Preparing a bed

Four things: mineral particles (sand, silt, clay), organic matter, air, and water. The air and water sit in the gaps between particles, and about half of a good soil is gap. Living organisms, mostly bacteria and fungi, are a tiny fraction of the weight and do most of the work.

Texture is the mix of sand, silt, and clay, and you can't change it much. Squeeze a damp handful: if it falls apart it is sandy; if it holds a shape and rolls into a ribbon longer than an inch or two it is clay. Or fill a jar a third full of soil, top with water, shake, and let it settle. Sand drops in a minute, silt within hours, clay over a day.

Structure is how particles clump into crumbs. Crumbs are held together by fungal threads and the sticky by-products of microbes, which is why healthy soil breaks into small, loose pieces and compacted soil comes up in slabs. Structure is what lets roots, air, and water move, and organic matter is what builds it.

A few percent organic matter changes how a soil behaves. In sand it holds water and nutrients; in clay it opens the soil up for drainage. Most garden soil is in the low single digits. Compost, leaf mold, and mulch are the way up.

Worms, pill bugs, millipedes, and beetle larvae shred dead plant material first. Bacteria and fungi finish it, digesting what's left and releasing nutrients a little at a time. What remains at the end is humus, dark and stable, which can persist in soil for decades.

Browns (dry leaves, wood chips, cardboard, straw) are mostly carbon and break down slowly. Greens (grass clippings, kitchen scraps, fresh weeds) are rich in nitrogen and break down fast. Decomposers need both. All browns sits for years; all greens turns to slime.

Decomposition happens where the mulch touches the soil, because that's where the organisms and the moisture are. Wood chips left on the surface feed the soil slowly and don't rob nitrogen from your plants. Digging fresh wood chips in does, for a season. Mulch on top, never mixed in.

Decomposition speeds up in warm, damp conditions and almost stops in cold or dry ones. That is why sheet mulch laid in fall works over winter and spring, and why a compost pile that has dried out simply sits there.

The gardener's job is mostly to keep a layer of organic material on top and leave it alone. Leave leaves where you can. Add an inch or two of compost a year. Skip rototilling: it burns through organic matter, breaks up fungal networks, and brings buried weed seeds up to the light.

Raise it if you're growing vegetables, most perennials, or lawn, which want 6.0 to 7.0. Limestone is the standard fix. Leave it alone if the plants are acid-lovers like blueberries, rhododendrons, and azaleas.

Lower it only for plants that need it, such as blueberries, or when yellowing between the veins points to locked-up iron. Elemental sulfur is the lasting fix. In strongly alkaline soil, growing in raised beds or pots is often easier than fighting the ground.

Don't adjust anything. Skip the lime and sulfur, and spend the effort on compost and mulch, which keep pH steady.

Used grounds are close to neutral. They're a fine addition to the compost pile, and they won't move your pH.

It acidifies for a few days at most, then the soil bounces back. It damages soil life and roots in the meantime.

It raises pH briefly and adds sodium, which damages soil structure. Use limestone.

They do contain calcium carbonate, but they break down so slowly that the effect on pH is negligible. Add them to compost for the calcium, not for the pH.

Layer or mix about two to three parts browns to one part greens, by volume. Keep it as damp as a wrung-out sponge. Air matters as much as the mix, so build on bare ground, not a slab, and fluff it now and then.

A pile at least three feet across and three feet high, turned every week or two, heats to 130 to 160 degrees and finishes in a couple of months. A smaller or unturned pile is a cold pile: it takes six to twelve months and doesn't get hot enough to kill weed seed reliably.

Fruit and vegetable scraps, coffee grounds, eggshells, leaves, straw, grass clippings, spent plants, and weeds that haven't set seed. Shred or chop big pieces, since small pieces break down faster.

Meat, dairy, and oils attract rodents. Dog and cat waste carries pathogens. Diseased plants, seeding weeds, and perennial weed roots only belong in a pile that really gets hot. Leave out glossy paper and treated wood.

A sour or ammonia smell means too wet or too many greens: add browns and turn it. A dry pile that sits there needs water and some greens. A pile that won't heat is usually too small, too dry, or all browns.

Finished compost is dark, crumbly, and smells like a forest floor, and you can't pick out what went in. Sift out the chunks and put them back in the pile. Spread an inch or two on top of a bed rather than digging it in.

Stop tilling, keep the soil covered, and add organic matter, and earthworms show up. Their tunnels carry air and water down, and their castings are rich in nutrients. Buying and releasing them doesn't help; they leave if the soil isn't right.

Red wigglers, which are a different species from garden earthworms, turn kitchen scraps into castings in a bin on a porch or under a sink. Give them moist, shredded cardboard or newspaper for bedding, bury scraps in it, and keep them between about 55 and 77 degrees. Harvest castings after three to six months.

Asian jumping worms are invasive in much of North America. They thrash and flip when handled, leave soil that looks like coffee grounds, and have a smooth, pale band that circles the body flush with it. They spread in mulch, compost, and potted plants. Don't use them in compost or share soil. Seal them in a bag and put it in the trash.

In forests that never had earthworms, they strip the leaf layer that native plants depend on. Don't dump bait worms or compost worms in the woods.

Garden soil packs down in a pot, drains poorly, and brings weeds and disease with it. Containers need a light mix that holds water and air at once.

Equal parts by volume: peat moss or coco coir for moisture, perlite or pumice for air, and finished compost for nutrients. Moisten everything before you mix, and wear a dust mask. Coir is the common alternative to peat; rinse it and soak it first.

Leave the compost out and use a finer blend of coir or peat with perlite or vermiculite. Compost can carry pathogens that rot seedlings. Sieved leaf mold can stand in for part of the peat.

Mix equal parts potting mix and grit, such as pumice or coarse sand. Sharp drainage matters more than richness.

Potting mix breaks down and compacts. Tip it out each spring, break up the root mass, and blend in fresh compost and some new mix before you refill.

Dig a hole a foot wide and a foot deep and fill it with water. Let it drain, then fill it again and time the second fill. About an inch an hour is about right. Under half an inch an hour is a problem, and faster than six inches an hour is sand that will dry out.

Puddles that last a day mean poor drainage, and a spot that stays soggy in spring will rot roots by midsummer. Walk the garden after a heavy rain and note where water sits and where it runs.

Add organic matter over the whole bed, not just the planting hole. Raise the bed. Or choose plants that like wet feet. Compaction is a common cause: skip the wheelbarrow across the bed, don't work wet soil, and loosen with a fork rather than a tiller.

Sand mixed into clay can make something like concrete. A layer of gravel at the bottom of a hole or pot doesn't help either; water stops at the change in texture and pools above it. Amend the whole bed, or build up.

Sandy soil holds little water or nutrient. Compost and a thick mulch both slow it down. Group the thirstiest plants where you can reach them and let drought-tolerant plants have the dry corners.

An inch a week from rain or hose is a rough baseline, delivered in one or two soakings rather than a daily sprinkle. Deep watering sends roots down; shallow watering keeps them at the surface. A drip line makes it automatic.

Raised beds help where soil is poor, contaminated, compacted, or drains badly, where you're building over grass, or where you want to garden without bending. On good, well-drained soil they are optional.

Keep beds three to four feet wide so you can reach the middle from either side. Eight to twelve inches deep suits most plants, and six is the minimum on loosened ground. Go to fifteen or more for root crops over bad soil or for accessibility.

Leave two to three feet between beds, wide enough for a wheelbarrow. Mulch the paths thickly so the weeds that come in don't reach the beds.

Untreated cedar or redwood lasts years. Galvanized steel, stone, and brick last longer. Avoid railroad ties and anything treated with older arsenic-based preservatives. Don't line the sides with plastic, which traps water against the wood.

Put cardboard on the grass underneath, then fill with a mix of about two-thirds topsoil and one-third compost. Bagged raised-bed mix works for small beds. For larger beds, buy by the cubic garden: length times width times depth, in feet, divided by 27.

Raised beds warm earlier in spring, drain faster, and dry out faster in summer, so they need more water than in-ground beds. The soil settles a few inches in the first year. Top it up with compost each spring.

Annual weeds are shallow and come out easily, and the job is to get them before they flower. Perennial weeds have deep roots or runners and return if any piece is left. Check the weeds page if you aren't sure, and check that a seedling isn't one of your own plants first.

Soil that's damp releases roots whole. Dry soil snaps them. If it hasn't rained, water the bed the evening before.

Pull low, close to the crown, with a steady pull and not a jerk. A dandelion weeder or hori-hori gets taproots out intact. If the root snaps, dig for it.

Bindweed, quackgrass, and creeping Charlie come back from any fragment. Loosen the soil with a fork, lift the root mass out, and shake it clean without letting it fall back on the bed.

On a dry, sunny day, slide a sharp hoe just under the surface to slice seedlings off. They dry out where they lie. Don't dig deeper than an inch or you'll bring up new seed. I like the Japanese gardening hoe specifically for this purpose.

Weeds that haven't set seed and have no runners can go in the compost. Anything seeding, and any perennial roots, go in the trash or soak in a bucket of water for several weeks before composting.

Ten minutes a few times a week beats an afternoon a month. A seedling is a one-second job; a flowering weed is a project.

Light is what wakes most weed seeds, and mulch blocks it. Wood chips, shredded leaves, or compost all work. Keep it a few inches off stems and trunks. Go thinner where you want self-sowers to seed.

Bare ground is a vacancy, and something will fill it. Plant close, use groundcovers between larger plants, or cover empty beds with mulch or a cover crop.

Every digging brings buried seed to the surface, and a bed holds years of it. A bed you don't dig grows fewer weeds each year. See the natural lawn guide for cover-crop timing.

Prepare the bed, water it, and wait two to three weeks for the weeds to sprout. Hoe them off shallowly, then plant or sow without digging again. You've used up a flush of seed before your plants are in the ground.

Drip lines and soaker hoses put water at the roots and leave the soil between plants dry, which holds back weeds. Overhead sprinklers water everything.

One weed gone to seed can drop thousands. Cutting or pulling flowers before the seed ripens is the single most useful habit. Perennial weeds give in if you keep cutting the tops, because the roots run out of stored energy.

A few harmless volunteers in a thick planting aren't a problem. Spend effort on the aggressive ones: runners, thorny weeds, and anything about to seed.