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Fruit Update - May 7, 2025

Madeline Wimmer- UMN Fruit Production Extension Educator This fruit update contains information about… Apples Growth stage update: pink- bloom. Considerations for fruit thinning during bloom Grapes Growth stage update: Early-season shoot thinning. Raspberries Raspberry cane diseases Honeyberries Growth stage update: bloom, and pollination compatibility Apples Images: (Left) Pink is the growth stage that occurs right before bloom, in apples. Here shows an apple bud in late-pink. (Right) Apples begin to bloom with one main flower, known as the king flower, emerging into full bloom before other blossoms. Photos taken at ApplesRus Orchard in Olmsted County (Zone 5a, 05/05/25). Growth stage update: Pink - King bloom. Pink! Is the apple landmark growth stage following tight cluster. This is the phase where the apple floral buds are continuing to develop, while surrounding leaves grow larger in size. Pink is the sign that bloom is just around the corner, which indicates the need to start thin...
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Bloom thinning apples: How the pollen tube growth model works

  Article written by Madeline Wimmer, UMN Extension Fruit Production Educator. Images: King blossoms are the first apple blossoms to open and generally produce the highest quality fruit. Their early timing is key to bloom thinning strategies that rely on pollen tube growth models. Photos taken at ApplesRus in Olmsted County, Minnesota (Zone 5a).  Apples benefit from fruit thinning. The first step to managing an apple’s crop load each year starts with dormant pruning. While pruning helps to reduce the total number of fruiting spurs, apples still produce more blossom/fruits per fruit spur than is ideal. This is in part because densely clustered apples increase the chance for development of fruit rot later as moisture can become trapped between large apples. Apples with shorter stems can additionally put pressure on one another, leading to increased drops before harvest. Biennial bearing is another condition some apple trees are also prone to that can be relieved with thinning pr...
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Crop planning deep dive: sweet corn

Natalie Hoidal and  Marissa Schuh , Extension Educators, University of Minnesota Extension. Originally published 2021, updated 2025. Choosing varieties & when to plant Consistent sweet corn emergence is more likely when seeds are planted when the soil is warm enough. Photo: Marissa Schuh, University of Minnesota Extension. While regular field corn is planted in late April or early May, sweet corn can be planted May through July. Many vegetable growers aim to grow the earliest vegetables possible to get a leg up at farmers markets, but sweet corn germination is very dependent on soil temperatures. For optimal germination, wait until the soil is:  55°F at an absolute  minimum, 60-65°F for supersweet varieties The Growing Sweet Corn in Home Gardens page has a list of sweet corn varieties and the optimal germination temperature for each. Super sweet corn (sh2 type) usually needs to be planted later (in warmer soil) than synergistic or sugar enhanced (SE types). If your v...
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Fruit update - April 30, 2025

Madeline Wimmer- UMN Fruit Production Extension Educator This fruit update contains information about… Apples Growth stage update: tight cluster. Pest highlight: European red mites (ERM) + Beneficial insect highlight: Predatory mites Grapes About grapevine foliar and fruit diseases. Additional fruit crop growth stage updates: Tart cherry, Pear, Plum, and Florican Raspberry Interested in growing day-neutral strawberries in a sheltered environment? Check out this UMN publication. Apples Growth stage update: Tight cluster Images: Zestar! ®   (left) and Rave®/First Kiss® (right) shown here in “tight cluster” growth stage, where floral buds are beginning to be exposed, but are still tightly grouped. Photo (left) taken at Northwoods Apple Orchard in Olmsted County, Minnesota (04/15, Zone 5a) and photo (right) at the University of Minnesota Horticultural Research Center (04/29, UMN HRC; Zone 5a, photo taken by Kate Scapanski, UMN Researcher).  The next major apple growth stage a...
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Crop planning deep dive: pondering potatoes

Natalie Hoidal and Marissa Schuh , Extension Educators, University of Minnesota Extension. Originally published 2021, updated 2025. Our biweekly crop by crop growing season prep series continues. This week we are digging into potatoes. Cutting seed: impacts on yield, tuber size, and disease pressure Due to the warm spring weather, many growers are getting ready to plant potatoes ahead of schedule. While you’ve likely already decided how you’ll be cutting your seed (since it influences the amount of seed you ordered), there are some things to consider as you proceed. Size of cuts and planting density A lot of research has gone into figuring out the optimal cut size and planting density for potatoes. There are tradeoffs no matter how large your seed pieces are, and how much space you leave between seed potatoes. In general, larger pieces produce higher yields, with diminishing returns after ~2.5 oz. If you’re cutting your seed potatoes into pieces larger than 2.5 ounces, the in...
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Fruit update - April 24, 2025

Madeline Wimmer - UMN Fruit Production Extension Educator This article marks the beginning of the 2025 UMN Fruit Updates, where information is gathered and shared in real time about current happenings and production requirements for fruit crops in Minnesota and the Upper Midwest. These articles are released regularly throughout the growing season, and readers can receive notice of new articles by subscribing to the UMN Fruit and Veg News newsletter email alerts. While apples and grapes are a large focus of this series, we’ll also include updates on other Minnesota-grown fruit crops—such as strawberries, raspberries, pears, plums, blueberries, honeyberries, and currants—based on field conditions and emerging needs throughout the season. Fruit management topics in this series include: tracking plant growth and fruit ripening stages; horticultural management options to improve fruit quality; integrated pest awareness sections that identify and describe various insect and disease-causing o...
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