Challenges of Growing Heirloom Tomatoes
Don't let diseases like fusarium wilt hinder growing your favorite heirlooms
This season, the Utah Plant Pest Diagnostic Lab identified many tomato problems, including soilborne diseases and the bacterial diseases mentioned in the previous article. One reason for the increase in these diseases is the popularity of growing heirloom (open-pollinated) tomatoes, which lack genetic disease resistance, leaving them susceptible to epidemics.
Although hybrids are generally more productive and disease-resistant than open-pollinated tomato varieties, many varieties lack the rich fruit flavor that heirloom varieties deliver. There are several horticultural options that can help these plants prosper, resulting in reduced risk of disease, increased productivity, and reduced fruit cracking.
When growing heirlooms, pick cultivars that have been shown to be successful in your area, which may take trial and error on your own farm. Some options include:
- Green Zebra: a prolific, medium sized variety with good flavor
- Cherokee Purple: although a modest producer, this variety performs well in cooler climates, bearing purplish slicing fruit with a smoky flavor
- Caspian Pink: beefsteak tomato similar to Brandywine but more prolific and suited to cool climates
- Wins All: a disease-resistant heirloom with large, juicy fruit
- Black Krim: a productive variety less prone to cracking, with a deep purple skin and flesh producing a salty-sweet flavor
Since many open-pollinated tomato varieties tend to take their time ripening, they grow best where they get enough heat to allow them to fully mature. Start plants early in a cold frame, greenhouse, or high tunnel to extend their season. Plants won’t grow in the field until the soil has warmed, which can be helped by wall-o-water, cages wrapped with plastic, thick row cover or mulches.
Heirloom tomatoes are vigorous growers and will need to be pruned regularly, and spaced wider than hybrids. Remove suckers and plant at a wide spacing to provide better air flow, which helps prevent foliar diseases, and encourages larger fruit production at the top of the plant.
When watering, avoid overhead irrigation because it increases humidity within the plants and splashes water, both of which improve conditions for spread of foliar diseases. Provide intermittent watering to reduce splitting skin, a common problem on heirlooms.
Monitor plants regularly for insect and disease problems (more than you would with hybrid varieties) and learn to identify tomato diseases.
Where soilborne diseases or poor production have put the kibosh on growing heirlooms, consider grafting. Grafted plants are made up of an heirloom scion (above ground part) and a hybrid rootstock, uniting disease resistance and enhanced vigor with fruit quality and taste. Grafted heirlooms can produce 30–50% greater yields than non-grafted heirlooms. In tube grafting, hybrid and heirloom seedlings are severed with a sterile knife at a slant just above the cotyledon. The heirloom scion is then secured to the root system of the hybrid with a tube or clip, and allowed to heal before transplanting (shown at right).
-Marion Murray, IPM Project Leader