Herbs are light feeders, and that is one of the things that makes them easy to grow. Most herbs evolved in poor, thin soils, and they produce their best flavour when they grow slowly in lean conditions. Feed them like vegetables — rich compost, regular liquid feeds, plenty of nitrogen — and they will grow fast, lush and tall, and taste of almost nothing. The essential oils that give herbs their flavour are concentrated when the plant grows steadily in modest soil, and diluted when it grows fast in rich soil.
That does not mean herbs never need feeding. Herbs in pots exhaust their compost within a season, soft herbs such as basil and parsley that are picked hard all summer do need a top-up, and any herb in poor soil will eventually look hungry. The skill is to feed lightly, to feed the right herbs, and to know when feeding helps and when it hurts. This guide explains the principles, the options, and the mistakes. If you are unsure what your soil needs, check your local extension service — a soil test is cheaper than a season of guessing.
Why most herbs need little feeding
The flavour of a herb lives in its essential oils, and those oils are the plant's defence against sun, drought and poor soil. A rosemary plant on a dry, sunny, rocky slope produces small, tough, intensely fragrant leaves. The same plant in rich, moist, heavily fed soil produces large, soft, pale leaves with far less fragrance. The same is true of thyme, sage, oregano and lavender: lean conditions concentrate flavour, rich conditions dilute it. This is the opposite of vegetables, where rich feeding usually means a bigger, better harvest, and it is the reason experienced herb growers feed so little.
There is a second reason to feed lightly. Over-fed herbs grow soft, sappy growth that attracts aphids and other pests, and that is more prone to disease. A basil plant fed heavily with nitrogen grows fast and tall, but its stems are weak, its leaves are thin, and aphids love it. A plant fed lightly grows more slowly, but its stems are sturdy and its leaves are thick and full of flavour. The rule for herbs is: feed to keep the plant healthy, not to make it grow fast.
Which herbs need feeding, and which do not
Mediterranean herbs need almost no feeding at all. Rosemary, thyme, sage, oregano and lavender in the ground, in a sunny, well-drained bed, usually need nothing more than a light dressing of compost in spring — and in poor soil, they may need nothing at all. If they are growing steadily and their leaves are a good colour, leave them alone. If they look pale and stunted, a soil test through your local extension service will tell you what is missing, and a light feed will usually fix it.
Soft herbs are hungrier. Basil and parsley that are picked hard all summer use up the nutrients in their pots quickly, and they benefit from a liquid feed at half strength every two to four weeks through the growing season. Mint and chives appreciate a spring dressing of compost and an occasional liquid feed. Cilantro and dill are short-lived annuals that are usually sown into fresh compost and need little feeding in their short life. In all cases, feed at half the rate you would use for vegetables, and stop feeding in late summer so the plants harden off before winter.
Compost: the best feed for herbs
Compost is the best fertiliser for herbs, because it feeds slowly, improves the soil, and is almost impossible to over-apply badly. A 2 to 3 centimetre layer of well-rotted compost spread around herbs in spring, kept clear of the stems, gives them a gentle supply of nutrients for the season and improves the soil structure at the same time. For herbs in pots, scrape off the top few centimetres of old compost in spring and replace it with fresh compost — a top-dressing that feeds without disturbing the roots. Our composting basics guide explains how to make good compost, and our compost ratio guide covers the mix.
Compost also suits the two herb groups differently. Soft herbs such as basil and parsley appreciate a generous compost dressing, because they want richer soil. Mediterranean herbs such as rosemary and thyme want only a light dressing, because too much compost makes their soil too rich and too moisture-retentive. If you are top-dressing a mixed herb bed, give the soft-herb end more compost and the Mediterranean end less — the same split as with watering.
Liquid feeds and organic options
When herbs in pots need a top-up, a liquid feed is the easiest option. A balanced liquid feed, or a seaweed feed, at half the label rate, once a month through the growing season, is enough for basil, parsley and mint. Fish emulsion is a good organic option — see our fish emulsion fertilizer guide — but use it at half strength for herbs, because it is high in nitrogen and can push soft growth. Seaweed feed is gentler: it supplies potassium and trace elements, it encourages sturdy growth rather than soft growth, and it is a good choice for Mediterranean herbs that need a light tonic rather than a heavy feed.
Avoid high-nitrogen feeds for herbs, and avoid feeding a stressed plant. A herb that is dry, cold, or recently transplanted cannot use fertiliser, and feeding it can burn the roots. Water first, let the plant recover, and then feed lightly. Never feed herbs in winter, when growth is slow and the nutrients will sit unused in cold compost. And always follow the label rate — for herbs, use half of it. Our fertiliser calculator can help you work out quantities for your pots and beds, and our guide to fertilizing vegetables explains the principles in more detail, though herbs need far less than vegetables do.
Signs of hunger and signs of over-feeding
A hungry herb is pale, slow-growing, and small-leaved. The lower leaves may yellow first, growth stalls, and the plant produces fewer leaves than it should. Basil that is short of nitrogen turns pale green and stops branching, and parsley that is hungry produces small, pale leaves. A light liquid feed and a compost top-dressing will usually revive a hungry herb within a couple of weeks. If the whole bed looks hungry, a soil test through your local extension service will tell you what is actually missing — it may be a specific nutrient, or it may be that the soil is too acidic or too alkaline for the plant to take up nutrients at all, which our guide to soil pH testing can help you check.
An over-fed herb is the opposite: lush, tall, soft and pale, with large thin leaves and weak stems. It grows fast but tastes of little, and it attracts aphids and whiteflies. If your rosemary has gone soft and leggy, or your basil is tall and thin with few side branches, stop feeding, pinch the tips to encourage branching, and let the plant grow steadily for a few weeks. Do not try to fix over-feeding with more feeding — the cure is time, light, and less fertiliser.
Common mistakes
The most common fertilising mistake with herbs is feeding them like vegetables — rich compost, regular full-strength feeds, and plenty of nitrogen — which gives lush, flavourless growth. The second is feeding Mediterranean herbs at all when they are growing well in lean soil: rosemary, thyme and lavender in the ground often need nothing. The third is feeding a stressed or dry plant, which burns the roots — always water first. The fourth is feeding in late autumn or winter, which pushes soft growth that frost damages. And the fifth is fertilising without a soil test, year after year, so nutrients build up to levels that lock up other nutrients. Feed lightly, feed the right herbs, and let the plant tell you when it is hungry.
| Herb | Feeding needs | What to use |
|---|---|---|
| Rosemary, thyme, sage, oregano, lavender | Very low; often nothing | Light compost dressing in spring only |
| Basil, parsley | Moderate; picked hard all summer | Compost plus half-strength liquid feed every 2–4 weeks |
| Mint, chives | Low to moderate | Spring compost dressing; occasional liquid feed |
| Cilantro, dill | Low; short-lived annuals | Fresh compost at sowing; little extra feeding |
| Herbs in pots (all types) | Higher than in the ground | Top-dress with fresh compost in spring; light liquid feed in summer |
Frequently asked questions
Do herbs need fertiliser?
Most herbs need very little. Mediterranean herbs such as rosemary, thyme and lavender often need nothing more than a light compost dressing in spring, while soft herbs such as basil and parsley benefit from a half-strength liquid feed every two to four weeks in summer. Over-feeding dilutes flavour.
What is the best fertiliser for herbs?
Compost is the best all-round feed — a light dressing in spring feeds slowly and improves the soil. For potted herbs that need a top-up, a balanced liquid feed or seaweed feed at half the label rate is enough. Avoid high-nitrogen feeds, which push soft, flavourless growth.
Why do my herbs taste weak?
Weak flavour is often a sign of over-feeding or overwatering, especially for Mediterranean herbs. Herbs produce their strongest flavour when they grow slowly in lean, sunny, well-drained conditions. Cut back on feeding and water, give them more sun, and the flavour should improve.
Can I use fish emulsion on herbs?
Yes, but at half strength — fish emulsion is high in nitrogen and can push soft growth on herbs. It suits basil, parsley and mint in pots during the growing season. See our fish emulsion fertilizer guide for rates and timing.
When should I stop feeding herbs?
Stop feeding in late summer so plants harden off before winter, and do not feed at all in winter when growth is slow. Feed only through the growing season, and only the herbs that are growing actively and being picked hard.