Small spaces, big appetites

In a small garden, every pot, trough and raised bed is working harder than it looks. Roots have less room to roam, so they exhaust the nutrients in their compost far faster than plants growing in open ground. A single tomato in a ten-litre pot can strip that compost of everything it needs within six weeks of planting.

That doesn't mean feeding more, though. The trick is feeding at the right time, with the right kind of feed, at the right strength. Get that rhythm right and you'll be rewarded with healthier growth, more flowers and a longer cropping season — without the root damage and salt build-up that comes from a heavy hand.

Spring: start gently

From March onwards, the temptation is to get everything going at once. Resist it. In cold, wet compost, roots aren't taking much up anyway, and unused nutrients simply wash through the pot and out across your patio.

• Fresh compost needs no feed. Most multipurpose and peat-free blends contain enough to keep plants going for four to six weeks after potting. Adding liquid feed on top of that is one of the commonest mistakes in small gardens.
• Top-dress instead. Scrape back the top couple of centimetres of compost in established pots and raised beds and replace it with a handful of garden compost or worm-worked material. It feeds slowly as it breaks down.
• Begin liquid feeding once growth is clearly underway — usually late April in the south, mid-May further north. Start at half the recommended strength for the first two or three weeks.

Early summer: balanced feeds for growth

Through late spring and early summer, plants are building stems, leaves and roots. This is the moment for a balanced feed — one where the nitrogen, phosphorus and potassium figures on the bottle are roughly equal, or simply a general-purpose feed.

For containers, a weekly dose at half strength beats a monthly full-strength one every time. It keeps nutrient levels steady rather than swinging between feast and famine. Always water first, then feed, so roots aren't sitting in a concentrated solution, and never feed dry compost or a plant that's wilting from drought.

Leafy crops, salads and herbs in a window box, young shrubs, and anything recently moved into a bigger pot all do well on this. Slow-release granules mixed into the compost in April will carry most containers through to midsummer on their own.

Flowering and fruiting: switching to tomato food

Once a plant stops building and starts producing, its needs change. Potash drives flowers and fruit, while too much nitrogen at this stage gives you a magnificent heap of soft green leaves and precious little else.

This is where tomato food earns its place. Wait until the first truss of tomatoes has set — small green fruits about the size of peas — before you switch. Then feed weekly and keep going until the last fruits are ripening.

• Outdoors: tomatoes, peppers, chillies, aubergines, courgettes, runner and French beans, and strawberries all benefit.
• Containers and baskets: petunias, fuchsias, begonias and most trailing summer bedding flower far longer with a high-potash feed from midsummer onwards.
• Don't switch too early. A hungry young plant pushed onto tomato food before it's established will simply stall.

Seaweed tonic: the gentle pick-me-up

Seaweed products aren't a replacement for a proper feed — the nutrient levels are far too low for that. What they offer is trace elements and natural growth compounds that help plants shrug off stress.

Reach for it after transplanting, after a cold snap, during a heatwave, or when something looks sulky for no obvious reason. Dilute according to the label and either water it in or spray it onto the leaves in the early evening, when the foliage won't scorch in the sun. It sits comfortably alongside your regular feeding rather than instead of it. A fortnightly dose through a difficult summer can make the difference between plants that limp along and plants that keep going.

Autumn, winter and the overfeeding trap

By late August, growth is slowing. Taper off liquid feeds and stop altogether by mid-September so plants can harden up before the cold arrives. Anything dormant over winter needs nothing at all; a light feed on a winter container of evergreens will only produce soft growth that the first hard frost will ruin.

Watch for the signs of overfeeding, which usually appear towards the end of summer:

• A white crust on the surface of the compost or around the rim of the pot, as salts accumulate.
• Scorched, brown leaf edges and roots that look dark and shrivelled rather than white and firm.
• Wilting despite damp compost, because damaged roots can no longer take up water.
• Lush, floppy growth with few flowers, plus a sudden crowd of aphids drawn to soft new tips.

If any of that sounds familiar, stop feeding and flush the pot with two or three volumes of plain water, letting it drain freely. In a small garden, a little restraint goes a long way: feed little and often, always onto damp compost, and let the plants themselves tell you what they need.