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Fertiliser for basil on UK windowsills and in pots

Updated: October 2026

A supermarket basil on a UK windowsill often arrives as a tight clump in a small pot, and a fertiliser for basil will not repair that on the first evening. Pale leaves, a flower spike, or a collapse after one hot weekend are usually light, water and crowding first, and food third. This page is from Peter F., the DIY and tools editor, on 20 October 2026. It covers basil, and the same pot logic for parsley, mint and chives. Rosemary, thyme and sage stay on the [herb fertiliser buying guide](/hub/fertiliser-soil-and-bark-mulch/herb-fertiliser/sub/herb-fertiliser-buying-guide). Figures come from the amazon.co.uk listings behind the [herb fertiliser comparison](/hub/fertiliser-soil-and-bark-mulch/herb-fertiliser). A qualifying purchase can earn a commission at no extra cost to you.

A supermarket basil on a UK windowsill often arrives as a tight clump in a small pot, and a fertiliser for basil will not repair that on the first evening.

Our top picks

Baby Bio Baby Bio Herb Food, pack of 2

Best overall

Baby Bio Baby Bio Herb Food, pack of 2
3.5/10about £5.98
View offer
Baby Bio Baby Bio Herb Food, 2 x 175 ml

Rank 2

Baby Bio Baby Bio Herb Food, 2 x 175 ml
6.9/10about £10.50
View offer
Substral Substral Naturen herb sticks, 30

Alternative

Substral Substral Naturen herb sticks, 30
6.2/10about £12.40
View offer
On this page
  1. 1.What basil in a UK pot is short of
  2. 2.A light feed, not a tomato feed
  3. 3.How the kept listings talk about basil
  4. 4.Parsley, mint and chives in the same pot logic

What basil in a UK pot is short of

Basil wants warmth, a bright sill out of a cold draught, and compost that is damp rather than soaked. The RHS grow guide used here does not give a fertiliser rate, so this page does not invent one. A supermarket pot holds many seedlings in one small root space. The RHS container notes describe those shop pots as soft and stressed. Splitting them into two or three pots does more in the first fortnight than any bottle. Feed comes after that split, and about six weeks after you pot on, which is the RHS container clock. If the new compost feeds for months, wait until that charge is due to run out. From October to March a British windowsill is short of light. Pinch a flower spike, as the RHS basil page asks, and keep it in leaf.

A light feed, not a tomato feed

Use a balanced feed for leaves, at or below the rate on your bottle, while the plant is growing. The RHS container page contrasts that with a high-potassium tomato feed, which is built for fruit. Plantura's UK page puts basil with the hungry herbs and says aroma suffers if you overfeed. None of the four amazon.co.uk listings states an NPK. If you hold the about £10.50 Baby Bio bottle, the listing ceiling is 5–10 drops in 0.5 litre or half a capful in 1 litre. That listing does not state the interval. The about £5.98 pack gives every two weeks and a ratio of 1:X. Do not copy the 5–10 drop line across unless that bottle prints it. The order of watering and mixing is on how to use herb fertiliser.
Baby Bio Baby Bio Herb Food, pack of 2

Testsieger

Baby Bio Baby Bio Herb Food, pack of 2
3.5/10about £5.98
View offer

How the kept listings talk about basil

Only Substral Naturen's 30 sticks, at about £12.40, name basil. The bullets also name parsley, with 1–5 sticks by pot size or two per plant in a balcony box, every two months. A small sill pot is the bottom of that range. The saved texts are Reviewed in Germany, so they are not UK basil evidence. Keep the count inside the label. Both Baby Bio listings say herbs, without the word basil in the bullets. One reviewer on the about £10.50 listing says potted basil died and sage wilted after use as directed. Another says failing basil and mint then grew strongly. The death report does not ban a product at 4.4 from 62 reviews. Neudorff's 250 ml bottle says culinary herbs and does not name basil or print a dose. Who each listing is for, beyond this crop, is on best herb fertiliser.

Parsley, mint and chives in the same pot logic

Parsley is the closest cousin: a hungry leaf herb on a balanced feed, with the label as the maximum. Mint is hungry and a spreader, which is why a pot suits it. The RHS note on Mediterranean herbs allows a richer compost or a slow-release for mint and chives once the plant has settled. Do not push a stick into compost that already feeds for months. Chives take that richer logic and still do not want a fruiting feed.

Common questions

How often should I feed basil in a UK pot?
After about six weeks in fresh compost, then on a light clock while it grows, and not as a winter routine. The about £10.50 Baby Bio listing gives a dose and no interval. UK notes often say every two to three weeks until September. Those gaps are rules of thumb until your label confirms them. A flower spike is a pinching job, not a signal to feed more.
Is tomato feed a bad idea for basil?
For leaves, yes, compared with a balanced herb feed. RHS container guidance points herbs away from high-potassium tomato food. Tomato feed supports fruit. Basil that runs to flower gives you fewer soft leaves. Pinch the spikes and stay with the herb rate. Tomato feed remains a sensible product for tomatoes. It is the wrong tool in this pot.
Will extra nitrogen make the leaves taste weaker?
It can. Plantura links overfeeding, and the soft growth that comes with it, to a weaker aroma. That is why the label rate is a ceiling. If the plant is huge, pale and almost scentless, lengthen the gap. We have no taste scores for these four listings, so this is a growing rule, not a result from our kitchen.
What about a crowded supermarket basil?
Split it. Those pots are many seedlings in a small volume, and the RHS describes them as soft and stressed. Move clumps into fresh compost, water without soaking the leaves, and give them light. Do not pour a full feed on the day you split them, and do not feed if they are wilted. Start a light dose only once they have rooted and any starter charge is spent.
A review said basil died. Does that ban the product?
No. It is one UK text on the about £10.50 listing, beside others that say herbs grew, including basil and mint that had been failing. The star line is 4.4 from 62. Stay inside 5–10 drops per 0.5 litre, water first, and do not dose a collapsed pot.

Related pages

Liquid herb feed or fertiliser sticks

Herb fertiliser

Best herb fertiliser if you will measure a drop dose

Herb fertiliser buying guide for UK pots, beds and boxes

How to use herb fertiliser on pots and balcony boxes

Sources

Public UK sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the four amazon.co.uk listings captured on 20 October 2026. An organic-farming line is not an organic-food certificate. Texts marked Reviewed in Germany are not UK reviews. This is not a laboratory test or a taste test.

  1. RHS, Growing herbs in containers (retrieved 20 October 2026)
  2. RHS, How to feed plants (retrieved 20 October 2026)
  3. RHS, Mediterranean herbs in a pot (retrieved 20 October 2026)
  4. GOV.UK, Manufacturing and marketing fertilisers (retrieved 20 October 2026)
  5. The Fertilisers Regulations 1991 (retrieved 20 October 2026)
  6. GOV.UK, Organic food labelling (retrieved 20 October 2026)
  7. Plantura, Feeding herbs (retrieved 20 October 2026)
  8. BBC Gardeners' World, feeding pots (retrieved 20 October 2026)