The information for this article was found in The New Age Herbalist: How to Use Herbs for Healing, Nutrition, Body Care, and Relaxation by Richard Mabey et al.
Herbs are tolerant plants. Most species will survive in a range of soil types, but you will get the best results if you grow plants in the soil types of their natural habitat. The soils described below cover the most important herb habitats.
Soil that forms over chalk is light and well drained. Because of the underlying rock it is also usually rich in calcium and alkaline in character, with a pH level as high as 8. Although you can increase the nutrient content of this soil by adding compost, it is difficult to lower the pH level significantly. If you have chalky soil and find that some plants do poorly, try making raised beds with a less alkaline. Plants from chalk uplands often have long, penetrating roots that bring water and minerals from deep down in the rock though some have shorter, thicker roots.
Herbs that can grow in chalky soil: Catnip, chicory, hyssop, juniper, lavender, lily of the valley, lungwort, marjoram, motherwort, pasque flower, rosemary, salad burnet, summer savory, wild marjoram.
Light Sandy Soil
A soil with a high percentage of sand is likely to be well drained and, because nutrients get washed away as the moisture drains through, it will also have low fertility. Sandy soil often has a pH level slightly lower than normal. Though this is a poor soil for vegetables and most garden plants – you may have to use a plant food in addition to building up the soil nutrients with compost – the many herbs from places such as the Mediterranean and Middle East will thrive here.
Herbs that grow well in sandy soil: Alfalfa, anise, arnica, borage, centaury, Roman chamomile, coriander, cumin, evening primrose, fennel, foxglove, lavender, pleurisy root, tarragon, thyme, wild carrot, wild marjoram, winter savory.
A loam soil is rich in nutrients and as a good overall balance of clay, sand, and silt. Some loamy areas become wet and unworkable during winter and spring, but you can usually improve the drainage by pushing a fork deeply into the soil at regular intervals. A well drained loam is ideal for herb growing, since it allows water to penetrate to the roots while also fostering the more open and aerobic conditions that they need in order to go deeper and break up the soil still further. The majority of herbs that do not require moisture-retentive or light soil will grow well here. The plants listed below do particularly well in loam.
Herbs that grow well in loam: Basil, bay, betony, blood root, burdock, caraway, catnip, chervil, chives, coltsfoot, coriander, dill, foxglove, fennel, lady’s mantle, lovage, parsley, rosemary, rue, sage, tansy, thyme.
This rich soil contains plenty of organic material, but is poorly drained and retains some water throughout the year. You can improve the drainage by forking through the soil, and by growing deep-rooted plants that break up the subsoil. This is a useful soil for the herb gardener – a wide range of herbs favor it and herbs whose natural home is heavy soil also do well.
Herbs that grow well in moist loam: Angelica, bergamot, comfrey, elecampane, French sorrel, lady’s mantle, lemon balm, meadowsweet, mints, parsley, skullcap, soapwort, sweet cicely, sweet violet, valerian.
Clay soil contains a predominance of tiny particles, which stick together in large masses. The soil bakes hard in summer and is heavy and sticky in the winter. Working compost into the first few inches will help make it better drained and easier to cultivate. The herbs that thrive on clay have deep penetrating roots that break up the heavy soil and are not affected by baking – burdock, for example. As well as the plants listed below, many others will tolerate clay.
Herbs that grow well in clay: Bergamot, burdock, coltsfoot, comfrey, lesser celandine, mints, wormwood. Provided that the topsoil is good and the drainage reasonable, loam and moist loam plants will also tolerate this soil.
Wet Marshy Soil
This type of soil retains moisture at all times either because it is very poorly drained or because it is only just above the water table, so that the water has nowhere to drain. A number of herbs are native to wet, marshy areas. Most have lush, green foliage that grows prolifically, taking advantage of the high nutrient levels usually found in this type of soil.
Herbs that grow well in wet marshy soil: Bogbean, golden seal, gypsywort, horsetail, iris, marshmallow, meadowsweet, skullcap, sweet flag, valerian.