July 17, 2014

In Search of the Perfect Summer Crop

Laura Genello

Laura Genello

Guest Blogger

Johns Hopkins Center for a Livable Future

Romano pole beans reach for the ceiling at the CLF Aquaponics Project

Romano pole beans reach for the ceiling at the CLF Aquaponics Project

For many farmers, summer is the time of peak production and abundant harvests, but at the CLF Aquaponics Project our harvests peak mid-spring and start to decline as summer approaches. Farming is a learning process; and higher pest pressure coupled with hot temperatures in our hoophouse has made finding ideal summer crops a challenge.

Leafy greens and herbs are naturally some of the best crops for an aquaponics system, because they thrive in a nitrogen-rich environment. However, many of these greens prefer cooler weather, and as the temperatures in the greenhouse climb past 100 degrees Fahrenheit, even heat-tolerant chard gives up. We’ve found that many of summer’s star crops in the field, such as squash, tomatoes, beans and okra, simply do not produce well in our aquaponics system. The reason for this likely lies in the fact that these fruit-producing crops require high levels of potassium and phosphorous in comparison with leafy greens to encourage reproductive growth. While the aquaponics system has an abundance of nitrogen (our nitrate levels range from 20-35ppm), which encourages growth of lush leafy greens, we have had trouble encouraging some of the heavy-feeding crops such as tomatoes, beans, and okra to produce fruit.

Every spring we begin seeding a variety of heat-loving crops so that by June we are ready to replace the cool-season leafy greens. In our search for productive summer crops, we have found that a pickling variety of cucumbers called little leaf, and the Japanese Shishito pepper perform well in our aquaponics system. In addition to heat-tolerant leafy crops like basil and watercress, in July our plant beds boast an eight-foot high wall of cucumber vines and a forest of dark green pepper plants. Although they are productive, these crops take up more space in the system for a longer period of time than the leafy greens, thereby yielding less value per square foot.

Insects pose another challenge in the summer. With all our summer crops we need to account for losing a certain proportion of each planting to pests, and we’ve chosen not to grow some crops that seem particularly susceptible to the insects we have in great abundance. It can be hard to dissuade the caterpillars from eating all of our basil! See our earlier blog entry on pest control for more information on how we manage insect visitors in the greenhouse.

Farming is an exercise in continual refinement and adaptation, and we are constantly looking to try new things. Over the past two summers we’ve tried growing over 20 varieties of plants. While we’ve had success growing watercress, leeks, basil, cucumbers and peppers, we’ve had no luck with many others including eggplant, tomatoes, beans, beet greens, collards, melons, mustard, arugula and okra. Have a suggestion for a crop we should try? Let us know below, and maybe you’ll see it at the aquaponics system and the Waverly Farmer’s Market soon.


  1. Wow – this is a truly awesome post! I’ve been wrestling with this issue myself for several years now. Basil is a no-brainer, but I love the suggestions of the specific pepper and cucumber varieties, and watercress. I’ll definitely try those next year!

    I’ve had some success with romaine and lollo lettuces.

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