Crinkly Specialty Lettuce, Red Sails and Green Ice

Specialty lettuce production in our second brand new 5500 sq. ft. greenhouse is finally under way. We had a minor delay involving the pumps for the Nutrient Pond. It seems that the first batch of pumps were of inferior quality. For some reason they worked fine in our Pak Choi greenhouse, but when we tested the equipment in the Specialty Lettuce one, they clogged up.

All of our pumps have been replaced by quality ones, including the ones in the Pak Choi facility, just in case. When you’re relying on everything from lighting to feeding and irrigation being done automatically in a computer-controlled environment, the hardware must measure up to the standard of excellence that was the intention of the system designers.

We decided to grow two crinkly leaf lettuce varieties, Red Sails and Green Ice. These are especially well suited to hydroponic production. The first one is red around the fringes, with a green base, while Green Leaf is a shiny, crinkly loose leaf that is firm and crunchy in salads.

Both of these varieties are slow to bolt, which means that they won’t surprise us by going to seed. Green Ice is a cross between a compact butterhead type and large, loose leaf varieties. It was one of the first to be patented after the passage of the Plant Variety Protection Act of 1970. The patent has since expired.

In the field, both of these varieties take 45 days from seed to maturity. We will, however, accelerate their growth initially to 40 days from seed to maturity, and then hopefully to 35 days, to match the production rate of our butterhead lettuce.

Red Sails is an All-American Selections Winner, and is considered a superior loose leaf lettuce. The seeds for both varieties should be refrigerated until they’re ready to plant. Germination should take place in a cool environment, 55º to 60º F (12.7º to 15.5º C) which must be gradually raised to 60º to 70º F (15.5º to 21.1º C) during daytime production. Nighttime temperatures should revert to the cooler levels.

Higher temperature than that will make the lettuce bitter. Tip burn might also happen due to higher temperatures. This illuminates the great advantage that greenhouse growers have over field growers. By being able to control the temperature, humidity, lighting, and feeding, along with all the other variables, we are able to accelerate the lifecycle of the lettuce to get it to market that much faster.

Nutrition is of optimum importance. Phosphorus deficiency, for instance, may result in the increased likelihood of bacterial infections. By using a well-balanced nutrition source, such as Advanced Nutrients Grow and Micro together, we eliminate the symptoms of macronutrient deficiency, such as stunted growth.

Nitrogen deficiency shows up as light green leaves, as opposed to the rich, shiny green leaves of a well-fed plant. These deficiencies can be corrected by feeding with adequate amounts of Phosphorus and Nitrogen, but they will cause a three to ten day delay in the time that the lettuce will be ready for harvest.

Adequate levels of Calcium are also essential for growing lettuce. For this reason we mix in Sensi Cal Mg Grow into every new batch of nutrient solution in our Nutrient Pond. The NPK of Grow is 2-1-6, that of Micro is 5-0-1, and Sensi Cal is 2-0-0. So the combined NPK of the three products is 9-1-7.

We’re only using 2-parts of the classic Advanced Nutrients 3-part, in order to keep our lettuce from bolting. But by not using Bloom, we are depriving our lettuce plants of Phosphorus. Therefore we use No Shock (NPK: 8-6-12) when we transplant our seedlings from the germination room to the Nutrient Pond. This provides an infusion of Phosphorus, which helps to ward off bacterial infections.

Other ingredients in our Nutrient Pond that have an NPK are Grandma Enggy’s Seaweed Extract (1.5-1.5-1.5), which is like a multi-vitamin, natural anti-biotic combination, and B-52 (2-1-4) which contains pharmaceutical grade B vitamins that combat stress in our lettuce plants.

The suggested ppm amounts for commercial hydroponic lettuce production are: N, 150; P, 50; K, 200; S, 45; Cl, 35; Ca, 175; Mg, 45; Mn, 0.5; Cu, 0.1; Zn, 0.3; B, 0.5; Mo, 0.1; and Fe, 3.

By combining these excellent Advanced Nutrients products we come close to this suggested ratio. But we must remember that plant science means nothing, unless it results in tasty, crunchy, nutritious salad greens to be enjoyed by our customers.

Three greenhouses going full tilt ahead!

The two brand new, 5500 square foot greenhouses are finished and in operation. We have gone through the first ten days of pak choi and specialty lettuce production. In this blog posting, I’ll concentrate on what we do with the pak choi.

Day 10 is for transplanting. We’ve treated our seedlings with No Shock and Jump Start, in order to minimize the stress of moving them from the germination area to the main Nutrient Pond.

Each seedling gets 42 square inches of space to grow in, with 37 pak choi plants per square meter polystyrene board.

Daytime temperature in the greenhouse is kept at a steady 25º C (77º F), and at night the temperature is allowed to drop down to 20º C (68º F).

The pH of the Nutrient Pond is automatically adjusted to 5.8 by adding small quantities of pH Up or pH Down, whichever is necessary. The EC of the Pond should measure 1.2 and the dissolved oxygen should be 4 mg per Liter.

Relative humidity goes from 30 to 70%, depending on the respiratory cycle of the plants, as well as the amount of CO2 being generated. Since the ppm of the solution is kept at 840 ppm (equal to EC 1.2) the computer-controlled system automatically sets the CO2 generator to 840 ppm as well.

These growing condition remain the same from day 10 to harvest, for the pak choi.

On Day 17 the leaves of the pak choi plants have filled the canopy and respacing is required. Polystyrene boards with 18 three inch holes are used to put half as many plants per square meter as before.

Piranha, Tarantula, and Voodoo Juice are added regularly at half strength to the pre-mix tank and then the reservoir, in order to colonize the roots of the pak choi plants with beneficial fungi, bacteria, and microbes, respectively.

In addition to their basic diet of Micro and Grow, we also add the usual supplements to the nutrient solution.

These include Grandma Enggy’s Humic Acid and Fulvic Acid, as well as her Seaweed Extract. They add the all important organic ingredients that simulate the composition of a rich, black, humus-like soil, only in liquid form.

Seaweed Extract is like a shot of multi-vitamin (as well as natural antibiotics) while we also add B-52 which is a B-complex for plants designed to reduce stress.

Sensi Cal Mg Mix Grow adds the vitally important Calcium and Magnesium, which help to grow robust, crisp vegetables (as well as salad greens). This is a proven recipe, we’ve been using it on our Boston Lettuce for a long time, and it always results in healthier produce.

Relatively low light levels for the pak choi might be 200 micromoles per square meter, while on sunny days the light level may be increased to 400 micromoles per square meter. The bank of 55 600W Metal Halide lights will be automatically adjusted to compensate for these levels by the computer system. There are also shading mechanisms built into the roof of the greenhouse to reduce the impact of sunlight, when necessary.

From Day 29 to Day 34 the plants continue to add weight and on Day 35 (from the time of seed germination) they will be harvested.

Since these greenhouses are larger than our original one, we had to hire extra staff. Instead of two full timers, plus two part timers, each new facility requires four full timers to run it properly, not counting Chuck and myself.