Soil provides us with a ‘template’ for groundedness and wholeness. When we take plants into our bodies as medicine, they deliver a reminder that we are part of a bigger whole. A message of wholeness and connection with the earth is a very potent agent of healing indeed.
Chalk downland meadow in West Dorset.
I first learnt properly about soils while studying at Oxford University. I was taught by the legendary soil scientist, Dr Philip Beckett. Phil Beckett was a very inspiring lecturer and tutor. He was quite a character, and we all loved his lectures. He was amusing and informative, and he encouraged us to think for ourselves. He once wrote in New Scientist magazine: ‘In research, as in life, most seminal ideas often arise before the mind and imagination have settled into a rut.’1
I vividly remember the magic of first seeing the relationship between the distribution of plant species and the soils beneath them. Our student cohort from the Agricultural and Forest Sciences undergraduate degree course was on a field trip to Blewbury Downs, a steeply sloping area of chalk downland near Oxford. We were divided into groups, and each group was tasked with digging a soil pit at a different point on the slope. Our location was a beautiful wildflower meadow. Around us was a hugely rich and diverse flora, including a multitude of grasses, Wild Thyme (Thymus serpyllum), Gentians (Gentiana spp.), Scabious (Scabiosa columbaria), Horseshoe Vetch (Hippocrepis comosa), Wild Carrot (Daucus carota), Eyebrights (Euphrasia spp.) and many more.
After the hard graft of digging our soil pits, we walked from the top of the hill down to the bottom, comparing the soil profiles at different locations. They varied quite a bit in different parts of the site, and we could see that the distribution of each plant species in the meadow was much influenced by soils and aspect. Not only did the plant species present vary on slopes facing to the south or to the north in the same area, but they also varied according to whether they were growing at the top of the slope, part-way down it or at the bottom. It was fascinating to see that even microclimatic variations in aspect and soil type created by large anthills had resulted in different distributions of plant species compared to the overall distribution on the main slope. Suddenly, I realized that I was seeing the meadow in a new light. The arrangement of the plants had become predictable and understandable, as well as beautiful. It was as though I had been taught to read a code that had previously been illegible to me. Everywhere I looked, the connection between soil type and plant distribution was clear and visible. That moment permanently changed the way that I view the landscape around me.
The portentousness of the revelation was healthily balanced by a great deal of hilarity when we all retired to a nearby pub for lunch. Bearing in mind that we were at Blewbury Downs, some of our group had selected Fats Domino's rendition of ‘Blueberry Hill’ on the jukebox, and, with impeccable timing, the first iconic chords had rung out just as Phil Beckett stood up to begin a detailed explanation of our findings. To his great credit, he joined in the joke and waited until the track had played out before starting to speak.
Wild Carrot growing on the downs above Blewbury.
So, while studying at university I learnt that if we understand the nature of soils, we can read the landscape around us and appreciate the intricate web of cause and effect that characterizes it. If we are aware of the link between soils, landscapes, and the plants that grow there, we automatically have a sense of place and a way of understanding different localities. Even in unfamiliar places we can find a sense of security and familiarity. We learn to associate particular plant species with certain soil types and, as wildcrafters, we learn to predict where we are most likely to find the plants that we need. As growers, when we understand our soil, we can discover which species will grow best on our land and which cultivation practices will help to ensure optimum plant growth and productivity. For a self-sufficient herbalist, soil really is fundamental.
Soils with different textures provide plants with varying levels of nutrients, aeration, and stability. They respond more or less quickly to the increasing warmth of the sun in the spring, and they vary in their ability to hold onto water or withstand being walked on or driven over without damage.
Particular soil textures are the result of the proportions of three different particle sizes: sand, silt, and clay. Pure sand feels gritty. Anyone who grew up making sand castles on the beach will know that dry sand will not stick together, but when wet it has enough cohesiveness to retain the shape that is has been moulded into. Sand is the largest of the three particle sizes. Since it cannot be packed really tightly together, water and nutrients drain easily through it. The second type of particle is silt. Silt particles are smaller than sand, and a silty soil feels smooth, soapy, and soft. If you squeeze a handful of silty soil, it sticks together better than sandy soil. The smallest particle size is that of clay. Clay particles are approximately 1,000 times smaller than those of sand. Clay is different in that it does not simply consist of weathered rock, like the first two particle types, it is actually a secondary product formed during the weathering process. Clay soils are usually described as ‘heavy’ because they are more difficult to cultivate than other soil types. When you squeeze a handful of a clay soil, it retains the shape of your fist and feels sticky. While pure clay soils can be challenging to cultivate, all soils benefit from the presence of some clay, as it helps to create healthy soil granules and acts as a nutrient store and a moisture retainer.
It is very rare to get soils that are made up of just one particle type. Most soils are a mixture of all three particle sizes and can be broadly divided into coarse-, medium-, and fine-textured soils. Coarse soils, which are higher in sand, allow water to drain through them more quickly than other soil types and have the advantage of warming up more quickly in the spring. Their texture gives them resistance to waterlogging and compaction. The downside of coarse soils is that they can be prone to drought and the loss of nutrients. If you have a very coarse soil, your management priority will be to add large amounts of organic matter in order to improve nutrient status and moisture retention. Medium soils are usually soils that are well balanced between sand, silt, and clay, so that none of these particle types dominates the characteristics of the soil. Medium-textured soils are ideal for cultivation and can be very fertile. They do not need any particular remedial management practices. Fine-textured soils are high in clay and are generally more difficult to work. Rainwater tends to collect on the surface in puddles, and the soil is slow to warm up in the spring, due to its higher moisture content. Soils with high clay content should never be cultivated or stepped on for harvesting when they are wet, as this will lead to compaction and permanent damage. When clay soils dry out, they form rock-hard segments surrounded by characteristic deep cracks, making cultivation very difficult. On the plus side, fine-textured soils retain moisture well in the summer. They can be improved by the addition of plenty of organic matter as well as by rough digging in the autumn, leaving large clods over winter to be broken down by the action of the frost.
The relationship between different soil types and which plant species they naturally support is fundamental. Top: Dartmoor; middle: the Scottish borders; bottom: the Jurassic Coast.
There are many parallels between soil types and patient constitutional types in herbal medicine, whether you understand those according to Galenical humoural theory, Tibetan medicine, Ayurveda or other traditions. Each constitutional type has its tendency to moisture, dryness, inflammation, and stagnation, for example. Once we understand our own constitutional type, we can nurture ourselves effectively, staying as close as possible to an ideal healthful balance. Likewise, once we understand the soil in our herb garden, we can nourish and manage it so that we are able to grow the best possible crops of medicines.
Overlaid onto the various soil textures is the effect of its pH. Chalky
