Package of Johnny's Selected Seeds
Package of Johnny's Selected Seeds
Grow Perfect Heirloom Tomatoes

10 Tips for Growing Heirloom Tomatoes

Heirloom tomatoes are a favorite crop of many growers, bringing both a premium price and 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 concern with 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 article, we recommend 10 strategies that can help make heirloom tomatoes profitable for your farm.

Graft heirlooms for best results

1) Learn to Graft

The single most effective cultivation practice for heirlooms is to use grafted plants, with the heirloom variety grafted onto a vigorous, disease-resistant rootstock. Grafted heirlooms can produce yields 30–50% greater than nongrafted 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, watch the Tomato Grafting Video, and read Grafting for Disease Resistance in Heirloom Tomatoes from North Carolina State University.

Protect and support your heirlooms

2) Protect and Support

Heirloom tomatoes do better when grown in high tunnels, where their foliage stays dry. Many tomato diseases thrive in moist conditions, including late blight, leaf mold, Botrytis and Alternaria. Because most heirlooms form big, vigorous plants, they require a tall tunnel and a 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, however, be trained to a double leader, so fewer plants are required (making grafting more cost-effective). To accomplish this, all suckers need to be pruned except the one directly below the first flower cluster. That sucker will grow into a second main stem. Labor-saving innovations such as the Rollerhook® simplify the lower-and-lean process.

Prune your heirlooms correctly

3) Prune Correctly

Because most heirloom tomatoes are vigorous growers, they do need to be pruned more often. Pruning (also known as suckering) is important because removing suckers provides better air circulation, which helps prevent foliar diseases. Pruning also encourages larger fruit production at the top of the plant.

For explicit instructions, watch Johnny's video on How to Prune Tomatoes.

Space heirlooms for optimal air circulation

4) Space Generously

Planting tomatoes with wider alleys between rows is another strategy to increase air circulation and thus reduce 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.

Mulching leads to increased yields

5) Grow on Mulch

In the field, tomatoes should be grown on mulch to prevent soil splash as well as to warm soil, conserve soil moisture, and prevent weeds, all of which benefit marketable yields. Black Solar Mulch, SRM Red Mulch, and Biotelo Biodegradable Mulch are options recommended for tomato production.

Practice drip line irrigation and fertilization

6) Lay Drip Lines

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.

Learn to identify and prevent disease

7) Prevent Disease

A disease prevention program is essential in areas where tomato disease pressure is high. Begin by applying Rootshield 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 has a Tomato Disease Identification Key that can help you learn the symptoms of diseases, as well as how to distinguish between environmental or nutrient-related causes. Once you have identified a disease, you can consult Johnny's Pest and Disease Chart to find a recommended treatment.

Choose your heirlooms methodically

8) Choose with Care

Adopt a methodical approach to choosing which heirloom varieties you grow. Trial a range of varieties and keep records, to pinpoint those that perform best in your conditions. Andrew Mefferd, Johnny's trial technician for tomatoes, offers advice on How to Choose Tomato Varieties, including heirlooms, in a recent article published in Growing for Market. We also offer a quick overview of tomato selection criteria in All About Tomatoes.

Water intermittently

9) Water Judiciously

Most heirloom varieties have thin skin, which helps enhance their eating quality but also makes them prone to splitting on the vine. Being careful not to overwater will reduce the number of splits. Plus, when tomatoes receive more water than needed, the excess is directed into the fruits and dilutes flavor. By providing whatever water is required intermittently, in several smaller irrigations rather than all at once, you can alleviate splitting and gain better flavor.

Keep abreast of best practices

10) Review Best Practices

Finally, review best cultural practices for tomatoes before you start. ATTRA's free publication on Organic Tomato Production offers excellent, comprehensive advice on all facets of growing tomatoes.

To grow the best heirloom tomatoes, you will want to keep abreast of new developments, experiment a little, and refine your practices over time. With careful attention to production practices, especially proactive disease prevention, heirloom tomatoes may become a successful, profitable crop for you, as well as a big hit with your customers.

 






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