by Rachel Carter
A few weeks ago, a consortium of local vegetable growers gathered at the Albion, ME research farm of Johnny’s Selected Seeds with one task in mind, to discuss the obstacles and opportunities related to growing tomatoes in the New England region.
The Tomato Growers Roundtable is a conduit for growers to listen to their peers and collaborate on potential solutions to the most prevalent issues. Topics ranged from thinning and pruning and planting density to disease and fertility challenges. Maine’s primary organic certifying agent, the Maine Organic Farmers and Gardeners Association (MOFGA), organized the meeting. The last time a similar group of growers came together was in 2010. MOFGA’s organic crop specialist, Eric Sideman, Ph.D. and Becky Sideman, Ph.D. Extension Professor and Sustainable Horticultural Production Specialist at the University of New Hampshire, moderated the meeting.
As host, Johnny’s Selected Seeds was honored to open the farm to this group of small- to medium-scale commercial growers. The trials performed at the research farm, as well as those conducted across New England and the rest of the country, provide variety and cultural information to growers of all sizes. Several members of Johnny’s research staff were present, diligently listening for feedback and contributing to the discussion.
Despite the volume of issues discussed, several were revisited throughout the afternoon. Each of the 20 or so growers present emphasized again and again the importance of tomato varieties that reliably produced the earliest fruits. Visitors to farm stands and farmers markets look for, and expect, availability of fresh, local tomatoes. With the aid of heated tunnels, growers reported being able to offer ripe tomatoes on their stands and at market by the middle of June.
Earliness wasn’t the only characteristic cited as a requirement for varieties they grow — disease resistance was a close second. These two traits led the most growers present to name ‘Geronimo’ and ‘Rebelski’ being almost their hands-down top varieties. Stories of the devastation left by late blight in the worst outbreak — 2009 — were recounted and still too fresh in the minds of many. Growers listened with great interest when Johnny’s tomato breeder, Emily Haga, spoke of her progress in breeding high-quality tomatoes with light blight resistance — not only red, but also pink, a color that is growing in popularity The feedback she received reaffirmed the importance of developing resistant field varieties for organic growers, as many of them had moved to protected culture to avoid the risk of losing their crops in the field.
With the exception of small-fruited tomatoes that are primarily grown outside, the large majority of tomatoes are grown in protected culture, in heated greenhouses or passive high tunnels, where proper management keeps the tunnels productive. Tomato plants in these situations are being asked for high yields over a long season, and require fertilizers and other nutrient inputs to aid them in reaching their genetic potential. Genetics are the basis for the success of any given variety, but favorable conditions and proper maintenance allow the plants to flourish.
The significance of fertility in tunnels was discussed at length. How fertile the growing medium is may dictate the overall yield potential and quality. To this end, many growers described grafting onto rootstocks to surpass the yield and vigor maximums commonly experienced later in the season, as factors such as fertility, day length and day and night temperature become more limiting. They also noted that grafted plants exhibit such high levels of vigor that it is necessary to prune the plants to two leaders instead of one, to achieve the appropriate balance between vegetative and reproductive growth.
All agreed that irrigation had to be carefully monitored, especially when it was close to harvest time. A fruit that has been irrigated too close to harvest will be less flavorful, with a watery flavor and texture. Not only is the flavor affected; once a fruit changes to its ripe color, its skin loses elasticity, and a sudden increase in water uptake by the plant can cause cracking and render the fruit unmarketable.
The correct amount of irrigation applied throughout the crop’s lifecycle provides for optimal quality and yield. The general rule of thumb is to provide the equivalent of one inch of rain per week. The actual amount required is dependent upon the soil or growing medium — a soil with a larger proportion of sand drains more quickly than one with a higher proportion of clay, which retains water. Some of the growers in attendance advocated frequent but small waterings to avoid splitting the fruits, whereas others were proponents of longer watering intervals to avoid problems associated with shallow root systems. Growers described different methods to achieve the ideal amount of water, whatever was best suited to their production systems.
It was emphasized that when the last fruits are harvested and the plants removed, what growers do next with the tunnel is almost as important as its management while full of tomatoes. The ideal option is to rest the house from tomatoes for at least one cycle by rotating plantings into different tunnels from season to season. Leaving the tunnel fallow is the most effective, but rotating in a crop that is not in the solanaceous family can also help avoid diseases and pests that affect this crop family from persisting. However, as many growers have a limited number of tunnels, making the most of the protected space available is what most frequently happens. This lack of rotation is one of the key reasons why disease-resistant varieties are important.
Again and again, the conversation turned to the pros and cons of grafting tomatoes versus the purchase of already-grafted plants. All of the growers were aware of the benefits of grafting: increased vigor, added disease resistance, an extended harvest season, and improved overall crop health. One grower in particular said his grafted plants yielded three times more pounds per plant than ungrafted plants of the same variety.
There are ample well-known benefits of grafting and the use of grafted plants, but at the same time there are also reservations. The process of grafting can be time consuming, and it requires specific facilities and materials to construct a healing chamber. Additionally, there is a component of trial and error in determining which varieties take more readily to being grafted under a given set of conditions. In purchasing plants, growers want assurance the plants were grown and grafted in conditions similar to their own, but very few nurseries sell their own grafted plants. There is also a limited selection of grafted varieties available, and not all are universally compatible with growers’ production systems.
Maine Organic Farmers and Gardeners Association holds tomato talk
by Rachel Carter