Laying Down Vetiver Hedges with Bags Along the Contour

We have been planning on conducting some Vetiver-in-bags experiments in catchments to slow water flow when these images were shared by  Jane Wegesa Fraser  of projects in Kenya. The images of the dry environment are from West Pokot County Kenya.
The images speak for themselves. 

I'm sure many  of you will relate to the soil profile in these photos and the dry conditions. 

Although you have to fill the bags and place them along the contour, the need for major earth works is lessened. Any chance that a downpour will wash your newly planted hedge away is also reduced as the bag creates its own levee, protecting the Vetiver roots from the force of any flow.

Using bags also allows for a more flexible bioengineering intervention, as it should be easier to follow the contour. Where lateral pressure is an issue -- either from water runoff, erosion or gravity -- wooden stakes are driven through the bags into the ground below to anchor them in place. 

The only problem is, of course, the plastic material -- polypropylene --  the bags are made from. Cheap and readily available as recycled waste,  polypropylene will break down and pollute the landscape.

Inevitably, microplastics will accumulate in the local soil and food chain. 

In the context of regenerating a degraded environment, maybe you may want to weigh up the efficacy of using these bags with the challenge of cost factors, as is the case in Kenya. 


One of our earliest experiments using hessian

What interests us is using bagged Vetiver like this, but with bags made from biodegradable material. You can purchase hessian sand bags and even hessian tubes that will suit landscaping work. But hessian, we've found, breaks down too quickly and is too porous to stand up to water flow. 

The best option we've found for biodegradable bags are 'potato sacks' made from jute. To make the investment go further, our plan was to split the bags down the middle length ways, and re-sew the flaps together so that you use a narrower and lighter bag. Unlike these images -- which have Vetiver slips planted in rows of three -- two rows would be the most you could fit into such a narrower bag. Maybe two would be a stretch in dry conditions.

Aside from the sewing labours -- the complication is cost. Jute is more expensive than hessian and a lot more costly  than bags made from polypropylene. 

However, cutting the bags in two, sewing them & stuffing with material -- needs to be compared to the energy outlay  required by other methods of Vetiver hedge planting. Once the bags are laid down -- it is a simple matter of stab and plant with slips. 

So stage one is bagging and laying down.  Stage two is planting.

The other advantage with the split potato  bag compared to these examples is that you'll require fewer slips as a single row should suffice in many instances. 

What you fill the bags with is another issue. Rather than have transport complications, filling the bags in situ makes sense. But  if you do that, why use the bags -- why not just dig a hole? 

If you check out this gallery, it's clear that just planting Vetiver in a hedge line leaves it open to many environmental challenges, which bagging would protect the plants from. 

While we had been thinking of concocting a mix that would energise plant growth inside the bags, sprinkling dry manure along the contour line and laying the bags on top would be a much easier process if you wanted to fertilise your plantings.

Just on bag mixes. Specific blends may be required if you intend to use bags across a watercourse.Some sand will be required if you want to create a dam or leaky weir. Otherwise the principles are the same except you also may want to stack the bags on top ofone another as well as together. Such as this example at right. Click on image to enlarge view.

In the Kenyan example, the mix was:

what we do is we fill bags quarters, carry and fill the ones on the contours 3 quarter full. Saw it and lay it down.. you also don't have to carry soils from very far away, we dig it inside the gully, mix it with 2 soils, 1 manure, 1 sand..

Jane Wegesa Fraser  kindly allowed me to share this gallery of images here. For a larger and consecutive view, just click on a photo.

Further examples of bagged Vetiver bioengineering: