Veg Connections: Seedless cucumbers in high tunnels

Seedless cucumber is a popular and high-value crop. High yield, climbing growth habit and parthenocarpic characteristics make seedless cucumber a valuable crop for growing in high tunnels.

Cucumbers are sold for premium prices in the early season markets like other warm-season crops. Nevertheless, cucumbers are susceptible to low soil temperatures in the spring. Even though the season extension benefits of high tunnels make it possible to plant warm-season crops before the last spring frost
date, low soil temperatures limit the early planting of seedless cucumbers.

Growing grafted cucumbers with cold-tolerant rootstocks enhances plant growth under less-thanoptimal soil temperatures and increases early-season cucumber production in high tunnels.

Harvesting seedless cucumbers from grafted plants grown in an unheated high tunnel is possible in April in southern Indiana. The yields of grafted plants were significantly higher compared to the yield of non-grafted plants until the soil temperatures reach 70° F, the optimal level for cucumber production.

The adaptation of using the grafting technique for cucumber production is low in the U.S. One challenge is the availability of grafted cucumber plants. Although grafting cucumbers does not vary much from tomatoes, grafting cucumbers requires a stricter post-graft healing condition. Without a well-controlled environment for post-grafting healing, it is difficult for farmers to graft cucumbers by themselves successfully.

Opportunities exist for specialized grafting plan producers, but the companies must be able to meet the needs of small-scale farmers who may require different cultivars and shipping dates and with relatively small orders. The grafted plants’ size must also meet the needs of high tunnel growers. Although grafted cucumber plants can grow better than non-grafted plants under low soil temperatures, they are less likely to achieve the early season harvest advantage if small seedlings are planted in less than optimal environments.

Poor performance of grafted plants in soils with high salts also limits the adaptation of the technique for early season cucumber production. It is not unusual to find soil fertility issues in high tunnels that have been in tomato production for years. When farmers switch to growing cucumbers in the soil, problems arise. Developing and evaluating rootstocks under multi-environmental stresses is becoming crucial for adapting the grafting technique in high tunnel systems.

— Wenjing Guan, clinical and engagement associate professor and Extension specialist at Purdue University, is a horticultural specialist at the Southwest Purdue Agriculture Center. Her Extension and research programs focus on developing and delivering sustainable vegetable and fruit production practices serving Indiana growers.