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Nov10

Winterizing our herbs garden : An experiment with hydroponics

We’ve only had one night of frost so far but that was enough to kill all our outdoor tía tô (perilla) plants. Luckily, we’ve already started winterizing our herbs garden. This year, we’re experimenting with hydroponically growing our herbs indoor with the hope that more godlike control over our plants’ world will keep us well supplied with fresh herbs until next spring. Growing hydroponically is a technique for growing plants without soil, with well defined nutrients solutions delivered directly to plant roots. Another advantage for us is the ability to heat up the nutrient solution coursing through the system and keep the plants warm in spite of the cold air temperature in the apartment. Lay the nutrient tubing underneath the other pots and even the non-hydroponic plants will have warm happy feet!

Winter garden : (front) tía tô / perilla, rau răm / Vietnamese coriander, lá chua / sorrel, kinh giới / Vietnamese balm. More of the same in the back & various húng varieties / basil and mints.

There are a number of ways to implement a hydroponic system. Our system is one where a low level of water is constantly flowing across the growth bed. This particular implementation was chosen because of its robustness – in the event of a pump failure, the minimal water level will keep the plants from drying out until the problem can be fixed. The minimal water level is determined by the filling and drainage holes drilled into opposite sides of the planters boxes. Rubber tubing and plastic hose barbs allow all the planters boxes to be connected to each other. The nutrient solution is delivered to one of the planter box and drained from the other end.

Plants were prepared for the hydroponics garden the same way we prepared them for rooting in the spring. In fact, the idea for the hydroponic system came when we noticed that plants in water waiting to be transferred to a proper pot of soil were actually thriving and growing new leaves, branches and so on. That wouldn’t have continued indefinitely – the plants needed food and well aerated roots – but the new growths were enough to spark the idea.

This tall guy here just kept on growing in water.

To root the plants we made an angled cut (to increase cut surface area in contact with water) in the stems of fresh looking veggies from the market, with both the stem and scissors submerged in water. We aimed to get about 4-5 inches off the top of the plant. All but the top 4 or so leaves were pinched off. Plants were placed in a clean cups with an inch or 2 of water and with at least 1 node (usually a bump on the trunk where side branches and leaves come off) under water.  (This was due to the hierarchy of plant cells: not all cells can form new tissues like roots and in many species the multipotent plant cells capable of forming new roots or stems are concentrated at or confined to the nodes. The special cells that could form new plant tissues were actually the original “stem” cells.) In 3-4 weeks, about 60-80% of the cuttings will grow roots. They were then transferred to small pots filled with pea gravel then placed in the flooded planter boxes.

The water system was very simple: An aquarium pump directed water through the planter boxes and an aquarium heater maintained the water temperature at 72 degrees.

Pump, drainage tube, and water heater

Upgrades being considered include an air pump and and airstone to make sure the water was well oxygenated. With all that, another upgrade would be a glass aquarium and a couple of fish – making our winterized garden an aquaponic system as opposed to simply a hydroponic system.

Right now though we’re just glad the apartment hasn’t been flooded yet.

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