Commercial Fruit and Vegetable Growers

From Northern Illinois (Rockford): High tunnel cucumbers yielding well

cucumber fruit hanging on a vine in a high tunnel

Northern Illinois Orchards Open

Apple season begins toward the end of August. Most orchards have announced their openings for the weekend of August 23rd, with almost all open by August 30th. This timing is driven largely by 'Zestar!', a Minnesota variety that kicks off the apple season. During my informal apple census at orchards years ago, I found 'Zestar!' at nearly all Northern Illinois orchards due to its reliable performance and consistent mid-August ripening. 'Honeycrisp' ranks as the second most common variety (to no one's surprise). Beyond 'Zestar!', some orchards will have 'Premier Honeycrisp' ready near Labor Day, with new varieties becoming available for picking each week throughout September.

Freeport High School Research

While school has started, students continue actively collecting data and harvesting cucumbers and tomatoes grown in high tunnels as summer winds down. Yields have been substantial, supplementing CSA boxes, farmers market booths, farm stands, and donations to local food pantries.

As an example, Table 1 lists yields of each cultivar from the week of August 11th (harvests on August 11th and 13th), totaling 183.12 pounds:

CultivarTotal Marketable Pounds
Corinto31.64
Marketmore61.94
H-1913.84
Gateway49.00
Maxpack26.70

One challenge with the cucumbers was a severe aphid outbreak in the high tunnel this summer. After implementing changes—including utilizing a fan, insect scouting, insecticidal soaps, and additional IPM practices—the plants have recovered. Additionally, the plants have reached substantial heights, hitting the top of the high tunnel and creating harvesting challenges.

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group of cucumbers in black bins
Yields for all varieties are hitting what feels like peak with a weekly harvest 2 to 3 times. Collectively from all varieties, yields seem to be hovering between 125 to 150 lbs per week. Photo credit: G. McCarty, Illinois Extension 2025.
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new growth on the top of cucumber vines with damaged leaves on the old growth
The plants have recovered from the aphid outbreak and new growth looks much better. You can see on this plant newer green growth higher up the plant. Photo credit: G. McCarty, Illinois Extension 2025.
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green tomatoes growing on plant in a high tunnel
Compared to the cucumbers, the tomatoes have been slower to yield though field grown tomatoes have been behind this year. The shade cloth improved color and yields. It’s just an overall late season for tomatoes, whether in the field or under high tunnels.

Tomatoes have been slower to develop, with a greater amount of unmarketable fruit. The placement of shade cloth in August improved both yields and quality.

Upcoming Events

Growing Great Apples Program

Friday, October 3rd at 2:00 PM in Rockton (Winnebago County)
Saturday, October 4th at 9:30 AM in Elizabeth (Jo Daviess County)

Both sessions are designed to discuss apple production basics for noncommercial/backyard growers while helping consumers better understand apple production in Northern Illinois and which cultivars to purchase at nearby orchards. Registration is open for the Rockton session, with Elizabeth registration opening soon. If your Northern Illinois orchard would like flyers or promotional materials for these events, please reach out.

Fruit Tree Pruning Fundamentals Workshop

Save the dates! Coming in November and December on Saturday mornings (10:00 AM–12:00 PM):

  • Elizabeth: November 15th
  • Freeport: November 22nd
  • Rockford: December 6th
  • Online webinar: December 17th (7-8:30 PM)

While trees haven't entered dormancy in Northern Illinois by November, I'm shifting the course to this month so you can learn, prepare, and be ready for January and February pruning season. This course, similar to what I've been teaching since 2017, is a classroom-style program that uses a color-coded process to teach pruning. It's designed for beginners, though it's also valuable as a refresher or for training new staff who will be pruning this upcoming winter. Registration and more information will be provided in subsequent newsletters.