All gardeners will eventually learn that exposed soil in a garden causes problems. It invites weeds, it loses moisture quickly, and it decreases the quantity of soil life which we need to support the life of our plants. Therefore, one of my top priorities throughout all soil management activities is to keep the surface covered.
In a perennial flower garden or orchard, it's pretty easy to cover the soil. We can just add a thick layer of organic mulch, and repeat as needed. In a garden filled with annual vegetables, our needs are a bit different. We need easy access to the soil surface at least once a year for direct seeding or the transplanting of small seedlings at the proper depth and spacing. If we use a bulky organic mulch material like leaves, straw, or wood chips, we'll have to spend a lot of time moving all that material any time we need to plant. That's possible but I'm never keen to add unnecessary work. What we really need is a quick way to cover and uncover our vegetable garden beds, and landscape fabric fits that need perfectly.
With just a few seconds of labour, I can thoroughly cover one of my garden beds with a sheet of landscape fabric and immediately gain full control of any exposed surface, conserving valuable moisture and killing any weeds that try to grow on the covered surface. When it comes time to plant another vegetable crop, I can remove the landscape fabric just as quickly to reveal a clear, moist, and weed-free bed of soil ready to accept my next seeds or transplants.
The trouble with landscape fabric is that when it covers an entire bed, it doesn't allow vegetables to grow either ... or does it? Imagine being able to keep the surface of the soil covered, plant your vegetable crops at the same time. It turns out that we can accomplish this with landscape fabric and some perfectly placed holes! You won't find these custom weed barriers in your local garden centre, but you can make them yourself.
Making the Custom Weed Barriers
To make our custom weed barriers, I roll out a sheet of landscape fabric cut to the same length of our standard beds, and use a plywood template to help me make evenly spaced holes in the fabric where each of my vegetables will be planted.
The holes are not cut, but rather burned with a small blow torch. The burning immediately melts the woven polypropylene fibres, bonding them to each other and preventing fraying. If you ever want to experience the nightmare of working with frayed polypropylene landscape fabric, just try cutting a few holes with scissors or a utility knife.
Once the hole burning is done, we've got ourselves a custom weed barrier that can be used repeatedly for decades to come, but of course, each custom weed barrier will only work for one hole spacing, so here's where some forward thinking can really benefit us in the long run.
Selecting the Hole Patterns
If I mindlessly start churning out custom weed barriers with unique hole spacing for every single crop, I will need a new plywood template for every crop and I'll be left with a very large collection of custom weed barriers that are all different and incompatible with most other crops. Instead, I'd rather look closely at the ideal plant spacings used in my crop selection and come up with just a few custom weed barrier patterns that will each work for multiple crops. This way, I'll need to make fewer wooden templates, and it won't be such a hassle to organize my weed barriers ... so that's exactly what I did.
I spent a bit of time playing around with our Seed to Table plant spacing calculator, which helps me optimize my bed spacing for each crop, and it turns out that I can satisfy the spacing requirements for all of our crops with just 4 custom weed barrier patterns. Well, I suppose I shouldn't say "all of our crops" because there are quite a few crops that just aren't compatible with this method of weed control. High density crops like carrots, peas, or baby greens would require so many holes in the landscape fabric that there wouldn't be any fabric remaining to suppress weeds. Therefore, we're really only able to use this technique for crops planted with a density of 3 plants/sqft and lower. Now, on with our hole spacings of choice.
The highest density spacing we use for these custom barriers is 4 rows spaced 6 inches apart with in-row spacing of 6 inches. With so many holes in this pattern, I felt that I should keep the holes as small as possible so I've been using 2 inch holes for this one. The small holes makes for tight transplanting space but I've gotten better at this (a dibbler helps) and it's worth the effort for the superior weed control. I used this 4 x 6" barrier a lot for lettuce when I ran my market garden. Today, I use it more for onions when I know I'll be working with in areas with higher weed pressure.
The next spacing we use is 3 rows with an in-row spacing of 12 inches. For crops grown at this spacing, we are usually transplanting 2 inch soil blocks so an increase in hole size to 4 inches makes the work a lot easier. We have been using the 3 x 12" barrier for corn a lot recently, but this planting density works for several other crops as well.
I used to grow strawberries with the 3x12" inch hole spacing but this proved to create a matted row that was too wide. Berries near the centre were harder to see and I started to have trouble with grey mold because of the limited air flow within the patch. This led me to create a new spacing template for our strawberries that had the same overall plant density but only two rows. We still use this pattern today and it uses 2 rows with in-row spacing of 8 inches.
The last custom weed barrier spacing I would recommend, is another 2 row pattern but with wider in-row spacing. This 2 row pattern moves the rows to 15" apart with an in-row spacing of 16 inches. This spacing is suitable for peppers, trellised melons and cucumbers that are pruned to one leader, small early cabbages, kale, broccoli, and cauliflower. I haven't created any custom landscape fabric covers with these specifications yet because our weed pressure is pretty minimal these days and the crops I would use it for are pretty easy to weed around. If I was starting from scratch again though, this would be one template in my collection.
This week I documented all of the exact dimensions of these 4 different templates, wrote down some instructions, and listed all of the the crops that are compatible with each spacing. Seed to Table course members can now find the guide for this Custom Weed Barrier Template Collection posted here in our online Classroom. If you follow the dimensions provided, you can cut all templates from one 4' x 8' sheet of plywood.
There are several other widely spaced crops that would be excellent candidates for custom weed barriers, such as tomatoes, squash, tomatillos, and sunflowers, but with our 30 inch wide beds, we only need one row of these crops to fill out the bed. Instead of cutting one row of holes in a full sheet of landscape fabric, I prefer to instead place the fabric over the pathway between two beds and let the edges reach up to the centre leaving a narrow gap there in which I can plant my widely spaced crop.
I guess we've come full circle now, since I started and ended with examples of using full unaltered sheets of landscape fabric. Let that be a reminder to never make your solutions more complicated than they need to be.
Using the Custom Weed Barriers
I'll wrap this one up by addresses a few common questions about using this landscape fabric.
Which fabric is best? The only type of landscape fabric I recommend is UV treated woven polypropylene. There are different brands out there that all work. What's important is the type of material, not that it is called "landscape fabric" or "weed barrier". You can find a link to one source on my Tool Shed page so you can see an example.
How do you hold the fabric down? We use metal landscape fabric pins (sometimes called staples) to fasten the fabric to the soil. I stick one at each corner and at least one every 5 feet along the edges. Once I use a pin with a sheet of fabric for the first time, it stays with the fabric so that each time I roll out the fabric the pins are there, ready to use again.
How do you water through the fabric? This was one of my biggest concerns before using this fabric. Sales staff at my local garden centre claimed that water could pass through this fabric easily, but it sure looked a lot like a tarp I would use for camping so I had my doubts. However, in the interest of weed suppression, I took a chance on the water issue and splurged for a few rolls of landscape fabric to put to the test. Based on my observations, water does indeed pass through the weave of the fabric because there are many very tiny holes, but this passage is very slow. As a result, water applied from above does tend to run to the low spots or off the side of the bed, so the water distribution under a bed covered with landscape fabric is going to be somewhat uneven. We avoid this problem by using drip irrigation under our landscape fabric.
So, now that you know the basics, is a collection of custom weed barriers something you want to add to your vegetable growing toolkit? I certainly have no regrets about experimenting with this technique and I am confident that we'll continue to use these barriers for many more years to come.
