Herbs are grown for their flavour, scent or medicinal properties, although many are also attractive plants. They are suitable for an organic garden because many attract bees and predatory insects (see Organic Gardening – Benefits of Garden Insects and Wildlife – Beneficial Garden Creatures) and are reputed to be good companion plants (see Organic Gardening – Preventing Problems), deterring pests and helping plant growth.
The efficacy of herbs results from the action of powerful natural substances, which are only produced in high concentrations if the plants are grown in the right conditions. The aromatic oils contained in shrubby herbs like thyme lose their strength if the plants are grown in wet or shady conditions or in rich soil.
Herbs do not have to be grown in a special herb bed. They comprise a wide range of plants: annual and perennial; herbaceous and shrubby; hardy and half-hardy. There are vigorous, invasive herbs and weak, low-growing ones. It can sometimes be easier to give each a suitable position if they are spread throughout the garden.
Although it is mostly the leaves that are used, some herbs are grown for their flowers, seeds, stems or even roots. To some extent this influences where they are planted: you must be able to harvest them easily without disturbing other plants or the look of your garden.
It is easy to grow most hardy annual and biennial herbs from seed, sowing them outside directly in their growing position (see How to Grow Plants from Seed). Many will self-seed in future. You can grow some perennials from seed, although herbs such as French tarragon do not set seed and others such as variegated herbs and named varieties do not come true. Alternatively, buy them from a garden centre or specialist nursery: it is often possible to obtain organically grown plants.
It is important to keep herb plants young and vigorous, and most perennials should be replaced every three or four years. Dig up and divide herbaceous herbs. Enrich the soil with compost before replanting young clumps from the outside of the old plants. Propagate shrubby herbs from seed or cuttings or buy new plants.
Hardy annual and biennial herbs: parsley Petroselinum crispum)z 5; coriander (Coriandrum sativum) z 8; dill (Anethum graveolens) z 8; summer savory (Satureja hortensis) z 8
These need a sunny position and fairly fertile soil. Grow them on ground manured for a previous crop or fork in compost before sowing. They are often easiest to grow in the vegetable garden, where sowing is easy and they can be part of the rotation. Parsley, for example, is more likely to suffer from virus diseases and carrot root fly if it is always grown in the same spot.
Shrubby evergreen herbs: lavender (Lavandula spp. Z 5; sage (Salvia spp.) z 3-10; hyssop (Hyssopus officinalis) z 3; thyme (Thymus spp.) z 5-9; rosemary (Rosmarinus officinalis) z 6
Most shrubby evergreen herbs need a very sunny, well-drained site and light soil. Add leafmould to heavy soils. Mulch with bark, shreddings or gravel to help keep the foliage clean and dry. If possible plant near the house or patio, where they will benefit from the reflected heat. On heavy or poorly drained soils, grow on raised beds. Most will grow in containers.
Herbaceous perennial herbs: lovage (Levisticum officinale) z 4; fennel (Foeniculum vulgare) z 5; tarragon (Artemisia dracunculus) z 3; lemon balm (Melissa officinalis) z 4; chives (Allium schoenoprasum) z 5
These are best grown in a sunny spot with fertile, well-drained soil. Fork in compost before planting and use it to mulch established plants. Put tall herbs at the back of a herb bed and short ones at the front. Some are attractive enough to grow in a flower border, but make sure that they are accessible for picking.
Herbs with invasive roots: mint (Mentha spp.) z 3-7
Mints do well in a partially shaded position in rich, moist soil, although they will tolerate other conditions. Grow them in an old bucket, thick plastic sack or other container about 30cm (12in) deep to prevent the roots spreading. Make drainage holes in the base. Sink it into the ground up to its rim and fill it with a mixture of soil and well-rotted manure. Plant a small clump of mint in the centre. Water regularly in dry weather. Dig up the container every year, renew the soil and divide and replant a small clump.
Herbs grown for their roots: horseradish (Armoracia rusticana) z 5
Horseradish will grow in sun or partial shade. It needs a fertile soil; dig in compost or well-rotted manure before planting. A clump can be grown in the herb garden only if occasional roots are needed, but even then, harvesting can be destructive. Alternatively, grow in a separate bed in the vegetable garden. Every year or two, dig up all roots, enrich the soil and replant.
Half-hardy annual herbs: basil (Ocimum basilicum) z 10; sweet marjoram (Origanum majorana) z 7
These need a warm, sunny spot and fairly fertile soil. In pots, use a nutrient-rich potting compost. Choose a sunny, sheltered, frost-free spot in a herb bed or flowerbed or grow them in pots on the patio.
Tender perennials: bay (Laurus nobilis) z 8; lemon verbena (Aloysia triphylla) z 8
These also need a warm, sunny, frost-free site and nutrient-rich potting mixture. Grow them in pots and move them to a frost-free greenhouse or conservatory in winter.
A Herb Bed
If you have room for a special herb bed, choose a sunny, well-drained spot as this will suit most herbs. Make sure you can picking them easily and design the bed so that you can reach all the herbs without stepping on the soil — put in paths or stepping stones, for example.
Cutting and Harvesting
Herbaceous herbs need picking and trimming regularly so that there is a constant supply of young foliage for use. Leave some shoots in the middle of the clump to flower and set seed and cut them back in late autumn or spring.
The leaves of shrubby herbs can be picked any time during the growing season. They generally peak in flavour just before the plant flowers, so this is when they should be harvested for drying. Let the flowers set seed for the benefit of the birds and trim them back in early autumn.
Put any herb clippings on the compost heap; the wide range of minerals that they contain are valuable to the soil.
Pests and Diseases
In the past, but now illegal, home-made infusions were used as sprays against pests and diseases. It is therefore hardly surprising that herbs themselves are relatively trouble-free. However, aphids can be a problem on young shoots; Umbellifers may suffer from carrot root fly; and mint may be attacked by rust (See Aphids as Garden Pests, Pests and Diseases of Lettuces and Pests and Diseases of Garden Flowers).