Beneficial weed
Encyclopedia
A beneficial weed is any of various plant
s not generally considered domesticated
, but which nonetheless has some companion plant effect, or else is edible or somehow beneficial. Beneficial weeds include a great many wildflower
s, as well as other weed
s that are commonly removed or poisoned
.
Many weeds protect nearby plants from insect pests.
One way they can do this is to repel insects and other pests through their smellhttp://www.informaworld.com/smpp/content~content=a905829894&db=all, as do alliums and wormwood
. Another is to entirely mask a companion's scent, or the pheromones of pest insects, as with ground ivy and wild oregano.
Some also are unpleasant to small animals, because of their spines or other features, keeping them away from an area to be protected.
s, distracting pests away from valued plants. Insects seeking a food plant search by smell, and then land at random on anything green in the area of the scent. If they land on an edible "weed", they will stay there instead of going on to the intended victim. Sometimes, they actively prefer the trap crop.
One scientific study said that simply having clover growing nearby cut the odds of cabbage root flies hitting the right plant from 36% to 7%. Statistically, this is enough to dramatically change the productivity of one's crop, all alone.
Many plants can grow intercropped in the same space, because they exist on different levels in the same area, providing ground cover or working as a trellis for each other. This healthier style of horticulture is called forest gardening
.
Among the obvious benefits are providing a wind break or shelter from noonday sun for more delicate plants.
effect, used by inhibiting the growth of any weeds that are actually harmful, and creating a humid, cooler microclimate around nearby plants, stabilizing soil moisture more than they consume it for themselves.
Plants such as ryegrass
, red clover
, and white clover
are examples of "weeds" that are living mulches, often welcomed in horticulture.
, through a chemical means known as allelopathy
. Specific other plants can be bothered by a chemical emission through their roots or air, slowing their growth, preventing seed germination, or even killing them.
For example, wild umbellifers attract predatory wasps and flies, that eat nectar, but reproduce by feeding common garden pests to their offspringhttp://www.wildaboutgardening.org/en/gardening-for-wildlife/animals/beneficial-insects.
Likewise, some weeds attract ladybugs or the "good" types of nematode
, or provide ground cover for predatory beetles.
, besides being edible if properly cooked, seems to increase essential oil production in nearby herbs.
Plant
Plants are living organisms belonging to the kingdom Plantae. Precise definitions of the kingdom vary, but as the term is used here, plants include familiar organisms such as trees, flowers, herbs, bushes, grasses, vines, ferns, mosses, and green algae. The group is also called green plants or...
s not generally considered domesticated
Domestication
Domestication or taming is the process whereby a population of animals or plants, through a process of selection, becomes accustomed to human provision and control. In the Convention on Biological Diversity a domesticated species is defined as a 'species in which the evolutionary process has been...
, but which nonetheless has some companion plant effect, or else is edible or somehow beneficial. Beneficial weeds include a great many wildflower
Wildflower
A wildflower is a flower that grows wild, meaning it was not intentionally seeded or planted. Yet "wildflower" meadows of a few mixed species are sold in seed packets. The term "wildflower" has been made vague by commercial seedsmen who are interested in selling more flowers or seeds more...
s, as well as other weed
Weed
A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-controlled settings, especially farm fields and gardens, but also lawns, parks, woods, and other areas. More specifically, the term is often used to...
s that are commonly removed or poisoned
Herbicide
Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...
.
Fertilization
Although errantly assumed to compete with neighboring plants for food and moisture, some "weeds" provide the soil with nutrients, either directly or indirectly.- For example, legumes, such as white cloverWhite cloverTrifolium repens, the white clover , is a species of clover native to Europe, North Africa, and West Asia...
, add nitrogenNitrogenNitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
to the soil through the process of nitrogen fixationNitrogen fixationNitrogen fixation is the natural process, either biological or abiotic, by which nitrogen in the atmosphere is converted into ammonia . This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g., nucleotides for DNA and RNA and...
, where bacteria symbiotically living in their roots extract nitrogen from the atmosphere, making it accessible in the soil for its host, and any nearby plants.
- Others use deep tap roots to bring up nutrients and moisture from beyond the range of normal plants, so that the soil improves in quality over generations of that plant's presence.
- Weeds with strong, widespread roots also introduce organic matter to the earth in the form of those roots, turning hard, dense clay dirt into richer, more fertile soil.
-
- In fact, some common plants like tomatoes and corn will "piggyback" on nearby weeds, allowing their relatively weak root systems to go deeper than they could have alone.
Pests
One way they can do this is to repel insects and other pests through their smellhttp://www.informaworld.com/smpp/content~content=a905829894&db=all, as do alliums and wormwood
Wormwood
Wormwood may refer to:*Various plants of the genus Artemisia but commonly Artemisia absinthium, also called grande wormwood or absinthe wormwood...
. Another is to entirely mask a companion's scent, or the pheromones of pest insects, as with ground ivy and wild oregano.
Some also are unpleasant to small animals, because of their spines or other features, keeping them away from an area to be protected.
Trap crops
Some weeds act as trap cropTrap crop
A trap crop is a plant that attracts agricultural pests, usually insects, away from nearby crops. This form of companion planting can save the main crop from decimation by pests without the potential issues and controversy involved in using pesticides....
s, distracting pests away from valued plants. Insects seeking a food plant search by smell, and then land at random on anything green in the area of the scent. If they land on an edible "weed", they will stay there instead of going on to the intended victim. Sometimes, they actively prefer the trap crop.
Host-finding disruption
Recent studies on host-plant finding have shown that flying pests are far less successful if their host-plants are surrounded by any other plant or even "decoy-plants" made of green plastic, cardboard, or any other green material.- First, they seek plants by scent. Any “weed” that has a scent reduces the odds of them finding crop plants. Obvious examples are Crow Garlic and Ground Ivy, the former being “wild chives” and the latter a form of wild mint, both dramatically masking both plant scent and insect pheromones. They cut down Japanese beetle infestation, and caterpillar infestation, for example cabbage worm, tomato hornworm, and even squash bugs.
- Second, once an insect is near its target, it avoids landing on dirt, but lands on the nearest green thing. Bare earth gardening helps them home in perfectly on the victim crop. But if one is using “green mulch”, even grass or clover, the odds are that they will make what's called an “inappropriate landing” on some green thing they don’t want. They will then fly a short distance at random, and land on any other green thing. If they fail to accidentally hit the right kind of plant after several tries, they give up.
- If they are there to lay eggs on the crop, weeds provide one more line of defense: Even if they find the right plant, in order to ensure that they didn’t hit on a dying plant or falling leaf, they then make short leaf-to-leaf flights before laying eggs. They must land on the “right kind of leaf” enough times in sequence, before they will risk laying their eggs. The more other greenery is nearby, the harder it is for them to remain on target and get enough reinforcement. Enough “inappropriate landings”, and they give up, heading elsewhere.
One scientific study said that simply having clover growing nearby cut the odds of cabbage root flies hitting the right plant from 36% to 7%. Statistically, this is enough to dramatically change the productivity of one's crop, all alone.
Forest gardening
Forest gardening
Forest gardening is a food production and agroforestry system based on woodland ecosystems, incorporating fruit and nut trees, shrubs, herbs, vines and perennial vegetables which have yields directly useful to humans...
.
Among the obvious benefits are providing a wind break or shelter from noonday sun for more delicate plants.
Green mulch
Conversely, some intercropped provide a living mulchLiving mulch
In agriculture, a living mulch is a cover crop interplanted or undersown with a main crop, and intended to serve the functions of a mulch, such as weed suppression and regulation of soil temperature...
effect, used by inhibiting the growth of any weeds that are actually harmful, and creating a humid, cooler microclimate around nearby plants, stabilizing soil moisture more than they consume it for themselves.
Plants such as ryegrass
Ryegrass
Ryegrass is a genus of nine species of tufted grasses in the Pooideae subfamily of the Poaceae family. Also called tares , these plants are native to Europe, Asia and northern Africa, but are...
, red clover
Red clover
Trifolium pratense is a species of clover, native to Europe, Western Asia and northwest Africa, but planted and naturalised in many other regions....
, and white clover
White clover
Trifolium repens, the white clover , is a species of clover native to Europe, North Africa, and West Asia...
are examples of "weeds" that are living mulches, often welcomed in horticulture.
Herbicide
Repel plants or fungiFungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...
, through a chemical means known as allelopathy
Allelopathy
Allelopathy is a biological phenomenon by which an organism produces one or more biochemicals that influence the growth, survival, and reproduction of other organisms. These biochemicals are known as allelochemicals and can have beneficial or detrimental effects on the target organisms...
. Specific other plants can be bothered by a chemical emission through their roots or air, slowing their growth, preventing seed germination, or even killing them.
Beneficial insects
A common companion plant benefit from many weeds is to attract, or be inhabited by, beneficial insects or other organisms which benefit plants.For example, wild umbellifers attract predatory wasps and flies, that eat nectar, but reproduce by feeding common garden pests to their offspringhttp://www.wildaboutgardening.org/en/gardening-for-wildlife/animals/beneficial-insects.
Likewise, some weeds attract ladybugs or the "good" types of nematode
Nematode
The nematodes or roundworms are the most diverse phylum of pseudocoelomates, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 28,000 have been described, of which over 16,000 are parasitic. It has been estimated that the total number of nematode...
, or provide ground cover for predatory beetles.
Human-useful
- Some beneficial weeds, such as lamb's quartersLamb's quartersLamb's quarter, lambsquarters and similar terms refer to various species of goosefoot, or pigweed.There are numerous variations, with or without hyphens and apostrophes, using one word or two, and singular or plural...
and purslanePurslanePurslane may refer to:* Portulacaceae, a family of succulent flowering plants, and especially:** Portulaca oleracea, a species of Portulaca eaten as a vegetable and considered a weed, known as summer purslane...
, are edible. This list of edible flowers includes many wildflowerWildflowerA wildflower is a flower that grows wild, meaning it was not intentionally seeded or planted. Yet "wildflower" meadows of a few mixed species are sold in seed packets. The term "wildflower" has been made vague by commercial seedsmen who are interested in selling more flowers or seeds more...
s that are considered weeds when not planted intentionally. Dandelion is an excellent example of an edible weed (see dandelion wine, dandelion coffeeDandelion coffeeDandelion coffee is an infusion or herbal tea, and coffee substitute, made from the root of the dandelion plant. The roasted dandelion root pieces and the beverage have some resemblance to coffee in appearance and taste.-History:...
). - A number of weeds have been proposed as natural alternate sources for latex (rubber), including goldenrodGoldenrodSolidago, commonly called goldenrods, is a genus of about 100 species of flowering plants in the family Asteraceae. Most are herbaceous perennial species found in the meadows and pastures, along roads, ditches and waste areas in North America. There are also a few species native to Mexico, South...
, from which the tires were made on the car famously given by Henry FordHenry FordHenry Ford was an American industrialist, the founder of the Ford Motor Company, and sponsor of the development of the assembly line technique of mass production. His introduction of the Model T automobile revolutionized transportation and American industry...
, to Thomas EdisonThomas EdisonThomas Alva Edison was an American inventor and businessman. He developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and a long-lasting, practical electric light bulb. In addition, he created the world’s first industrial...
. - CockleburCockleburCockleburs are a genus of flowering plants in the family Asteraceae, native to the Americas and eastern Asia.-Growth:They are coarse, herbaceous annual plants growing to 19.69-47.24 in tall. The leaves are spirally arranged, with a deeply toothed margin. Some species, notably X...
and stinging nettle have been used for natural dyeNatural dyeNatural dyes are dyes or colorants derived from plants, invertebrates, or minerals. The majority of natural dyes are vegetable dyes from plant sources – roots, berries, bark, leaves, and wood — and other organic sources such as fungi and lichens....
s. - Studies have shown that milkweed is actually a more effective insulator than goose down.
Flavor
Some plants seem to subtly change the flavor of other plants around them, in a way humans find desirable, for example stinging nettleStinging nettle
Stinging nettle or common nettle, Urtica dioica, is a herbaceous perennial flowering plant, native to Europe, Asia, northern Africa, and North America, and is the best-known member of the nettle genus Urtica...
, besides being edible if properly cooked, seems to increase essential oil production in nearby herbs.
Examples
- CloverCloverClover , or trefoil, is a genus of about 300 species of plants in the leguminous pea family Fabaceae. The genus has a cosmopolitan distribution; the highest diversity is found in the temperate Northern Hemisphere, but many species also occur in South America and Africa, including at high altitudes...
is a legume. Like other beanBeanBean is a common name for large plant seeds of several genera of the family Fabaceae used for human food or animal feed....
s, it hosts bacteria that fix nitrogenNitrogen fixationNitrogen fixation is the natural process, either biological or abiotic, by which nitrogen in the atmosphere is converted into ammonia . This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g., nucleotides for DNA and RNA and...
in the soil. Its vining nature covers the ground, sheltering more moisture than it consumes, providing a humid, cooler microclimate for surrounding plants as a "green mulch". It also is preferred by rodents over many garden crops, cutting down on the amount of desired vegetables that get eaten. - Dandelions possess a deep, strong tap root that breaks up hard soil, benefiting weaker-rooted plants nearby, and draw up nutrients from deeper than shallower-rooted nearby plants can access. They will also excrete minerals and nitrogen through their roots.
- Crow garlic, the wild chives found in sunny parts of a North American yard, has all of the companion plant benefits of other alliumAlliumAllium is a monocot genus of flowering plants, informally referred to as the onion genus. The generic name Allium is the Latin word for garlic....
s, including repelling japanese beetles, aphids, and rodents, and being believed to benefit the flavor of solanumSolanumSolanum, the nightshades, horsenettles and relatives, is a large and diverse genus of annual and perennial plants. They grow as forbs, vines, subshrubs, shrubs, and small trees, and often have attractive fruit and flowers. Many formerly independent genera like Lycopersicon or Cyphomandra are...
s like tomatoes and peppers. It can be used as a substitute for some alliums in cooking, if its slightly more bitter flavor is masked by sweetness or lipids. - Bishop's lace (Queen Anne's Lace) works as a nurse plant for nearby crops like lettuceLettuceLettuce is a temperate annual or biennial plant of the daisy family Asteraceae. It is most often grown as a leaf vegetable. It is eaten either raw, notably in salads, sandwiches, hamburgers, tacos, and many other dishes, or cooked, as in Chinese cuisine in which the stem becomes just as important...
, shading them from overly intense sunlight and keeping more humidity in the air. It attracts predatory wasps and flies that eat vegetable pests. It has a scientifically tested beneficial effect on nearby tomato plants, and when young has an edible root, both of these because the domesticated carrotCarrotThe carrot is a root vegetable, usually orange in colour, though purple, red, white, and yellow varieties exist. It has a crisp texture when fresh...
is simply a cultivar of this "weed".
External links
- Plants for a future -- Useful weeds
- Good Weeds -- it has an especially good list of "soil indicator" weeds
- Insect Olfaction of Plant Odour