Why Bother Rooting Supermarket Herbs?

Those bunches of basil and mint on the supermarket shelf have usually travelled a long way to reach your kitchen, and most of them are sold as living plants, still capable of producing roots. A single pot of basil costs about the same as a packet of seeds, yet it offers you a dozen potential new plants. For anyone with a windowsill rather than a garden, that is a genuinely useful bargain. You get fresh flavour within weeks, you learn how herbs grow, and you avoid paying again for something that regrows for free.

The trick is knowing which herbs will co-operate and which will sulk. Some root in a jam jar of water on the kitchen sill with almost no effort. Others need gritty compost, patience and a bit of warmth. Match your method to the plant and you will have far more success.

Pick Your Battles: Which Herbs Root Readily

Not everything sold in a supermarket will root from a cutting, and it saves frustration to know the difference before you start.

• Easy in water: basil, mint, lemon balm, and sometimes oregano and marjoram. Basil and mint are the reliable pair — roots appear in ten days to a fortnight in summer.
• Possible but slower: rosemary, thyme and sage. These are woody, so take cuttings from the softer new growth at the tips and expect three to six weeks. A little rooting hormone powder helps.
• Not worth trying: parsley and coriander. Both have a taproot that resents disturbance, and supermarket plants are usually old and already running to flower. Grow these from seed instead — coriander sown in a pot on the windowsill will crop in about a month.

Also consider splitting rather than rooting. A supermarket basil pot is usually a dense clump of seedlings crammed together. Easing them apart and potting them into three or four separate pots gives you stronger, bushier plants than any cutting will.

Rooting Cuttings in Water: The Simple Route

Take a stem about 10–15 cm long, cutting just below a leaf joint with a clean pair of scissors. Strip the lower leaves so that no foliage sits below the waterline — submerged leaves rot and turn the water sour. If you are rooting mint, take a piece with a node or two, as roots emerge from those joints.

Stand the cuttings in a clean glass jar with about 5 cm of water. A clear jam jar is ideal because you can watch progress. Place it somewhere bright but out of direct midday sun, and change the water every two or three days. Skipping this is the single most common reason cuttings fail; stale water encourages bacteria and slime.

Roots should appear within a fortnight in warm weather. Don't leave them swimming for weeks — once they reach about 3 cm, move them into compost. Longer roots become brittle and often struggle to adapt.

Potting On into Compost

Use a peat-free multi-purpose compost mixed with about a fifth grit or perlite for drainage. Herbs loathe sitting in sodden roots, and small pots on a windowsill are easy to overwater. A 9 cm pot is a good size for a single cutting; anything larger holds too much wet compost for a small root system.

Make a hole with a pencil, lower the roots in gently, and firm the compost around the stem. Water lightly and keep the pot somewhere warm and bright for a few days while it settles. If you are potting up in spring or early summer, growth will be quick. In November, expect everything to slow to a crawl — that is normal, not failure.

Keeping a Small Space Productive

A south- or west-facing windowsill gives the six hours of light most culinary herbs want. Turn your pots a quarter-turn each week so they grow evenly rather than leaning towards the glass. Keep them clear of radiators, which dry the air and scorch foliage.

Harvest by pinching out the growing tips just above a pair of leaves. This is the single best thing you can do: it gives you something for the pot and encourages the plant to branch rather than grow into a leggy spike. Feed with a weak liquid feed every fortnight from spring to late summer, and not at all in the darkest weeks of winter.

Common Problems and Quick Fixes

• Cuttings turn to mush: the water went stale or leaves were left submerged. Start again with a clean jar.
• Yellowing leaves on basil: usually cold or waterlogged roots. Move the pot somewhere warmer and let the compost dry slightly between waterings.
• Small flies around the pots: fungus gnats, a sign of constantly wet compost. Water less and add a layer of grit to the surface.
• Greenfly on soft new growth: rinse them off under a lukewarm tap or squash them with your fingers before they spread.
• Nothing happens for weeks: check the light. A north-facing sill in January simply will not support new growth, so wait until spring.

Start with a bunch of basil and a clean jar. Within a month you will have rooted plants, a fortnight after that you will be pinching leaves into pasta, and you will never look at a supermarket herb pot quite the same way again.