Z...do I understand the bottom of the soil mix in your container touches the ground soil? If this is the case....you are good! My 10 inch pipe containers are on a concrete stepping stone. That wicks, as well. I would say drainage holes within 1 or 2 inches of the bottom would be fine. Your water will drain out through the native soil....if I am reading you right.

It is the water remaining in the soil after gravity has drained all it can, that could pose a problem. You have not indicated the mix you are using which would determine how much of a problem you may have. If your pots had no bottom you would have soil to soil contact and your pots would in effect be raised beds. If you have a one inch drain in your pot you have soil to soil contact for that one inch and how well it will drains will depend, again on the mix used. Al

I am experimenting with various mixes. If I use 511 or the gritty mix I don't think earth wicking would be necessary or make a difference because the potting soil is designed to drain fully. I have assembled the ingredients for these mixes and plan on using them in some of the containers.

The question is for mixes that don't drain as well as 511 or gritty. I have a few yards of mushroom compost that I have been using as the base for some mixes. My bell peppers and basil are doing much better in this compost mix in 5 and 15 gal containers on the ground than the same plants are doing in my garden. I want to experiment with earth wicking to improve the drainage of a compost mix. The mushroom compost drains quickly but I am sure there is a perched water table.

The container garden ranges from 5 to 15 gal. I am adding 20 and 25 gal containers with plans for bottomless containers. I am working on a form design for a 24 inch diameter x 24 inch tall poured concrete *pipe* to use as a bottomless container.

My question is for the plastic black nursery pots in the 5 to 25 gal range with a peat or compost based mix with soil to soil contact. Should they rest directly on the existing granular well drained soil or would a layer of absorbant soil like Turface or kitty litter on top of the existing ground assist in draining the container?

Thanks for the responses

Zeuspaul

Z...I would say again....you are good. Why would you want an absorbent/wet mess at the bottom of your container? I have been using free irrigation pipe (I like 10-12 inch diam) for my tomatoes. They work well. The tomato roots run down 3 feet in no time!

Hi Fireduck...do you have a photo of your set up? I have a tiny square patch of ground. I planted 4 tomatoes that are just not thriving. My soil is so poor even with amendments. Everything else I have are in pots. I would love to find a way to use my little square effectively.

Thank you! Jude

I do not see any advantage of putting your containers on a really porous surface like gravel to increase drainage in the container. Any interface with a different material will be an added barrier to the passage of water. Most plants in containers setting on the ground will soon have their roots finding their way through the drainage holes into the native soil. The connection of your container soil with your native soil will act as a wick on the water in the container. Al

Fireduck, where does one find 12 inch drainage pipe? How tall are your bottomless containers? What kind of soil do you use?

Fireduck said

Why would you want an absorbent/wet mess at the bottom of your container?

Because it's better than having the wet mess inside the container. I have learned from reading this forum that containers can develop a pearched water table if the soil inside the container does not drain well.

I have no wet mess outside the container. Water drains quickly into my coarse soil.

Calistoga said

I do not see any advantage of putting your containers on a really porous surface like gravel to increase drainage in the container.

I have been doing a little reading on soil water movement at the site linked below.

A quote

After the upper layer becomes saturated, water enters the underlying layer (Figure 3.8b). The practical implication of this demonstration is that in shallow soils underlain­ by sands, like those found in the Platte River Valley, water movement is actually slowed by the underlying coarse sand and gravel layer.

My understanding is the coarse sub layer has no draw due to capiilary forces.

A quote referring to a clay sub layer

What happens to water movement if the upper soil layer is underlain by a finer textured material like clay? As Figure 3.9a illustrates, water moves rapidly­ into the clay. Compared to the overlying layer, the smaller pores associated with clay layer have a greater attraction on the water. This causes the clay to wet immediately when the wetting front reaches the layer. Although the clay layer wets rapidly­, the small pores hold the water tightly and effectively­ retard the advance of the wetting front. The slowing of the wetting front causes lateral water movement in the overlying coarse soil. Finally, after the clay layer is saturated, the wetting front will move below the clay, Figure 3.9b. The situation illustrated in Figure 3.9 is typical of soils with buried claypans­. The claypan restricts­ the downward (or upward­) movement of water. If a claypan is at or near the soil surface, excessive runoff may become a problem during rainfall or irrigation events even though the soil below the clay pan is dry. A subsurface clay layer also can cause the soil above it to become­ fully saturated forming a perched water table. Perched water tables often cause drainage and aeration problems in the upper soil layers.

My take is a non saturated clay sub layer draws water from the container due to capillary forces. However a *normal* clay layer would saturate quickly under a container.

It seems to me a thin layer of clay chips (kitty litter) perhaps mixed with a little similar sized grit placed on a well drained base would not saturate. Wouldn't it then use the capillary force of clay to draw water from the container reducing the perched water table inside the container?

Thanks

Zeuspaul

Here is a link that might be useful: Water movement in soil

Your reference 'Water Movement in Soil' is very good. However it is water movement in containers we are discussing. On this forum' tapla' has much information offered that is relevant to water movement in containers, and is easy to find. It is very easy to assume that there is no difference. Al