How to Feed Herbs — What, When, and How Much

Herb feeding is one area where less is genuinely more. The popular assumption that more feeding means more growth is wrong when it comes to most herbs — particularly the Mediterranean varieties. Over-feeding produces lush, soft growth that tastes bland, is more susceptible to pests and disease, and can actually shorten a perennial herb's productive life. The right fertiliser strategy varies significantly between herb types.

Mediterranean Herbs — Feed Sparingly

Rosemary, thyme, sage, oregano, and marjoram evolved in nutrient-poor, well-drained soils. In rich, highly fertile conditions they produce excessive lush growth with lower essential oil concentration — which means less flavour. In the ground, established Mediterranean herbs in reasonable soil generally need no feeding at all beyond a top dressing of compost in spring. In containers, feed once a month at most with a balanced fertiliser at half the recommended strength. Never use high-nitrogen feeds on Mediterranean herbs.

Leafy Herbs — Moderate Feeding

Herbs grown primarily for their leaves — basil, parsley, chives, mint, coriander — benefit from a higher nitrogen supply because nitrogen drives leaf growth. In the ground, incorporating well-rotted compost before planting provides a slow-release nutrient supply that is usually sufficient for the season. In containers, feed with a balanced liquid fertiliser every two weeks during the growing season. A feed with a higher nitrogen ratio (such as a liquid seaweed concentrate or diluted nettle tea) boosts leaf production without the risk of the overly soft growth caused by synthetic high-nitrogen feeds.

When to Feed and When to Stop

Feed herbs only during the active growing season — from early spring when growth resumes until late summer. Stop feeding in late August or September so that the plant's new growth has time to harden before the first frosts. Soft, lush growth produced by late-season feeding is far more vulnerable to frost damage. Do not feed plants during winter dormancy — the nutrients will not be taken up and may leach into the surrounding soil and water table. Resume feeding in spring as soon as you see new growth beginning.

Organic Feeding Options

Many herb growers prefer organic feeding methods, which release nutrients more slowly and improve soil structure at the same time. Well-rotted garden compost dug in before planting is the best all-round option for in-ground herbs. Liquid feeds include diluted nettle tea (steep nettles in water for two weeks, dilute 1:10), comfrey tea, or liquid seaweed — all provide a balanced range of nutrients without the risk of overdosing. Worm castings added to potting compost provide a slow-release nutrient supply that can reduce the need for liquid feeding by half.

Signs of Overfeeding and Underfeeding

Overfed herbs typically show lush, dark green, soft, floppy growth that lacks flavour and aroma. The leaves may be unusually large. Underfed herbs (particularly in containers) show pale, yellowish leaves with reduced growth and small leaves — the soil has run out of nutrients. When in doubt, err on the side of less feeding rather than more, especially for Mediterranean herbs. A slight nutrient stress keeps aromatic oils concentrated and improves flavour.