Much of the state is under water as we write this update, following torrential rain storms across Minnesota on Wednesday. Wet fields and air quality alerts followed by hot, humid weather this weekend likely mean less time in the field for a couple of days. Next week is supposed to bring drier, cooler weather, just in time to harvest any remaining garlic and plant final successions of fall crops like carrots and broccoli.
“Farm hacks”
While many of our readers are experienced farmers, we know plenty of our readers are just getting started. There are simple “hacks” that may seem obvious to folks who have worked on or visited their fair share of vegetable farms, but are not necessarily intuitive. For the next couple weeks, we’ll highlight some “farm hacks” that save farmers time and money. It’s hard to think about irrigation right now after months of heavy rain, but we often see hot dry spells in August, and it’s good to be prepared. This week we’re focusing on some common issues with irrigation systems that can be easily fixed with the right equipment:- If you’re running a long hose from your well / faucet to your field and the pressure is dropping significantly by the time the water reaches your field, try a larger hose or pipe. A hose / pipe with a wider diameter can hold water pressure much better than a smaller one. We often see people running garden hoses over long distances; instead try investing in some “lay flat”. These hoses are usually made of flexible vinyl, are usually blue, and have a diameter of 1.5” or 2”, and can be purchased in lengths of 100’, 150’, or 250’. You can cut it to fit your field area, and it can withstand being walked over, driven over, etc. (though it will last longer if you treat it well).
- Use the right size pressure regulator. A 10 PSI / 0.5 - 15 gpm pressure regulator is the right size for about ¼ acre of drip tape, equivalent to 22 rows that are 100’ long. This size pressure regulator can also be used for most high tunnels. If you have a pressure regulator controlling a larger area than this, you’re likely not getting sufficient pressure. If you’re using a much larger pressure regulator (e.g. 30 PSI) for a small area, you may run into the opposite problem. Too much pressure can cause your fittings to break, or can cause your drip tape to be pushed out of your fittings.
Reviewing postharvest guidelines
Which crops need to be washed, and which crops can be simply wiped or packed and sold as-is? Take a few minutes on a rainy day to review our postharvest handling webpage. At the end of the webpage there’s a table of common vegetable crops that shows whether each vegetable is typically washed or not, how it’s typically cooled, and ideal temperatures and humidity levels for storing each crop.
For those who prefer to learn hands-on, we’ll be hosting a field day in St. Paul in two weeks (Thursday August 7th) all about postharvest handling, including washing, sorting, and packing vegetables. Check out the details here.
Crop updates
Tomatoes
Tomato harvest is lagging way behind on most farms. We’ve seen a few nice flats of high tunnel tomatoes, but even high tunnel tomatoes are not doing great. We’ve heard many reports of blossoms just simply drying up and turning brown, never producing fruit. In most cases, this is likely a heat stress response. It seems to be more common in slicer types than in cherry tomatoes. As our summers get hotter, growers should consider shade cloth for high tunnels. Numerous Midwest trials have shown yield benefits from 30% shade cloth in high tunnel (50% is too much). As an added benefit, shade cloth makes it so much more pleasant for people to be in high tunnels this time of year.
We’re also seeing a lot of foliar disease. Managing foliar disease will be super important this week. We’ve had so much water across most of the state, and will likely see high humidity for the next few days. These are ideal conditions for most fungi and bacteria to spread. Wait for a hot, dry day and take some time to catch up on pruning. Many growers should also consider fungicide options. Read Marissa’s recent article on tomato leaf spot diseases for more info.
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| Blossoms drying up in tomatoes. Photo: Natalie Hoidal |
Cucumbers
While we’re seeing plenty of beautiful cucumbers, we’re also hearing reports of cucumbers shriveling up before they have a chance to develop. On most farms, this is likely heat stress (especially in tunnels). But, there is one more thing to consider: pollination is complicated in cucumbers, and I’ve seen quite a few growers mixing insect pollinated cucumbers and parthenocarpic cucumbers in the same tunnel. Why does this matter?- Standard cucumbers require insect pollination. When the do not get pollinated (or only get partially pollinated), the cucumbers either don’t develop at all, or they grow in funky shapes.
- Parthenocarpic cucumbers grow cucumbers that are not formed via pollination. The flowers never get fertilized, and they are able to produce seedless fruit. These are specially bred species; not every cucumber variety can form fruit without pollination. The problem is… if these parthenocarpic cucumbers do get pollinated, the fruit are funky, and end up looking sort of like standard cucumbers that don’t have enough pollination.
So, when growers plant both types in a high tunnel, it is fairly likely that at least one type of cucumber, if not both, won’t turn out very well. If you’re encouraging pollinators in your high tunnel and they pollinate the parthenocarpic flowers, the fruit turn out funky. If you’re not encouraging pollinators in your tunnel or are excluding insects with insect netting, the standard cucumbers don’t get pollinated.
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| Poorly pollinated cucumbers. Photo: Natalie Hoidal |
Beans
Harvest is ongoing. We are seeing some spots where we suspect bean viruses. Signs of viruses include stunting, twisted leaves, and light green and yellow “mosaic” patterns in leaves. There are tons of viruses in beans, and some really impact flowering and pod set while others don't. Pull suspect plants. If you are hesitant to do this, keep an eye on whether plants are flowering and setting pods as normal – if not, pull them out. Do not save seeds from plantings where you see virus activity.
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| Mottled leaves and concentric rings are two common viral symptoms. Photo: Natalie Hoidal |
Carrots
If you planted carrots last week and they were washed away in a torrential downpour, the week ahead (after Thursday) is looking more reliable for planting. This is really the last week to plant carrots with some certainty that they’ll be harvested this fall. There are some small, quick varieties (e.g. 55 days) that can probably still be planted after this week, but reliability of harvest later in the fall can be dicey. Some years it’s totally do-able, others it just doesn’t work out.Onions
We heard a report of onions bolting in central MN this week. Unfortunately, onions are much different than garlic when it comes to flowering and setting bulbs. When garlic flowers (produces scapes), we harvest them and the garlic continues to grow its bulbs. When onions flower, they have a distinct shift in their lifecycles, and the bulbs will not continue to grow. Instead, the bulbs become more prone to rotting, often develop a hard center, and they will not be shelf stable for very long once harvested. If your onions bolt, the best thing you can do is harvest them asap and sell them as fresh onions for immediate use.Garlic
Heavy rain is making garlic harvest challenging. Based on the amount of aster yellows we saw early this spring, we suspect that there was significant carryover from 2024 seed. Therefore, it is extra important to sort through your garlic at harvest time and cull out anything that looks potentially infected with aster yellows. This garlic is still edible, but should be stored separately from any garlic you plan to save for seed.
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| Garlic with aster yellows. Photo: UMN Extension |
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