipment for mechanical weed control. Get hands-on experience with human and machine powered tools, from a variety of collinear hoes to two and four wheel tractors.
• Keep your eyes out for two-day vegetable intensives we are going to host around the state. The course covers how to pick markets, crops, and standardize production in order to meet quality and quantity bigger buyers need. It features lots of hands-on components around crop planning, irrigation, pest management, and post-harvest handling.
• In a couple of weeks we’ll post registration for five climate adaptation retreats we’re hosting around the state in November and December. These are two day retreats where farmers develop comprehensive climate adaptation plans for their farms, in collaboration with the Land Stewardship Project and Regional Sustainable Development Partnerships.
• Winter conferences - we’ll be at all of the common winter conferences including the Emerging Farmers Conference, the MN Organic Conference, the MN Fruit and Vegetable Growers Conference, the Sustainable Farming Association's annual conference, and Marbleseed. Come say hi if you’re attending any of these!

Final crop updates

Pumpkins and squash

Winter squash are being harvested and sold, but many pumpkins (and plenty of squash) still need to make it through the fall. Here's an old, but still really good article written by our colleague Ben Phillips at Michigan State about getting pumpkins through the final stretch of the season. 

Tomatoes

Tomatoes have been a mixed bag this year. Most started late, and while slicer tomatoes seemed to catch up and do fairly well at most farms, many farms have been struggling with diseases, drought, and generally sort of drab tomatoes.

If you suspect disease is partially to blame for less than ideal tomatoes, it's really worth submitting a sample to the Plant Disease Clinic so you can invest in resistant varieties, and potentially grafting next year. 

If you're seeing extensive yellow shoulder or internal whitening, there's a good chance you are low on potassium. These disorders are complicated and get worse under heat and drought, which we've had plenty of. Soilborne pathogens that infect vascular tissue can make it hard for plants to transport nutrients. Try cutting into the stems to look for browning or discoloration to help rule out soilborne pathogens. If the stems look healthy, it's more likely that low potassium is driving the issue. 

Tomatoes with yellow shoulder next to a healthy, red tomato. Grower submitted photo. 

Fall beans and peas

Peas planted for fall harvest have started to respond positively to cooler nights, and beans are chugging along well. At farms where bean leaf beetles caused major damage earlier in the season, later successions of beans are generally looking better. However, it is possible for them to produce a second generation in Southern MN. 

Onions: Update written by Cindy Tong

Leaves of alliums, like shallots and onions, should be flopping over or exhibiting leaf (50-80% of leaves) yellowing now. These are signs that the alliums are ready for harvest. 

Onion leaves flopping over and turning brown. Photo: Lindsey Miller

Cull alliums that show signs of defect, like mechanical or insect damage, decay, sunscald, sprouting, or abnormally thick necks and undeveloped bulbs. If properly harvested and handled, dry onion bulbs can be stored for 6-9 months at 32 °F under 65-75% relative humidity. After carefully lifting onions, dry the bulbs in open-ended high tunnels or sheds or in the field (if no rain is forecast) for at least two weeks. Good ventilation is key to successful curing. Adequate curing is done when outer scales are dry, making a rustling noise when bulbs are handled, necks are tight, and scale color is uniform.

After this, bulbs can be stored at lower temperatures, with good air circulation. Proper curing can help decrease the incidence of some postharvest diseases, like Botrytis neck rot, which starts with watery decay at the neck that spreads to the bulb, and leads to gray mold covering the bulb. Another disease that can be decreased, but not stopped with proper postharvest handling, is black mold. Like neck rot, the neck of the allium will shrivel, but the bulb scales will turn black. This disease can spread from bulb to bulb in storage, so infected bulbs should be culled as soon as the disease is detected. Blue mold rot leads to softening of the neck and bulb scales, which turn blue due to the Penicillium mold.

With bacterial soft rot, the bulb will look water-soaked, smell bad, and will feel like it’s turning into a thick liquid. This disease progresses under humid, warm conditions.

If you’ve been successful harvesting and curing your alliums – congratulations! However, for long-term storage, avoid storing onions at freezing temperatures, which can lead to scales turning translucent. Also, avoid storing onions under lighted conditions, which can turn outer scales green.

Fall cover crops

Last week we wrote about how vegetable growers often use really really high seeding rates for cover crops. I planted oats in my garden a few weeks ago in a spot where my tomatoes died from Verticillium wilt. I used a rate that was well above the recommended rate and broadcast seeded, basically covering the soil in oat seeds. They germinated beautifully, and now that they are about 8 inches tall, they are looking pretty bad, with a lot of lodging. Oats may be more likely to lodge when planted too shallow (which is likely to happen with broadcast seeding), and when the planting density is too high. Lodging may not matter much if your goal is to get some good cover crop biomass before a frost, but, let this be another nudge that it's ok to use the average seeding rate, and that over-seeding may not always be beneficial. 

Garden oats, broadcast seeded with a very high seeding rate, now lodging. Photo: Natalie Hoidal

Some fall fun

I was inspired by our colleague Dan Fillius in Iowa to grow Johnny's Coco marigolds, and then make them into festive garlands. It was a fun little project. If you want to grow them next year, know that these are not your average marigolds! They grow to about 3-4 feet tall, and benefit from some sort of trellising or staking. 

Coco marigold garland. Photo: Natalie Hoidal

Managing crop residue

As certain crops slow down, finding time to clean them up can be a challenge in the fall. A common integrated pest management recommendation is “promptly remove” or “promptly destroy” crop residues. This is for a couple of reasons…

• Removing or incorporating residues removes places for insects that have many generations to build their populations – like cabbage maggot, swede midge, or cole crop caterpillars. Tilling residues into the soil can reduce the overwintering of squash vine borer.
• It also starts the process for plant pathogen populations to start declining instead of increasing. Many plant pathogens can remain on the farm as long as they have some infected crop residue to hang out on.

So, a goal in crop residue management is to either remove residues entirely, or break them down into small pieces and incorporate them into soil. Tillage accomplishes this well, by chopping residues into smaller pieces and then working them into the soil, where soil microbes can access them. While many growers are interested in no-till (for good reason!), dealing with residue in a no-till system is challenging at scale. 

• If practicing no-till, mowing is an option. A flail mower can be super handy, and may be something you can fund with help from a MDA Soil Health Financial Assistance grant.
• Using plastic to cook down residues – depending on if we use clear or black plastic, we call it solarization or occultation. Mowing, followed by tarping, can help to kill any remaining vegetation, and can get it ready to break down quickly in the soil. 
• How much does removing roots matter? Depends on the pathogen. Some pathogens infect plants locally, others are systemic and move throughout the plant. Systemic infections often discolor vascular tissue.

Cover crop residues after being chopped with a flail mower. 

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