Practical Botany Basics for the Gardening Enthusiast
Mary’s garden, according to the nursery rhyme, grew with “silver bells, and cockle shells, and pretty maids all in a row.” Of course that’s the completely wrong answer, as any botanist will tell you. Trouble is, the right answer doesn’t rhyme as well.
Plants are at the bottom of the food chain (except a few notable exceptions, such as the Venus Flytrap). What this really means, however, is that plants form the foundation of the food chain. Most beneficial nutrients that we consume have their origins in plants. And this isn’t limited only to edible plants, either. Many types of shrubs and berries that are poisonous for humans are still nutrient-rich, and are favorite snacks of a variety of non-human fauna.
Plants are like chemical factories, taking sunlight, carbon dioxide and water, mixing them all together and producing carbohydrates. They also pull in nutrients from the soil and convert them into edible forms. So, how do plants accomplish this?
Plants are made up of a few different kinds of structures. Most plants have them, and they are critical to understanding how plants do what they do. It is also valuable information for those of us who enjoy gardening. Some of these things may be familiar to you already, but a refresher is always worthwhile.
The idiom, “Out of sight, out of mind” comes to my mind when thinking of roots. Most people forget all about the roots of their garden plants, at least until a particularly vigorous root starts to turn up a sidewalk or driveway! Yet roots are perhaps the most important element of a healthy plant. If a plant has a strong root system it can weather harsh conditions, recover from pestilence or drought, and is generally going to be a much more vigorous plant.
Roots serve two main functions. They provide the underground support structure that anchors the plant in place and keeps it upright. And they absorb moisture and nutrients from the soil. When a new plant first puts on roots they appear as bright white slivers of growth. Over time they darken, thicken and become more “hairy”. Young, thin, hairy roots are called fibrous roots, because they are thin, like tiny fibers. These young fibers form a massive network of roots that do the work of absorption. They are like the capillaries of the blood stream – tiny, but they spread all over. They are soft, supple and full of life.
As roots age they thicken, harden and become rigid. At this point they are only minimally involved in absorbing nutrients and water, but they still serve an important task – that of support and stability. They are much like the larger older limbs of a tree. Big branches don’t usually bear many leaves, but they support smaller branches that do.
Roots need oxygen to do their job. Heavy clay soils can make it difficult for roots to get enough air. It is important not to overwater plants, because this can cause a plant to literally drown from lack of air. Keeping the soil around your plants loose and light will help in this, but getting them off to a good start when they are planted is most important.
Roots also need nutrients, not just to pass on to the rest of the plant, but also for their own well being. Fertilizers that are rich in macronutrients and micronutrients are critical for the health of the plant. Mixing compost into the soil is also a good way to ensure roots are happy and healthy.
Leaves may be beautiful, but that is not their primary function for the plant. Leaves are nature’s solar panels. They collect sunlight and convert it into energy through a process called photosynthesis. In fact it doesn’t even have to be sunlight. Any light energy can be converted by a plant into food, but sunlight is the most efficient, since it is abundant and free most of the year. Photosynthesis is the reason life is possible on earth. All of the carbohydrates (sugars) we need to live come, ultimately, from the sun; and only plants are able to convert that sunlight into sugar. We may feel like we are making our own food when we grow vegetable and fruit crops. The truth is, only plants have the ability to “make their own food”. Maybe scientists ought to work on a way to enable humans to perform photosynthesis. That would solve world hunger!
Not only do plants turn sunlight into carbs. The process of photosynthesis requires another key input known as carbon dioxide, and this results in the production of a little-known gas called oxygen, which has a few useful purposes such as being essential to all creatures.
Applying nitrogen fertilizers in the soil enhances the plant’s ability to perform photosynthesis by “greening-up” the leaves and enabling them to perform more efficiently. If you have a green house you can also speed up the processes by increasing carbon dioxide and light levels.
Yet, none of this would be possible without the stems of the plant. Stems make up the bulk of the body of the plant, from the trunk of the tree to the large limbs and smaller branches and twigs; or from the multi-stemmed and branched habits of shrubs and perennials. Stems control the overall habit or structure and appearance of the plant. More important than appearance, though, the stems connect the roots and leaves into one single unified system.
As water is evaporated out of leaves through a process known as transpiration, this causes a draw throughout the system that causes the roots to pull more water from the soil. As nutrients are brought into the plant by the roots they are sent throughout the plant through the stems.
As stems age their interiors become hard and, mostly dead. They are incapable of transporting liquid throughout the plant. They still provide structure and stability however, and the outer layers of even the largest branches or trunk are capable of moving fluids and nutrients.
Botanists distinguish between two types of stem structure – dicots and monocots. Most deciduous trees and shrubs, as well has many herbaceous plants are dicots. Their stems grow in rings as they age, adding another layer onto the outside of the stem (think rings on a tree stump). Most of the life of the plant occurs only in the outer ring. This makes such plants susceptible to disease, and it means that a surface wound or cut can have devastating effects to the plant. Monocots, on the other hand, such as grasses and lilies, do not grow in this way. You can lop off the top of a blade of grass and do it little harm. It will just keep growing and your lawn will have to be mowed every few days during peak growing season.
Seeds and Seed Vehicles
Flowers are really just leaves that have gone mad. Leafy parts are modified by the plant to be able to perform reproductive activities. It all starts with a bud. Flower buds may appear similar to leaf buds on a plant. They are usually larger, and once they begin to open it is obvious they are flowers, not leaves.
Flowers may be beautiful, but their sole purpose is to perform fertilization in order to produce seeds capable of producing more plants of the same species that are similar to, but not exactly the same as, the parent plant. Many of the plants we purchase in the stores are not species plants but cultivars. If you try to grow seed from a cultivar parent the resulting new plant will not be of the same cultivar, but from the same species.
Once fertilization is accomplished the plant works to produce seed as well as a protective delivery system. These may come in the form of shells (acorns, nuts), cones (fir trees), fruits and vegetables, berries, and other forms. There is a tremendous and wondrous variety of ways that plants ensure the survival of seeds to give them the best chance to spread.
Plants that we usually think of as weeds are very very good and efficient at producing and delivering seed. Dandelions can produce flowers and then seeds very quickly, in just a few days from when they first begin to grow. Once the seeds are ready they are caught by the wind and blow all over your yard, ready to germinate within just a couple days and start the process over again.
Some garden plants are not quite weeds, but they are pretty successful at reproducing. To prevent this all you have to do is remove the spent flowers, head and all, before the seed is mature.
Plants are Wonders
Yes, plants are a wondrous part of creation. They provide food, water, and air for us to live. They provide beauty, comfort and joy that enrich our lives. Now that you know a bit more about how plants grow, get out there and help them do it!