What Is A Weed?

What is a weed? Broadly speaking a weed is any plant growing where it is not wanted. Usually this means a plant that is invasive, or harbours pests or diseases that are harmful to desirable plants. Weeds are not a total curse as some attract beneficial insects (milkweed attracts monarch butterflies), some add organic matter to the soil and those with deep roots break up compacted soil while others are harvested for food (dandelion for salad greens).

Weeds prefer poor nutrient-deficient soil usually. Stinging nettle is an exception and grows in nutrient rich soil. Germination speed can be a good indicator it is a weed as most germinate quickly. How the plants are distributed can identify if a weed or not too. Randomly and in a mixed pattern resembling a native planted meadow is likely weeds. Weeds are usually hard to remove. Weeds tend to have a weedy-smell which can resemble a mowed field to quite rank from their broken stems.

IMG_1544Weeds produce abundant seeds as a survival strategy. Most weeds have a tough coat to their seeds and can lie in the soil until conditions are good for germination from one year to the next. Botanist have studied and shown that some weed seeds have remained viable for 120 years then germinated and grown when planted. Weeds adapt extremely well to adverse conditions so it is important to understand their life cycles in order to identify and eradicate them effectively.

Annuals such as crabgrass, lamb’s quarters and ragweed complete their life cycle in one season growing from seed in the spring, then flowering and producing copious amounts of seeds before dying. One ragweed plant can produce 117,000 seeds in a single year.

Plants such as Queen Anne’s lace, mullein and burdock are biennial weeds so they die at end of their second year after they have flowered and set seed.

Perennial weeds such as bindweed, dandelion, nutsedge and quack grass are most persistent, resilient and toughest to control. Dig often and dig deep.

Certain weeds favour specific soil types. Stinging nettle prefers nutrient rich high in nitrogen and phosphorous soil. Dandelion grows well in compacted soils low in calcium and sometimes high in phosphorous. Weeds such as plantain and knotweed have special roots to deal with excessively compacted soil. Spurge will grow on edge of asphalt. Fireweed is a pioneer weed in that it is first to thrive after a fire on the nitrates found in ashes.

Removal of Weeds

Weeding by hand, trowel, hoe or cultivator is important. Watering the day before weeding your garden moistens the soil making weeding easier. Use a hoe on a dry, sunny day so that small seedlings will bake when they are uprooted. A Dutch hoe or circle hoe slices off young weed seedlings just below ground level

When removing a mature weed manually it is vital to get the entire root to be successful. Use a cultivator to loosen the soil around large weeds; then pull them straight out. Use a garden fork to weed a border to keep weed roots intact so they cannot re grow. Do not use a spade as this slices through the roots leaving behind small pieces that can re grow. Purslane is a weed that needs only a tiny piece left to allow it to re grow vigorously again.

Weeding of interlocking, patio stones, flagstone and river-wash stone areas can be done with thermal weeding with propane torch, horticultural vinegar applications, pressure washing, boiling water, steam, hand weeding with interlock cleaning tool.

Landscape fabric and black plastic can be laid down over an area to smother and prevent weed growth. Remember than use of landscape fabric under river-wash stones is vital to prevent weeds from growing up under the rocks; but this does not prevent the weed seeds that blow in and grow on top. Fortunately most that grow from on top are fairly easily removed. Landscape fabric ‘breathes’ and allows moisture to penetrate thru which is desirable. Black plastic is used to smother the weeds in an area prior to a garden being developed in this space. Sometimes used around plants to keep weeds under control for the season; usually seen when planting market gardens.

Mulches can smother weeds by removing light and air for growth. Flowerbeds should be mulched, after being thoroughly weeded and cleaned up, to help control weeds. The finer the mulch the more effective is the weed control. Thus composted pine mulch, which is ‘soil-like’ consistency, is more effective for weed control than bark chip mulches. Mulch needs to be applied a minimum of 5cms(2 inches) to 10 cms. thick and preferably 10cms.(4 inches) thick.

what is a weedThe saying ‘one year’s seed gives seven years of weeds’ is actually quite true. The key to successful weed control is to remove weeds or at least their seed pods before the seeds ripen. Cut down those weed-forming seed pods with a line trimmer, hedge shears, hand pruners or the lawn mower depending on the weed and where it is growing.

Facts about Common Weeds

Annual sow thistle is a prolific annual from Europe with ovate, shiny cotyledons with mid vein on underside. Each plant can produce 26, 000 seeds in one season that are viable for up to 8 years. Remove with a hoe and garden fork.

Common burdock is a biennial from Europe with elliptical dull green cotyledons with purple green stem below with roots that are extremely dense and hold their ground. Remove entire root with garden fork.

Lamb’s quarter is an annual that is easily removed with a hoe. Can steam young plants and eat like spinach.
Canada thistle is a perennial with an underground root system that may be more than 30cms. below the surface. Well established plants can have as many as 200 nodes for sending up new plants thus every single root must be removed. Seeds can last for 21 years in the soil but must be near surface to germinate. One plant can produce 40,000 seeds each year.

Field bindweed is a perennial with seeds that can live 50 years in the soil and roots can be as deep as nine metres and spread 30 metres. Must remove all root pieces with a garden fork.

Dandelion is a perennial with deep roots which can be individually removed with a dandelion weeder or trowel to dig out.

Purslane is an annual that even pieces of stem that are broken will root. Dig out carefully and completely.

Common plantain is an annual, biennial and a perennial that has invaded gardens and lawns. Remove by digging out.

Contact Harmony Gardens Landscaping Inc. for weed management– removal, control and prevention – within your flowerbeds, interlocking, river-wash stones and lawns.