|We have also tried to grow salad mix using plastic germination trays and large tomato packing trays. We have found that the most efficient way of harvesting salad mix in trays is to cut it with an electric knife while propped up on its side. The lettuce falls into a container below.
We planted all of our greens into a soil mixture that is made up of 20% worm castings. This helped reduce or even eliminate the need for additional fertilization. With the addition of some fish emulsion fertilizer, and if there were no serious aphid problems, we could often get 2-3 harvests from one planting.
Our most common insect pest in the salad mix is aphids. These are treated with insecticidal soap if it is a severe problem and followed with subsequent releases of ladybird beetle larvae. Another problem with greenhouse production of salad greens is that they are often “soft”. We find that putting a fan on the greens when the plants are around 1-2″ tall helps to give the lettuce more resiliency and a thicker texture which also helps to extend its shelf life. The salad greens grown in our greenhouse with these methods lasted 2+ weeks.