For most people gardening is about plants.
Admittedly, features like paths, walls, fences and decks play part in creating the overall garden picture. But without plants, it is very hard to consider any space to be a garden
Indeed, for most of us, it is plants that draw us to gardening in the first place – for me there was a kind of sudden awakening to the mind-boggling variety and beauty of the plants all around us. So much so, that I wanted to grow every plant I could get my hands on.
Anyway, I think it is pretty self-evident that if you want to learn to garden, and garden well, plants have to be the starting point of your studies.
When you garden, you need to know how to choose plants, how to keep them thriving, how to maintain them within their allotted space and, if possible, how you can get more plants from the plants you already have.
Those are all aspects of gardening that I’ll cover in this course, but to help you fully understand those things, we first need to answer the question = ‘how do plants grow?
Because if we can understand how plants grow, we can understand what we need to do to help them grow well.
Plants grow by means of photosynthesis. This is the incredible process whereby plants transform energy from the sun into the material that forms plant cells.
The cells in the green parts of plants contain structures called chloroplasts. Chloroplasts contain chlorophyll and chlorophyll is the substance that performs the plant growth magic.
In the simplest terms, photosynthesis works like this:
- Water via the plant’s roots and carbon dioxide from the atmosphere are drawn into the chloroplast.
- Light from the sun energises the chlorophyll in the chloroplast, causing it to split the water into its component parts – hydrogen and oxygen.
- The oxygen escapes back into the atmosphere, whilst the energised chlorophyll stores some of the sun’s energy in a rudimentary form of sugar (ribulose diphosphate).
- The hydrogen, previously liberated from the water, then combines with the ribulose diphosphate to form more complex sugars, and it is these that form the building blocks of the plant’s cell structures.
- By combining further with water and nutrients from the soil, these complex sugars create the cells that take the form of the plant’s roots, leaves, stems and flowers.
Roots, leaves, stems and flowers are the principal parts of most plants (conifers and ferns are slightly different in that they don’t technically have flowers).
Now that we understand how these come into being, if we can understand how they function, we can get the full picture of how plants work.
Roots grow down and out into the soil beneath the plant. They anchor the plant in position and are the means by which the plant takes in water from the soil and the nutrients that are dissolved in that water (the soil solution).
At the tip of each root is an area of hardened cells called the root cap. This allows the root to burrow through the soil without damage. Just behind the root cap, is a band of microscopic hairs. The root takes in the soil solution through these hairs.
Finally, roots also act as storage site for the sugars created by photosynthesis.
Leaves are the means by which a plant gathers the light than it needs for photosynthesis.
Therefore, leaves need to be thin enough to enable sunlight to penetrate into the chloroplasts. The arrangement of leaves on a plant is designed so as to maximise the surface area of leaves that are presented to the sun.
The veins that you see on a leaf are the vessels which bring water to the chloroplasts and take sugars away to be used for cell growth.
Leaves also have tiny openings called stomata which allow carbon dioxide into the plant and oxygen and water vapour out of the plant. The escape of water vapour is part of a process called transpiration.
As the water escapes, the pressure within the xylem (which is part of the plants internal ‘plumbing’ system), along with pressure emanating from the roots, causes water and nutrients to be drawn up through the plant to where they are needed for growth.
Stems provide strength and structure to a plant. They are the framework upon which the other vital parts, such as leaves and flowers, grow.
The framework usually consists of main stems and branches. At the tip of each of these is the growing point, also called the apical (from apex) meristem. This is where the building blocks provided by photosynthesis, plus the water and nutrients taken in by the roots, combine to form new leaves, stem and buds.
The buds which form on the stem are called axillary buds. They may grow into branches or remain dormant. The dormancy of the ones that do not grow into branches can be broken when the apical meristem is removed.
We do this deliberately when we prune a plant in order to make it put on more leafy growth.
Stems contain the phloem, which carries food around the plant, and the xylem, which carries water.
Flowers are what most plants and many gardeners live for.
Plants have evolved to produce flowers, and thereby seeds, so that their genetic material is passed by means of sexual reproduction to the next generation. In that way they ensure the survival of the species.
Some flowers have only male parts and some have only female plant parts, but many have both.
The male parts are collectively called the stamen and consist of the anther and filament. These produce pollen which is transferred to the female parts by some external agent, such as a bee, the wind or even rain.
The female part that receives the pollen is called the stigma. When the pollen lands on the stigma, it germinates and sends a tube down the style, which is the column supporting the stigma, and into the ovary.
Sperm travels down this tube and fertilises the flower’s egg or ovule. The ovule then grows and matures into a seed whilst the ovary enlarges and becomes a fruit.
These basic facts about how plants grow and about the functions of the various main parts of plants are the foundational knowledge for almost everything else in gardening that is connected with raising plants.
For example, when we prune plants we usually do so to restrict or promote growth or to restrict or promote flowering or fruit production. Understanding the relationship between the plants main stem, its buds and branches enable us to carry out these tasks to achieve the ends we seek.
There is a lot here to understand I know (and there is also a lot more that I haven’t included). But once you know this stuff, it will give you a solid foundation to your gardening knowledge.
In the next step in this Becoming a Gardener series, I’ll look at how to assess your own garden, in the light of what you now know about the needs of plants.
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