Organic September: What It Means for Your Greenhouse and Garden

Every September, the UK food world goes organic for a month. Shelves get rearranged, logos turn green, and somewhere between the veg aisle and the checkout you end up asking yourself: should I be buying organic?

If you grow your own, that question lands closer to home. You already decide what goes in your soil and what gets sprayed on your tomatoes, so you're most of the way there already.

But what does being organic mean in a practical sense? And how achievable is it for us gardeners? Rather more achievable than you might think.

What does organic actually mean?

For a gardener, organic means growing without synthetic chemicals. No chemically derived fertilisers, no synthetic bug sprays, no weedkillers.

What you use instead is the fun part. Fertility comes from compost, manure and feeds you make yourself (or good organic feeds!), which build up the soil rather than just topping up the plant. Pest control comes from encouraging the insects that eat your pests, putting up barriers, and keeping plants healthy enough to shrug things off.

That's the whole of it. The commercial version of the word involves certification, inspections and a conversion period of a few years, but none of that applies to your back garden. Nobody's inspecting your greenhouse!

Does organic mean no pesticides?

Not quite, and this catches a lot of people out. Organic growing allows some naturally derived treatments, like insecticidal soaps and certain plant-based sprays. What's out is the synthetic stuff.

It's worth knowing that "natural" doesn't mean harmless either. Plenty of approved organic sprays will kill ladybirds and lacewings alongside the aphids.

TOP TIP: Spray at dusk when pollinators aren't about, and only spray when you actually have to.

What to stop using, and what to use instead

Here's the shed swap list. Nothing here is difficult, and most of it will save you money.

Two of those are worth a word. Metaldehyde pellets have been banned for outdoor use in Great Britain since 2022, so that one isn't a choice. And peat isn't technically banned under organic rules, but peat extraction wrecks bog habitat that took thousands of years to form. Retail bagged peat is being phased out in England anyway, and every decent supplier now has a peat-free range, so it's an easy one to put right.

Feeding the garden organically

This is where most gardeners assume organic gets complicated. It really doesn't. It's just slower, cheaper and a great deal more satisfying.

Start a compost heap. Everything else follows from this. Two bays if you have room, one working and one rotting down. Rough rule is half greens (grass clippings, veg peelings, coffee grounds) to half browns (cardboard, autumn leaves, prunings). Turn it when you remember. You'll have lovely usable compost in six to twelve months, made entirely from things you were going to throw away.

Grow a comfrey patch. Bocking 14 is the variety to get, because it doesn't set seed and take over. Cut it three or four times a season, stuff the leaves in a bucket or a length of downpipe with a lid, and let it rot. It doesn't smell wonderful, but it produces a black liquid that's high in potassium, which is exactly what tomatoes, peppers and courgettes want when they start fruiting. Dilute it roughly fifteen to one.

Nettle feed for leafy growth. Same method, nettles instead. Higher in nitrogen, so it's the one for early season growth and leafy crops rather than fruiting ones.

Seaweed extract. The one bought-in product we'd always find shelf space for. A great general tonic, and especially useful for plants under stress and for hardening off.

Well-rotted manure. Horse or cow, from a local farm if you can find one. Needs to be at least a year old. Spread it on beds in autumn and let the worms do the digging for you.

Blood, fish and bone or chicken manure pellets. Both are organic-friendly slow-release options for when you want something straight from a bag.

Green manures. Sow field beans, phacelia or crimson clover on empty beds over winter. They stop nutrients washing out, add organic matter when you dig them in, and phacelia in particular will be humming with bees if you let some flower.

Pest control without the spray

Bring in the predators. A single ladybird will get through hundreds of aphids. Lacewings, hoverflies and parasitic wasps do the same job for free, and they'll happily move in if you make them welcome.

Just remember to grow things with small open flowers they can actually feed from, like:

Poached egg plant (limnanthes), the best hoverfly magnet there is

Phacelia

Calendula

Fennel and dill

Yarrow

Marigolds

Let a couple of carrots or parsnips run to seed as well and you'll be knee-deep in hoverflies by midsummer.

Companion planting.

Some companion planting advice is folklore, but these four really do earn their place:

Biological controls in the greenhouse. This is the big one, and it's where a greenhouse really earns its keep. An enclosed space means the predators you introduce stay put and get to work. You order them by post, they arrive in a sachet or a tube, and you simply hang them up.

Nothing outdoors works this reliably, because your predators simply fly off.

Nematodes for slugs. Watered onto the soil, they work underground and target slugs without touching anything else. More expensive than pellets, but wonderfully effective, especially on a raised bed or a treasured hosta collection.

Physical barriers. Copper tape round pots, sheep wool pellets and crushed egg shells for slugs. Fine mesh or fleece over brassicas for cabbage white. Cardboard collars round brassica stems for cabbage root fly. Unglamorous, but they work beautifully.

Beer traps and evening patrols. A sunken yoghurt pot of beer catches a surprising number of slugs. A torch and ten minutes after rain catches plenty more.

Ferric phosphate pellets. If you do want pellets, these are the organic-approved option and the legal replacement for metaldehyde.

Good growing conditions. Half of all pest problems are stress problems. A plant that's been kept properly watered, isn't pot-bound and has plenty of air moving around it will shrug off things a struggling one won't. Good ventilation in the greenhouse matters enormously here, which is exactly why every Rhino comes with automatic roof vents and side louvres as standard.

The upsides to organic gardening

Your soil improves every year. This is why gardeners who go organic tend to stay organic. A well-fed bed in year five is a completely different substance to one in year one. Better structure, holds water better, needs less from you.

Fewer pest problems over time. It sounds backwards, but it's true. Stop blanket-spraying and the predators move in and do the work for you. Spray broadly and you lose the ladybirds along with the aphids, so the aphids come back faster.

It's kinder on the wallet. Compost and comfrey cost next to nothing once you're going. Bottles cost money every single season.

You know exactly what you're eating. No residues, no wondering. If you're growing for little ones, that usually settles it.

More wildlife. Your garden becomes part of a corridor rather than a gap in one, and a garden full of bees and hoverflies is a lovely place to spend an afternoon.

The honest downsides to organic gardening

It's more work. Hoeing takes longer than spraying. Making compost takes longer than opening a bag. Although plenty of us would call that the good bit.

Yields can dip at first. While the soil's still building, you may get a little less than you would with synthetic feed. It evens out after a couple of seasons, but the first year can test your patience.

Some things have no good organic answer. Blight on outdoor tomatoes and spuds is the classic. Resistant varieties, spacing and timing all help, and some wet Augusts you still lose the crop. Under glass you control the moisture on the leaves, which is why greenhouse tomatoes are so much safer.

It's slower to react. When aphids explode, a synthetic spray sorts it by teatime. Organic methods work over days or weeks, so you'll want to spot problems early and accept a little damage along the way.

Organic-branded products aren't automatically better. An expensive bottle with an organic logo is often no more effective than a bucket of comfrey, and considerably less satisfying.

Where to start

Don't convert the whole plot at once. Start with the greenhouse.

It's your most controlled space, it's where biological controls genuinely come into their own, and it's where you'll see results fastest. Switch to peat-free compost, get a comfrey bucket going, order a biological control for whatever pest keeps coming back, and run a season.

Then get that compost heap going, because everything else grows out of it.

By next September you'll know whether the rest of the garden is ready to follow.