Supplementary notes to
California Master Gardener Handbook
Chapter 2: Introduction to Horticulture pages 10-22


The relationship of care and sustenance between people and plants comprises our everyday life and existence.  Materially speaking, we are inseparable from plants and horticulture.  The fruits and vegetables in the market are horticultural products, as is the morphine drip in the hospitals. Horticultural or agricultural work drives peoples across state and country lines to pick and harvest. In the recent past, the need for labor in plant work moved peoples from Africa to the Caribbean and North and South America, it moved Filipinos Portuguese East Indians and Japanese to the Pacific Islands.  Or, in the case of plant disease, a sickness of the potato brought the Irish to the Americas. Or ask some elder folks in Appalachia about all the dead chestnut trees in the woods at the turn of the 20th century. Horticultural cultivation of plants drugs like coca, marijuana and opium fuel economies and cultures worldwide.  Stimulants like coffee, yerba mate, and tea keep everybody awake for work. Horticulture is also beauty and pleasure – the blooms of forsythias and roses, a grand row of magnolias along the street.  The importance of horticulture is absolute.   Our lives are totally and completely dependent on living and dead plants.  This is not to mention oxygen, fossil fuels, meat production, rubber, pharmaceuticals, and other industries wholly or partially originating from, and dependent on, plants.


According to the amazonian indians, plants are sentiment and conscious beings who are more ancient than us, and are our teachers. This view comes to us from a culture that evolved in the rainforest for the past 15,000 years + alongside about 40,000 different species of plants. Plants of course do not speak our language or have concentrated focussed intelligence centers like our brains, nor are they ‘mobile’ in being able to walk around. But you may say that their ‘intelligence’ is spread out through their roots and connected to the soil and all the creatures that create and enable life on this planet. This has been the direction of recent scientific research into communication and the ‘mind’ of plants. Plants have been around for about 470,000,000 years, while we are a relatively newcomer at 200,000 years. Ratio wise plants are about 2350 times older than us.

An easy way to observe the cementing agent in plants known as pectin is to make jam. Many fruits when cooked, boiled down, and cooled, gel together nicely. That is the pectin in action. If a fruit is lacking in pectin you can buy some to put in the pot while you stir it. Try to make some jam with either the ripening blackberries around town or lesser known fruits of garden plants like strawberry tree Arbutus unedo, autumn berry Eleagnus umbellata, or fuchsia berries. Make it a fun day long activity that starts with a hike and baskets, pauses in the kitchen in the middle while jam is cooking, and ends with a PB and J on the sofa for dinner.


Meristems are the actively growing cells that make a plant grow wider or grow taller. The taller you get or the wider you spread the more leaves you grow – the more food and energy you can make.

The roots are usually in the soil and anchor the plant in place. Another function of roots is to spread out in the ground and gather whatever water and nutrients it can find and suck them up into the plant. Nutrients are dissolved in the water as electrically charged ions. Kinda like that vitamin water is always advertising. The ion nutrients have names like calcium, phosphate, magnesium, and so on.

They say some 85% of all plants have an association with fungi in the soil whereby they are friends and help each other out. The plants give sugars to the fungus, and the fungus will channel and give the plants water and nutrients from miles and miles around. This is a symbiotic and mutually beneficial relationship. Roots can go very deep and very wide. The fescues in the Midwest prairies have roots that go down 10’+, and a big 100’ tree can have roots that extend outwards to three or four times that (300’ – 400’). Sometimes you will see roots growing right from the trunk itself out in the air. Around here it is most prominent on the commonly planted street tree called New Zealand Christmas tree. If you see these long red strands hanging off of a tree, those are roots wanting to reach the ground and become another trunk.

Stems conduct materials up and down the plant. On the stem are buds from which emerge leaves,stem shoots, flowers, and sometimes even roots. When a stem goes sideways above ground it is called a stolon, like on Bermuda grass lawns. When its underground going sideways it is called a rhizome, like bamboo or ginger. When it becomes swollen with the food energy it is called a tuber like in a potato.

It is confusing – the potato stem tuber, versus a sweet potato, which is classified as a tuberous root. They both just look like swollen chunks of starches. Well the best sense I can make of it is that in cultivation and growth they are different. The potato tuber has those little sunken ‘eye’s all over it, each is buds that can sprout. So if you cut it up into a few pieces they can all grow. It can grow from all over. But a sweet potato, a tuberous root, has a more up and down orientation whereby only one part of the chunk grows. It does not have buds all over it.

sweet pot

When you look at a stump or a piece of cut lumber, you can see the growth rings which show this system of channels moving substances up and down. In general, there is the xylem tubes which conduct water and nutrients, mostly going up. Then, there is the phloem tubes which conduct sugars made by the leaves down, up, and even side to side. This depends on where the plant wants to store it, or on where the plant wants to use it as an energy source.

When you tap a sugar maple tree in the springtime, you are catching the rising sugar sap in the xylem. Aside from the xylem and phloem there are also other tubes in which flow other substances. The thick sticky gooey stuff that comes from a cut wound in pine trees – that is a resin or pitch. It is good for making varnish, for incense, or for hafting a stone ax to a wood handle in the olden times. With time it turns into amber. The sticky resin on the hairs of cannabis flowers – that gets made into hash which is a big commodity in North Africa into Europe. Latex is a white sap exuded by plants in order to defend against insects eating it. Chicle chewing gum is a natural latex, as is the rubber used in tires.  Especially tires in airplanes.  The dried substance from opium poppies is also a latex from which both legal opiates as well as illicit ones are derived.

If you look or feel a branch you can sometimes identify the buds readily. They are funny little nuggets or bumps that are all along it. They are arranged in different ways that make a plant easily identifiable even if you cant see the leaves or flowers. In some plants the buds are hidden under the skin the bark, but as soon as they are called upon to activate they will spring into action. They are called dormant or epicormic…  Say theres a sunlit opening in a gap of the shady canopy.  Grow that way!

Leaves are the energy factory of the world. Plants breathe air through little holes on the leaf called stomata, and leaves receive water and nutrients though the roots, stems, and veins. As light passes through the stacks of green cells called chloroplasts in the leaf, the plant is able to make sugars from the carbon dioxide it inhales and the water it sucks up. It then stores the sugars as starch or as oils for hard times, and it exhales oxygen as a waste product of its energy production.

Carbon dioxide makes up about .04 % of the gases in our atmosphere. It is a product of stuff burning and dying. It gets released into the atmosphere when volcanos blow, forests catch on fire, and bodies decompose. In plants, that same carbon from the CO2 gets strung up or bound in rings into the molecules we call sugars and carbo hydrates.  The oxygen in our atmosphere that we all breathe is made by algae and trees. It is about 21% of our atmosphere’s gases.

A showy flower attracts insect or bird or animal pollinators with pollen, nectar, smells and colors. Pollen is male plant sperm which is a yummy protein rich food for many insects. Nectar is sweet liquid, sugars good for energy. Smells can be really sweet and come on only in the evening for moths, or smell like putrid flesh if the flower wants to attract flies.

Many flowers are not showy. They do not have to attract anybody because they rely on the wind and occasionally the water for pollination. These flowers are often small and insignificant and produce copious pollen because their method of pollination is like a scatter bomb approach.

Many plants do not have flowers at all. These are the cone bearing plants like pines and firs, the ferns and mosses and horsetails, or the weird cute little plants in moist places called liverworts. These plants also rely on the wind and water to get together.

Pollination is the touching of male and female parts of a plant. The male pollen touches the female sticky part called the stigma. After the parts touch, eventually the sperm makes it to the egg cells. This results in fertilization which means the plant is gonna make babies. The babies are called seeds. And the seeds are usually sitting in some kind of a structure. The structure is sometimes a woody cone whose scales open when mature to reveal the seeds, or the structure is some kind of a container or vessel called a fruit. The fruit can be juicy and tasty, or it can be dry and hard, or any number of other variations.

The seed is the product of sexual reproduction. Female and male. Many plants make seeds sexually through pollination and fertilization, but also reproduce asexually (without sex) by cloning and dropping themselves on the ground in some way. Both strategies are useful and help survival. Seeds are comprised of the baby plant itself (the embryo), a little bit of food to help it along in the beginning, and a coat that protects the whole package.

After fertilization, the flower fades away because its job is done. Then the ovary of the plant which is the storehouse of the seeds grows big and becomes a fruit. There are yummy fruits which attract bats or rodents or elephants to eat them and disperse the seeds in the dung. There are exploding fruits which throw the seeds several feet away like the squirting cucumber or the impatiens. There are fruits that can float on the sea for years until they dock on desert island sands like coconuts. Sometimes what we call the fruit is not the swollen ovary but the plant part at the base of the ovary, like in a strawberry fruit with its little seeds all on the outside not on the inside.

We will lump the classification of plants into three broad categories. (1) Folk, (2) horticulturist/gardener, and (3) scientific. Folk is what everybody around world does – teach their kids about the plants useful in day to day life. That way when you are out foraging, you dont take the poison hemlock root home thinking it is a white carrot root crop. Or when you are gathering firewood, you don’t pick up all that light pithy termite filled wood that is no good for cooking and burning and keeping warm. You want that dense hard wood. Some cultures developed their folk classification systems to a very high level. One such culture was documented by the local botanist Dennis Breedlove along with anthropologist Robert Laughlin in the book The Flowering of Man: A Tzotzil Botany of Zinacantán. The following is category (2) – the ways gardeners classify plants:


More appropriately lifespan when talking about annual, biennial, and perennial plants.

When you go to the nursery, usually this is how plants are grouped. Trees are in one section, vines in another, and so on.

If you lived in a place that got really cold in the winter with the sun low in the sky, then at some point it is a waste holding onto all them leaves because they are not doing anything. They are not making energy or doing work. Better to drop em and grow them again come warm spring. This is the fate of many trees with names like sweet gum and oak and maple and beech and larch.

In another scenario it gets so hot and so dry in the summer that the leaves are breathing and breathing and pretty much gonna endanger the whole plant because its losing tons of water. So then the plant decides to drop all the leaves and grow them again in the fall winter months when the rains come. This is the fate of shrubs and trees with names like sagebrush Artemisia and red bud.

All of these are deciduous plants. Winter deciduous or summer deciduous. In the wet tropical rainforest the plants are more likely to be evergreen, not deciduous. This means that they keep leaves on all year, but still they will drop a few leaves time to time – the old leaves, the leaves that are not working so well anymore cause they are in too much shade.

Look up zone maps. There are two that are commonly used around here, one is by the U.S. Department of Agriculture, and the other is put out by Sunset Garden. Look both up, and see if you can figure out what ‘zone’ you live in.

Use is going back to folk classification, category (1).
One more system or criteria we neglected here is based on the plant being ‘woody’ or herbaceous. Woody is hard and stiff, breaking when sufficient force is applied. Herbaceous is soft and bendy. Trees and shrubs – woody. Leafy perennials like anemone heuchera pansies – herbaceous. Taken as a whole, you can have an herbaceous evergreen perennial, for example new zealand flax. Or you can have an herbaceous deciduous perennial that dies back to the ground, like a hosta. Maybe somebody would say well that is not deciduous.  Sigh.  Okay.  Then herbaceous diebackalacious perennial.  How about the banana tree? Herbaceous or woody? Gotta go squeeze and push on one to find out…

This is the classification system which grew out of Europe in the 1700’s and is now worldwide. It groups plants into families based on the characteristics and structure of the flowers, for the most part. For example there is the Brassicaceae Cruciferae family with flowers that are four petaled and shaped like a cross. A crucifix. There is the Lamiaceae Labiatae family with flowers that are like labia with lips up and down, and often but not always square stems. Sage, mint, rosemary, oregano, thyme, lavender, and basil are all in this family. Go check out their flowers!  The current estimate is about 300,000 species of plants and anywhere from 150 – 200 – 400 families. Botanists do not agree on the number because nature is very diverse and the plants do not fit easily into boxes.

Within each family are its similar members grouped into genera and species. In cultivation we further classify particularly useful individual clones/populations as cultivars (cultivated varieties). The cultivar is always written with single quotes like this   ‘ ‘. So in apples there are European crab apples Malus silvestris, and Japanese flowering crab apple Malus floribunda. The apple we eat is Malus domestica. Domestica means something like lives with people. And by the way sativa means cultivated.  The apple cultivars have names like ‘Red delicious’, ‘Gala’, ‘Pink Pearl’, etc. You can do this same exercise with wine grapes, plums, and so on.

If you are going to be a designer or landscaper it is good to learn the names of plants using their scientific names. Not only is it cool to know a little bit of Latin and Greek, it will also ensure that you are talking about the right plant when communicating with others. Not “Yeah the one with the blue flowers, you know, blue bells or blue devil or blue eyes or something like that. The one with the green leaves. Let me show you on my phone. Grr… the battery is dead!”