Creating a Small Indoor Garden on a Budget

Start with supermarket herbs

The cheapest indoor garden you will ever build begins in the chilled aisle, not the garden centre. A living pot of basil, mint, parsley, coriander or chives costs roughly the same as a bunch of cut herbs, and it keeps growing instead of turning to slime in the fridge drawer. Buy two or three, and you have the beginnings of a green corner for under a fiver.

The catch is that these pots are not really pots — they are seed trays in disguise. A single supermarket basil can hold twenty seedlings crammed into a thimble of compost, all fighting for the same water and nutrients. That is why they flop within a fortnight and why so many people assume they simply cannot grow herbs indoors.

Give them room and they repay you. Water the pot well an hour beforehand, then tip the whole rootball out into your hand. Tease the roots apart with your fingers, or cut the block into three or four sections with a knife, and pot each clump into its own container of peat-free multipurpose compost. Water them in, keep them out of bright direct sun for a few days, and you have four or five plants for the price of one. Mint is usually a bundle of separate cuttings and will happily become four pots on its own. Rosemary and thyme are woodier and prefer a cool, bright spot, so keep them away from radiators.

Containers you already own

You do not need to buy a single pot. Yoghurt tubs, mushroom trays, tin cans, cut-down plastic bottles, old teapots, colanders, cracked mugs and Kilner jars all work beautifully. Terracotta looks lovely and lets roots breathe, but plastic holds moisture longer, which suits thirsty herbs like mint and parsley.

The one thing every container must have is drainage holes. Punch them with a hot skewer, a drill or a sturdy nail, and remember that a layer of gravel in the bottom of a closed pot does not improve drainage — it just raises the water table closer to the roots. Holes, then a saucer or an old side plate to protect the windowsill, is the whole system.

• Size sensibly: pot up when roots appear through the drainage holes, not before. Going too big too soon leaves soggy compost around tiny roots.
• Keep it tidy: file down sharp edges on tins, and give glass jars a saucer as they have no drainage at all — use them for water-propagated cuttings instead.
• Line wire baskets with an old cotton t-shirt or a bit of hessian before filling with compost.

Compost and feed without the expense

Buy the largest bag of peat-free multipurpose compost you can store — the price per litre drops sharply with size, and a bin liner full will keep for a season if you keep it damp-ish and out of direct sun. Mix in a handful of perlite or horticultural grit for anything that likes sharp drainage, such as rosemary, thyme or succulents.

On feeding, be sceptical of kitchen folklore. Banana peel water and eggshell tea offer very little in a form plants can use. A single bottle of general-purpose liquid feed, diluted to half the recommended strength and given every fortnight through spring and summer, will last you years and costs pennies per plant. That is the whole fertiliser budget.

Free plants are everywhere once you start looking. A stem of trailing pothos or tradescantia rooted in a glass of water becomes a new plant in three weeks. Spider plants throw off babies you can pot straight up. Swap cuttings with neighbours, and ask at community gardening groups — most growers are delighted to offload spare rooted offcuts.

Light without a big spend

A bright south- or west-facing windowsill will carry most herbs and leafy plants through the summer. Rotate your pots a quarter turn each week so they grow straight rather than leaning into the glass, and wipe the inside of the window now and then — grimy glass can cut light levels noticeably.

For the darker months, a cheap LED grow bulb in an ordinary E27 fitting is the single best investment you can make. Around 10 to 20 watts of full-spectrum or 6500K daylight output is plenty for a shelf of herbs. Screw it into a clip-on desk lamp, position it 15 to 30 centimetres above the foliage, and put it on a plug-in timer for twelve to fourteen hours a day. Any further away and your plants will stretch into pale, leggy stems.

White walls, white card or a sheet of kitchen foil behind the shelf bounces light back onto the leaves for nothing. In winter, move plants off single-glazed sills at night — the cold draught and condensation do more damage than the darkness.

What grows best for very little

• Mint, chives and parsley: near-indestructible, happy in a partly shaded kitchen.
• Basil: loves warmth and light; pinch out the tips to keep it bushy.
• Cut-and-come-again salad: a living salad tray from the supermarket can be split and potted on for weeks of leaves.
• Spring onions and leeks: stand the root ends in a glass of water, then pot them up once roots appear.
• Pothos, spider plants and tradescantia: tolerant, easy to propagate, and forgiving of a forgetful watering can.

Keeping costs — and plants — down

Most indoor plants are killed by kindness rather than neglect. Water only when the top couple of centimetres of compost feel dry, and always empty the saucer afterwards so roots are not sitting in a puddle. Fungus gnats, the little flies that hover over houseplants, are almost always a sign of constantly wet compost.

Hard tap water leaves white marks on leaves and gradually raises soil alkalinity, so let it stand overnight to reach room temperature, or collect rainwater in a bucket outdoors if you can. Group plants together on a tray of pebbles to lift humidity, and keep a new arrival away from the rest for a fortnight in case it brings pests with it.

Finally, do the sums. A supermarket herb plant that you divide and keep going can supply you for months, while the equivalent in cut bunches runs into pounds every week. Add a reused jar, a bulb on a timer and a bit of patience, and the greenest corner of your home may well end up the cheapest too.