Botany Primer For Gardeners

Botany Primer for Gardeners
Linda R McMahan, PhD
Botanist & Extension Horticulturist
Oregon State University Extension
linda.mcmahan@oregonstate.edu

What We Will Cover
Plant Diversity
Algae, fungi and lichens
Spore producing plants – mosses, liverworts, ferns
Seed plants – conifers, ginkgo, and flowering plants
Plant Structure and Growth
Stems and roots
Leaf structure
Flowers and reproduction

Plant Diversity
From ancient time when we began studying the world around us, we tried to understand our surroundings by labeling plants and animals
Our current scientific understanding continues to refine relationships, but historically, many organisms have been considered to be plants even if they are not now considered to be so
I will use the historic understanding and explain modern differences as we proceed

Plant Diversity
The classification of various kinds of plants is based on reproduction
Spore producing plants appeared on earth before seed producing plants
Later, seed plants became more common—these are also the ones most common in our landscapes and gardens

Plant Diversity
Goal: Learning the patterns of diversity will help us learn to garden with nature rather than working against it
Fallen leaves inside umbrella plant, Darmerapeltatum

I. Organisms that reproduce through spores
Algae and fungi
Lichens
Slime Molds
Mosses
Liverworts and relatives
Horsetails
Ferns
Sori, the spore carrying bodies on ferns, here a sword fern

Algae and Fungi
Some algae are considered to be plants and some are not--fungi now reside in a separate Kingdom but many people think of them as plants
Both reproduce using some form of spore or similar structure

Algae
Include many different kinds, but the most familiar are those of streams, ponds and at the ocean shore washed up on the sand or growing on rocky shores

Are Algae A Problem?
Algae by themselves are not a problem-it is not a parasite for example
Because growth of algae requires moisture and nutrients, it will grow where these are available, such as polluted streams. Algae grows in nutrient rich streams and on sidewalks because it can find required nutrients there. Control may be necessary for safety or other reasons, but the algae itself is not the cause of the harm, they just take advantage of the conditions.

Fungi
Many kinds of fungi occur on earth
When you say “fungus”, most people will answer “mushroom” but fungi are much more complex
As we shall see, by far the most fungi are beneficial organisms but a few do cause diseases which are of concern to gardeners
It is important to distinguish between different kinds and not label all fungi as “bad”

Fungi
Some mushrooms and other fungi are also toxic, but this is rarely a concern. Unless you know they are a problem, please don’t treat mushrooms with fungicides because this will interfere with their positive interactions with plants and the environment.
For controlling fungi that cause disease, follow the recommendations of your local or state cooperative extension office.

Mushrooms in the Lawn
Gardeners who are worried about safety can seek positive identification and information, or rake up the mushrooms and discard or compost them

Positive Benefits of Fungi
Fungi are one of earth’s major decomposers, helping to return organic matter to enrich our soils
Soil fungi form mutually beneficial relationships with plants called mycorrhizae

How Fungi Reproduce
Fungi reproduce through spores that become airborne
The visible part of a fungus is usually the spore-producing body
The larger mass of the fungus is fine fungal strands that are often underground or inside a decaying organism
A “mushroom” is one kind of fungal spore producing body

Fungi
Mushrooms and other spore producing bodies are often the most visible part of the fungus
Mushrooms growing in an arc or ring are sometimes called a “fairy ring”
Yellow houseplant mushroom

Not all spore producing bodies are “mushrooms”
Cup-like spore producing bodies in cracks in a brick walkway
Cup style spore bodies in moss on a decaying branch

Mycorrhizae
Most soil fungi form relationships with most plants in a mutually beneficial relationship called mycorrhizae
Perhaps every plant shown in this forest clearing has associations with soil fungi

Mycorrhizae
Mycorrhizae are found in the roots of the plants where tissues of the two organisms intertwine
Fungal strands are in contact with the soil and extend the absorption capacity of the roots
Fungi gain the benefit of photosynthetic nutrients made by the plants

A new way to look at forests and gardens
Part of the magic of this relationship is that individual plants may form associations with dozens of different fungi
And, each fungus may form associations with dozens of trees
Together, these create a network of interactions

Slime Molds
Slime molds are not technically fungi nor plants
They grow in moist, usually warm conditions such as forests and damp gardens
They are another form of decomposer but can alarm people who have not seen them before
Slime mold spore producing bodies on turf grass. Oregon State University Plant Clinic

Slime molds in the garden
Slime molds have two phases. A moving mass first grows on decaying leaves, compost, or stumps. The spore producing phase is harder and often colorful. Both phases are ephemeral, disappearing only a few days or weeks after their appearance.
Spore producing structures of a slime mold on the back of an oak leaf

Lichens, a “special” group
Lichens are usually small and are not individual organisms
Instead, they are a combination of two different organisms—one is a fungus, and the other is algae
British soldiers, a ground dwelling lichen

Lichens
Most are gray or greenish
The visible part is the fungus, the algae are inside
Lichens are another mutually beneficial relationship
Several kinds of lichens on a tree branch

Lichens
Both algal and fungal partners benefit from this relationship
Algae gain a moist environment and the fungus gains photosynthetic nutrients
Together, they inhabit places like this rock where neither could if they were alone
Lichens growing on a rock

Lichens
Some gardeners are worried about lichen, but they are not a disease and cause no harm to the plant
Various lichens are indicative of good or bad air quality, an aid to understanding our environment
White and brown lichen on a tree trunk

Mosses
Are common in the moist habitats
Reproduce by spores
Are of short stature because they lack an organized vascular system to move water and nutrients
Help maintain moisture and provide homes for small creatures
Mosses and tiny mushrooms on a downed log

Mosses
Mosses are a healthy part of gardens and ecosystems
They often grow in lawns when the lawns themselves are not robust
Mosses are opportunists and will grow wherever the habitat is appropriate

Liverworts and other forest floor plants
Liverworts and their relatives have been on earth since ancient times
They reproduce by spores
They usually grow in natural habitats but sometimes can be found in gardens
They are not harmful in a garden setting
Selaginella, usually a forest dweller

Liverworts
One species of liverwort has become adapted to live in nursery pots and is considered to be a pest by nursery owners
Once in the garden, they usually disappear after a time and cause no harm

Horsetails
Perhaps no plant has caused such concern to tidy gardeners as the common horsetail. Rapidly spreading underground in a favorable environment, this plant can become quite a pest.
Horsetail, Equisetum, showing the spore producing branches that appear before the typical green branches

Horsetails
Here is the familiar horsetail form
Horsetails of many kinds are native around the world
Control is usually through persistent hand weeding or tolerance

Ferns
Ferns also reproduce by spores
Ferns are popular garden plants and some forms thrive in most, shady garden conditions
Licorice fern growing on a tree trunk

Ferns
Typically the fern leaves, called fronds, uncurl as they open such as shown here
Bracken fern in spring

Ferns
Spores are produced on the backs of the fronds or sometimes on separate modified leaves that only bear spores
Sword fern spore bodies

2. Plants that produce seeds
We will cover three kinds of seed bearing plants
Ginkgo
Conifers
Flowering Plants
Fruits of red osier dogwood, a flowering plant

Ginkgo
Very ancient plants once though to be extinct
Related to conifers but have different reproductive structures
They are neither conifers nor flowering plants but in a group all their own
Fall foliage and seed bearing structures on a mature female tree

Ginkgo biloba
Good landscape tree, drought and pollution tolerant
Distinctive leaf form often used in artistic work
Native to China

Conifers
Bear their seeds in cones
Conifers also have needles or scales
When seeds mature, cones usually open

Conifers
Large group with many trees and shrubs
Popular in gardens, particallybecause most are evergreen
Pines, firs, cedars, juniper, larch, and many more
An ornamental conifer with colorful cones

Conifers
Cones are made up of overlaping scales
In new female cones, the ovules are inside the cone but the scales are open to allow pollination
After pollination, the scales usually close while the seeds mature
Cone on an ornamental larch

Conifers
Pollination time differs for each species
Pollen is produced in tiny cones (dark orange in this tree) which is transferred by the wind to the tiny female cones at the tips of the branches
New cones and year-old cones on a pine species

Flowering Plants
A very large group, the latest to appear on earth
Developing seeds are protected within a solid structure which becomes a fruit
Pollen must actually grow through tissue to fertilize the ovum

Flowering Plants
Include trees, shrubs, herbaceous plants, vines
Are very popular garden plants
Are highly adapted to particular forms of pollination
Many have very close mutually beneficial relationships with insect pollinators
Gaillardia or blanket flower attracts bees and butterflies

Pollination
Is the process of transferring pollen from one flower to another
Typically, can be by wind, insects, water, birds, bats, or human intervention
Honey bee pollinating a Ceanothus flower

Pollination
Plants pollinated by insects are typically sweet smelling, colorful, and have places for insects to land
The “reward” for pollination is food from nectar or pollen
Bumblebee on an aster

Pollination
Plants attracting butterflies also provide nectar—they often have a large flat surface to support the butterfly’s body
Butterfly pollinated plants often have “butterfly partners” that use the plant as places to lay their eggs

Pollination
Many other garden plants are pollinated by hummingbirds
These flowers tend to be red or orange
Birds can see these colors but bees cannot
Red columbine, Aquilegia canadensis

Pollination
Plants pollinated by wind have less colorful flowers
Pollen is usually produced in catkins which contain only male flowers
Pollen is carried by the wind to female flowers that produce seeds
Catkins on a willow

Fruits
When seeds mature, they are carried in fruits
Fruits can be fleshy or dry and take many forms
Berries as shown here are one type of fruit
Calicarpa americana, the American beautyberry

More Fruits
Mimulus guttatus, yellow monkey flower has dry fruits called pods
Big leaf maple, Acer macrophyllum has dry fruits called samaras

3. Plant Anatomy
Seed bearing plants all share the same basic structures
Typical parts include leaves, stems, roots, and flowers
Differences are in the “details” which help us tell one plant from another

Overall Plant Structure
This is sweet cicely, a plant native to Oregon
Botanists know this because it has white flower heads, each with many flowers of a certain type
Another clue is the finely divided leaves in a particular pattern

Stems
Provide overall support
Create the “architecture” characteristic of each plant
Have internal vascular systems for transport of water, minerals, and photosynthetic nutrients

Stem Structure
This stem is woody, with wood cells for support
The main stem has a side branch at a place called a node
The side branch has two buds, one at the end – a terminal bud, and one on the side, called a lateral bud

Stem Structure
Here is another winter twig with no leaves
Plants that loose leaves during dormancy are called deciduous
Note the leaf scars on the side where the leaves fell off in the fall
Also note that the terminal bud has scales

Stem Structure
Each year, when the buds break or start to grow, the bud scales fall off, leaving bud scale scars
If you look carefully, you can sometimes see these scars circling the branch
This helps us determine which is this year’s growth and which is last year’s

Plant Growth Structure
Buds are of many types including flower buds, branch buds, and mixed buds
Lateral branch or mixed buds can grow into branches under the right conditions

Plant Growth Structure
Note that the small branch is growing from a node area, just above the leaf
The buds that produce branches are usually in this location, leading to another name: axillarybud

Kinds of Branching
The kind of branching on the last slide is called alternate
Here, the type of branching is called opposite
The kind of leaf pattern and branching pattern leads to different shapes of plants

Woody Stems
Woody plants grow differently than herbaceous plants
Herbaceous plants are most commonly annuals, biennials, or perennials, which create new aerial growth each year

Woody Stems
Here is a cross-section through a tree, showing typical woody structure
On the outside is bark
Right inside the bark is tissue called phloem that actively transports photosynthetic nutrients

Woody Plants
The inner part is xylem tissue that transports water and is considered to be the “woody part”
This is also where we see growth rings, which can indicate the age of the tree

Woody Plants
One growth ring is formed each year
At the beginning of each growth season, cells are large
At the end of the season, they are smaller and more dense, leading to the darker “rings”
The oldest growth of the tree is in the center

Woody Plants
Nutrient and water transport happen on the outer edges of the tree or shrub
For this reason, it is important to protect the bark; injury can lead to disruptions of nutrient and water flow and growth

Leaves
Leaves are usually the site of the process of photosynthesis, using the sun’s energy to create sugars and other nutrients
They also have unique patterns that help us identify plants

Leaf Characteristics – Vein Patterns
The vascular system of plants moves through leaves in 3 kinds of patterns
The pattern shown here is called a parallel vein pattern
Parallel veins on a lily plant

Parallel Vein Patterns
Parallel vein patterns
Occur in a group of plants called Monocotyledons or “Monocots” for short
They include grasses, lilies, onions, and many other related groups

More Parallel Vein Patterns
Mianthemum dilitatum, false lily of the valley
Disporum species

Pinnately Veined
Vein patters are also sometimes called venation
Pinnatelyveined leaves have veins in a feather-like pattern
This is a common pattern and signifies that the plant is in the group Dicotyledon or “Dicots” for short

More Pinnate Vein Patterns
Leaf skeleton of a magnolia

Palmately Veined Leaves
Palmately veined leaves are the third pattern
Main veins arise from the point of attachment, sort of like the fingers from the palm of a hand
These are also found in the group called “Dicots”
Coltsfoot

More PalmatelyVeined Leaves
Fringecup, Tellima gandiflora
A water lily

Petioles
Most leaves have a stem like structure connecting the leaf blade to the stem
These are called petioles
Some leaves do not have petioles, which helps us distinguish one plant from another

Leaf Edges
Patterns of leaf edges also help us distinguish plants
This is one of many edge patterns or margins
This one is called a toothed margin

Simple Leaves
Leaves with just one undivided leaf blade are called simple leaves
Several simple leaves on a branch are shown here
Oceanspray, Holodiscus discolor

Simple Leaves
Remember, each leaf has a bud associated with it to facilitate branching
Several leaves and the associated axillary buds are shown here
Salal, Gaultheria shallon

Compound Leaves
Compound leaves have more than one blade, each is called a leaflet
There are several patterns of compound leaves, this one is pinnately compound and has 7 leaflets
Oregon ash, Fraxinus latifolius

Compound Leaves
Here is another example of a pinnately compound leaf
Remember, you can determine what is a leaf by looking for the bud at its base
This plant gives us a clue because the entire leaf is reddish- it has 11 leaflets
Berberis nervosa, long leaf Oregon grape

Compound Leaves
Another pattern is palmately compound leaves
This one has 7 leaflets

Compound Leaves
Once again, the way to tell a leaf from a leaflet is to look for the axillary bud
This is difficult to determine in a photographs but is usually much easier in a hand-held sample
Wild lupine

Compound Leaves
One more pattern is also common and is doubly compound
This particular pattern is called bipinnately compound
Sometimes they are described as finely divided in herbaceous species

Leaf Adaptations
Leaves can be modified to perform many different functions
These leaves are modified to catch insects in an insectivorous plant
California pitcher plant, Darlingtoniacalifornica

Modified Leaves
This Pacific Northwest native plant has leaves modified for vegetative reproduction
Piggyback plant, Tolmiea menziesii

More Modified Leaves
Floating leaves on a water lily
Spines on a cactus

Roots
Since roots are underground, we seldom think about their presence
Major functions include support, absorption of water and minerals, and storage of carbohydrates and other photosynthetic nutrients
Large underground storage root of the wild cucumber

Roots
Even though we do not usually see roots, they are sometimes massive structures underground
For example, roots of this ash tree, and even the herbaceous plants beneath it, will extend many feet beyond the canopy of the above ground part of the plant
Veratrum emerging in the spring next to the trunk of an Oregon ash, Fraxinus latifolius

Roots
Woody plants also have woody roots
Clip art showing roots of a tree

Roots
Carrots, like those shown here in a pretend bunny, are tap roots. Their main structure is a single enlarged root with smaller roots off the surface
Tap roots often serve as storage for carbohydrates and other nutrients

Roots
Roots of many if not most herbaceous plants are fibrous, such as in this bulb
Clip art

Flowers and Fruits
The existence of flowers is one of the reasons we garden
Even vegetable gardens usually require flowers because fruits cannot form without them
passionflower

Flowers
The purpose of flowers is to produce seeds
A side product is that gardeners and pollinators can enjoy the benefits they provide
Flowers of Rosa nutkana (Nutka rose) and Physocarpus capitatus (ninebark)

Flowers
A typical flower has four countable parts: Sepals, petals, stamens and pistils
Sepals and petals are the outer parts—sepals are usually green and petals are usually colorful

Flowers
Many flowers are not typical
In this iris, for example, the three smaller petal-like structures are acutally sepals. The larger three are the petals

Flowers
This trillium has the more typical pattern with three green sepals and three white petals
The sepals are the outer layer of a flower and usually cover the flower bud before it opens
Both iris and trillium are Monocots
Trillium ovatum

Monocot Flowers
Plants with flower parts in groups of 3 or multiples of 3 are usually in the subgroup Monocots
Note the parallel venation on this plant, which support that classification
Slinkpod, Scoliopus bigelovii

Dicot Flowers
Flowers with flower parts in groups of 2,4,5 or multiples are usually Dicots
This flower has 4 petals so is most likely a Dicot
Notice that the central stigma (we will cover those later) is also split into 4 at the tip
Flower of a Clarkia species

Dicot Flowers
These flowers also have 4 petals
Look for the 4 smaller sepals
Also note the vein pattern is pinnate
This is a Dicot
Fireweed, Epilobium

Dicot Flowers
In this penstemon, the petals are fused into a tube
You can still determine that it has 5 petals however by looking at the number of flower lobes
Notice the nectar guides, lines that point toward the center of the flower

Dicot Flowers
Notice that these flowers also have a fused petal tube, and you can distinguish 5 lobes
Also note the nectar guides in this flower
This is another Dicot
Yellow monkeyflower, Mimulus guttatus

Flowers That Break the Rules
Many flowers “break the rules”—learning to be observant will help you know plants better
In skunk cabbage and some other plants, the colorful part is a spathe and the flowers themselves are very small and located on the whitish spikes

Flowers That Break the rules
In dogwoods, what appear to be petals are actually modified and colorful leaves called bracts
The many flowers are in clusters in the center of the bracts

Some flower form tight clusters such as this wild carrot
Each structure has many flowers, and each of these can bear seeds
This kind of flat-top structure is called an umbel-umbel plants often attract butterflies

All plants of the sunflower family form flowering structures called flowering heads
It looks like one large flower but instead is many tiny ones grouped together
Each “petal” is a separate flower for example

Flowers That Break the rules
This is another member of the sunflower family
Notice the tiny circular ring of flowers in the flowering head in the lower right
Each of the tiny flowers in this ring is blooming and each will produce a single seed

The Sexual Parts
Although petals and sepals can be attractive, the real work of the flower occurs in the sexual parts
Stamens bear the pollen
Pistils bear the ovules that become seeds when fertilized
Erythronium flower with pendulous stamens and pistils

The Sexual Parts
Look carefully at the central part of this flower
Look for 6 stamens and 1 central pistil
The pistil ends with a pink stigma split three ways
The stigma is usually sticky and will hold pollen delivered by a pollinator, in this case probably a bee
A cat’s ear, Calochortus species

The Sexual Parts
In this flower, note the 5 stamens and central pistil
Flannelbush, Fremontodendron californicum

The Sexual Parts
This flower has numerous stigmas ready to release their pollen
In the center is one pistil with the stigma divided into many parts
Camelia sasanqua

Fertilization
Once pollination occurs, the pollen grain begins to grow and sends a tube down through the pistil
This leads to fertilization and the production of seeds
A species of wild rose, Rosa sp.

Fruits and Seeds
Seeds of flowering plants are carried in some kind of fruit structure
This Asian pear is a kind of fruit called a pome and the seeds are inside
Seeds are disseminated by foraging animals and the seeds pass through the digestive system

Fruits and Seeds
Seeds of this wild plant called a baneberry are most likely disseminated by birds
The seeds are toxic, but since birds do not chew, the seeds pass unharmed through the bird’s digestive tract
Actea rubra

Fruits and Seeds
Seeds of these lupines are carried in pods
Pods open along lines to release the seeds when they are ready
The red flowers are another species, Mimulus cardinalis
Lupinus polyphyllus

Fruits and Seeds
Seeds of milkweeds have white parachute like attachments
These are disseminated by wind

Fruits and Seeds
This is cow parsnip which has flowers in the umbel form
This flat-topped structure persists in seed formation
This is one of the plants that also supports the growth of butterflies

Fruits and Seeds
Beechnut produces seeds that are nuts
The nuts are carried within an outer structure that splits open at maturity and releases the seeds to the soil below
They may also be carried by animals to new locations

Fruits and Seeds
This pod has opened to reveal the seeds inside
Each seed is capable of producing a new plant which grows from a tiny embryo inside
Peony seeds

Seed Germination
Under suitable conditions seeds germinate into new plants and the cycle starts anew
Clip art

This is the End
This is the end of our brief beginning tour of botany for gardeners
We have only touched the surface and there is much more to discover and know
I wish you luck on this journey
Echinacea purpurea ‘White Swam’

Botany Primer for Gardeners
Created by Linda McMahan, Botanist and Community Horticulture Faculty, Oregon State University Extension Service in 2010
All photographs except as noted are those of the author. This presentation and included materials may be freely used for educational purposes. For other uses, please contact the author at
linda.mcmahan@oregonstate.edu

Botany Primer For Gardeners

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