Blooming Times: The Answer Lies in the Soil

Wednesday, 23 October 2024 08:00

By Flo Whitaker

Soil is the gardener’s greatest asset. Understand it, look after it – and many of your horticultural problems will resolve themselves, writes Flo Whitaker

An elderly gardening acquaintance reasoned that if he strived to lead a good life on earth, he might be rewarded with first class soil in heaven. Although a meet ‘n’ greet choir of angels, accompanied by cherubs tootling a welcome on celestial trumpets would be very nice, uncertainty regarding soil quality remained a concern. Alas, he’s long-departed this realm and I personally have serious doubts about a life hereafter. However, he was a forceful character – and if I somehow received a cosmic message, saying he’s growing prize-winning fruit and veg in heaven, I wouldn’t be remotely surprised.

So, what do we mean by ‘soil’? Technically-speaking, soil is defined as a material containing free-moving particles of ‘humus’ and rock. Humus is regarded as anything organic in nature; such as decayed plant material, animal droppings and the bodies of once-living organisms. From a microscopic bug, to an elephant – and everything in- between; their fur, feathers, hair, skin, muscles and skeletons are attacked by bacterial and fungal pathogens, then further broken down by sunlight, frost, wind and rain. The resulting material is nutrient-rich and bulky. Seen under a microscope, humus has a multi- textured surface area, similar to a bath sponge. It is this sponge- like quality that gives humus its moisture-retaining properties.

Although humus provides vital resources for life, it is only one half of the soil story. Mineral deposits are equally important. Geology is a complex subject, but from a general gardening perspective, soil can be described as a four-layered cake. At the bottom we find ‘parent’ rock, which may extend for miles into the earth’s crust, (out of reach of even the most maniac, spade-wielding, double-digging gardener,) but parent rock is important horticulturally because it influences the upper levels and affects local soil type.

Above this is ‘bedrock’, which you may come across when excavating foundations for buildings and suchlike. Bedrock can also form natural features above ground; where outcrops have been pushed to the surface as a result of seismic activity, or when surrounding geology comprised of softer materials has eroded away.

Next, we have ‘subsoil’; an environment mostly comprised of water and broken/pulverised rocks and gravels. Subsoil often has a plasticine- like texture and a sulphurous smell. It’s distinctly different to the layer above – put a spade in the ground and you’ll clearly see a horizontal line where two worlds meet. Roots of larger plants pass through subsoil, but not much actually lives there, due to the absence of light and minimal levels of oxygen and humus. However, subsoil has two important roles; it acts like ‘glue’, holding soil layers together and its water reservoir slowly erodes the rock deposits. These minerals, now in a mobile, dissolved form, migrate from the subsoil to feed plants above.

At the top of the geological cake you’ll find the magical ‘topsoil’ layer. Topsoil depth varies dramatically, depending on local factors. For instance, conditions on the Arctic tundra are harsh, cold and dry. Plant growth is limited, there is minimal compostable material available and it can take decades for a few centimetres of topsoil to form. At the other end of the scale, you can literally watch plants growing in a tropical rainforest. The warm, humid atmosphere provides super-fast composting conditions and a metre of topsoil can be formed within a year.

Garden soil is a highly active environment. Fuelled by sunlight, moisture and humus, topsoil is home for billions of creatures leading frantically busy lives. Their lifecycles maintain soil structure and fertility, so we should avoid disturbing this fine balance. Worms and beetles aerate and manure the soil as they tunnel and burrow, while garden ‘pests’ help to maintain order. It’s heartbreaking to lose seedling plants to slugs – however, many slugs and snails actually prefer dead plant material and spend their lives ‘tidying-up’ our borders.

We all know about the pollinating powers of bees and hoverflies, but wasps are definitely in need of a good PR campaign, as they pollinate too, while also consuming a great number of corpses. If it wasn’t for wasps, we’d be knee-deep in dead insects. Birds scratch and peck, preventing compaction of the soil surface, while a hidden army of microscopic creatures live, reproduce and die, aerating the soil and generating heat and excreta.

These activities sustain the growth of plants, whose roots help prevent soil erosion. Plants manufacture starchy and sugary compounds collectively known as ‘sap’. This is rocket fuel for aphids, who are preyed upon by countless birds and insects – and the cycle of life continues...

Soil is self-sorting; its components arrange themselves into purposeful layers. While some digging is inevitable when gardening, the ‘no-dig’ notion of using a surface ‘mulch’ of compost to avoid soil damage and suppress weeds is gaining credibility. Some plants benefit from a specific feeding regime – particularly containerised plants that have no access to open ground, but we can over-focus on feeding ‘things’, when we should be taking a broader view and feeding the soil instead.

You can never make enough compost. If home- composting is difficult, consider buying a large bulk bag of mulch. This can be an efficient, relatively inexpensive solution if you share the cost/workload with a neighbour. A mulch is the best gift you can give your garden. Your plants will grow better, stronger and be more resilient to disease. Increasing soil fertility will also support a more diverse wildlife population, helping you to create your own earthly paradise.

Blooming Times: The Answer Lies in the Soil

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