Summer is the herb garden's best season. Basil grows fast in the heat, mint threatens to take over the bed, rosemary and thyme thrive in sun and poor soil, and the gardener who cuts herbs regularly will have more of them, not less, because cutting is what makes a herb plant branch and grow. The summer herb routine is therefore a pleasant one: water in the morning, cut what you need for the kitchen, dry or freeze the surplus, and keep the plants from flowering too soon. This guide covers watering, feeding, cutting and harvesting the main culinary herbs through summer, and how to preserve them for winter. For local advice, check your local extension service.
Watering herbs in summer
Herbs fall into two groups when it comes to water, and treating them the same is the most common mistake in a herb garden. Soft, leafy herbs — basil, parsley, cilantro, mint, chives and dill — need regular watering in summer, because they have soft leaves that lose water fast and shallow roots. Water them at the base, in the morning, and mulch around them to hold moisture. Mediterranean herbs — rosemary, thyme, oregano, sage and lavender — come from dry, sunny places and prefer poor, free-draining soil and far less water; overwatering them is more damaging than underwatering, and they will rot in wet soil.
Herbs in containers need checking daily in hot weather, because a small pot in full sun dries out fast. Group pots together so they shade each other, mulch the surface of the compost, and water until it runs from the drainage holes. Basil in a pot is the thirstiest herb of all in summer, and it will wilt dramatically on a hot afternoon if it is allowed to dry out — though it usually recovers overnight if it is watered promptly. The watering calculator can help with quantities, and our summer watering guide covers the principles.
Feeding and soil for herbs
Most herbs need very little feeding, and too much fertiliser makes them grow fast and soft, with less flavour — the oils that give herbs their taste are more concentrated in plants grown slowly in poor soil. Mediterranean herbs in particular should be fed rarely, if at all, and grown in gritty, free-draining soil with little added compost. Soft herbs such as basil, parsley and mint benefit from a light liquid feed every few weeks, and from a compost mulch that feeds the soil slowly, but even they should not be fed heavily.
Soil matters more than feeding for herbs. Rosemary, thyme, oregano, sage and lavender need soil that drains freely, and they will fail in heavy, wet soil no matter how much you feed them; add grit or grow them in a raised bed or a pot if your soil is heavy. Basil, parsley and mint prefer richer, moister soil, and they will grow well in a vegetable bed with regular watering. If a herb is pale and slow despite adequate water and light, a light feed may help, but check water and drainage first — those are the usual causes.
Cutting and harvesting herbs
Cut herbs regularly, and cut them properly. Basil should be cut above a pair of leaves, so the plant branches from that point and produces two new stems; never strip a basil plant bare, and never let it flower if you want leafy growth, because flowering changes the flavour of the leaves. Mint and oregano can be cut back hard when they get leggy, and they will regrow quickly. Parsley, chives and cilantro can be cut leaf by leaf or in handfuls, and a regular harvest keeps them producing all summer.
Pick herbs in the morning, after the dew has dried but before the sun is strong, when their oils are at their most concentrated. Use scissors or sharp secateurs, cut cleanly, and do not take more than a third of the plant at once, so it can recover. Rosemary, thyme and sage can be cut as sprigs through the season, and lavender should be cut as the flowers open, before they fade, and tied in bunches to dry. For growing detail, see growing basil, growing mint and growing rosemary.
Pests and problems
Herbs have fewer pest problems than most garden plants, partly because their strong oils repel many insects, but they are not immune. Aphids cluster on the soft tips of basil and mint in summer, and a strong jet of water will dislodge most of them. Mint rust shows as orange spots on the undersides of leaves, and the affected stems should be cut out and put in the green waste bin, not the compost heap. Basil is prone to damping off as a seedling and to downy mildew in warm, wet weather, which shows as yellowing leaves with a grey fuzz underneath — improve air flow, avoid wetting the foliage, and do not plant basil in the same place year after year.
The most common herb problem in summer is not a pest but a cultural one: a Mediterranean herb rotting in wet soil, or a soft herb wilting in dry soil. Check the soil before you reach for a treatment, and remember that most herbs would rather be a little dry than a little wet, with the exception of basil, parsley and mint, which like moisture. The pest identifier helper can help you identify a problem before you act.
Drying, freezing and storing herbs
Summer is the season to preserve herbs for winter, and the simplest methods are also the best. Tie small bunches of rosemary, thyme, oregano, sage and lavender with string and hang them upside down in a cool, dark, ventilated place until they are crisp, then strip the leaves into labelled jars. Basil does not dry well — it loses its flavour — and it is better frozen, either as whole leaves in a bag or chopped and frozen in ice cubes with a little water or oil. Parsley, cilantro and dill can be frozen in the same way, or used fresh through the season.
Harvest herbs for preserving in the morning, when their oils are strongest, and choose healthy, undamaged leaves. Do not wash herbs before drying them, because the moisture slows drying and can cause mould; shake off any soil and pick over the leaves instead. Store dried herbs in airtight jars in a cool, dark place, labelled with the herb and the date, and use them within a year, because their flavour fades with time. A herb garden preserved well in summer will flavour your cooking all winter.
A summer herb checklist
Water soft herbs regularly at the base and Mediterranean herbs sparingly, in free-draining soil. Feed lightly, if at all, and never feed a stressed plant. Cut herbs regularly and properly — basil above a pair of leaves, mint and oregano back hard when leggy — and pick in the morning when oils are strongest. Dry or freeze the surplus, and note which herbs thrived and which struggled, so next year's planting is better.
A herb garden is one of the most rewarding parts of a summer garden, because it asks for so little and gives so much, and the habit of cutting a handful of herbs for dinner is the habit that keeps the plants productive. For the rest of the summer routine, read our summer harvesting guide and browse the guides hub and the planting calendar for the full seasonal series.
Frequently asked questions
How often should I water herbs in summer?
Soft herbs such as basil, parsley, mint and chives need regular watering at the base, while Mediterranean herbs such as rosemary, thyme and oregano prefer far less water and free-draining soil. Herbs in containers need checking daily in hot weather.
How do I harvest basil without killing it?
Cut above a pair of leaves, so the plant branches from that point and produces two new stems. Never strip a basil plant bare, take no more than a third at once, and pinch out flower buds so the plant keeps producing leaves.
Should I feed herbs in summer?
Very little. Too much fertiliser makes herbs grow fast and soft with less flavour, and Mediterranean herbs should be fed rarely, if at all. Soft herbs benefit from a light liquid feed every few weeks, but check water and drainage first if a herb is struggling.
How do I dry herbs for winter?
Tie small bunches of rosemary, thyme, oregano, sage or lavender and hang them upside down in a cool, dark, ventilated place until crisp, then strip the leaves into labelled jars. Basil does not dry well — freeze it instead, chopped in ice cubes with a little water or oil.
Why is my rosemary dying in summer?
The usual cause is wet soil — rosemary comes from dry, sunny places and rots in heavy, wet ground. Grow it in gritty, free-draining soil, in a raised bed or a pot, and water sparingly. Check your local extension service if the problem persists.