Using a wattle fence as retaining wall on terraced garden, bad idea?

My garden area at our new place is on a slight slope. I recently marked out the garden area and am planning to position the rows on the contour with the garden beds and walkways terraced a bit as it slopes downhill. I had initially planned on staking some logs on the lower edge of each bed to help hold in the soil as the terraces are cut. Realistically, I will not have enough straight, consistently sized logs to make this work and a single log may not be tall enough anyway. So then I was thinking, what if I made a wattle-type fence on the lower edge of the beds to hold the dirt similar to the photo below but wider terraces and not as steep. I have plenty of small black locust poles to use for the stakes and a massive hedge of forsythia and oriental bittersweet that I want to remove anyway that could work for the weavers. But, will it decompose too quickly to make it worthwhile since it will be against the soil on one side? My hope is that the soil will settle in the first season or two and since I won't be tilling it up every year, as the wattle breaks down the soil should be stable enough for me to replace the wattle every 5 years or so without having to re-do the whole bed.

What sort of ecosystem - in my constant winter "wet", I'd consider it pretty temporary, but it would allow me to get plants started while I looked to scrounge/purchase alternatives.

What do you intend to plant? If you could put deep rooted perennials against the wattle fence, or were planning to plant shrubs/bushes etc, I think it might work as the system would help the shrubs get started, and would be like hugel wood and hold moisture as it rotted.

What you don't want to create is the opportunity for a massive mud-slide, so you're wise to consider the angle of the slope, the potential extreme rainfall and whether you can redirect extreme rain away from the terraces.

The rows with the proposed wattle fencing on the down slop side would be for annual veggies unfortunately... all of the perennial shrubs and dwarf trees are around the perimeter. I'm not sure how to describe the climate, it's neither super wet or very dry... it's Mid-Atlantic US, western PA to be more precise. Temperate I guess... we do have wet periods though, and can get pretty heavy downpours at times.

It really isn't too steep, I can measure the actual slope tomorrow, but the soil map puts it around 15% if I recall correctly (that may be high actually) **Edit... the garden area has a 9% slope, it drops 4.5ft over the 50ft length. That means that for each 5.5ft terrace (40" planting bed and 2ft walkway) the 'retaining wall' on the downslope side will only have to hold back about 5 inches of soil height (realistically it will be more like 8 inches with the addition of compost and mounding of the row, but still... less than a foot of soil/material).

Howdy,

Locust is a rot resitant tree species. Removing/peelimg the bark will help the wood last longer, especially underground.

I did something similar in my garden. Here is my thread about it. Though it is too young to give a definitive answer.

Time will tell. I do plan to use more dry tolerant annuals until I get perrenials established, as this is the driest area of my garden.

Having built the terraces, it would be a shame to waste that labour and have them eventually wash out.

For me, I would start scrounging rock and broken brick to stomp into the edge of the terraces, and also to pile on top to capture soil that might otherwise erode.

I have heard that similar things are done on slopes here on the mountains, but in my many walks in the mountains I haven't seen many... so I'm assuming they eventually give way and are more of a stop-gap measure. The things I do see that have lasted are all dry-stack stone walls, some of which look older than the trees growing there now, so at least 20 years, probably more likely over 50. In some cases I'd guess there are dry-stack stone walls here that have been there for 100s or possibly approaching 1000s of years here. It's an old technique.

If I had the stone I'd look into dry-stacking it. Otherwise a living barrier might work better long-term.

Melissa, that wattle fence is going to look great when you get done.

Joylynn's garden looks really nice.  I can't really tell though it looks like she might have used lots of pine needles and leaves as mulch.

I wonder if a lot of leaves against the wattle fence would help with dirt washing away as suggested above?

L. Johnson wrote:The things I do see that have lasted are all dry-stack stone walls... In some cases I'd guess there are dry-stack stone walls here that have been there for 100s or possibly approaching 1000s of years here.

If I had the stone I'd look into dry-stacking it. Otherwise a living barrier might work better long-term.

I agree with L. Johnson here. All of the terraces that I have seen, in the Alps, Himalayas or here in Wales, use stacked stone. Many of them are incredibly old and seem to need minimal repair.

That said, I do think your terraces look beautiful and I'm sure they will serve you well. I've heard about the (legendary!) rot-resistance of black locust and, if it sticks around for long enough that your planting takes hold, the roots of those plants might hold everything together.

Is there a chance that your locust poles will strike roots? That could be seen as either a maintenance issue or a form of living barrier, as L. Johnson mentions.

A final thought is that, over time, terraces accumulate any soil that is washed downhill by rain and snowmelt, naturally building up miniature swales. I wonder if your retaining walls will have this effect or whether their "gappy" nature will prevent this. Certainly, they are less likely to collapse after a heavy rain as they will drain well.

With only about 5" (plus mounding) of step per bed, I think the locust posts will have no problem holding a wattle or sapling fence until the soil firms up. Just a few stones or a larger sapling (wrist/arm size) would likely hold the top edge for a long time. I think you would be better off just stacking the branches behind the posts as the photo shows rather than weaving a true wattle fence.

I made a wattle-edged garden bed for my kids' kiwi garden bed (more pictures in this thread). I built it with bamboo 4 years ago, and it's still doing well. My kiwis only needed to be watered two or three times last year, and it was a stupidly hot year last summer/fall.

the taller back-end of the garden bed

view from the side

view from the front--I think it might have cropped maybe 3 inches off the bottom

Looking at the pictures more closely, it looks like the bottom layers--and the upright posts--were bamboo. The entire front is woven bamboo. I ran out of bamboo, though, and switched to using alder from the woods for the edges. Alder rots a lot faster than bamboo, so I'm curious to see how much it's shrank in 4 years.

My main complaint has been weeds! Buttercup and grass really like to grow in those cracks, and that's really annoying. The above pictures are from 4 years ago--I'll try to take some new ones in the morning.

Melissa - Can the wattle-type fence made from black locust poles and plant material hold the soil effectively on the lower edge of the beds, or will it decompose too quickly since it will be against the soil on one side?

"Too quickly" is a relative term - black locust posts will be solid for decades, while the wattle material could weaken in two years if small and soft, or be good for five years if larger (say 1" plus) and more durable wood. Using 1" to 2" locust branches for wattling could last for a decade or more depending on climate. If you have unneeded trees of 5-6" size, simply laying logs where you want terraces will last for several years, and as the wood decomposes it will become fertile soil. In a reasonably damp climate with sun exposure, the logs will support grass that will resist erosion.