Humidity plays an important role in hydroponics, but if you are growing in a house or apartment, you will find that this is the one aspect of climate over which you have relatively little control unless you have a humidifier-dehumidifier. Too much humidity will probably be less of a problem than too little humidity. If your growing area is too dry, you could install an inexpensive humidifier. Because the growing area is usually small and confined, greenhouse hydroponics for the hobbyist makes humidity easier to adjust, although it may be expensive.
Do keep in mind, however, that a hydroponic system in your home is a wonderful, natural humidifier during the winter. In most North American homes, the air is far too dry, leading to various respiratory problems and colds. A hydroponic system provides humidity in two ways; through evaporation of the water in the nutrient solution, and through plant transpiration. This is yet another area where hydroponics give Mother Nature a helping hand.
Anything can be taken beyond reasonable limits, though, and I can remember a few years ago having sixteen tanks in an enclosed, ten by ten foot room. Needless to say, the room was soon like a rain forest! I ended up installing an air conditioner to pull some of the moisture out. It is important to remember that plants need some humidity, especially during germination, but that a balance needs to be struck between the rain forest and the desert.
The pollination period is also affected by humidity. As mentioned in Chapter 2, growing indoors makes it necessary for you to do your own pollinating, and if the humidity is too high or too low this process becomes more difficult. The whole question of pollination will be covered in Chapter 10.
Indoors, lighting affects temperature, while temperature and humidity go hand in hand. An ideal temperature-humidity combination for vegetables is 40 per cent relative humidity at70°F (2 1 °C). This simply means that 40 per cent of the atmosphere is moisture vapour at that temperature. Because warm air is capable of carrying a greater proportion of moisture than cold air before it precipitates (rain, fog), the 40 per cent figure at 70°F means a greater amount of moisture is present than at 65°F (18°C) with the same humidity reading.
Plants prefer relatively high humidity. If the air around them is too dry, they will transpire more in an effort to increase the amount of moisture in the air. In effect, low humidity could make the plants exhaust themselves. When people perspire, they need to replace the lost body fluids or they risk dehydration. Plants must also be able to absorb high amounts of water under low humidity conditions to keep up with the rate of transpiration. Often they are unable to do so, and the plants wilt. Tropical vegetables and fruits, such as cantaloupe and cucumber, like an even higher humidity level than most other plants. A good idea during the intense heat of a summer afternoon is to mist your plants two or three times. This will lessen the need for water through the root system and also reduce the rate of transpiration.
Because our indoor living environments are frequently very dry, it would be a good idea to purchase an inexpensive humidity measuring device and give high priority to both humidity and temperature. High humidity is not nearly as much of a problem for two reasons: first, it is unlikely that you will be able to create such a situation in your home, and second, plants can cope with a high reading, but not its opposite. The only possible problems that could be caused by too high a humidity are the development of mold or mildew and, as mentioned earlier, the effect it could have on pollination.
When using your hydroponic unit indoors, make sure you establish a definite daily temperature variance with warmer days and cooler nights. There are energy saving thermostats on the market that do this automatically. In fact, I should point out that plants, like children, love a routine. The daytime temperature, nighttime temperature and the periods of having your lights on and off should always be as consistent as possible.
Here are the temperature preferences of the most common hydro-ponically grown vegetables. Keep in mind that 40 per cent humidity at 70°F (21°C) is your base figure for measuring the environment.
Broccoli Lettuce Brussels sprouts Onion
Chive Watercress Kohlrabi
Chinese cabbage Tomato Corn
Remember, too, that an indoor atmosphere often contains dust and smoke. Regular spraying with water, about once a week, will clean plant pores and wash off dirt accumulations. Although such plants as cantaloupe, cucumber and zucchini like high humidity readings, they are not fond of excessive amounts of water on their leaves. Washing may cause a mildew infection on the leaves.
Was this article helpful?