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Mulching Options for Semi-Dwarfs

Posted by Brian Roseth 
Mulching Options for Semi-Dwarfs
June 24, 2015 08:46PM
Greetings from the Polaris Project!

We are reclaiming a rather poor soil in California's Sierra foothills and it's a slow process. We are heavy in clay, poor in nitrogen and acidic in pH. The first year we tilled in compost and oyster shell lime, plus Azomite for trace minerals. We then planted a mixed cover crop of vetch, grasses and tap-rooters to begin breaking up the soil. After that, we started planting our trees (mostly apples, but also a few peaches, pears and cherries). We have continued annual top dressings of compost and lime to slowly add organic matter and raise the pH. In total we have about 45 fruit trees of various sorts. The trees are just coming into bearing.

About half of our apples are planted on dwarfing rootstocks that do not like competition from weeds or grass and should be mulched (G-202, G-30 and G-935). Like the rest of California, we are in a drought and mulching to conserve moisture would be good anyway. We irrigate with dripline.

I would love to dump a few inches of ramial chipped wood over the whole orchard, but that is not practical. At our elevation, most of the trees around here are coniferous. Asking local tree trimmers and landscapers for chipped trimmings would result in the wrong kind of mulch. Importing ramial chipped wood from a few counties away (downhill) might work, but the hauling costs would escalate quickly.

My current plan is to find space on our property to plant fast-growing, woody trees and plants that I can 'chop and drop' annually to slowly build up a fungal duff. We've already got some trees I can do this with (mulberry and filbert) and I've seen references to others that might work (Siberian pea shrubs and Goumi), although I don't know if they would handle our hot summers. This plan is undoubtedly the best long-term solution, but it won't be a quick fix and I'd like to make a significant impact on a shorter term.

Here are my questions:

(1) Would vineyard trimmings work for ramial chipped wood? I think I can access some of these locally. I'm not familiar with the cultural practices of vineyardists, so I'm not sure what kinds of chemicals I would be importing (I'd certainly ask).

(2) For weed suppression, would a thick layer of hay or straw be compatible with the orchard. I've seen this done on several websites. Laying it on top and not mixing it in would block weeds and grass--at least in the aisles. Keeping it undisturbed might skew the balance toward fungal growth, rather than bacterial growth (but I'm not sure). Would spoiled hay be better in this regard? If this is an issue, perhaps I could even inoculate the hay/straw with fungal (root-dip) spores and let it age before deploying it.

Thanks in advance for any advice or guidance.
Re: Mulching Options for Semi-Dwarfs
June 25, 2015 03:52PM
These Geneva rootstocks deemed semi-dwarf are all in the 40% to 50% vigor class. These are roots able to coexist with taprooted plants nearby. I get that you're in California and water is BIG ISSUE ... yet here I rely on comfrey (mostly), lovage, burdock, rhubarb, goldenrod, Echinacea, and other "surface covering plants" to keep more ground open (relative to root mass) around such trees. I can't say enough about the book Farming with Native Beneficial Insects (available on the network Bookshelf) as regards orchard companions for different ecosystems.

Shallow cultivation in the immediate tree circle (up to a three foot radius) gives the tree some headway early on but this zone can certainly be mulched as well as long as voles are not in the picture. A diverse patchwork of ramial wood mulch, hay, leaf litter, and "living mulch plants" works well beyond that inner zone. Hay or straw alone does not provide the lignins which fuel the white rot saprophytes that create fertile soil for trees. Growing woodsier "chop and drop" plants nearby will help. Figuring out local resources to create that fungal-rich soil ecosystem will vary somewhat for each of us but it's the most important work we do as orchardists.

A savvy grape grower should be using those prunings for vineyard mulch. Such might be tricky to chip however ... though running over a pile of vines with a brush mower will kind of get there. You really have to be wary of the chemicals used in non-organic vineyards otherwise.

Lost Nation Orchard
Zone 4b in New Hampshire
Re: Mulching Options for Semi-Dwarfs
June 26, 2015 06:58PM
Thanks for the advice, Michael!

I will look into the plants you mentioned to see what might work best here. I'm also in the middle of reading Teaming with Microbes, and I suspect this fascinating book will also provide relevant advice. (I'll also check out Farming with Native Beneficial Insects).

I've noticed a change in the weeds over the past 3 years. They are still as thick as ever, but the early pioneer species have begun to be displaced by middle pioneer species. We've beat the Star Thistle and now have more Queen Anne's Lace and Mustard. I guess that is progress--a result of the work we've done so far. We weed-wack several times per year to keep them down and suppress flowering (and build organic matter). We stopped tilling last year to avoid disturbing the tree root/fungus networks.

Its a slow process but I think we are on the right track.
Re: Mulching Options for Semi-Dwarfs
June 26, 2015 07:59PM
As I am researching understory plants, I can't help but wonder what the understory looks like in an original, apple-climax forest (if there are any left). Perhaps there are understory plants with "special relationships" with apples. Anyone know?
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