Start a compost heap in September: materials, ratio and timing

TL;DR

A compost heap is free soil improvement: collect autumn leaves (brown), green plant stems and vegetable kitchen scraps (green), layer them in 1:2 ratio, and in 3-6 months you have nutrient-rich compost for your garden. Upload your front yard to [gardenworld.app](https://gardenworld.app) and see what soil type you have; compost will transform it.

Why September for composting

September is harvest month (green plant stems abundant) and leaf month (brown leaves start falling). This is PERFECT timing: both ingredients in abundance. Moreover, compost started now has 3-6 months until spring to break down - next March you have ready-to-use compost for your spring planting.

Compost heaps without good brown-green ratio (or without enough of one type) work poorly. September gives you both. This is no accident: nature works this way.

Materials: brown and green

Two categories of matter:

BROWN (Carbon-rich): Leaves (deciduous trees, shrubs), straw, chopped twigs (fine), unglazed paper, cardboard boxes, wood chips. These are DRY, CARBON-RICH materials. They break down SLOWLY but give structure to compost.

September leaves are king. Use all falling leaves. Collect in rubbish bags, store outside. This is free brown matter!

GREEN (Nitrogen-rich): Vegetable kitchen scraps (peels, cores, lettuce-ends, food scraps non-meat), mowed grass, green plant stems from garden pruning, manure (horse, chicken, cow), food-scraps. These are WET, NITROGEN-RICH materials. They break down FAST and give heat.

September green stems from autumn pruning are perfect.

AVOID:

• Disease vectors (fungal/viral infection): do not compost
• Weed seeds: do not compost (compost doesn't get hot enough)
• Animal waste (meat, fish, bone): attracts animals and stinks
• Waxed paper: doesn't break down
• Feathered creatures (birds, rabbits)

Ratio: the golden formula

This is where many gardeners fail. Too much green and you get stink-mud. Too much brown and it doesn't break down for months.

Perfect ratio: 1 part GREEN to 2 parts BROWN (by volume, not weight). This is the minimum for well-mannered compost without stink.

Practical building scheme:

1. Layer brown (10 cm) - leaves, paper
2. Layer green (5 cm) - grass, vegetable kitchen
3. Layer brown (10 cm)
4. Layer green (5 cm)
5. Repeat until heap is roughly 1 meter tall

Heavier compost heaps (1.5+ meter) get hotter and break down faster. Light heap (0.5 meter) is slower but works too.

Moisture content: Dry as straw? Too dry. Dripping with water? Too wet. Gold: feels moister than crumbs, but squeezing doesn't produce dripping water. Start with this moisture and your compost is golden.

Construction

No expensive compost bin needed. Three options:

Option 1: Corner of your garden. Toss heap right on ground. Cheap, simple, works great. Advantage: soil organisms (worms, insects, fungi) migrate from surrounding soil into your heap and accelerate decomposition.

Option 2: Pallet framing. Use four wooden pallets (free from discount goods stores) and bind them together in square. This makes ~1 m x 1 m x 1 m container. Cheap, open (airflow helps).

Option 3: Plastic compost bin. 100-300 euros, compact, closed (less smell/animal attraction). Better for small gardens than loose heap.

Location: Partial shade, not full sun (sun dries faster). Good drainage underneath. Not right against your house (compost can have mould spores).

Process: breakdown

Now you let it work.

Month 1 (September-October): Heap starts to stink (normal!). This is bacterial activity. Smell disappears in week 2-3. Temperature in heap rises (you can feel warmth when you place hand on top if close enough).

Month 2-3 (October-November): Original materials become unrecognisable. Leaves fall apart. Grass disappears. Vegetable kitchen-scraps are slimy and gone. Temperature starts dropping (bacteria have spent energy).

Month 4-6 (December-March): Material is now black, crumbly, earth-like. This is compost-gold. Smell is earthy, not stink. Original structure completely unrecognisable.

Microbes: Your compost does NOT work by itself. Bacteria, fungi, worms and insects do the work. These are free gardeners. They need nutrition (green), structure (brown), moisture and enough oxygen. Good heap-building provides this.

Turning (optional): Many gardeners "turn" their compost monthly (forking/remixing). This accelerates breakdown by introducing oxygen. This is OPTIONAL. Lazy composters don't turn and compost takes 6+ months - OK. Ambitious composters turn and takes 3 months - OK. Your choice.

Frequently asked questions

Can I put meat in my compost?

Not really. Meat attracts rats and other animals. Also, compost doesn't get hot enough to kill bacteria. Keep meat/fish/bone out. Vegetable-kitchen-scraps only.

How long until I can use my compost?

3-6 months if you do it right (good brown-green ratio, moist). 6-12 months if you let it break down slowly. January-March next year is realistic time for first harvest.

Will my compost really stink?

Yes, weeks 1-2 will smell like rotten-eggs (ammonia). This is normal and disappears. Permanent stink means: you have too much green (not enough brown). Add brown and mix/turn.

Can I use compost before it fully breaks down?

Yes. Partially broken compost is also nutrition. Use it once it is crumbly enough to work into planting holes (not too many slimy chunks).

What if I have no leaves?

Not ideal. Use paper, cardboard, straw. Plenty of grass (green) helps too. Not perfect 1:2 ratio? Use what you have. Careful moisture-keeping and turning helps.

Step-by-step

Step 1: Gather materials (mid-September)

Collect all leaves in plastic bags. Chop green stems and plant waste. Collect vegetable kitchen-scraps in bucket. Start stacking what you have.

Step 2: Build your heap (late September to October)

Layer brown, layer green, layer brown, repeat. Target roughly 1 meter tall. Check moisture (hand-test).

Step 3: Months of waiting (October to March)

Let bacteria do their work. Optionally turn monthly. Smell normal weeks 1-2. No other care needed.

Step 4: Harvest compost (March)

Compost looks black, crumbly, earthy. Toss in garden borders. Use for potting soil when seeding. Use for planting holes when planting.

Plan your own September garden

At [gardenworld.app](https://gardenworld.app) you can upload your front yard and see what soil type you have. Compost will soon become the best investment for soil improvement. Start your compost now in September and next spring you have nutrient-rich earth for every planting hole. No expensive artificial fertiliser needed; your own compost does the work.