The Weeder's Digest
Identifying and Enjoying Edible Weeds
By Gail Harland, Debs Cook, Dave Hamilton, Gary K Smith/Alamy, iStock, Gary K. Smith/Alamy FloraImages/Alamy
Green Books Ltd
Copyright © 2012 Gail Harland
All rights reserved.
ISBN: 978-1-900322-99-7
Contents
Introduction,
PART 1 Know your weeds,
1 The good, the bad and the ugly: Characteristics of weeds,
2 Achievable weed control: A question of balance,
3 A case of mistaken identity: Poisonous plants,
PART 2 A bouquet of weeds,
Glossary,
Notes,
Bibliography,
Index,
CHAPTER 1
The good, the bad and the ugly
Characteristics of weeds
A large number of plants can be classed as weeds, although, as a proportion of known plants, surprisingly few are really troublesome. Any species may be considered a weed in a garden if it grows to dominate other plants, but most weeds have a number of common features. They are usually fast-growing and able to out-compete other plants for food, light and water. They are tolerant of a variety of soils and situations. They spread readily by seed or vegetative growth. Some weeds may show resistance to herbicides and be very difficult to control.
Weeds will vary depending on the conditions in which they grow. A weed can be relatively innocuous in one garden but run rampant in another where the conditions are more to its liking. Some may be found in just a few parts of the country, whereas others, such as groundsel, may occur in virtually every garden.
Of course, as well as the weeds themselves, gardeners vary. Some people aim for a perfectly kept garden and show zero tolerance for any weeds. Other gardeners may not be so particular and can enjoy the shaggy golden flowers of dandelions without feeling the urge to leap up and grub them out. Much depends on the style of garden; weeds may be accepted in a casual orchard setting that would not be tolerated in a formal flowerbed close to the house.
Perhaps the important thing is to get to know your weeds and their characteristics and to understand which of them can be tolerated, used or even enjoyed, and which are best kept firmly under control.
Annual weeds
Annual weeds are those such as shepherd's purse and chickweed, which complete their entire lifecycle within one year.
Some, such as hairy bittercress, are termed ephemerals, as they have a particularly short lifecycle with several generations produced in one season. Thale cress (Arabidopsis thaliand) has a lifespan of just four to six weeks. Its short lifecycle has proved of value in the study of molecular biology, and this species has even been grown in a shoebox-sized mini-glasshouse on the International Space Station. While its life may be short, it is certainly productive, and a single plant of thale cress can produce nearly 3,000 seeds.
The old adage 'One year's seeding means seven years' weeding' is certainly true in the case of annual weeds, and to control them it is important that they are removed before they have a chance to set seed. Many produce small light seeds that are easily distributed on the wind and are quick to germinate. The seeds can, however, lie dormant in the soil for many years until they are brought to the surface, when they will germinate and begin to grow rapidly. Annual weeds are found most often in places which are regularly cultivated or disturbed, for example arable land and in vegetable plots or on allotments. They grow rapidly and can compete with and smother slower-growing plants.
Perennial weeds
Perennial weeds such as spear thistles are able to survive from year to year. Herbaceous perennials usually die down to ground level in the winter and survive as fleshy rootstocks or rhizomes, for example docks and stinging nettles. The roots of some species can go down to great depths in the soil, making them extremely difficult to dig out. Horsetail roots have been found at depths of 2m (6'6"). Deep-rooted perennials will usually regrow if the top is pulled up or burned off. There are also many woody-stemmed weeds, including brambles, elder and ivy. Tree seedlings such as ash and sycamore can be a particular problem in many gardens.
Perennial weeds spread by means of seed, or vegetatively, often by creeping rootstocks. Perennial weeds are often more difficult to control than annuals, as hoeing and digging may break the roots and rhizomes into pieces which are often able to regrow into individual plants. The bulbs of wild garlic may be distributed by digging or even by burrowing mammals such as rabbits. Woody weeds with thorns such as brambles and roses can be painful to deal with, as the long spiny stems need to be cut down before you can attempt to dig out the roots.
Spreading the seed
Weeds are notorious for the prolific quantity of seeds they can produce. A single plant of shepherd's purse can produce 150,000 seeds and common purslane can produce a staggering 1,800,000 seeds per plant. The majority of these seeds lose viability quite quickly, but some can remain viable in the soil for 40 years or more, awaiting suitable conditions for germination. It is not just the quantity of seeds produced, but also the ingenious ways in which they are dispersed that enables weeds to be so successful.
Wind
The seeds of many plants have elegant silky plumes that enable them to be carried for long distances on currents of air. The dandelion clock with its seeds surmounted by silvery hairs is the classic example of this. Other examples include thistledown, bulrushes and the fluffy seeds of the willowherbs. Tree seeds often have stiff wings enabling them to spin as they are carried along by the wind. The seeds of the ash tree, known as keys, have just one wing, whereas sycamore seeds are dispersed as two-winged pods that later split into two separate portions to release the seeds. The seeds of weeds such as poppies and corncockle develop in pods like little pepper pots and are shaken out by the wind.
Mechanical
Oxalis species, hairy bittercress and many legume plants have seedpods in which great pressure builds up as the pod ripens. It then takes just the slightest touch for the pressure to release and the contents to be flung over a wide area. If you walk past heath land gorse bushes on a hot sunny day, you can often hear the explosions as the seedpods burst open. The seeds of Himalayan balsam can be dispersed 7m (23') away from the parent plant by this method.
Water
Obviously, aquatic plants will depend on water to carry their seeds downstream to colonise new areas, but many land plants too will use water. Himalayan balsam seeds that land in water after being ejected are carried away, buoyed by the corky seed coat. The jimsonweed (Datura stramonium) has flat, corky seeds that float easily.
They can be carried downstream and deposited on the riverbanks, where they will germinate. The giant hog-weed can also spread along riverbanks by virtue of its corky seeds.
Birds
Many birds will cheerfully gorge themselves on the fruit of plants such as brambles and elder. They can then fly far from the parent plant and deposit the seeds complete with a neat dab of fertiliser to ensure a good start in life for the new seedling. Some birds such as jays will deliberately cache seeds, for example the nutrient-rich acorns of oak trees, for eating later. Inevitably not all these saved seeds are retrieved and many may well live to germinate in...
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