OK to Add Sand in Lasagna Bed?

15 years ago

Hi,

We are going to be building several large lasagna beds for shrubs, and later on flowers. There will most likely not be enough material (believe me we are doing some major scrounging!) and we are wondering if its okay to add some sand during the layering process? We want to plant in September and will put good amended soil around the plants. Just wondering if the sand might delay the composting? It will be clean quarry sand. Also we have access to a lot of fir wood chips. They are fairly small and slightly decomposed and have quite a few needles in them. Can we add some of this, or would that also retard the decomposition?

Thanks very much for your help! This forum has been a wealth of information as I have learned about Lasagna Beds.

Rod

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Comments (10)

Kimmsr
15 years ago
Why add the sand? What would sand contribute to the Lasagna bed?
nwboater
Original Author
15 years ago
We would add the sand to help raise the height of the bed. The beds will be on top of grass that is on top of very rocky sandy soil which is almost impossible to dig in. Since I don't think we can get enough material this summer to build the beds to the height we need to hold the plants I wondered if it would be okay to add the sand for additional bulk.

I have no idea what it would contribute, other than the bulk we need, thus my inquiry to find out if it would be detrimental or okay to use.

Thanks for your response.

Rod
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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 ....
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jbann23
15 years ago
Ah, I don't think so. I can't visualize planting shrubs in a lasagna bed as you probably won't get all that much support for the plants. Couldn't you dig nice sized holes for your shrubs amongst the lasagna bed and blend in a goodly amount of compost? Maybe then a bit of sand wouldn't hurt. IMO shrubs need a fairly good root zone.
adirondackgardener
15 years ago
The lasagna scheme may work for short-lived annuals but I think I see a fatal flaw in using it for perennial shrubs.

Since the so-called "Lasagna Method" is little more than the age-old sheet-composting technique, and the goal of sheet composting is to quickly rot and feed your soil, I think I would first decide if my soil will benefit from adding more sand. Perhaps a lot of reasonably good top-soil rather than straight sand may be better in the long run.

The reason: your horizontal compost pile will disappear pretty quickly, having been incorporated by natural forces into your soil. That's the ultimate goal of compost, to become part of the soil's compostion. (Humus is the organic portion of your soil that is left after all decompostion of organic matter has taken place.) Consider it often takes Ma Nature thousands of years to create an inch of soil. And she burns through a lot of organic matter in the process.

My point is to consider that if you are going to be planting shrubs by setting them on top of your natural soil line and building up the "new soil" line mainly by sheet composting, you will have to maintain that level of composting forever lest your shubs find themselves sitting high above the actual soil line like a beached whale. "New soil" in quotes because compost (ephemeral) is not soil (permanent.) The sand you are considering as fill should be deep enough to raise the true level of your soil to the height needed by the root balls of your shubs. That will be what lasts, the compost will be gone in a relative heartbeat. That's why I suggested using topsoil, so the permanent soil is of a reasonable quality once the compost is exhausted.

In your case, I would forget the "lasagna scheme" since this is to be a permanent bed with deep rooted perennials. Look to loosening the existing soil as much as possible (with a pick axe or roto-tiller if necessary) to get your shubs' roots down to a level they will survive should you lose all interest in adding huge amounts of fresh compost every year, or else build the soil up with actual soil, augmented by compost. Or combine those two thoughts, dig down some and build up some.

Good luck.

Wayne
Kimmsr
15 years ago
The only thing sand might contribute, other than unneeded bulk, would be drainage and drainage will not be an issue on the sand you have.
annpat
15 years ago
Wayne, thank you for mentioning that "lasagna" gardening is just Pat Lanza coining a cute name for gardening methods she didn't think up, but pretended she did. Her book irritates the heck out of me. Not so much as a nod to Ruth Stout.
burry
15 years ago
Hi Annpat,

I just read one of the three Pat Lanza books and she did mention Ruth Stout. I think there is even a drawing. I think it might not be in the first book, but the one on herbs or small areas.

Gina
adirondackgardener
15 years ago
Annpat,

When anyone asks me about "lasagna" I suggest a good Italian cookbook or Ruth Stout's books on gardening.

I was also a fan of her husband, Rex's books, absolutely not about gardening but when Nero Wolfe was not solving mysteries, he was very often investigating food. (Maybe not lasagna and perhaps a little too often shad roe...)

Wayne
nwboater
Original Author
15 years ago
Hi Wayne et al,

Thank you all very much for the good information and explanations. Looks like I am going to have to seriously reconsider my approach. Sure glad you explained all this before I did a lot of mis-directed work!

Rod
softmentor
15 years ago
and sand????
(horrified look of terror) NOOOOOOOOOOOOOOO!
-smiles his jolly smile-
consider the ingredients of concrete and you will understand. It's cement and sand and water.
No, do NOT add sand

as to the phrase lasagna gardening:
annpat said:
* Posted by annpat (My Page) on
Thu, Jul 3, 08 at 8:37

Wayne, thank you for mentioning that "lasagna" gardening is just Pat Lanza coining a cute name for gardening methods she didn't think up, but pretended she did. Her book irritates the heck out of me. Not so much as a nod to Ruth Stout.

that is correct. She actually got the word/idea from me. I described the way I stack a compost pile and called it compost lasagna. I also described the way I do mulching, mentioning that it was very much like Ruth Stouts method, (and Max Alth "How To Farm Your Back Yard The Mulch Organic Way") I had learned a lot from both of them. I described adding the layers of different materials over time right in the garden instead of composting in piles and having to turn and move the material. I have used some variation of this method since 1977.
She did ask me if she could use the idea in her book and I said yes. It would have been nice to get a mention, but it's not a big deal, and I'm not looking to get rich. I'm just glad the idea got out there and people are using it.
as Paul Harvey would say. "and now you know the rest of the story"
Arthur Futterman
Indio CA

OK to Add Sand in Lasagna Bed?

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