Plant Profile: Tropicana Lettuce
In our final blog before the holiday season, we’ve decided to highlight one of our favorite crops, Tropicana Lettuce. We’re currently growing Tropicana in our Iowa greenhouse, and considering that this lettuce variety was developed with greenhouse growing in mind, we have a steady stream of Tropicana Lettuce on hand year-round. Learn all about caring for Tropicana Lettuce and find out how we do it in our own greenhouse in this month’s Plant Profile.
Tropicana Lettuce Lactuca sativa
Days to Bloom: 42 in summer, 63 in winter
RS Corky Root
To produce our Tropicana Lettuce, we first propagate the seeds in our Ebb & Flo system for two weeks during summer and three weeks during winter. We place our seeds in Grodan A-OK Starter Plugs before placing them into the Ebb & Flo System. This allows for a root system to develop so that the seeds receive the proper nutrition when placed in the NFT channels. Like most plant varieties, the colder winter months mean that all-around growth is slowed, but we have found that allowing your seeds to mature for just one extra week prepares them for proper growth during the cold season.
Once the seeds are mature enough to be transplanted, they are moved from the Ebb & Flo System into the NFT channels, where they remain until they are ready for harvest. Tropicana is a single harvest crop, so once the seeds have been transplanted, they are left to mature for the next four to seven weeks until they are ready for harvest.
Our NFT system contains a 550-gallon reservoir tank, which re-circulates water at one liter per minute. This keeps our Tropicana plants healthy, and enables us to keep up with the accelerated growth rate of the crop. Tropicana is the fastest growing lettuce variety that we produce in our greenhouse, so it requires special attention from both a nutritional and harvesting standpoint. At full maturity, these crops will grow anywhere from 10 to 13 inches tall and can be fairly top heavy, so try to minimize moving the NFT channels as much as possible.
Tropicana Lettuce requires 16 hours of supplemental lighting. We light our crop using 1,000 W metal halide light fixtures, which are highly energy efficient and produce a high-quality light for plant growth.
Temperature and Humidity
Tropicana is a relatively heat-tolerant crop, so there is no need to be terribly concerned with elevated greenhouse temperatures during the summer months. We keep our temperature between 68 to 75 degrees Fahrenheit, with humidity between 60 to 75 percent.
As we mentioned previously, our 550 gallon reservoir tank re-circulates water at 1 liter per minute, feeding a total of 170 NFT channels. We keep the waters pH at 6.5, with our nutrient concentration at 1.8 EC during the summer and 2.5 EC during winter. Currently in the greenhouse we do not have chillers installed in our reservoir, so to keep the water at an ideal temperature, we have installed a sheet of TekFoilTM above the tank to act as a thermal barrier against heat from the sun. This has helped to drop the surface temperature of our reservoir by over 25 degrees Fahrenheit, which helps keep our Tropicana, and other lettuce varieties, healthy.
No support is required for this crop.
Tropicana requires minimal care. When transplanting seeds from the Ebb & Flo System into the NFT channels, be sure that no plants fall into the holes sideways. Once you are sure that all plants are upright, monitor the plants for the first few weeks after transplanting to ensure that each plant is receiving proper amounts of water. If your channel is not leveled appropriately, water may skip over holes, resulting in missed cells and dead plants.
Once all crops are transferred and receiving proper nutrition, monitor your crop daily for any invasive pests. We monitor our Tropicana daily, but we have also implemented biological pest controls, including beneficial organisms, like lady bugs, predatory mites and parasitic wasps. We also monitor for powdery mildew and apply dissolved sodium bicarbonate to the affected area if needed. Remove any diseased or damaged leaves as needed, and if you notice tip burning occurring in your crop, we have found a few tricks to help. First, try increasing the airflow around your plants, if that does not solve the problem, check your nutrient solution temperatures, as they may be at a dangerously high level. If neither of the previous solutions work, check your calcium levels, as there could be a significant calcium deficiency.
Pollination is not necessary for this crop.
Tropicana is ready for harvest after a total of six to nine weeks, depending on the season. When harvesting, gently lift the leaves to expose the stem, then pull the entire plant out of the channel. When grown hydroponically, there is the option to remove the roots and sell the lettuce in bulk, or keep the roots attached and sell individually as living lettuce. Living lettuce typically can survive for up to one month in a refrigerator, so keep that in mind when determining whether to sell in bulk or individually. With hydroponic lettuce production there is no need to rinse prior to packaging, unless pesticides or fungicides have been used. This helps make harvesting and packaging easier and less time consuming.
Tips and Tricks
We use a temporal spacing model in our greenhouse to supply a larger growing space for each successive harvest. Trays are staggered by week when transplanting so that older plants are next to younger plants. This gives the older plants more room to grow, and by the time that the younger plants begin crowding the older plants, the older plants are harvested and replaced with transplants. Following this model has resulted in lower loss at harvest and a decrease in the spread of disease, as the plants are not nearly as crowded.
If you have any questions about producing Tropicana Lettuce, leave us a comment, and we will get back to you! Be sure to check back with us in January to see what plant we choose to feature next.