by Elizabeth A. Tomlin
“If you prune early and often it will take a lot less time and make harvesting more efficient later on,” says CCE ENY Commercial Horticulture Program Vegetable and High Tunnel Specialist Amy Ivy.
Folks traveled for hours to attend the hands-on, high tunnel tomato pruning workshop instructed by Ivy and CCE ENYCHP Horticulture Specialist Crystal Stewart, hosted by Ray Zimmerman’s High Tunnels near Fort Plain, NY, earlier this year.
“Out of all of the crops you can grow in a high tunnel, tomatoes are king,” Ivy reported, citing years of research confirming this. “There’s no doubt about it.”
Whether organic or conventional, tomatoes thrive in high tunnel conditions, protected from wind and rain.
“The fact that the leaves stay dry makes a huge difference with tomatoes because of so many foliar diseases. Because the leaves stay dry, it is not a conducive environment for blight.”
White mold is one disease to watch for. When scouting, look for plants with shriveled stems and an overall appearance of unthriftiness. Be extremely careful not to contaminate other plants — or surrounding soil— with diseased plants. Some molds will live in the soil for many years; therefore, it is imperative to remove diseased plants away from any growing areas.
Disease resistant varieties are recommended. Heirlooms are especially challenging when confronted with molds.
Soil testing should be done before planting — and at timely intervals after — to be sure nutrients are readily available. An overabundance of nutrients can be as detrimental as a deficiency.
“One of the things that happens in tunnels — because you never get rain to flush out any extra nutrients and also because they are concentrated areas,” said Ivy, “is that usually you put down too much.”
When 40 pounds is required and you have a 50 pound bag, it is easy to be tempted to put down all 50 pounds instead of setting the extra 10 pounds aside for future use.
“That may work out in a field. But if you do that in a tunnel, very often you’re going to get your levels too high,” remarked Ivy. “Then the nutrients are going to interfere with each other and inhibit the uptake of one over another. They compete with each other.”
Once production has been ongoing two or more years, test soil for soluble salt, which may build up in organic or conventional crops.
Ivy reported one of the biggest problems found building up in high tunnels is phosphorus. Phosphorus should test lower than 45 pounds and preferably closer to 25.
Once symptoms of nutrient deficiency appear, it is difficult to bring crops back. Tomatoes are reported to be heavy potassium users. Among other conditions, potassium deficiency will cause tomatoes to have a white-shouldered, gray-walled appearance and fruit will have a white ring just below the skin’s surface.
Calcium overload interferes with uptake of potassium. Calcium can be brought in through several means, including with applications of lime, water and fertilizers like poultry products.
Both Ivy and Stewart stressed the importance of providing plenty of irrigation to tomato plants.
Ivy stressed that optimum pH levels in irrigation be at 6.5, not 6.7 and not 6.8.
Ivy said there may be nutrients in the soil that the plant is not taking up and the only way to confirm plant health is through foliar testing. She stressed nitrogen deficiency is only detected through foliar testing.
“What we would recommend in a production tunnel, if you’re serious about it — and think about how valuable this crop is — we recommend that you start with the soil test before you plant, and then 2–3 weeks after you plant we would take a foliar sample and send it off to a lab.”
Water testing is also recommended.
Lower leaves will naturally yellow as plants develop fruit. Although, ideally you are pruning those lower leaves off before that occurs.
“The big thing we worry about are the suckers,” explained Ivy. “The suckers can become very aggressive.”
Ivy demonstrated removal of suckers and leaves on determinate tomatoes, directing attendees to be sure not to injure the plant when snapping suckers or leaves off.
Snapping, greatly preferred to cutting, allows suckers and leaves to separate at the natural point of attachment. Tearing can cause slow-healing injury to plants.
“A clean snap will seal off quickly,” Ivy said.
“Remove the leaves up to the first flower cluster. If the leaves only bend and do not snap, use a sharp knife to cut them off close to the stem.”
The sooner suckers are removed, the better for the plant. The bigger they are, the larger the wound.
“The first sucker below the first flower cluster is usually very dominant. Leave that sucker and remove all suckers below that point,” Ivy instructed. “Eliminate those side suckers because they’re just pulling energy away from the main stem.
“The stem should now look like the letter ‘Y’.”
Ivy calls this the “strong Y” point on the plant.
No more pruning should be required on these plants.
With indeterminates, first look for a single or double leader.
“For a single leader, remove all suckers and all leaves below the first flower cluster. The result is one long vine — like a leader with no side shoots.
For a double leader, establish the “Strong Y” and each arm of the Y will become a leader.
These leaders are maintained throughout the growing season by vigilant weekly pruning of all developing suckers, especially during the first 6-weeks of growth.
“Remove leaves gradually, a few each week; rather than too many at once.”
“The good news about the tunnels,” said Ivy, “is you get a longer season, a bigger yield, and you have less input because you’re not having to spray so much.”
Grants are available for those interested in beginning high tunnel production.
For more information contact Amy Ivy at