Hydroponic and Organic Gardening

Lettuce, basil, Swiss chard and most other herbs are grown for their foliage — or vegetation — and not for the fruit that they may bear. As such, they are known as vegetative plants. They are harvested while they are still in the vegetative plant growth stage. The F1 hybrid breeding program is usually not used to develop cultivars of this type of plant.

When most people grow lettuces in the greenhouse, they grow bibb or other types of leaf lettuce. With these types of lettuces, the entire plant is edible. Growers can begin to harvest and consume the lettuce even at an immature stage so that one planting can be used over a period of time. Most growers will seed lettuce every week or so to have different-stage lettuce plants in the greenhouse at all times.

Bibb lettuce cultivars are developed in Europe and are developed for greenhouse production. The cost of the seed is high compared to garden lettuce seed, but it offers the disease resistance and other characteristics that make it well adapted to the greenhouse environment. A selection of cultivars is available. Some do better during the cooler winter weather while others like more light and are resistant to bolting and tip burn. Rex is a tip burn and bolt- resistant cultivar that does well in the summer. Hawaii and Natalia are a couple newer cultivars for the spring, summer and fall time period. They have more disease resistance than do some of the older cultivars.

Some Grand Rapids-type leaf lettuces perform well in the greenhouses. Although the leaf lettuces have been developed for outdoor growth and production, some of the cultivars are well suited for greenhouse production. Their suitability has been determined by trial-and-error methods by greenhouse growers and seed providers. In Johnny’s Seeds Catalog, the lettuce cultivars that have done well in the greenhouse are identified. In this group, Black Seeded Simpson, Waldamann’s Dark Green, and Two Star are included.

Newer red lettuce cultivars have been doing fairly well in the greenhouse the last few years. Cultivars in the Lollo Rossa and Redina groups generally grow well and develop fairly good red color if the light levels are adequate. Dark Lollo Rossa is one cultivar available from Johnny’s.
Romaine or cos lettuces present more of a challenge to greenhouse growers in the summer. Many cultivars will tip-burn fairly readily during the summer in the greenhouse. Johnny’s Green Forest is one cultivar that has been grown successfully by many greenhouse growers all year long.

Most herbs can be grown fairly successfully in the greenhouse. Most are grown from seed, but a few need to be grown from cuttings. The herbs grown from seed do not have special cultivars for greenhouse cultivation.

Edible flowers can be grown in the greenhouse if you are interested in having them available to adorn salads and other dishes. No special cultivars are used for them. Any pansy or nasturtium cultivar can be used to provide a number of fresh blossoms over a period of time.

Choosing the right cultivar or combination on cultivars can have a profound impact on the outcome of your greenhouse production experience. There is not one right answer for everyone. Hopefully,
you can use the information provided above to reach your production objective.