The windowsill
Most windowsills fail at food because the light is worse than it looks. Here's what actually works.
What works, and what doesn't
- Cut-and-come-again salad leaves — reliable; snip above the tip, regrows
- Chives — reliable on a bright sill
- Spring onions — fast, undemanding, sow thickly
- Mint — grows well but contain it to its pot
- Tomatoes — usually too leggy before they go out
- Basil — wants warmth, full sun, resents overwatering
- Parsley — very slow; an outdoor-started plant beats a sill-grown one
What the sill can and cannot do
A south-facing windowsill in summer gets perhaps five or six hours of direct sun, less in winter, and the glass cuts some of that. It sounds generous until you compare it to what herbs, tomatoes and chillies actually need outdoors: eight or more hours, plus the full spectrum that glass partially blocks. Etiolated seedlings — the pale, leggy ones listing toward the pane — are the window's honest report on its own limits.
What thrives indoors is mostly leaf rather than fruit. Cut-and-come-again salad leaves (loose-leaf lettuce, rocket, mizuna) will grow quite willingly on a bright sill and can be snipped above the growing tip every couple of weeks. Chives do reliably well. Mint grows, though it needs containing; left to a pot it takes over nothing worse than itself. Spring onions sown thickly in a deep-ish pot will give usable shoots in three or four weeks and don't ask for anything special.
What routinely disappoints: tomatoes need outdoor heat and light, and the ones started on a windowsill are usually too leggy before they can go out. Basil is famously difficult — it wants warmth, lots of light and resents overwatering, which is the default error on a sill where pots sit in their own drainage. Parsley is slow to germinate and slower to establish; a garden centre pot started outdoors will outperform a sill-grown one by midsummer with no effort from you.
The single most controllable variable is watering. Small pots on sills dry out faster than expected in summer and stay wet far longer in winter when growth slows. Push a finger an inch into the compost before watering; if it's still damp, wait. Terracotta pots dry faster than plastic and are better for plants that hate waterlogged roots (most herbs). Drainage matters more than pot size: a pot without a hole will eventually drown whatever is in it.
Leggy seedlings can be buried deeper when potted on — tomatoes do this particularly well, rooting along the buried stem — but if a plant is struggling for light on your best windowsill, moving it outside once frost has passed is always the answer. The sill is a starting place, or a place for robust cut-and-come-again crops; it is not a substitute for the garden when the garden is available. Know what you have, grow to match it, and you won't feel cheated by a tray of pale, disappointed herbs.
Where we stop
No mains electricity, gas, water mains, boilers, flues, roofs, ladders past single storey, structural work or anything requiring a qualified person. If a job could hurt somebody, it is not in this register.