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Gardening: Growing your own lettuce hydroponically by Rock Wool Cubes

Various hydrponic rock wool slab and cube available at Hairui Machinery,

It’s not difficult, it can be a lot of fun and would be a great learning project for families to do together.

Throughout the centuries, people have found very unique and interesting ways to grow plants.

Imagine the first person who decided that it would be a wonderful addition to a home to have live plants growing indoors. That’s one of the great things about human beings: innovation and experimentation seems to be part of our genetics.

Hydroponics and aeroponics are two methods of growing plants which are gaining the attention of plant enthusiasts.

Hydroponics may be defined as growing plants in a water-based nutrient solution without the use of soil or media. Hydroponics originated back in the days of the ancient city of Babylon around 600 BC with the ‘Hanging Gardens of Babylon’, one of the ancient Seven Wonders of the World. Marco Polo found floating plantations on his trip to China in the 13th century.

The technique may be ancient, but hydroponics have been refined to produce certain fruits and vegetables very efficiently in our modern world; thousands of acres of peppers, cucumbers and tomatoes are grown hydroponically to be sold in grocery stores every day.

How does it work?

Seeds are sprouted in an inert material like rockwool, which looks like small cubes of fine yellow fiberglass insulation. These sprouted seeds are then placed in an open or closed channel of nutrient-rich, constantly flowing water. Water trickles past plant roots, like a liquid conveyor belt, with the help of gravity and a pump.

This method of hydroponics is called the ‘nutrient film technique’. As the water passes by the roots of the seedling, the plentiful and readily available nutrients in the water are absorbed by the bare roots of the plant. Plants grown under hydroponic conditions grow faster and often produce higher yields compared to plants grown in soil or a peat-based media.

Besides the nutrient film technique, another hydroponics method that is easier to set up and more suitable for small scale growing in the home is the aeroponics technique.

Plants are grown without soil or media; however, unlike the hydroponics system, plant roots are placed in a closed, humid environment, usually constantly misted by a nutrient solution. Several plants can be grown in a closed container with the plant canopy sticking out above the container while the roots are located in the container that is set up as a misting chamber.

A plastic tote that is 1 m long x 0.5 m wide x 20 cm deep could easily grow six full-sized heads of leaf lettuce from seedling to harvest in eight weeks. The key is to provide adequate oxygen and nutrients to the roots via a root misting system.

Growing plants hydroponically can bring its own source of new problems. Because the plant roots are in direct contact with the nutrients, these nutrients must be monitored very carefully. Electrical conductivity (EC) and pH of the water must be monitored constantly.

A slightly higher than optimal level of nutrients in the irrigation water can result in plant toxicity as these extra salts in the water (nutrients = salts) can easily desiccate and kill plant roots. Furthermore, if nutrients are not balanced properly, even though there may be an ample supply of one nutrient, the shortage of another nutrient can result in nutrient deficiency symptoms.

A major function of roots in a traditional growing situation with soil or media is that the roots are large and anchor the plant in the ground as well as providing a good structure for the plant. In hydroponically grown plants, roots are often smaller than with traditional growing methods and they do not support the plant structure.

Any upright plant growing in hydroponics (ex. tomatoes or peppers) must have supporting structures to hold plants and fruit.

Simple hydroponic systems can be set up in your home for fast, easy production of fresh lettuce and herbs.

Check out the University of Saskatchewan’s Gardening webpage at gardening.usask.ca for detailed instructions on growing your own fresh lettuce hydroponically this winter. It’s not difficult, it can be a lot of fun and would be a great learning project for families to do together. Good luck growing some of your own food this winter.

This column is provided courtesy of the Saskatchewan Perennial Society (SPS; saskperennial@hotmail.com ). Check our website (saskperennial.ca) or Facebook page (facebook.com/saskperennial). All Saskatchewan Perennial Society events are on hold until further notice.

Jackie Bantle