Constructing my raised beds for vegetables and getting rid of the grass in my yard by sheet mulching is reminding me of how important two things are in our world — the soil and the trees that grow from it. My raised beds are made of trees. The paper and cardboard I’m laying down as a weed barrier within and without them are made of trees. The mulch that I’m laying down over the grass to make paths, smother weeds, and benefit my perennials is made of trees. And eventually, all that wood will become a part of the soil. And that soil, again, may nurture trees — and in turn, all the things that depend upon them.
(Rich earth and wood chip: White Lightning planting mix from Dean Innovations and free chips from an arborist via Chip Drop.)
The chip is wood waste from an arborist that I got delivered to my house by signing up with Chip Drop — and I didn’t have to spend a red cent to get it. This was especially great because I need A LOT of chip to sheet mulch my large lot, which was mostly lawn when we bought the place. And I can do this as many times as I need to replenish the mulch for my landscaping. Chip Drop is available in places other than Portland, too.
I’ve been reusing cardboard boxes as a weed barrier for my sheet mulching. The biggest challenge has been getting enough boxes to do such a big job. I used all of our moving boxes, and all of the boxes in which new purchases for the house were packaged, but there’s still a lot of area left to cover. I just can’t bring myself to buy new cardboard for this — yet — so we’ve been hitting up local businesses for empty boxes. Big stores now usually recycle their boxes themselves — which is good, but it makes this harder for me! Even smaller establishments apparently have a high demand for their cardboard waste — also a good sign that Portlanders are reusing, but another obstacle to my sheet mulching success.
In addition to getting rid of weeds and unwanted grass, sheet mulching will improve our yard’s soil, which is rocky and sandy, being a former river bed. After the mulch and cardboard have degraded, I’ll have a much better growing medium for native plants and lawn alternatives in my garden.
The wood I used to build most of the frames for my raised beds is juniper, from Sustainable Northwest Wood. I chose this product because juniper is invasive in eastern Oregon. Which is weird, because it’s actually a native. But former fire suppression has caused Western Juniper to go wild east of the Cascades, and it’s ruining the grasslands. So cutting and using that juniper is the best solution to the problem. Juniper is also a great material for outdoor use, because it’s naturally water resistant. NSW told me it will last IN THE GROUND for fifty years. If it performs that well, I will never have to replace my bed frames or the posts for the grape trellis, which are also juniper; at least, not until I’m ninety years old.
(Red rosin paper as a weed barrier within a juniper raised bed frame — just waiting for that lovely black planting mix.)
Since I’m experiencing a used cardboard shortage, I’m experimenting with a different material as a weed barrier in my raised beds. A roll of red rosin paper was left in our basement by previous owners. I’m guessing they used it as an under layer of the new laminate flooring that covers most of the rooms. I did some research on it, and I think it may work well for this purpose. It’s made of recycled materials, it’s biodegradable, non-toxic, and ecologically safe — at least the kind that isn’t coated in polyurethane is. This roll of paper is rough and, well, papery, not like plastic, so I doubt it has a polyurethane coat. I’ll be turning over the soil and weeding in my beds regularly, so a weed barrier doesn’t need to be as thick there as it does for the rest of the yard. The one drawback to using the rosin paper may be that it does contain alum, which could lower the pH of soil. But most vegetables tolerate or prefer more acidic soil, rather than more basic soil, and amending soil accordingly for each type of crop to give it the preferable pH is the best practice, anyways.
The soil I’m using to fill my raised beds, White Lightning planting mix from Dean Innovations, I’ve used before, with great results. It’s made of pumice, worm castings, mycorrhizal fungi, mineral dust, topsoil, fruit and vegetable compost, dairy manure compost, mushroom compost, and river sand. Pumice provides aeration and drainage and improves water retention. Worm castings are just earthworm poo. It’s refined nutrition for plants and contains beneficial microbes. Mycorrhizal fungi forms a symbiotic relationship with plant roots that both helps them absorb nutrients and protects them. Mineral dust provides minerals that plants need, topsoil is just soil, compost provides nutrients, and sand improves drainage. I’m not sure a planting mix can really get better than this. I’ll plant straight into it the first year, then turn it into the soil at the bottom of the beds, and still have a great medium for growing my veg, only topping it off with my homemade kitchen compost once a year. Earthworms will move into my beds themselves or come from my compost bin, and I can keep the fungi alive by growing crops year round and keeping turning to a minimum. It won’t take much to keep the soil in my beds healthy and thriving!