Saving Seeds in the Garden

Soil Preparation and Backfill for Planting:

I was at a party tonight (Happy birthday, Eileen!) and a lady told me a tale I had heard before. She bemoaned the fact that the more carefully she amended her clay soil, the worse her trees did.

There is a problem with the common wisdom on the subject. For as long as I remember, my dad insisted on mixing soil amendments into the planting holes of everything we planted – he was a landscape contractor, and that was a lot of plants and trees over the years. We made large holes, mixed in fertilizers, course redwood sawdust, blood and bone meal, etc.

We worked on the ory that you made life easy for the tree or shrub to get going and give it a nice place to live. Sounded good, and worked pretty good, most of the time, but we were often lucky in the soils we had to work with.

Today, research has shown that amending the backfill material with organic matter does not help, and may in fact hinder, plants becoming established.

The theory is that the change in soil texture creates a barrier to soil-moisture movement. The more sudden a change is soil texture occurs, the strong that barrier is. In the lady’s case, the clay soil is extremely dense, and the amended soil was very light.

In her case, whenever you watered the tree or plant, it would sit in a bathtub of water until it drains, which in clay soil is very slow. When you don’t water the trees or other plants, the root ball dries out too quickly, even though the clay soil still retains a lot of moisture, since available moisture is blocked from the roots by the sudden change.

Furthermore, the discontinuity in soil textures may prevent the roots from ever venturing out of the prepped hole. The roots may simply cirlce the hole, never moving out into the native soil.

The accepted way of planting is to plant in the native soil and enrich the surface, letting the natural soil denizens devour and distribute the amendments.

If your soil is really horrible, amend the entire area, not just the planting holes. One of the best ways to amend a large area is to ‘double dig’ it; this loosens the subsoil and speeds up the soil forming process. See the article on raised bed gardens for more on double digging. (http://gardening-coaches.com/raised-bed-vegetable-garden.php)