Hey Karen- I'm sorry- I just call it witch grass, (I heard a neighbor call it that......) acts similar to Quack grass up north... It is a perennial, it goes dormant & brown in the winter & drought of summer, then greens up every spring..... I don't have to reseed it every year...It's indestructible! I put it on the bottom of my 5' tall compost pile last summer, & it snaked up & through it..... I'm terrified of this stuff, at least back home in NY, you could cover it with black plastic & it would die..... I don't want to resort to that, I'm hoping that it will give up the ghost, so I can plant my babies in my new beds.....

The reason the I turned it was because it wouldn't get wet, and I thought that was the only way to get moisture throughout. It didn't seem to be doing anything when I just let it sit. I will try to get some browns in there I guess. I don't have enough UCG or veg. scraps to make much difference. And I purchased the cotton seed hulls for the veg. garden because I like the way they mat and don't blow away, but seems like everything I read suggests not to use them on veg, because they can use whatever chemicals they want on cotton since it isn't a food crop. I didn't want to risk it. thanks, justsaymo

The how, the why? I haven't used this method for over 20 years, but I'll take a shot at it. What I have to say is about marginal soils, not the deep silt soils of agricultural areas, nor mostly sand soils. People who have deep silt topsoil don't often come here looking for help and sand is a special situation. Most all marginal soils support plants of some kind. It's not that they won't grow anything, but they fail to grow the plants we want in a vigorous fashion. A typical marginal soil has a thin layer of topsoil over a compacted subsoil. The subsoil is often seen at a depth of 6 inches and the clay faction of the subsoil is usually 20% or greater. Compacted subsoils that contain clay suffer oxygen deficiency. Plants differ in their ability to tolerate an oxygen deficiency, and most of the plants that gardeners want can't use soil where the oxygen is depleted. Such plants have their root zone restricred to the top 6 inches. Roots that do grow deeper are inefficient and add little to the plant growth. But you don't even get a 6 inch depth for roots. The top 2 inches are subject to swings in moisture and temperture that remove this area from the active root zone. Now let's look at putting a lasagne layer over such a soil. The first thing that happens is the temperture and moisture in the top 2 inches of soil is stabilized and becomes a part of the active root zone. Where you had 4 inches, you now have 6, a 50% increase in available soil volume. It's like having a plant in too small a pot and moving it to the next size larger. Both organics and clay act as a buffer to hold plant nutrients loosely. When pure water comes in contact, these nutrients are given up and the water becomes a solution of the the things plants need. Rainfall perculating through a lasagne bed results in a weak compost tea seeping into the soil. So now we have 6 inches of root zone and a source of plant nutrients. Not great, but a big improvement over the original soil condition. Maybe this is good enough. If you choose plants that have some tolerance to oxygen deficiency and space them wide enough apart to give each plant it's needed soil volume, the result is good. An example might be hosta spaced with mulch between the clumps. It can be a neat look and is in fashion. There can also be a delayed benefit to a lasagne bed. Depending on the severity of the soil, the line of oxygen deficiency can be sudden and hard or it can be a gradient over several inches. Where the case is the latter, the increase in biomass in the active part of the soil leads to an increase of worms. Because the upper part of the oxygen deficiency zone is not completly devoid of oxygen, worms now encroach this area. As worm tunnels open airways, the upper part of the depletion zone gains oxygen and the line of oxygen deficiency is pushed ever deeper into the soil. This is one of the cases where you should not dig the soil.Where this occurs over a period of years, you may achieve a deep active root zone where plants of all types can be grown with much closer spacing. The delayed benefit is not always seen. It happens very slowly, if at all, where the clay faction of the subsoil is greater than 30%. If this is the type soil you have and you want to grow closely spaced plants of low tolerance to oxygen deficiency you will be disappointed with a lasagne bed. The best method of remediation of oxygen deficiency will differ with each soil type. Do whatever is needed and you too can have closely spaced vigorous plants ....

If you create the bed now, using the technique you describe, it will not be "mature" until next spring. You cannot grow the Nassella or Cortaderia in pots over your zone 7 winter. I would pot up the grasses when they arrive, and let them grow until early fall. Then plant them in pockets in your new bed. Use regular garden soil as backfill, somewhat amended with something which will provide good drainage, if necessary. Woodchips as mulch is no problem. They will not "burn" the small plants. Try not to mix the chips into the soil, and keep them a couple of inches away from the crowns of the plants.