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Selected Seeds logo10-Tips-for-Heirloom-Tomatoes

10 Tips for Heirloom Tomatoes

Heirloom tomatoes are a popular crop for many growers, bringing both a price premium and droves of customers in search of old-fashioned tomato flavor. Heirloom tomatoes can be tricky, though, requiring more labor and producing lower yields than modern tomato varieties.

The biggest issue for heirloom tomato production is disease. Most old-fashioned varieties have no disease resistance bred into them, unlike modern hybrids. As a result, heirlooms may not produce as long as disease-resistant varieties. And if they lose a significant amount of foliage to disease, they won’t taste as good as they should because it’s the leaves that convert sunlight into sugars and other flavor compounds. Preventing disease, then, is paramount for commercial production of heirloom tomatoes.

In this issue, we’ll recommend 10 strategies that can help you make heirloom tomatoes profitable for your farm.

The single most effective practice for heirlooms is to use grafted plants, with the heirloom variety grafted onto a vigorous, disease-resistant rootstock. Grafting heirlooms can increase yields 30 to 50 percent over ungrafted heirlooms. Grafting reduces the risk of soilborne diseases, and many growers feel that it leads to an overall vigor that helps the plants resist foliar diseases as well. To learn more about grafting tomatoes, visit Johnny’s Grower’s Library and videos. and read “Grafting for Disease Resistance in Heirloom Tomatoes” from North Carolina State University.

With or without grafting, heirloom tomatoes do better when grown in a high tunnel, where their foliage stays dry. Many tomato diseases thrive in moist conditions, including late blight, botrytis, alternaria, and leaf mold. Because most heirlooms are big, vigorous plants, they require a tall tunnel and strong trellising system. Most greenhouse and high tunnel tomatoes are pruned to a single leader and trained to a string that can be lowered later in the season so that fruits remain accessible from the ground. Grafted heirlooms can be trained to a double leader, so fewer plants are required (making grafting more cost-effective). To accomplish this, prune all suckers except the one directly below the first flower cluster. That sucker will grow into a second main stem.
Because most heirloom tomatoes are vigorous growers, they need to be pruned more often. Pruning (also known as suckering) is important because removing suckers provides better air circulation, which is important in preventing foliar diseases. Pruning also encourages larger fruit production at the top of the plant. If you don’t know how to prune tomatoes, watch this video.
Planting tomatoes with wider alleys between rows increases air circulation and thus reduces disease pressure. The standard recommendation for tomato spacing is 1 foot between plants and 4 feet between rows. With heirlooms, wider spacing in either or both directions will improve air flow.

In the field, tomatoes should be grown on mulch to prevent soil splash as well as conserve soil moisture and prevent weeds. Black Solar Mulch, SRM Red Mulch, or Biotelo Biodegradable Mulch are recommended for tomatoes.

To keep foliage dry, drip irrigation is preferable to overhead watering, and fertigation (fertilizing while irrigating) through the drip line is preferable to foliar feeding.

A disease prevention program is essential in areas where tomato disease pressure is high. Begin by applying Rootshield or Plantshield to transplants before setting them out; the active ingredient, a beneficial fungus, grows onto plant roots and provides protection against root diseases. Once planted, tomatoes should be inspected regularly for any sign of disease — easy to do with heirlooms because you’ll be pruning them often. If you don’t already know, learn to identify tomato diseases. Cornell University’s Vegetable MD Online site has a Tomato Disease Identification Key that will not only help you learn the symptoms of diseases, but also know how to tell when a problem is environmental or nutrient-related. Once you have identified a disease, consult Johnny’s Fungicide chart to find a recommended fungicide spray.

Trial heirloom varieties to find those that perform best in your conditions. Andrew Mefferd, Johnny’s trial technician for tomatoes, offers advice about how to choose tomato varieties, including heirlooms, in this article in Growing for Market.

Most heirloom varieties have thin skin, which helps flavor but also makes them prone to splitting on the vine. Being careful not to overwater will reduce the number of splits. Plus, when tomatoes have more water than they need, the excess goes into the fruits and dilutes flavor. Giving whatever water is required in several smaller irrigations rather than one big one will help alleviate splitting and give better flavor.

 Finally, review best cultural practices for tomatoes before you start. ATTRA has an excellent free publication “Organic Tomato Production” that offers comprehensive advice on all facets of growing tomatoes.

With careful attention to production practices, especially disease prevention, heirloom tomatoes may become a profitable crop, as well as a hit among your customers.

Protected fruit production
High tunnels have proliferated in the past decade, and there is no question that they can be extremely profitable for vegetable crops. More recently, researchers have been analyzing fruit production in high tunnels and — not surprisingly — are finding numerous benefits to growing fruit under cover. Those benefits include higher yields, better quality, longer harvests, and higher prices in the off-peak season. If those sound like good reasons to grow fruit in a high tunnel, read on. We’ll tell you some of the latest research results, and maybe help you consider whether fruit could be a profitable part of your crop mix.

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Reprinted from JSS Advantage February 2013