A field guide to backyard composting in Western Washington. Pick a method, troubleshoot a pile that isn't cooperating, decide what's safe to add, and know when it's ready to use. Numbers come from WSU's Pacific Northwest Gardener's Handbook, chapter 6.
What your compost thermometer is telling you
40°F6080100120140160°F
Worm binideal range
Curing80°F or below
Hot phasewell-managed pile
Kills weed seedsand most pathogens
Worms go dormant below 50°F and die above 80°F. Slow piles never reach the kill zone, which is why they can't handle weed seeds or diseased plants.
What are you composting, and how much effort will you put in?
Lots of yard waste, and I'll turn it weekly
Hot pile
Size
At least 3 × 3 × 3 ft. About 1 cubic yard (roughly a 5 × 5 ft base, 3 ft high) holds heat year-round, even through cold winters.
Mix
About 2 parts bulking agent to 1 part energy material by volume, blended rather than layered. See the materials table below.
Moisture
Damp; a squeezed handful gives a drop or so of water.
Turn
Weekly with a pitchfork for the first 4–6 weeks, adding water as needed.
Ready
At least 3 months: the hot phase, then 2–3 months curing.
Why
Reaches 130–150°F, so it kills most weed seeds and pathogens, and it's done fastest.
Bins are optional. A three-bin setup (two for turning, one for curing) makes it easier.
Yard waste, but I'd rather not manage it
Slow pile
How
Build a pile and keep adding fresh material through the first year. Then turn it once and leave it alone for a second year.
When
Start during spring or fall cleanup, when yard waste is plentiful.
Result
Usable compost after about two years. Leftover stems and rinds can go straight into the garden.
Keep out of slow piles: diseased plants, weed seed heads, weed runners (rhizomes), and unchipped woody branches. The pile never gets hot enough to kill or break them down.
Mostly kitchen scraps
Worm bin, kept indoors
Why
Indoors you control temperature and moisture, and worms keep working through winter. See worm bin setup.
Scraps can also go into an outdoor pile if buried fully, be buried directly in the garden, or go in the municipal yard waste cart.
Seeded weeds, runners, diseased plants, or meat
Municipal yard waste cart
Why
Commercial piles get hot enough to kill weed seeds and pathogens. Some cities also take food waste like meat; check local rules.
Sorting your materials
Type
Character
Examples
Bulking agents
Dry, porous, low nitrogen
Chipped tree and shrub prunings, sawdust, wheat straw, corn stalks, chipped Christmas trees
Energy materials
Wet, dense, high nitrogen
Garden trimmings, fruit and vegetable waste, grass clippings, livestock manure
Balanced on their own
Compost well alone
Deciduous leaves, horse manure with bedding, spoiled hay
Chop or shred coarse materials. You don't need soil, starters, or activators; the raw materials already carry the microbes.
Ch. 6, Composting Methods and Materials
The pile won't heat up
A working hot pile reaches 120–150°F within days and holds it for several days to several weeks, shrinking to about half its starting volume.
Squeeze a handful from the middle. What happens?
It's dry and crumbles
Fix
Add water while turning, then recheck until a squeeze gives a drop or so.
Water streams out
Fix
Mix in dry bulking agent, cover the pile, and in the rainy season build a larger pile.
Why
Waterlogged piles lose air and stall.
Moisture is right
What's it made of, and how big is it?
Mostly woody or dry material
Fix
Add energy materials like grass clippings or garden trimmings. Nitrogen fertilizer works too, but greens are preferred.
Smaller than about a cubic yard
Fix
Build it bigger. Small piles lose heat and dry out fast, especially in cold weather.
None of the above
Fix
Let it be a slow pile. It will still decompose; it just won't kill weed seeds.
Ch. 6, Hot Composting and Troubleshooting
It smells
Is the pile wet and packed down?
Yes, or it's heavy on grass and food scraps
Fix
Turn it more often and mix in bulking agent. Hold back on water.
Why
Odor comes from too much wet material and too little air.
No, but food scraps are near the surface
Fix
Bury scraps fully in the middle of the pile.
Ch. 6, Troubleshooting and Odors
Rodents, raccoons, or flies
Where's the problem?
Outdoor pile
Fix
Bury fruit and vegetable scraps completely. If animals keep coming, switch to a pest-resistant bin or move scraps to a worm bin or the yard waste cart.
Prevent
Keep meat, cheese, fats, and baked goods out entirely.
Worm bin with fruit flies
Fix
Stop overfeeding and keep all food covered under bedding.
Worm bin with rodents
Fix
Keep the lid shut, weighted, or latched, and keep meat and dairy out.
Ch. 6, Pests; Vermicomposting
Can this go in?
What is it?
Weeds that have gone to seed, weed runners, or diseased plants
Is your pile reaching 130–150°F?
Yes, a managed hot pile: it can go in
No: put it in the yard waste cart instead
Better yet, pull weeds before they set seed.
Dog or cat waste
Never. Parasites survive composting and stay infectious.
Meat, cheese, fats, baked goods
Not in home piles. They attract pests and cause odors. Some municipal programs accept them.
Woody branches
Fix
Chip them first. Chipped wood is a good bulking agent; whole branches won't break down.
Fire isn't a backyard risk. Moist piles and small piles don't ignite. Only large piles with a very hot zone next to a dry zone can.
Ch. 6, What Not to Compost and Fire Safety
Using manure or straw
What's the concern?
Food safety from manure
Where will the compost go?
Root crops, leafy greens, or strawberries eaten raw
What
Keep fresh manure out of compost for these beds, or wait a year or more before applying it.
Why
These crops carry the highest risk from Salmonella and E. coli O157:H7.
Crops you'll cook thoroughly: low risk
Herbicide residue in hay, straw, or manure
What
Ask the supplier whether clopyralid or aminopyralid was used on the hay or straw, including any fed to or bedded under the animals.
Why
These herbicides survive composting and damage tomatoes, peppers, potatoes, beans, and peas. They don't harm people or animals.
Neither is labeled for home lawns, so your own grass clippings aren't the usual source. The chapter doesn't describe a test for residues.
Ch. 6, Manure and Pathogens; Persistent Herbicides
Worm bin setup and trouble
Household
Bin size
Kitchen waste
Worms
Two people
~14 gal (2 cu ft)
~2 lb per week
About 2 lb of worms for every 1 lb of waste added per day
Four to six
1 × 2 × 3 ft (6 cu ft)
~6 lb per week
Example: 3.5 lb a week (0.5 lb a day) needs about 1 lb
Setting it up
Worms
Red worms (Eisenia foetida or Lumbricus rubellus). Nightcrawlers and garden earthworms won't survive in a bin.
Bedding
Corrugated cardboard or newspaper torn into 1-inch strips, no glossy paper. Wet it with about 3 lb of water per 1 lb of dry bedding.
Grit
About ¼ cup of topsoil per cubic foot of bin.
Cover
Keep 4–6 inches of clean bedding over the worms and food.
Feeding
Bury food under bedding, rotating among spots (a 2 × 2 ft bin has about nine). Vegetable and fruit scraps, coffee grounds and filters, tea bags without staples, crushed eggshells, paper, bread.
Avoid
Meat, dairy, oils, citrus and other acidic foods, onion and garlic, bones, salty food, glossy paper, pet waste and litter.
What's going wrong?
Squeezed bedding drips five or more drops
Fix
Too wet. Add dry shredded bedding. Target is 75–90% moisture: just a few drops on a squeeze.
Worms are sluggish or dying
Fix
Check temperature. Keep the bin at 59–77°F; below 50°F they go inactive, above 80°F they die.
Going away for a few weeks
Fix
Feed a little extra before you leave. Worms can go 3–4 weeks without food.
Too many worms
Fix
Give some away, start a second bin, or add them to an outdoor pile.
Harvesting castings
When
At least once a year.
How
Push everything to one side. Put fresh bedding and food in the empty side and wait about a month for the worms to move over, then scoop out the old side.
Ch. 6, Vermicomposting
Is it done, and how do I use it?
Has it been at least 3 months, and does it stay cool when turned?
Not yet, or it reheats
Wait
Keep curing. Finished compost is dark and crumbly and stays at or below 80°F.
Why
Uncured compost can carry compounds that harm plants. That matters most in seed-starting and potting mixes, less when small amounts go into garden soil.
Yes, it's dark, crumbly, and cool
What will you use it for?
New bed
How much
Mix 1–3 inches into the soil before planting.
Screen?
No need; chunks keep breaking down.
Established bed
How much
½–1 inch per year.
Mulch
When
Early summer once plants are established and soil has warmed, or after fall harvest to cut winter runoff and erosion.
Note
Nutrient-rich compost feeds weeds too, so it's a poor long-term mulch. Work it in at the next planting.
Potting mix or seed starting
How
Fully cured only, screened through a ½-inch screen.
Runoff-prone site? Soil test before adding compost, since excess nutrients can wash off.
Ch. 6, Finished Compost and Using Compost
The composting year
Western Washington timing for a backyard pile and worm bin.
Shaded entries are my inference from the handbook's general rules, not timing the handbook states outright.
Season
Do
Why now
Mar–May
Spring cleanup: start a slow pile or build a hot pile. Dig finished compost into new beds.
Yard waste is plentiful.A hot pile built now and turned weekly should be ready around mid-summer, based on 4–6 weeks hot plus 2–3 months curing.
Jun–Jul
Spread compost as mulch once plants are established.
Soil has warmed; mulch holds moisture through the dry season.
Aug–Sep
Keep piles damp; add water when turning.
Dry piles stall.Late summer is the driest stretch here, so piles are most likely to dry out. Based on the moisture guidance.
Oct–Nov
Fall cleanup: start a slow pile with leaves and trimmings. Mulch beds with compost after harvest. Cover piles as rains start.
Leaves are a balanced material that composts on its own. Mulch cuts winter runoff; covering keeps piles from waterlogging.A slow pile started now will be usable in fall two years out.
Dec–Feb
Keep outdoor piles covered and at least a cubic yard. Keep the worm bin indoors.
A big pile holds heat through winter; small ones stall. Worms go dormant below 50°F.
Yearly
Harvest worm castings. Top-dress established beds with ½–1 inch.