Re: planting in heavy soils

pkssreid@comcast.net wrote:
Having grown up with adobe soils, the point of wisdom we always adhered to was to chunk up the sides of the planting hole quite roughly, so as not to make a smooth "pot-like" surface, which can fool the roots into growing round and round. Often when larger trees blow down in the strong winds, one can see that the roots which pulled up had acted as though they were in a large pot. Whether we amended as we used to, or not so much as we do now, that has seemed to be a significant factor in our very heavy soils.
It has become increasingly evident with the passing years that when it comes to planting in difficult soils something more sophisticated than a "one size fits all" is definitely called for.

Here I have no personal experience of heavy soils at all, I do not even have any heavy soil at all in my property which lies on a light stony alluvium left by the local river that long ago changed is course and moved to the other side of our valley. However there has been a good deal of investigation in this country of planting in the heavier soils (none I think quite as bad as your adobe) and it has been generally recognized how easy it is to unwittingly construct a sort of buried plant pot which will permanently confine the roots of a tree planted in it, causing its roots to endlessly spiral instead of spreading out and anchoring the plant securely, while enabling it to tap the fertility of the surrounding ground. Another equally unhelpful possibility is that the hole will act as a sump and before long drown the unfortunate tree or shrub.

The answer to this it is now generally agreed seems to be using a wider much shallower hole and filling it with a light humus-rich soil, which is also in most cases piled up to some extent on the surface for some distance around, so that the tree is encouraged to develop a wide-spreading root system as soon as possible. At the same time the presence of a lot of organic matter in the surface layers gradually beings about an amelioration of the natural soil lying directly beneath the humus, so that the tree can increase its penetration of the deeper layers as the years go by. In fact the encouragement of strong penetrating roots in itself goes a good way to breaking up the soil and permanently increasing its porosity.

I have in fact over the last few years learnt a good deal about adobe soils from those members of the Organic Gardening group who have to deal with them. What comes over loud and clear from all the successful growers is that trying to make usable garden beds by breaking up the soil and lightening it with organic matter and/or sand is definitely doomed to failure. The only successful growers are those who do not attempt to plant direct into the natural surface, but construct their own artificial one with large amounts of organic matter right on top of it. Several people have claimed that they were able to bring about sufficient change in the adobe in as little as one year to allow the planting of at least annual crops and that within a very few years they have actually achieved a good garden soil of considerable depth which can apparently be maintained for as long as required, provided the lower unimproved layers are left alone. I presume that with long use such soils would continue to slowly increase their usable depth.

Moira
--
Tony & Moira Ryan,
Wainuiomata, North Island, NZ. Pictures of our garden at:-
http://mywebpages.comcast.net/cherie1/Garden/TonyandMoira/index.htm
NEW PICTURES ADDED 4/Feb/2004

Other Mailing lists | Author Index | Date Index | Subject Index | Thread Index