posted 11 years ago
The most important lesson I learned the hard way is to not put any amendments into the planting holes in heavy clay. Trees are best planted bare-root, and the original clay tamped carefully around them. Apply any amendments on top of the soil as a mulch, or in dryland, or with problematical amendments like humanure, dig a hole beside the root system and place the amendments there. The problem with improved soil in planting holes is that it will retain more pore space than the surrounding clay, and in rains this space will fill with water, which will not be able to drain into the tight packed surrounding soil. The tree will quickly drown, especially if this happens in the growing season. Some trees are more sensitive to this than others (stone fruits and citrus are supposedly notorious), and these might best be planted on mounds or slightly raised beds. Mostly it's a problem with newly planted stuff....once it's been growing a few years the roots are every which way and can tolerate a lot more. Planting stuff from containers, with a root ball of fluffy potting mix intact, directly into a tight clay is also a recipe for disaster. Make a mound in this case.