All plants need a regular supply of light, oxygen, moisture, and nutrients to thrive. It helps us to become better gardeners if we understand how this process takes place and how we can help to provide the right conditions in our gardens for the plants that we grow.
Once you reach that stage in life where the idea of cultivating a garden is more interesting than shouting over loud music in a bar, however, botany ceases to be quite so boring and actually becomes relevant. In fact, as the third clematis you have bought in as many summers fails to thrive and dies, you begin to wish you had paid more attention in school!
Learning the techniques of gardening while steadfastly refusing to inquire about how the plants themselves function leaves you at a considerable disadvantage. You may know how to carry out the necessary tasks, but you have no clear idea at all about why you are doing them. The instructions are much easier to remember if you have some idea as to the reasons behind them. It is usually extremely tempting to ignore w hat appears to be a lot ol fuss over nothing, disregard the fine print, and do what comes naturally. Only when you lose a large number of plants, or realize that those you have planted have failed to grow properly, do you then consider re-reading the instruction manual and, maybe, move on to read the bits about botany.
Most of us can manage to recognize the primary elements of a plant: roots, stem, leaves, flowers, and fruit or seed (although plants are quite good at disguising themselves; what we think ol as a root—the bit that is underground—may well turn out to be a swollen stem, as in the case of a crocus). What we are less clear about is how the plant nourishes itself and grows, and why it does so only at certain times of the year.
The one common feature of all plants is that they survive by a process known as photosynthesis. Here, energy from sunlight is absorbed by the green pigment in a plant’s leaves (chlorophyll), and water from the soil and carbon dioxide from the air are changed into sugars and oxygen. Water, along with certain minerals, is absorbed by the plant’s roots and then carries these sugars to the cells of the plant. The oxygen is released into the air.
The neglected part of any plant is often the root system. The state of the leaves will focus the gardener on the welfare of the plant, but the trouble often starts farther down, out ol sight. Contrary to what you might expect, roots need oxygen. Soil that is too dense, without any air in its makeup, will eventually cause the plant to suffocate. It is of vital importance to ensure that the plant’s root system is well cared for and that the soil around it is nutritious and uncompacted. For this reason, it is a good idea to create a planting hole several times the diameter of the root ball. The fine roots will reach out in an expanding circle to draw water and nutrients from the soil, and they can only do so if they encounter favorable conditions. Only the toughest plants can barge through solid clay.
Once you realize that roots are not all alike, you will also understand that you have to provide the right conditions. Plants with fine roots spread out close to the soil surface; those with tap roots can search deep lor water.
While trees, climbers, shrubs, and perennials survive from year to year—provided they receive adequate light, nourishment, and moisture—a small number of plants (known as annuals) will need to be started afresh each year from seed, because they die after flowering; biennial plants will grow from seed one year and flower the next before they die.