Sawdust is inexpensive, readily available, and has many practical uses in the garden. It often gets a bad rap for "stealing" nitrogen from growing plants, but when used properly it can actually support the growth of your plants by helping to improve your soil. Sawdust can also be used to store crops, repel pests, deter weeds, and is handy for cleaning up accidental spills.
- Amend Your Soil: Add small amounts of sawdust to your soil to increase organic matter and improve its texture. Because sawdust is very slow to decompose, it works especially well in moist, heavy soils like clay, where soil amendments tend to break down quickly.
- Compost It: For composting purposes, sawdust is considered a "brown" (carbon) material, which can be added in alternating layers to balance out the "green" (nitrogen) materials like grass clipping and food scraps. Sawdust also acts as a bulking agent, allowing air into the pile. It takes approximately a year to transform raw sawdust into finished compost.
- Discourage Weeds: Not many gardeners know this, but sawdust (especially from hardwoods like walnut trees) is a natural weed killer. Sweep it between the cracks and crevices of concrete sidewalks and in between stepping stones to help prevent weeds from popping through.
- Grow Mushrooms: If you have ever considered growing your own mushrooms, sawdust can make a good growing medium. Unlike green garden plants, mushrooms lack chlorophyll and rely on other organic materials for their food. In nature, logs work well for this. In the garden, you can use a mixture of sawdust and woodchips. Growing mushrooms successfully requires monitoring temperature and light. For information and supplies, check out: http://www.mushroompeople.com
- Mulch With It: Sawdust has an acidifying effect on the soil, and is a good choice for mulching around acid-loving plants like conifers, blueberries, strawberries and rhododendrons. Keep in mind that fresh, non-composted sawdust will hog nitrogen as it decomposes, so using too much of it without adding supplemental fertilizer to the soil can cause a nitrogen deficiency in your plants.
- Pave a Path: Sawdust is the ideal material for creating an inexpensive garden path. It's soft, looks natural, helps control erosion, and it smells really great! Start by marking out your path. Clear away existing grass and weeds to expose the soil. Apply a thick layer of sawdust and tamp it firmly into place. Walked-on sawdust compacts quickly, so expect to refresh your path every few years.
- Repel Slugs: Sawdust (especially coarser sawdust) can help keep slugs at bay. Raise the foliage around susceptible plants and apply several inches around the base of stems.
- Soak Up Spills: Sawdust is highly absorbent, which great for cleaning up occasional drips and leaks from lawn and garden equipment. Keep a bucket handy in your garage or garden shed. Toss a handful of sawdust over the spillage, wait for it to be absorbed, then sweep it up cleanly with a broom.
- Store Root Crops: Root vegetables like carrots, beets, and turnips can be placed in a single layer and kept over the winter in a box filled with fresh sawdust. To maximize their shelf-life, store the box in a cool place like a semi-heated garage or unheated basement at approximately 35-40 degrees F.
Warning: Sawdust Can Rob Soil of Nitrogen
Using sawdust in the garden is not without its problems. Like other wood products, as sawdust breaks down and decays it locks up important nutrients in the soil - namely nitrogen. Spreading raw or "green" sawdust in the garden can lead to a nitrogen deficiency resulting in the malnutrition of your plants. Fortunately, there are a couple of ways around this:
- Let the sawdust simmer in the compost pile for at least a year before using it in the garden.
- When using raw or "green" sawdust, provide regular applications of a slow-release organic fertilizer to counteract any nitrogen deficiencies.
- Avoid using large quantities of sawdust around plants at one time. Start with small amounts and see how your plants react.
If your soil is low in organic nutrients to being with, pay extra attention to your plants during the growing season. If they start to appear light yellow in color, they may be suffering from nitrogen deficiency. You can counteract this by side-dressing them with an organic fertilizer such as alfalfa meal or blood meal, compost, or manure.
The best sawdust for garden use has a slightly course texture - the type created as a byproduct of sawmills or chain saws. Very fine sawdust, like the dust created from sanding furniture or cabinets, has a tendency to become packed down and anaerobic so it's not a good choice. Also, make sure you know what type of wood was used to create the sawdust.
Walnut, cedar, and chemically treated wood should never be used on garden plants, but may be suitable for soaking up spills or creating garden paths. To source sawdust in your area, check with local lumberyards and tree removal companies. Many will offer sawdust for free (or at least very inexpensively), especially if you're willing to pick it up and haul it home yourself.