Establishing gound cover and tree planting placement in PNW hugelkulturs

Hi folks. I just finished up a half acre ish of hugels on a flat field with total southern exposure in a puget sound creek valley. I have a couple of questions:

What will give me complete ground cover the quickest? I am planning on broadcasting a cover crop mix of clovers and vetch with some grasses. Possibly rye or oats, and maybe some mustards, and various others. Is this sufficient? I may intersperse red alder for quick stabilization and n fixing. But I am looking for complete cover of this area as quickly as possible. Any specific suggestions? Anyone know where to get bulk lupine seed in the seattle area?

My second question is about tree planting. Originally I was planning on planting the fruit trees on the top of the mounds (dug down a little in bowls) to provide them with maximum rooting depth over the high water table and flooding zone (wetland and creek adjacent, water table 5-6 ft below pre-hugelkultur soil level after one of the dryest winters on record. Flood levels bring water table to 1 foot of soil and dissipate slowly). Many of these species (fig, mulberry, cherry, jujube, pawpaw, persimmon) do not like waterlogged soil. On the other hand, planting on the top of hugels can have the opposite result in putting your trees in the place that dries out the quickest. Typically trees are planted downslope from hugelkulturs if there is any slope, correct? Thoughts?

Also, what are my best options for pathway cover? The bobcat I used to mound the soil over the hugels ate up the grass and topsoil so the place is just a muddy mess right now and more so soon with coming rains.

Hugels are approximately 3-4" tall and 5-8"wide.

Any ideas or help is much appreciated,
Thanks
Andy

Hi Andy,

Hugels can erode/subside. I wouldn't want to put any long-term trees in them, or at least not until they've reached a longer-term sort of geometry.

I've seen a ~1/4 acre food forest which used hugel mounds for trees to give them a bit of space in a high water table; at 2.5-3 years, when I saw it, there were quite a few exposed roots and dead trees. Many trees died of thirst in the summer as the hugels had degraded and were letting water through rather than holding it effectively. The muscovies loved the insect population inside the mounds, and their assistance certainly didn't do the trees any good either; they were excluded from around each tree, but this A: took a while to happen and B: the fence circles probably weren't as big as ideal.


Maybe you could ameliorate this issue with very robust hugel mounds, prompt hugel maintenance if problem crop up... and maybe no ducks. You are clearly already aware of the urgency of getting that soil covered.


I would agree that typically trees go downslope from hugels, where slope exists...


Can you excavate a pond to lower the water table? Would give more soil for the Hugels, too.


Do you have a plan for irrigating your trees while they are young? The plan at this food forest was manually placed 4-litre jugs with a pinhole in the bottom for each tree. In the drought/heatwave last summer, this proved insufficient water, at an overly high time input. Water table was at least as high as yours, but the young trees still couldn't reach it in the summer.

Swale berms, being straight earth, are great for planting trees and are used to get elevation above a high water table in some cases. Hugel beds are not recommended for trees.

As for placement up or down slope, it is important to consider not What is commonly done, but Why it is done, so you can evaluate whether it is appropriate for your situation.
I do not know the reasoning for placing trees downhill of the hugelbeds, but what if it is usually done to catch water coming down from the big sponge? Might not be your best bet.

For fast cover, buckwheat is pretty common. Also, for the high water table, fast growing hybrid poplars can pull lots of water out of the ground.

Peter, I believe you're correct that the placement of trees downhill from swales/hugels is indeed to place the trees for access to the underground 'plume' of water coming off the swale/hugel. In the case of swales, on top of the swale is also used...


I dug into one hugel bed I built about 3 years ago; the soil has settled and infiltrated all the gaps, and the 6-8 inch logs, mostly maple/alder, are very decomposed. The smaller branches are completely gone. This one started with dead wood, mostly a least a little decomposed. I wouldn't be worried about planting trees into it at this point, I don't expect it will do much more shifting at all.

Transpiration to lower the water table seems a little dubious to me in the pacific northwest; while the trees are dormant, not much transpiration will take place, and I am assuming your high-water-table problem is predominantly a fall-spring deal....


I'm sure you're already considering alder; it should like the wet soil, and nitrogen fixation is always nice.

Some desirable species of fruit tree can be grafted to more water tolerant root-stock; apple and pear come to mind.

U
Dillon and Peter,
Thank you so much for you're responses and information! It is much appreciated.

I have (possibly unfortunately in hind sight) already purchased most of my fruit trees. I am wondering what my best options at this point are. What I am considering most strongly is to dig 3 ft. round bowls into the hugels about halfway down the southern faces (hugels are in sun trap "U" shapes facing south) and plant the trees in the bowls. I would make the bowls 1.5 ft deep maybe so that when everything settles in the next years there is less chance of root exposure.

These hugels are probably 75% soil and only 25% wood (no wood was on site so all was brought in via free craigslist folks). So in reference to planting these trees I hope there is enough soil in these hugel berms that I'm able to get away with it. I did concentrate the wood in small piles under where I am planting the trees however, but even in these places the mounds are only 1-1.5 ft of wood and the other 3-4 ft is soil on top.

I cannot excavate a pond for drainage (draining the wetland area would be impossible in this case), and my biggest concern with the water table is with root death in flood scenarios. Which are more and more frequent these days.

As for irrigation, drip is out because there is very little water pressure on site so I am leaning towards running a hose with a splitter to a couple different locations and filling one 5gal bucket per tree and dumping it on every week. A lot more work but not sure if there's a better option.

Peter, could you talk more about why swale berms are used for trees and hugels are not? I am very interested in the WHY behind this as you were referencing. I would think that because of the moisture retention potential of the decaying wood they would be perfect for trees as well. But I am not sure...

There will be alder planted, and some other N-fixers (goumi, buffaloberry) guilded in with the trees for stabilization etc...

Thanks again!
Andy

Hugels are, inherently, somewhat unstable. The wood in them will break down over time and the soil will slump as that happens. Trees do not really care for having the earth around their roots dropping inches.
Sepp Holzer, the guy that pretty much taught permaculture about hugelkultur, says not to plant trees in hugelbeds. Between them, yes, but not in them.

Swale berms are solid soil. Uncompacted, but still they are all soil. With them holding your tree on slightly raised ground where water is infiltrated beneath them, you get really good conditions for trees;)

Hi Andy, no problem, just wish I had more in the way of a solution!

What Peter is describing is exactly the pitfall I saw in action last summer.


The fact that your hugels are 3/4s soil seems hopeful; I think it was probably more like 50-50 originally, in the hugels I saw with trees in them... the one I built, about the same. More wood than soil available!


Still got bobcat access? If you can do more earthmoving, what about adding more soil mounded directly against the hugel, perhaps half as high, on the south side, then plant the trees into that? Might be more stable than the cups you describe. With the cups, they may fill with water, and then overflow, and erode... groundcover, groundcover, groundcover!

Plus, if the hugel is 4' high, and you dig a 1.5' hole at the halfway mark, you're nearly back at ground level!


If you do plant the trees directly into the hugels, maybe you could tweak the placements so each is next to, rather than right above, the concentrated wood piles?


I take it there isn't any more elevated area that could accept some of your most flood-sensitive trees, so that more suitable ones could be planted in the floodiest parts?

Andy Roo wrote:As for irrigation, drip is out because there is very little water pressure on site so I am leaning towards running a hose with a splitter to a couple different locations and filling one 5gal bucket per tree and dumping it on every week. A lot more work but not sure if there's a better option.

I would suggest coming up with a better irrigation plan if there is even the slightest doubt that someone will be able to water them as described. Once per week in a bad august drought sounds optimistic for young trees. Better options... Well, you could add infrastructure to address the water pressure, a reservoir and pressure tank sorta deal... The water in the pond here is pretty mucky, can;t be used in a drip system without major filtering, so the orchard uses sprinklers. Watered in segments to keep the plumbing and electric requirements down, off a pressure tank fed by a pump in the pond.

Andy Roo wrote:I cannot excavate a pond for drainage (draining the wetland area would be impossible in this case)

That's unfortunate; note that while draining the wetland would be impossible, and quite possibly undesirable anyhow, even a smallish pond can have a localized impact on the water table. I certainly can't quantify this, though... A pond could also help with the irrigation issue as above... and provide soil to mound against the hugels...


I guess the bright side is that once you get through the first few years, however you do it, the hugels will have become defacto swales with excellent soil, and should be a great place for trees!

[quote=Andy Roo]What will give me complete ground cover the quickest? I am planning on broadcasting a cover crop mix of clovers and vetch with some grasses. Possibly rye or oats, and maybe some mustards, and various others. Is this sufficient? I may intersperse red alder for quick stabilization and n fixing. But I am looking for complete cover of this area as quickly as possible. Any specific suggestions?[/quote]

In my recent smaller scale hugel I broadcast red clover only (for nitrogen fixation) and it sprouted within a week. A greater variety of cover crops is a plus I'm sure. For immediate cover you can use some kind of seed-free mulching material.

How bad are your floods? At least Persimmon and PawPaw are supposed to be fairly flood tolerant.

As for getting above the Water Table, Ben Falks describes having this problem in his book A Resilient Farm and Homestead [in Vermont where they have summer rains as well as winter ones] and the swale berms work wonderful for him. I'd guess your trees should do pretty well in the soil-dominant sections of your hugel beds, between the wood cores.

While I'm here, would you mind divulging which cultivars of Pawpaw, Persimmon and Jujube you chose? [I'm trying to figure out cultivars which will ripen well in our part of the world.)

Thanks for all the help everyone. I planted most of my trees yesterday. I'm very interested to see how they do. I hope that intensively cover and intercropping them with guild species will secure the mounds and that the trees will no loose their stability. Hopefully my high soil to wood ratio will help with this.

Paw paw species that I found in my research were earliest for my area (time we be the test): Pennsylvania Golden; NC-1; Campbells No. 1.
If I were to plant a fourth it probably would have been the variety 'Prolific'.

I was just reading Ben Falk's book myself. Really impressive.

Andy

Jujube are Li and Lang and persimmon are Nikita's Gift hybrid.