Growing a Garden From Seed, Part 1

Tristram was three when I decided we should have a vegetable garden. For one thing, he seemed like he would enjoy helping take care of it. Our neighbors had a garden, and he would “help” water it sometimes, by taking his little toy watering can, filling it up in the kiddie pool, and tottering over to the garden and watering the plants. But the main reason was that I wanted him to have a sense of where food comes from. I wanted him to know that fruits and vegetables don’t just magically appear in the grocery store, that they come from living things and have to be grown.

What makes something alive? Thought experiment - make a list of 10-15 living things. What do all these living things have in common? Chances are, your list is mostly made of familiar animals like cats, dogs, horses, squirrels, or picture-book animals like elephants, giraffes, and lions. All of these creatures are a particular kind of animal - mammals. And they all do have characteristics in common - brains, bones, breathe oxygen, have hair. But what about other animals, like bees, or worms, or squids? Or things that are not animals, like maple trees, or button mushrooms, or pond scum? What characteristics do all of these examples have in common?

Are the mushrooms growing out of this rotting log alive? © dmwoodman 2004

All of the things I listed are alive. A living thing, or organism, is defined as anything that can grow and develop, reproduce, adjust to its surroundings, adapt to changes in the environment, and is made of one or more cells*. Having a brain, or even breathing oxygen are not necessary to be considered alive.

The yeast colonies and the green mold in this Petri dish are both living things. © dmwoodman 2004

In fact, there is a whole group** of organisms, a kind of thermophilic, or heat-loving, bacteria, that eat basically sulfuric acid. They live in the hot springs of Yellowstone National Park, and in underwater volcanic vents.

A hot pool in Yellowstone National Park. The colors are made from mats of thermophilic bacteria. Some can live in temperatures of up to 185 °F (85 °C) © dmwoodman 2005

Plants are living things with their own life cycle, which is why I chose to start our garden from seed. The seed will sprout into a small plant, with few leaves. The plant will develop into a larger, taller plant with more leaves. Eventually, the plant will produce a flower or other reproductive structure, make seeds, and the cycle starts again. A plant life cycle is not that dissimilar to an animal life cycle. A frog is a typical elementary school example. Frog eggs to tadpoles to tadpoles with legs to frogs to eggs again.

What’s missing from both of these examples? Well, quite frankly, sex. Sexual reproduction is one of the two basic forms of reproduction for all living things. Sexual reproduction happens when two organisms of the same species*** combine some of their DNA to make new combinations of genes. The process of combining genes to make an new individual can happen in many ways. For frogs, and many other aquatic animals, the fertilization is external. The female releases unfertilized eggs into the water, and the male releases sperm on top of those eggs. No penetration is involved in frog sex.

Plants can also have sex, though it looks so different from what we think of a S-E-X that we often don’t realize what’s going on. First, the plant has to go through plant puberty, which for many plants means growing flowers. (Not all plants make flowers - conifers, or gymnosperms to use the scientifical**** term, make cones, and ferns make spores. But let’s stick with flowers for now, they’re more familiar and more attractive.)

Flowers are the reproductive organs of the plant. Yes, flowers. Think about that next time you lean over to smell one! In my biology class, I usually get the flower sex lesson in May. It’s pretty good timing for some interesting realizations on the part of the students, what with prom and Mother’s Day coming up and all. Although February would be just as good.

Most flowers consist of three major parts - the pistil (sometimes called a carpel), the stamen, and the petals. The pistil is the female part. It contains an ovary - the same term used for animals - which has one or more ovules, or eggs inside. They look basically like tiny seeds.

The stamen is the male part, and contains the anther, or head of the stamen. Inside the anther are millions of developing pollen grains. The pollen is what will be transferred to the top of the pistil, called the stigma, to eventually fertilize the ovules.

In other words, pollen is plant sperm. You may, in fact, be allergic to plant sperm.

A pumpkin flower. This flower has male parts only (the female flower is on a different part of the pumpkin vine). The stamen with fuzzy pollen on the top is clearly visible in the center.
© dmwoodman 2016

The petals, of course, are the big brightly colored beautiful parts (mostly - some are small, dull, and boring, but they’re usually way up high in trees anyway). These large, showy petals serve to attract pollinators, usually bees but sometimes butterflies, moths, flies, beetles, ants, birds or bats. I’ll write more about pollen and pollinators in the next post, but basically, these animal help transfer pollen from one flower to another. The transfer of pollen, by insects, wind, or chance, is how plants have sex. The pollen fertilizes the ovule inside the plant's ovary.

The fertilized ovules then develop into seeds. A seed is sort of like a baby plant. The correct term is embryo, which is actually the same term used for animals at this stage of their life cycle (often described as a fertilized egg when referring to animals). It is the earliest stage of development, after fertilization. The seed also contains nutrients that supply energy to the embryo. You may remember that plants perform photosynthesis to get energy. But seeds can’t photosynthesize. For one thing, they are underground, so don’t receive any sunlight. For another thing, the embryo may not have any chloroplasts yet, the cell parts necessary to capture the sunlight. So the seed comes with its own energy stores, usually in the form of sugars or starch, that the plant embryo can digest and get energy from until it grows big enough to do photosynthesis. (The process of breaking down sugars to get energy, for plants and animals, and fungi, and protists** is called cellular respiration.) The plant life cycle continues.

The first year we planted our garden, I really didn’t care if we even got much of a harvest, I just wanted plants that would be sure to sprout, and would grow big and impressive. So I chose corn, green beans, pumpkins, and sunflowers. Then I threw in cucumbers as well, on the chance that they would actually produce fruit (yes, fruit, more on that in “Growing a Garden From Seed, Part 2”), since I love to eat them. Turns out that not only did everything grow, flower, and make produce, but Tristram discovered that his favorite vegetable was garden-fresh green beans. Win! So now we are sure to plant plenty of green beans every summer.

Tristram eats a green bean. © dmwoodman 2012

*This last characteristic of life, being made of at least one cell, is why viruses are not, at the moment, considered living things. They are made of less than one cell. They don’t have a cell membrane. Some don’t even have their own DNA. But the great thing about science is that scientific principles are continually modified and revised as we discover new information about our world and universe. I suspect someday the definition of “alive” will be adjusted to include viruses.

** The science of organizing living things into groups according to similarities in called Taxonomy. Taxonomists have organized all life into six major groups, called Kingdoms. The Kingdoms are: Archaebacteria, Eubacteria, Protista, Fungi, Plants, and Animals. Within each kingdom, the organisms are further divided into groups, then further divided within those groups, and again, and so on, until the groups consist of species.

***More or less. For animals, one way to define a species is a group of organisms that are genetically compatible, that is, they can mate and produce fertile offspring. The definition of species is more variable for other kingdoms of organisms. Plants, for example, can often breed with closely related species, a process called hybridization. In fact, most of our modern crop varieties were developed through purposeful hybridization. Humans have been genetically modifying our crops since the beginning of agriculture.

****Special thanks to Tony Millionaire, author of the wonderful comic Sock Monkey, for the excellent word “scientifical.”