Clearing beds in September: what belongs on the compost heap

September empties the beds, and suddenly you’re standing next to heaps of haulm, leaves and roots. Most of it is excellent compost material — a small part is not. Sort it wrong, and you’ll spread the same pathogens back across your beds next spring.

Most of it can go on the heap without a second thought

Healthy foliage, spent flowers, cabbage leaves, courgette vines, lettuce trimmings, carrot tops — all compost. The coarser the material, the more it helps to shred or chop it first; thick stems otherwise take two years to break down.

The mix matters. Lush green material on its own turns slimy and starts to smell. Always add a layer of structure: leaves, chopped twigs, straw or cardboard. A good rule of thumb is roughly equal volumes of soft green and dry brown.

Three kinds of leftovers to keep off your own heap

Late blight on tomatoes and potatoes. Brown, scalded-looking patches on leaves and stems are the giveaway. The pathogen overwinters mainly in living tissue — forgotten potato tubers in the soil, for instance. Where both mating types occur it also forms tough resting spores that persist in plant debris. So infected haulm should stay off a home compost heap, which rarely gets hot enough.

Clubroot. If you pull up knobbly, distorted brassica roots while clearing, that’s the classic culprit. Its resting spores persist in the soil for decades. Those roots never go on the compost — and that patch should stay free of brassicas for at least seven years. That means not just cabbages, but radishes, mooli and kohlrabi too, and mustard or fodder radish sown as a green manure.

Perennial weed roots and seed heads. Ground elder, couch grass and bindweed resprout from the tiniest fragment. And anything that has already set seed will germinate straight out of your finished compost next spring.

Powdery mildew is the big exception

Those white, floury coatings on courgettes, cucumbers and squash look dramatic in September — but they’re the harmless case. Powdery mildew lives on living host tissue and goes with the plant you clear away. The second point matters more: the species involved are highly host-specific, so courgette mildew won’t jump across to your brassicas.

In short: mildewed leaves can go on the compost. There’s no need to carry every white leaf to the bin.

Where the diseased material should go

The right destination is your municipal green-waste bin or collection point. Commercial composting facilities run their windrows at 55 to 70 degrees Celsius for extended periods, which reliably kills spores and weed seeds. The heap behind your shed reaches those temperatures at best briefly, and only in a few spots.

What you should not do is burn the material. Open burning of garden waste is generally prohibited in Austria and Germany, with only a few regional exceptions, and Swiss cantons restrict it in much the same way. The green-waste bin is the easier route anyway.

Beans and peas: leave the roots in the ground

A trick that costs nothing and pays off: when clearing beans and peas, cut them off close to the soil rather than pulling them out. The roots carry nodules full of nitrogen-fixing bacteria. Leave them in place and they rot down right there, releasing that nitrogen exactly where the following crop will need it.

The top growth goes on the compost as usual. And the bed is now nicely set up for a hungry feeder next year — brassicas or courgettes will thank you for it.

Write down where things went wrong this year

The bed is empty in October, and by March you no longer remember which row the blight hit first. That’s exactly the moment two lines in a garden journal pay off: which bed, which disease, how severe.

Come spring, you have a real basis for crop rotation instead of planning from memory. In Rootivo the note stays attached to the bed itself, and the bed planner flags it when you bring a crop back to the same spot too soon.

Im Lexikon: Tomate