Herbs are plants that are used for culinary and medicinal purposes, for making teas and also for their aromatic qualities. The leaves, flowers, seeds and roots of many herbs can be harvested for these purposes.
For best flavour, aroma or potency, herbs are usually harvested and used fresh as required. They can also be dried and stored for use throughout the year, since many herbs aren’t available all year round.
In this article we’ll look at how to harvest and dry herb leaves, roots and seeds, and explain the drying procedure for each in detail.
What is the Best Time to Harvest Herbs?
The best time of the day to pick herbs is in the morning, when the concentrations of essential oils which impart the aroma and flavour are at their highest.
The ideal time in the season to harvest sprigs of herbs (stems with leaves) is when the flower buds are just beginning to open. The one exception to this rule is mint of any kind, as the oil concentrations are highest in mint plant when they’re in full flower, so it’s best to harvest them at that time.
How Much of an Herb Can be Harvested?
When harvesting herbs, how much the plant that can cut at any time depends on whether the herb is an annual or a perennial.
Annual plants only live for one year. They grow and bloom for one season, produce seed, and then die down. Examples include sweet basil, chervil, coriander, dill, and summer savory.
Biennial plants, such as parsley are similar to annuals, but only live for two years. They grow in the first year, then produce seed during their second year, dying down after that.
Perennial plants live for more than two years and may produce seed each year. If their foliage doesn’t die down in winter, they’re classed as evergreen perennials, and herbs such as these include marjoram, rosemary and thyme. However, if the foliage dies down to the ground in winter and regrows in spring, while the roots remain alive below the soil, they’re classed as deciduous perennials, and these include herbs such as chives, fennel, French tarragon, lovage and winter savory.
How much of these herbs can be cut when harvesting?
- Perennial herbs can be reduced to half their height, and no more. It’s vital to leave enough leaves so the plant can quickly regrow. Plants need their leaves to gather sunlight for photosynthesis, to produce carbohydrates which they use as a source of energy to fuel their growth.
- Annual herbs can be cut back even harder, and the whole plant can be taken towards the end of the season before it dies down completely.
How to Harvest and Dry Herb Leaves
Best time of the day – harvest leaves in the morning after the dew has evaporated. This is the time when herbs contain the highest levels of essential oils which give them their aroma and flavour. For the greatest levels of these aromatic oils, harvest on a dry day that has been preceded by at least two sunny days.
Best time of the season – the ideal time to harvest sprigs of herbs (stems with leaves) is when the flower buds are just beginning to open. One exception is mint, the oil concentrations are highest when it is in full flower.
When harvesting herbs, use a container that allows air to flow through it such as a basket, as plastic bags can heat up excessively in the sun and ruin the quality of the herbs.
Herb Leaf Drying Procedure
Most herbs can be preserved by drying them. To dry herb leaves, hang them up, or lay them flat on trays, indoors, in a well-ventilated area, away from direct sun. The ideal room temperature for drying is 21 – 32 °C (70 – 90 °F). Under these conditions, in around 3-4 days, the leaves should be dry.
To dry herb leaves:
- After gathering the herbs for drying, wash them immediately in cool water and lay them on paper towels.
- Pat them gently with a paper towel to dry them.
- Lay the herbs on a tray to dry. Small-leaf herbs can be tied into little bunches and hung up for drying. Small bunches of herb sprigs that aren’t too densely clumped together permit better air circulation and allow for drying. Another more complicated option is to use a frame covered with netting, such as flyscreen or cheesecloth, which allows good air circulation and fast drying.
- Place the drying trays, herb bunches or drying frames in a well-ventilated room, in a location that is not exposed to direct sunlight, with a temperature between 21 – 32 °C (70 – 90 °F). Direct sunlight degrades the aromatic oils in herbs. In humid climates, air conditioning in a room helps speed up the drying process by reducing the humidity in the air.
- In 3-4 days, the leaves should be dry. If the weather is humid, it may be necessary to put the leaves in a food dehydrator, or oven-dry them by spreading out the leaves on a baking tray and drying them in the oven at a low temperature of around 50 °C (125 °F) for a few minutes.
- Store the dried herb leaves in an airtight container and label the container.
For herbs with large leaves, such as sage, or bay leaf tree for example, it’s best to strip the individual leaves from the stem first before they are dried.
Conversely, when drying herbs with small leaves, such as marjoram, oregano, rosemary, thyme, summer and winter savory, it’s easier to strip the tiny leaves from the stems after they have dried.
It’s important to note that some herbs such as basil can’t be dried because they lose their flavour, and are best frozen. Either put small batches of basil into freezer bags, or place chopped fresh basil into an ice cube tray, cover with water, and freeze.
How to Harvest and Dry Herb Roots
To dry roots of plants such as angelica and lovage, harvest by digging them up during late autumn to early spring. Harvest turmeric and ginger tubers when the plants die down to the ground and all the nutrients are stored in the roots.
The process for drying roots and tubers is fairly straightforward, just wash them thoroughly, slice up them into smaller pieces, and dry them on a tray in the same way as leaves.
To dry herb roots and tubers:
- Wash the roots/tubers thoroughly to clean off any soil adhering to them. There is no need to peel the roots/tubers to clean them, but just like any other root crops that are used fresh, they can be peeled if desired.
- Slice the roots/tubers into very thin pieces so they can dry more easily. To slice them thinly, use a sharp knife and a cutting board. A potato peeler can be used to create extremely thin slices which will dry very easily, but it’s a slower process.
- Lay out sliced roots/tubers to air dry on a sheet of greaseproof paper on a tray, trying to keep them evenly spaced and not laying on each other.
- Place the drying trays or drying frames in a well-ventilated room, in a location that is not exposed to direct sunlight, with a temperature between 21 – 32 °C (70 – 90 °F). Direct sunlight degrades the aromatic oils in herbs. In humid climates, air conditioning in a room helps speed up the drying process by reducing the humidity in the air. When drying is taking a long time due to excess air humidity, the partially dry slices can be put into a food dehydrator, or in an oven at low heat, around 50 °C (125 °F) for long enough to complete the drying process.
- When the root/tuber slices become brittle and can be snapped in half, they’re dried and ready to be stored.
- Store dried root/tuber slices in a labelled airtight container.
Note, it may take a while for the root/tuber slices to dry, depending on indoor temperatures, air humidity levels, and the thickness of the slices.
When I place turmeric slices on a tray, on the kitchen bench away from a window, they usually dry in 5-6 days in the middle of winter in temperate Melbourne, Australia. The indoor temperature is around 21 °C (70 °F) with a relative humidity at approximately 60%, which is maintained by the ducted gas heating.
In the worst-case scenarios, it may take up to 6-8 weeks for root/tuber slices to dry properly.
Using an electric dehydrator, the optimum dehydrator drying temperature for turmeric and ginger rhizomes is 60 °C (140 °F). The time required will vary between dehydrators, but the model I own (Ezidri) takes around 10 hours when the slices are less than 5mm thick.
For anyone interested in drying turmeric root, see article – The Easiest Way to Dry and Process Turmeric Root to Make Turmeric Powder
How to Harvest and Dry Herb Seeds
Some herbs, such as caraway, dill and fennel produce seeds which can be harvested. To harvest herb seeds:
- Cut off the seed heads when the plants begin to turn yellow.
- Place the seed heads on a tray to dry for a week, after which the seeds should fall out quite easily.
- Separate the seeds and leave them to dry on a tray for another week. Stir them around often to ensure they dry evenly.
- Store the dry seeds in a labelled airtight container.
How Long Can Dried Herbs be Stored?
Store the dried herbs in an air-tight container such as a glass jar with a tight-fitting lid, placed in a cool, dark place, such as a kitchen pantry for the best shelf-life.
Remember to label the container with the name of the herb, and the harvest date, to know how long to keep the dried herbs for.
Dried herbs can be stored for two to three years, after which they quickly degrade, losing flavour, aroma or medicinal potency. If you haven’t used them in that time, throw them away. Dispose of them into the compost or garden, as they are plant materials after all!