Natalie Hoidal & Marissa Schuh
This spring has been pretty ideal for planting. Cooler weather with fairly consistent, gentle rains have allowed farmers to get crops in the ground, reduce transplant stress, and keep cool season crops like Brassicas happy. Looking ahead, the NOAA 3-month forecast has shifted from projecting an “average” summer, to a summer that is likely to be hotter and drier than usual. While many crops seem slightly slow to establish at this point, they’ll catch up quickly as the weather warms up in June.
Garlic is scaping, so here is your annual reminder about best practices for garlic scape harvest: Accidentally removing leaves during scape removal can result in major yield losses. Doing garlic scape removal by hand is time consuming, but is the best way to minimize damage to the plant.
Carrots are being harvested from high tunnels, and won’t be too far behind in fields. On one farm growing carrots and parsnips for seed, we saw carrot seed moths, a new invasive species that feeds on the flowers of plants in the carrot family. For most growers this isn’t an issue since we only grow carrots for one season, but it poses a major challenge to growers who are growing plants in this family for seed.
We saw some peas planted the first week of April that were ready for harvest.
Brassicas are for the most part happy with the cooler spring weather, but we saw some bolting and brown bead after the mini heat wave and heavy rains last week.
This spring has been pretty ideal for planting. Cooler weather with fairly consistent, gentle rains have allowed farmers to get crops in the ground, reduce transplant stress, and keep cool season crops like Brassicas happy. Looking ahead, the NOAA 3-month forecast has shifted from projecting an “average” summer, to a summer that is likely to be hotter and drier than usual. While many crops seem slightly slow to establish at this point, they’ll catch up quickly as the weather warms up in June.
Crop updates
Greens galore: Many farmers are starting their CSAs and farmers markets this week with an abundance of leafy greens. We’ve seen a few disease related lettuce questions including bottom rot and some mysterious leaf spots. Remember that when you’re seeing pathogens, you’re always welcome to reach out to us for help with identification and figuring out management strategies.Garlic is scaping, so here is your annual reminder about best practices for garlic scape harvest: Accidentally removing leaves during scape removal can result in major yield losses. Doing garlic scape removal by hand is time consuming, but is the best way to minimize damage to the plant.
Wait until scapes start to curl before harvesting them. The yellow tips of the leaves are typical for this time of year. Photo: Marissa Schuh, UMN Extension.
Carrots are being harvested from high tunnels, and won’t be too far behind in fields. On one farm growing carrots and parsnips for seed, we saw carrot seed moths, a new invasive species that feeds on the flowers of plants in the carrot family. For most growers this isn’t an issue since we only grow carrots for one season, but it poses a major challenge to growers who are growing plants in this family for seed.
Carrot seed moth creates a we around and feed on seeds and flowers of plants in the carrot family. Photo: Natalie Hoidal.
We saw some peas planted the first week of April that were ready for harvest.
Brassicas are for the most part happy with the cooler spring weather, but we saw some bolting and brown bead after the mini heat wave and heavy rains last week.
We had one interesting question from a farmer about broccolini: more and more farmers are moving to broccolini instead of broccoli. As our climate gets warmer and more unpredictable, it’s becoming more challenging to produce perfect broccoli heads. Broccolini continues to produce many small shoots rather than forming one main head, and customers don’t seem to mind when it flowers, making it a much easier crop to grow. The farmer we talked to was seeing brown bead in her broccolini. This is a complex physiological issue that can be caused by rapid growth, hot & humid nights, too much nitrogen, and boron deficiency. In this case, we assumed that it was likely a result of very rapid growth and high humidity. In broccoli, a head with brown bead is a total loss. However, in broccolini, it’s likely that the crop can be saved if you get rid of the shoots with brown bead, as long as the weather is more favorable while the next shoots grow.
There is some damage from early season caterpillars out, as well as plants showing the damage of cabbage maggot. If you are seeing stunted plants that are turning yellow and purple, digging at roots may reveal tunnels and maggots in the stem.
Strawberries are soon to be ripe in Southern MN. Some of the common issues we see in early strawberries include delayed flowering (this can be caused by too much nitrogen prior to flowering), thrips damage (bronze colored, seedy berries), and leather rot (smelly, brown, rough skinned berries). For more info on these and other strawberry pests, see the our page on strawberry farming.
Potatoes: We saw our first three-lined potato beetle this week. These beetles are very similar to the regular Colorado Potato Beetle, but we tend to see them more on tomatillos and groundcherries, whereas we see Colorado potato beetles on potatoes and eggplant. Management strategies are fairly similar: read more about management here.
Where might we go with aster yellows this year? Only time will tell. Aster yellows is vectored by a fast moving, migratory leafhopper that doesn’t spend the winter in MN. Every year, a different number of aster yellows will end up in Minnesota, and the amount of aster yellows carried by these leafhoppers will vary. For example, in Michigan they collect and test leafhoppers for aster yellows. In early June of 2024, 4 to 11% of the aster leafhoppers tested positive for aster yellows. In early June 2025, 1.5 - 15% have been positive for aster yellows with significant variability across counties. We don’t know how much the source population we have in Minnesota differs from the population they have in Michigan, and we also know that aster leafhoppers can pick up the disease when they get here.
The spring window was really interesting - more and more farmers are growing winter crops like spinach, and there’s an awkward window between spinach harvest in March, and warm season crop planting in May or June. You could absolutely plant some leaf lettuce or something like radishes in this window, but we were surprised by the number of growers who were excited to try growing a cover crop.
Why grow a cover crop in this window rather than a cash crop? One reason is to add some nitrogen to your soil. In our 100 farms project, 89% of high tunnels had too much phosphorus, and it’s a perennial challenge to figure out how to meet your crop nitrogen needs without adding more phosphorus to the system, especially on organic farms. So, we’re trialing a variety of legume cover crops to see whether we can get a meaningful amount of biomass and nitrogen in this short window of time.
The photo below is from a visit to a participating farm yesterday. They were planted in mid-March, and we were amazed by how much they had grown, and by how many root nodules they had (indicating that they were fixing a lot of nitrogen!). We’ll have more data from this trial later in the year, including better estimates of how much nitrogen we can assume from high tunnel cover crops.
Brown bead. Photo: Anna Racer
There is some damage from early season caterpillars out, as well as plants showing the damage of cabbage maggot. If you are seeing stunted plants that are turning yellow and purple, digging at roots may reveal tunnels and maggots in the stem.
Strawberries are soon to be ripe in Southern MN. Some of the common issues we see in early strawberries include delayed flowering (this can be caused by too much nitrogen prior to flowering), thrips damage (bronze colored, seedy berries), and leather rot (smelly, brown, rough skinned berries). For more info on these and other strawberry pests, see the our page on strawberry farming.
Potatoes: We saw our first three-lined potato beetle this week. These beetles are very similar to the regular Colorado Potato Beetle, but we tend to see them more on tomatillos and groundcherries, whereas we see Colorado potato beetles on potatoes and eggplant. Management strategies are fairly similar: read more about management here.
Aster yellows check-in
We are hearing reports around the state that growers are seeing the impacts of last year’s aster yellows on this year’s garlic crop. Some growers are reporting high percentages of some plantings being lost to aster yellows. Garlic emerging from infested cloves may not emerge at all, and plants that do make it up will be stunted and bright yellow. This sometimes appears in the center of the plant, as opposed to the yellow leaf tips we see this time of year. Some varieties of garlic start to produce red pigment, leading to red tinged cloves and lower leaves. Suspect plants can be tested at the UMN Plant Disease Clinic. Infected plants should be removed so that there is one less place where aster leafhoppers can pick up the disease.Where might we go with aster yellows this year? Only time will tell. Aster yellows is vectored by a fast moving, migratory leafhopper that doesn’t spend the winter in MN. Every year, a different number of aster yellows will end up in Minnesota, and the amount of aster yellows carried by these leafhoppers will vary. For example, in Michigan they collect and test leafhoppers for aster yellows. In early June of 2024, 4 to 11% of the aster leafhoppers tested positive for aster yellows. In early June 2025, 1.5 - 15% have been positive for aster yellows with significant variability across counties. We don’t know how much the source population we have in Minnesota differs from the population they have in Michigan, and we also know that aster leafhoppers can pick up the disease when they get here.
Spring cover crops in the high tunnel
We’ve been working with Julie Grossman’s lab (U of MN), and Becky Sideman’s lab (U of NH) on a high tunnel cover crop project, with groups of farmers across the Midwest and Northeast trialing different legume cover crops in high tunnels during the fall / winter, spring, and even during the summer. The fall / winter cover crops went about as expected - people who left their tunnels covered over the winter had pretty good establishment and some nice cover crops, which they were able to terminate in time for spring and summer crops.The spring window was really interesting - more and more farmers are growing winter crops like spinach, and there’s an awkward window between spinach harvest in March, and warm season crop planting in May or June. You could absolutely plant some leaf lettuce or something like radishes in this window, but we were surprised by the number of growers who were excited to try growing a cover crop.
Why grow a cover crop in this window rather than a cash crop? One reason is to add some nitrogen to your soil. In our 100 farms project, 89% of high tunnels had too much phosphorus, and it’s a perennial challenge to figure out how to meet your crop nitrogen needs without adding more phosphorus to the system, especially on organic farms. So, we’re trialing a variety of legume cover crops to see whether we can get a meaningful amount of biomass and nitrogen in this short window of time.
The photo below is from a visit to a participating farm yesterday. They were planted in mid-March, and we were amazed by how much they had grown, and by how many root nodules they had (indicating that they were fixing a lot of nitrogen!). We’ll have more data from this trial later in the year, including better estimates of how much nitrogen we can assume from high tunnel cover crops.
Look at all that growth! Photo: Natalie Hoidal.
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