Specialty Gardening: Container Soils: Water Movement and Retention II, 1 by tapla

tapla wrote:
"For me, I like using some sort of hardwood mulch as one of the ingredients because I know that the plant will only be in it for a year or so before i have to move up to a larger pot."

When you make this statement on a thread where we are discussing a soil that has as it's primary component pine bark - approx 75% of the total volume, it is easy for readers to believe you can substitute whitewood chips for pine bark with no problems. We know that is not true. It was only as an afterthought that you chose 15-20 as the % of the soil taken up by chips. There was no way for anyone to tell if you were using 1% or 90%, but regardless of the ratio of wood chips you use, it doesn't change the chemistry or what I said about how the chips perform/react in soils.

Why would we WANT to use any wood chips in a soil when we have a bag of pine bark at hand and it provides the same physical characteristics as the wood chips for a longer time w/o the N problems?

You mention keeping the soil on the dry side to compensate for the N tie-up, and using different fertilizers. How practical is that for most hobby growers? Most of the folks are here because watering issues have given them problems in the past. One of the primary points of this thread was to help people develop a soil that could be watered freely with little or no risk of the anaerobic conditions caused by the combination of poor soils and a heavy hand on the watering can. 'Keep it on the dry side' makes things more complicated and it's unnecessary if you use an appropriate soil. Additionally, I'm speaking primarily to hobby growers who need or want help here, not people who have the knowledge and wherewithal to make the necessary adjustments in their nutritional program to compensate for things like media induced N deficiencies. I try to make this easier, not more difficult.

Just because you can MAKE something work does not mean it's a good choice for everyone. I once grew a perfectly healthy spruce tree in a container filled with nothing but broken glass for a full year before planting out, just to prove it CAN be done, but that doesn't mean I want to adopt the practice across the board. I grant you that the including 15-20% wood chips as a soil component is likely to affect the N supply much less than 75%, but again, it doesn't change the chemistry, it's unnecessary, there's no structural advantage, and there is probably more expense involved because of the higher fertilizer rate. We also know there is more decision making & complications that accompany the practice .....

I have no problem with hardwood mulch being applied to the top of soils, but if you go to any soil/composting book/forum and check what it says about the practice - invariably they caution against the N immobilization that accompanies the practice to varying degrees - depending on the size of the material, type of material, and other cultural conditions. Incorporating it into container soils presents most of the same reactions as incorporation into garden (mineral) soils.

"When I brought up the subject of bonsai plants, it wasn't to "leave the subject of soils", I had thought it at least somewhat obvious that I was trying to think of a plant that would perhaps stay in a container without needing to be moved up to a larger pot because of root growth. There aren't many plants that don't need moving up, and bonsai seemed like a real choice of one that didn't."

I'm sorry I didn't understand the question. Bonsai is not 'A' plant. It is a way of treating plants to make them old-looking and keep them diminutive, so I couldn't have answered the question as asked anyway. A 'bonsai' could be an apple tree, pine, juniper, forsythia, ....... or any one of thousands of other plants. I have pelargoniums, snapdragons, coleus, and several herbs that are extremely believable as (they very much look like) small trees mixed into the collection of trees and shrubs I've styled. All bonsai eventually need to be bumped (moved up in pot size). With careful attention to regular root pruning, the owner can greatly increase the intervals between increases in pot sizes, but the unattended or neglected tree must be moved up in pot size regularly. Root pruning slows growth and the confinement of the container produces the dwarfing effect - that being primarily comprised of shorter internodes, less branch extension, and smaller leaves. A very good understanding of soils and their composition is also CRITICAL to the health and vitality of bonsai. I hope I've now offered a better answer.

Take care.

Al

This message was edited Nov 23, 2008 1:13 PM