Basic Hydroponic Plant Requirements

Weather you grow plants indoors, outdoors or in a greenhouse, There are some basic things you need to consider in order to have healthy plants. A knowledge of the environmental requirements for the kind of plants you wish to grow is important and essential for success. There are many books, articles and extension services available that can provide this information on the specific plants you wish to grow, so I wont go into detail about specific plants. But I will mostly just focus on the basic plant needs of all plants in general.

The most important needs are:

1. Proper atmosphere, air, co2, water vapor (humidity) and oxygen both in the air and at the roots.
2. Proper temperature, both in the air and at the roots.
3. Correct environment, right temperature, pH, Humidity and light.
4. Good growing medium, both in hydroponics or soil. Non toxic, well draining, absorbent and supportive, with oxygen provided to the roots.
5. Balanced nutrition, with all the mineral elements plants need in the proper form and amounts. This can vary significantly from plant to plant.
6. Adequate lighting (proper color or frequencies at sufficient intensities. Growing in natural light (sun) you wont need to worry about this much, but the color spectrum, as well as the length of the days will vary depending on your location and time of year.
7. Proper moisture (not too wet or dry)
8. Tender loving care (an awareness of their needs during all various stages of growth.

Most hydroponically grown green Plants will do well with 800 to 2000 foot-candles of light, and between 20% to 80% humidity. Although it’s important to know the needs of your plants. High humidity and inadequate air flow can lead to bacteria and fungal diseases. Most  green plants grown hydroponiclly do quite well at temperatures between 65 and 95 degrees F., and 800 to 1600 PPM (parts per million) of total dissolved salts.

Most hydroponic plants will do well with a pH of 5.5 to 6.5 and can be measured using a pH meter. It’s not always necessary to be exact with the pH, this is because plants will be able to absorb the nutrients within a pH range. There are many factors like temperature, and the exact nutrient composition that will affect how the plant is able to absorb the nutrients at a particular pH. These factors can change daily. That’s why it’s best to just be within a particular pH range, rather than an exact pH all the time. Even the adding of pH adjusters to your nutrient solution will affect the nutrient composition, so the less you need to add the better.

Plants get the Hydrogen and oxygen they need for growth directly from the air and water. Carbon, along with water makes up the bulk of a plants total mass, this comes from Carbon Dioxide (co2) from the air. This small amount (0.3% of the atmosphere) is absorbed by pores on the leaves called Stomata or Stoma when temperature, humidity and light are proper for the plant to do so. Carbon is not absorbed in quantity by the roots of a plant, so it’s not considered a “nutrient” in the same way that nitrogen, phosphorous, potassium and the other mineral elements plants need. These must be dissolved in water before they can be absorbed by the plants.

Plant Nutrition
In organic, or soil gardening, these elements are provided by weathering, decay and erosion of rock as well as the decomposition of organic matter through bacterial action. Hydroponics is simply “growing without soil,” so in hydroponics these elements are provided by mineral salts that need to be completely dissolved in water to make the nutrients available to the plants. Liquid nutrient solution is a bit easier to measure and mix than dry, but are not quite as concentrated or cost effective as the dry powders. So the choice here is mostly a personal preference.

“Grow” formulas are generally for the vegetative stage of the plants growth, and “Bloom” formulas are generally for the fruiting/flowering stage of the plants growth. That’s because the plants will require different concentrations of the mineral elements for these different stages of growth. Plants like tomatoes or peppers flower/fruit continuously, so they are considered continuously fruiting/flowering plants. Most nutrient manufactures make a nutrient formula for these continuously fruiting/flowering plants. Some of these will also be formulated for specific plants or crops.

As the plants grow, they absorb, or use up the nutrients in the nutrient solution, so it’s generally best to replace and replenish the nutrient solution every two to three weeks. The growing medium that holds the plant roots should also be flushed with fresh water at that time to prevent a toxic salt buildup. These salt buildups in the root zone can prevent the plants from getting their proper nutrition. You’ll usually see a whitish brown crusty material growing (building up) on the growing medium when this happens.