Save the hugels!

I recently moved to a farm where several hugel mounds were built, and then didn't receive the love they deserved. Now the grass is encroaching (I wish I knew my species better so I could tell you what kind, but alas...), the voles are a-tunneling, and the sides are eroding. The soil here is pretty clayey and full of rocks. I have a feeling that when they were built, not a whole lot of nitrogen was added.
There are two sets of hugels - we'll call them the north bed and the south bed. On the north bed, the mounds are pretty low, just a couple of feet. It's shaped sort of like an elongated E, with the outer sides being taller and the middle fork just a little mound running down the center. Some apple trees were planted in it (I think the idea was to make it a nursery area, or something), but I think they're all done for. This thing is covered in grass and full of vole holes. There is no irrigation here, so that's a likely cause of apple tree demise.
The south bed has received a little more attention overall. It's been planted with some cover crops (clover and I don't know what else) and is taller - between 5 and 6 feet. It has a drip system running along the top of it, which is making it look a little sad and eroded. I planted some buffalo berry, Nanking cherry, and serviceberries on the inside of it (it's shaped like a long u).

So the questions are:
1) how do I reclaim them from grass? Cover crops? Tubers? I'm into the idea of planting Jerusalem artichoke on the north side.
2) what to do about increasing organic matter? This is clearly not an overnight situation, but any advice helps.
3) erosion control/keeping the thing watered. It's really dry here (30ish inches of rain annually, I believe, most in May and June) but I feel like the drip system isn't the best option.

Can't wait to hear what you think! Thanks for existing, all you permies.

How long are the huguls ? Do you have access to some machinery? If it was me, I would start again dig them up and do them properly with wood and put the soil back with compost etc. huguls should last years and should save you a lot of work., and they hold the water beautifully .. These mounds sound like a pain in the ..... If you have to do it all by hand, break it down into sections and start at one end, and do them properly it bit by bit. It will take ages but worth it. The rest I would use for potatoes etc, to break up the soil and make it easier for you.

If you use dense plant covering to save the initial problem. I don't think long term you will be happy.,

The fruit trees need to be moved... See other posts re this problem with trees in mounds... sorry lots of work. 😬

I would cover the grass with hay.

I would also cover the irrigated top portion, in fact all top portions, with hay.

Our clay hugels really benefit from the hay we put all over them. It slows erosion and allows the microbes and worms to begin working the clay into nice breathable soil.

It's our 2nd year with the hugels and to be honest I'm not sure how the planting of annual veggie seeds and perennial species will take place with all that hay, but it is what it is. We'll just move the hay for now.

The clover could stay if it's not too infested with unwanted plants. Just plant into the clover area.

I don't know what to tell you about the voles.

http://www.vegetablegardener.com/item/2430/how-to-control-voles-in-your-garden

You may want to get some traps for the voles, but I would check for a year to see what they're eating. It describes in the link above what vole damage to trees looks like, so if you find that I would trap them this year.

I just bought a pack of 2 reusable mouse traps and they are SO much nicer than the old wooden kind. Less blood (none), and even if it landed on your finger it wouldn't really do anything. In fact, I might move mine to the garden tonight to see what those holes in my hugels are.

Thanks for the ideas, guys!
George, doesn't covering the grass with hay lead to more grass seeds -> more grass? I could see straw working. I'll likely end up piling compost and straw on top of the whole thing. More biomass for all!
I found out today that the whole thing has been planted with clover and Jerusalem artichokes already. I guess it's not as hopeless as I imagined!

Emily Gilquist wrote:So the questions are:
1) how do I reclaim them from grass?

one of my many types of landscape work included being the lead horticulturalist at Indian Creek Country Club (an exclusive golf course, island, limited property, secure gated enclave...)

several of our native bunch grass beds had been neglected and were deeply invaded by an intense, barbed-wiry-tough, finger-slicing, strong grass among other south Florida invasive grasses, there were three primary "invaders."

the only solution that worked for long term was sitting in the beds and digging down with a long forked end weed eradicator, digging, pulling, digging, pulling... some invasive grass roots are fiercely strong and tenaciously deep/long... dried and woven, they make a great basket? or beneath veggie beds layered for ground fence animal prevention?

Emily Gilquist wrote:Thanks for the ideas, guys!
George, doesn't covering the grass with hay lead to more grass seeds -> more grass? I could see straw working. I'll likely end up piling compost and straw on top of the whole thing. More biomass for all!
I found out today that the whole thing has been planted with clover and Jerusalem artichokes already. I guess it's not as hopeless as I imagined!

In my case, which I should have shared, I have a bunch of old wet hay that has rotted over the last 10 months. We did use fresh hay last year though too. We have not seen much resprouting...yet. From my standpoint, when you're trying to get control of an already grassy area, using a lot of cut grass to smother it works fine. A 5-10 inch blanket of hay - or often times a machine packed section of a square bale that is 2-3 inches thick, really kills whatever it falls on. From there, as Ruth Stout proclaimed, you just keep adding hay each year.

We are early in our establishment, so a blanket kill is not an issue. As we add more and more perennials, I think this will become a challenge to mulch properly when unwanted plants come up. Although, if it isn't planted too densely with valuable plants, then a 2-3 inch thick square bale section will always have it's place.

In one section of grass that was killed by the hay last summer, I planted a fall cover crop with rye and some other stuff. It has come back up this year and is looking pretty nice, actually. So, if you wanted to select an area to sheet mulch or kill off with hay or straw (go thick), then come back with an ideal cover crop mix after removing the mulch, that may well work. It's a path I will likely take this year or next. All that hay on the hugels would be fine if I were doing transplants into it, but wanting to add seed, especially a seed mix broadcast, makes it a short term fix for me.