Practical Botany for Gardeners provides an elegant and accessible introduction to the world of botany. It presents the essentials that every gardener needs to know, connecting explanations of scientific facts with useful gardening tips. Flip to the roots section and you’ll not only learn how different types of roots support a plant but also find that adding fungi to soil aids growth. The pruning section both defines “lateral buds” and explains how far back on a shoot to cut in order to propagate them.
The book breaks down key areas and terminology with easy-to-navigate chapters arranged by theme, such as plant types, plant parts, inner workings, and external factors. “Great Botanists” and “Botany in Action” boxes delve deeper into the fascinating byways of plant science. This multifaceted book also includes two hundred botanical illustrations and basic diagrams that hearken to the classic roots of botany.
Part handbook, part reference, Practical Botany for Gardeners is a beautifully captivating read. It’s a must for garden lovers and backyard botanists who want to grow and nurture their own plant knowledge.
|Publisher:||University of Chicago Press|
|Product dimensions:||6.60(w) x 9.00(h) x 0.90(d)|
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PRACTICAL BOTANY FOR GARDENERS
Over 3,000 Botanical Terms Explained and Explored
By GEOFF HODGE
THE UNIVERSITY OF CHICAGO PRESSCopyright © 2013 Quid Publishing
All rights reserved.
The Plant Kingdom
For the study of nature to be possible, humans have long sought to arrange the great diversity of living things into groups that bear similar characteristics. This is known as classification, and depending on the system used, all living things are split into a number of major groups known as Kingdoms.
From a gardener's perspective, the starting point for plant classification begins with the question, "Is it a tree, a shrub, a perennial, or a bulb?" Botanists also recognize these groups, although they are not used as a basis for taxonomy (scientific classification)—in other words, the Plant Kingdom is not classified scientifically along these lines.
The organisms within the Plant Kingdom are classified according to their evolutionary groups, starting with the more simple algae and ending with the more highly developed flowering plants. With a few exceptions, all organisms within this Kingdom share the ability to manufacture their own food from sunlight, through photosynthesis.
At a first glance plant classification can seem confusing. However, knowing how plants are classified will help you achieve a greater appreciation of what you grow in your garden and provide a sound basis for further study. In this chapter, the main groupings into which the Plant Kingdom has been separated are discussed.
It has to be said that gardeners may have very limited interest in algae (singular: alga). other than pond algae, and the slippery slime that can accumulate on damp decks and patios, these organisms play a minor role in gardeners' minds.
Before we dismiss algae, however, it is worth mentioning that much of the Plant Kingdom is made up of these simple life-forms, and they play a massively important role in the world's ecosystem. They are considered "simple" because they lack the many different cell types of other plants and do not possess complex structures such as roots, leaves, and other specialized organs.
Huge variety is seen within this group of organisms. Most of us will be familiar with seaweeds, which are multicellular algae, but also prevalent are single-celled phytoplankton, which fill the seas and generate food using the sun's energy, thereby supporting all marine life. One curious group of algae are the diatoms: microscopic, single-celled algae that are an ever-present, yet invisible feature of any watery habitat. They are encased in fascinatingly beautiful, silicon-based cell walls.
As would be expected from such a "simple" form of life, the reproductive strategies of algae are not as complex as those seen in higher plants. Mostly, algae reproduce vegetatively, through the splitting of individual cells or larger multicellular units, and sexual reproduction is achieved by the meeting and ultimate fusion of two mobile cells.
Algae in the garden
Because algal cells do not produce a waterproof cuticle or have other means to prevent themselves drying out, they are either found in water or in damp, shady places. They also need the constant presence of water for growth and reproduction.
In the garden, algae will almost certainly be found in any garden pond or other area of standing water or constant moisture. Algae will also be found in the soil.
The pond is where most gardeners will encounter algae, and they can become quite a problem, especially when the weather warms up in spring. If conditions are favorable, algae can quickly discolor pond water, form unsightly scums, or choke the water with filamentous growth (blanket weed). Left to their own devices, algae can deprive the water of oxygen to the detriment of other pond life.
Despite this, algae are an essential part of the natural food chain in water gardens, and when kept "in balance," they help to maintain a healthy water environment. Problems seem to occur when ponds are exposed to too much sun, when temperatures fluctuate too widely (particularly problematic in small ponds), and where nutrient levels are too high. High nutrient levels may be caused by a build-up of debris in the pond and on the pond floor, as well as by fertilizers leaching into the water.
Algae will also grow on wet paths, fences, garden furniture, and other hard surfaces, especially those in cool, shady areas. Mosses, lichens, and liverworts may also be present in such situations. Contrary to popular belief, algae do not damage the hard surfaces on which they grow (though they may leave stains or marks), but they can make surfaces very slippery and treacherous. It is therefore worth trying to remove them, either with a pressure washer or a proprietary path and patio cleaner.
Mosses and liverworts
To botanists, this group of plants are known as the bryophytes. They are generally restricted to moist habitats; many are in fact aquatic. as multicellular organisms, these plants are considered more advanced than algae. However, they are still relatively simple plants with little differentiation between the cells, though some do have specialized tissues for the transport of water.
To the gardener, mosses are more significant than liverworts as they are commonly seen in almost all gardens, tending to grow in wet or damp, shady places in clumps or mats. Sphagnum moss in particular is of considerable benefit to gardeners as it is a major component of peat, still heavily used in plant potting composts. Liverworts are less noticed by the gardener; they are quite different to mosses in appearance, having a flattened, leathery body, which is sometimes lobed. Mosses have a more elaborate structure than liverworts, often with upright shoots bearing tiny "leaflets." In common with algae, bryophytes can only reproduce sexually in the presence of water. Without the medium of water, the male and female sex cells (sperm and egg) would not be able to meet.
The alternation of generations
With bryophytes, we see the appearance of a complex life cycle, known as "the alternation of generations," which is a phenomenon seen in all plants beyond this level of complexity. There are two generations to the life cycle: gametophyte and sporophyte. In mosses and liverworts, the plant spends the majority of its life cycle in the gametophyte stage; in ferns and all higher plants the sporophyte stage is dominant. In flowering plants, the gametophyte stage is so reduced that it is often not referred to in these terms (see p. 22).
In the gametophyte stage, each and every cell carries just half of the organism's genetic material. Thus, the structures we know as mosses or liverworts are actually just made up of unpaired "half cells" (haploids). It is only when these structures release sperm and egg cells, which meet and fuse in the presence of water, that a "whole cell" (diploid) is brought into being. This becomes the sporophyte generation, and in bryophytes the sporophyte generation is reduced to a simple spore-producing body that remains attached to the gametophyte. As the name suggests, the diploid sporophyte generation releases spores, which are created by the division of sporophyte cells. Thus, the spores themselves are haploid, and upon release they are dispersed by the rain or wind, after which some of them will grow into a new moss or liverwort gametophyte.
Gregor Johann Mendel
Gregor Johann Mendel, now regarded as the father and founder of the science of genetics, was born Johann Mendel in what was then Heinzendorf, Austria, which is now in the Czech republic.
He lived and worked on the family farm and during his childhood mainly spent time in the garden and studying beekeeping. He went on to attend the Philosophical Institute of the University of Olmütz, where he studied physics, math, and practical and theoretical philosophy, distinguishing himself academically. The head of the university's natural History and agriculture department was Johann Karl Nestler, who was conducting research into the hereditary traits of plants and animals.
During his graduation year, Mendel began studying to be a monk, and joined the Augustinian order at the St Thomas Monastery in Brno, Czech republic, where he was given the name Gregor. This monastery was a cultural center and Mendel soon became involved in the research and teaching of its members and had access to the monastery's extensive library and experimental facilities.
After eight years at the monastery Mendel was sent to the University of Vienna, at the monastery's expense, to continue his scientific studies. Here he studied botany under Franz Unger, who was using microscopes and was a proponent of a pre-Darwinian version of evolutionary theory.
After completing his studies at Vienna, Mendel returned to the monastery where he was given a teaching position at a secondary school. During this time he began the experiments that would make his name famous.
Mendel began to research the transmission of hereditary traits in plant hybrids. At the time of Mendel's studies, it was generally accepted that the hereditary traits of the offspring were simply the diluted blending of whatever traits were present in the parents. It was also commonly accepted that, over several generations, a hybrid would revert to its original form, suggesting that a hybrid could not create new forms. However, the results of such studies were usually skewed by short experimental times. Mendel's research continued for up to eight years and involved tens of thousands of individual plants.
Mendel used peas for his experiments because they exhibit many distinct characteristics, and because offspring could be quickly and easily produced. He cross-fertilized pea plants that had clearly opposite characteristics, including tall with short, smooth seeds with wrinkled seeds, green seeds with yellow seeds. After analyzing his results, he showed that one in four pea plants had purebred dominant genes, one had purebred recessive genes and the other two were intermediates.
These results led him to two of his most important conclusions and the creation of what would become known as Mendel's laws of Inheritance. The law of segregation reasoned that there are dominant and recessive traits passed on randomly from parents to offspring. The law of Independent assortment established that these traits were passed on independently of other traits from parent to offspring. He also proposed that this heredity followed basic mathematical statistical laws. Although Mendel's experiments involved peas, he put forward the hypothesis that this was true for all living things.
In 1865, Mendel delivered two lectures on his findings to the natural science society in Brno, which published the results of his studies in its journal under the title "experiments on Plant Hybrids." Mendel did little to promote his work and the few references to his work from that time indicate that much of it had been misunderstood. It was generally thought that Mendel had only demonstrated what was already commonly known at the time—that hybrids eventually revert to their original form. The importance of variability and its implications were overlooked.
In 1868, Mendel was elected abbot of the school where he had been teaching for the previous 14 years, and both his increased administrative duties and failing eyesight stopped him from carrying out further scientific work. His work was still largely unknown and somewhat discredited when he died. It was not until the early 1900s, when plant breeding, genetics, and heredity became an important area of research, that the significance of Mendel's findings became fully appreciated and recognized and began to be referred to as Mendel's laws of Inheritance.
Only 150 years ago did scientists discover the true nature of lichens. They are a curious partnership between fungi and algae, living together in a symbiotic relationship. Today they are classified by their fungal component, which puts them outside of the Plant Kingdom, but they are included here as they have long been a subject of botanical study.
Lichens seem to be able to grow in every habitat on earth, and in some extreme environments, such as on exposed rock in polar climates, they seem to be the only thing that can grow. In 2005, scientists even discovered that two species of lichen were able to survive for fifteen days exposed to the vacuum of space. More commonly, they are seen growing on trees and shrubs, bare rock, walls, roofs, paving and on the soil. Informally, they are generally divided into seven groups depending on how they grow; thus we have crustose, filamentous, foliose (leafy), fruticose (branched), leprose (powdery), squamulose (scaly), and gelatinous lichens.
Lichens in the garden
More often than not, lichens are noticed on lawns, where their appearance, quite rightly, often causes gardeners concern. Lichens not only affect the appearance of the lawn, they block light from reaching the grass (so killing it), and they can make surfaces slippery.
In turf, the most common lichens are the dog lichens (Peltigera). They are either dark brown, gray, or nearly black, and are formed from flat structures that grow horizontally in the turf. They are usually worse on lawns with poor drainage, compacted soil, and shady conditions, and as they grow in similar conditions to moss, the two often appear together. Interestingly, dog lichens have the ability to fix atmospheric nitrogen, so they are beneficial in soil fertility.
To prevent lichens on a lawn, you need to improve drainage, thereby correcting the underlying conditions that enabled them to grow in the first place. There are few, if any, effective chemical controls available to gardeners, but path and patio cleaners can be used to scrub them off hard surfaces.
Ferns and their relatives
From an evolutionary point of view, ferns and their relatives represent a significant development: when plants began to show increased cell differentiation. Here we see the first vascular systems—vessels for transporting water and nutrients around the plant—as well as structures concerned with the support of the plant. These were also the first plants to truly colonize the land.
Botanists classify this group of plants as pteridophytes, and they include club mosses, true ferns, and horsetails. Gardeners are likely to have heard of horsetails, and they will definitely know about ferns, but club mosses (sometimes called spike mosses) remain obscure, even though one or two forms are cultivated. Club mosses are not mosses; they are more advanced.
Like the bryophytes, pteridophytes exhibit a clear alternation of generations, but the crucial shift is that pteridophytes spend most of their life cycle in the sporophyte phase. This allows for the production of vertical branches or fronds, sometimes specialized, bearing tiny swellings called sporangia. When the sporangia burst, they release the spores, which germinate to become the gametophyte generation.
A gardener could be easily forgiven for assuming that spores are simply the same as seeds. While they are both used as ways for a plant to disperse themselves and there are similarities in their culture, it is important to note that there are vital differences: a spore is generally much smaller than a seed and its production does not rely on fertilization. Ferns do not produce seeds.
Allowed to grow on a tray of seed compost, and given sufficient moisture as well as the required amount of light and heat, fern spores will begin to grow. But rather than growing into baby ferns, they will grow into the next stage of the life cycle: the gametophyte generation. These odd-looking plants are called prothalli, and if kept moist and misted they will slowly begin to grow into new ferns—what the human eye does not see is that during this interval, the prothallus has itself produced sperm cells that have fertilized the egg cells (this is the stage of sexual reproduction), which then grown into the new sporophyte generation of the fern.
Ferns in the garden
There are approximately 10,000 species of fern, all varying quite remarkably in size and growth habit, from the stately royal fern (Osmunda regalis) to the tiny, floating aquatic water fern (Azolla filiculoides). The water fern is considered invasive in some parts of the world, due to its prolific nature, while in others it is highly valued in agriculture for enhancing the growth rate of crops grown in water, such as rice. Either way, Azolla is a highly successful plant, and one that needs to be avoided like the plague in a garden setting. bracken (Pteridium aquilinum) is a land fern with a similarly invasive nature, and is considered to have the widest worldwide distribution of any fern.
There are many, many more fern species that are commonly used as ornamental garden and indoor plants, and from them plant breeders have selected countless cultivars with variations in frond form and color. Most ferns grow in moist, shady woodlands and these are the conditions in which they tend to grow best in the garden.
In recent years, some of the most popular ferns in gardens have been those referred to as tree ferns. Any fern that grows with the fronds elevated above ground level by a trunk can be called a tree fern, and in cool climates perhaps the most familiar example would be Dicksonia antarctica from Australia. The "trunk" is not like that of a tree or shrub; it is in fact a mass of fibrous roots that are built up over time as the crown of the fern continues to grow. In the wild, many tree fern species are threatened with extinction because of deforestation.
The most notable relatives of the true ferns must be the horsetails (Equisetum). Although a handful of species (such as E. hyemale and E. scirpoides) are grown as ornamental plants, Equisetum is best known for E. arvense, field horsetail, which is a notorious weed in many areas of the world. It is very difficult to eradicate, and in a garden situation it becomes a persistent and overbearing nuisance.
The most extraordinary fact about Equisetum, however, is its status as a "living fossil." It is the only genus alive today of its class, which dominated the understory of the world's forests approximately 400 million years ago. Fossils found in coal deposits show that some Equisetum species reached over 100 ft (30 m) tall.
Excerpted from PRACTICAL BOTANY FOR GARDENERS by GEOFF HODGE. Copyright © 2013 Quid Publishing. Excerpted by permission of THE UNIVERSITY OF CHICAGO PRESS.
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