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3R Lighting Tutorial: The Stratum Method for Container Gardens





Q: What is the Stratum Method for Container Gardening?
A: The Stratum Method uses a planter pot and soil, and takes advantage of the best properties of coir fibers and grow rocks to allow the plant's natural abilities to keep the plant healthy. It is mostly used for growing vegetables or herbs it is not generally used for houseplants.

Plants that are grown in soil in containers have to be watered more frequently than plants grown in soil in the ground. Since all the nutrients a plant needs are water soluble, the balance of water and fertilizer is one of the largest challenges in container growing.

Look at this diagram.


The word "Stratum' just means "Layer". The growing medium in the Stratum Method arranges the growing mediums in layers. The Bottom layer is made from grow Rocks and will drain pretty well. The next layer up is made from coir; coir is made from coconut husks which have been cleaned with fresh water. Coir will hold water. The top layer is made from soil.

There is also a small reservoir of water in the bottom of the planter, because the drain holes in the pot are a little above the bottom of the pot. The advantages the stratums and reservoir give you is that even in the limited space of one planter pot, there are a variety of moisture conditions for the roots.

This method of container garden is set up for the pots to drain very quickly in comparison to a houseplant. If you are growing in a container outdoors not protected by a porch, deck, or patio, etc. on hot days (over 100 degrees) you may have to water a large enough plant up to three times a day. Indoors, you are usually watering the plant every third day, every other day, or sometimes once a day. On a terrace, patio, porch, or lanai you will be somewhere between the two extremes. Watering schedules vary on the temperature, amount of light, size of the plant, etc. The root zone should be kept damp and moist.

The extra air in the root zone will help the plant grow faster and fuller. There is less chance of developing any root pathogens which hurt the plant. The trade off is a greater chance of the plant drying out. The arrangement pictured above provides a good deal of air to the roots, while providing a couple of pockets of moisture for the plant's safety.

As the plant grows and the days pass, the plant will adapt to the moisture conditions of the pot. Different people have different schedules and will water and fertilize their plants in different ways. On sunny and dry days the plant will use more water; during a cloudy and rainy week the plant may use very little water. On days where there is an abundance of water, the drain holes in combination with the grow rocks ensure that the roots do not drown. On days between waterings, the coir will hold onto the water and nutrients, but still allow some air to the roots.

Q: How often should I water?
A: The larger the plant, the more water and nutrients the plant will use. When the plant is young and small, it uses significantly less.

The rule of thumb is that on average, water your plants every three days to once a week. A moisture meter can help guide you. A week of sunny days will usually coax the plant to use more water than a week of cloudy days; a growlight can help even that out.

If your pot drains well enough, and if you choose, you may be watering once a day. Outdoors, in container gardening it is not uncommon to water every morning and also each afternoon when it is sunny and dry. Indoor plants are protected to a much greater extent.

There is another rule of thumb that every third watering should have some fertilizer, but that is one that is hugely variable. House plants grow slowly and can often be fertilized twice a year, sometimes just once in the spring. Vegetables grow much more quickly and benefit from more fertilizer. Look at the Mineral Trouble Chart in this tutorial to help you figure out if the plant is asking for more nutrients. Too much fertilizer often creates a mineral salt build up on top of the soil, but if you add kelp and encourage healthy microbes in the soil, you will not see a salt builup; the extra fertilizer will wash away through the drain holes.

If the moisture in the soil grows fungus, the problem is less likely to be excess moisture and more lack of moving fresh air. The soil should only be wet right after watering; otherwise the soil should only be damp, moist.

There is also a rule of finger: stick your finger into the pot and see how moist or dry it is.

The growing conditions can vary inside the same house from room to room. It takes a little bit of time and testing to figure out what works best as the watering schedule for each particular location.

One of the advantages to the Stratum Method is that you can adjust the amount of coir in relation to the growrocks and soil. So, for example, if one tomato is growing in a South facing window, it gets more coir in the coir layer to hold a little more water a little longer. Another tomato is growing in an East window; this tomato gets less coir and gets a few more growrocks for better drainage. If the proportions are done right, then even though both tomatoes have very different growing conditions, you can keep them both on the same watering schedule.

You need to try what you think is best and if it doesn't seem like it's working, then adjust your watering schedule. It is always good to keep a clip board to keep a record.

Q: Don't you lose growing space where the growrocks are draining?
A: No.

The growrocks use the surface tension of the water to stay a little bit wet, moist for a little while. Roots will grow just fine through the growrocks stratum.

Q: How dry do they get?
A: That depends on you and how you water them.

A second Stratum Method uses two pots at the same time. The growrocks keep the overflow water from oversaturating the soil. You line a container with growrocks and place a smaller insert container on top of the growrocks.
Look at this picure of 3 cucumbers grown in a one gallon pot under sunlight.



There is a 2 to 3 inch layer (or stratum) of growrocks in the larger container. The plants grow in a soil/coir mix in the smaller insert pots which are placed on top of the growrocks. This cucumber plant has been harvested before and at the moment has three cucumbers grown from a container garden.

This plant was grown in sunlight outdoors; an HID growlight grows cucumber plants very well.




















© 2005-2006 K.Kelly