7 Obnoxious weeds you should be wary of in your garden

PIG WEED (Amaranthus spp)

Weeds have the potential to wipe out your entire crop or lawn. In fact, sometimes, they cause harm to livestocks. Such cases abound every year where animals succumb from feeding on poisonous weeds.

Weeds reduce farm and forest productivity, they invade crops, smother pastures and in some cases can harm livestock. They agressively compete for water, nutrients and sunlight, resulting in reduced crop yield and poor crop quality.

However, some weeds are friendly and which are foe. For some of them, their advantages outweigh the disadvantages that we can afford to live with them in our gardens.

Therefore, to be able to successfully control weeds in your lawn, garden, or pastures; you must first of all understand them beyond common knowledge. By doing so you’ll know better how to sustainably keep them under control.Here are some of the invasive weeds in your garden and lawns.

1. PIG WEED (Amaranthus spp)


You might find two common types of pigweeds; low amaranth (deflexus) and tall amaranth (palmeri).
Palmer pigweed is a broadleaf species of edible flowering plant in the amaranth genus.

This wild edible can be a beneficial weed as well as a companion plant serving as a trap for leaf miners and some other pests; also, it tends to shelter ground beetles (which prey upon insect pests)
The plant can be toxic to livestock animals due to the presence of nitrates in the leaves.

Palmer amaranth has a tendency to absorb excess soil nitrogen, and if grown in overly fertilized soils, it can contain excessive levels of nitrates, even for humans.

Like spinach and many other leafy greens, amaranth leaves also contain oxalic acid, which can be harmful to individuals with kidney problems if consumed in excess.

Palmer amaranth may be the most aggressive pigweed species with respect to growth rate and competitive ability.

2. Lamb’s quarters – Chenopodium album



Chenopodium album is a fast-growing weedy annual plant in the genus Chenopodium. Though cultivated in some regions, the plant is elsewhere considered a weed.

It is one of the more robust and competitive weeds, capable of producing crop losses of up to 13% in corn, 25% in soybeans, and 48% in sugar beets at an average plant distribution.

It may be controlled by dark tillage, rotary hoeing, or flaming when the plants are small. Crop rotation of small grains will suppress an infestation.It is easily controlled with a number of pre-emergence herbicides.

Chenopodium album is vulnerable to leaf miners, making it a useful trap crop as a companion plant. Growing near other plants, it attracts leaf miners which might otherwise have attacked the crop to be protected.

It is a host plant for the beet leafhopper, an insect which transmits curly top virus to beet crops.
As some of the common names suggest, it is also used as a feed (both the leaves and the seeds) for chickens and other poultry.

Thistle – Onopordum acanthium

Thistle is a flowering plant in the family Asteraceae. It is a vigorous biennial plant with coarse, spiny leaves and conspicuous spiny-winged stems. It is a biennial plant, producing a large rosette of spiny leaves the first year.

Thistle forms a stout, fleshy taproot that may extend down 30 cm or more for a food reserve.
For the same reason, the thistle is now considered a major agricultural and wildland noxious weed. It has been recorded from nearly 50 countries.

It is difficult to eradicate because of its drought resistance. It can spread rapidly and eventually dense stands prohibit foraging by livestock.

The weed adapts best to areas along rivers and streams, but can be a serious problem in pastures, grain fields and range areas.

A single plant is imposing enough, but an entire colony can ruin a pasture or destroy a park or campsite, sometimes forming tall, dense, impenetrable stands.

Besides creating an impenetrable barrier to humans and animals, the plant nearly eliminates forage use by livestock and some mammal species such as deer and elk

Small infestations may be physically removed or cut a few centimetres below the soil surface ensuring that no leaves remain attached to prevent regrowth.

Because of their shorter life cycle, cotton thistle plants can be effectively treated with herbicides. All herbicide treatments should be applied at the rosette stage of the plant.

3. Bind weed – Convolvus arvensis



Bindweed is a perennial vining plant that snakes its way across the ground and over fences, plants, or any other stationary thing in its path.

It has medium-green arrow shaped leaves, and white-pinkish flowers that look like those of morning glories.

The roots of field bindweed are similarly deep-rooting, with underground stems and shoots arising directly from the roots.

Bindweed produces seeds freely and they can remain viable in the soil for several years. By persistent digging and hoeing it is possible to eradicate these weeds in a couple of years.
4. Creeping Charlie Glechoma hederacea



Creeping charlie (Glechoma hederacea) is often called ground ivy due to its appearance and growth habits. Creeping charlie weed is a green vine whose leaves are round with scalloped edges.
The vines have nodes at each of the places where leaves grow and these nodes will form roots if they come in contact with the soil.

This is part of the reason that creeping charlie weed is so frustrating, as you cannot simply pull it up.
While creeping Charlie is considered a broadleaved weed, it cannot be eliminated by broadleaved spectrum herbicides.

5. Crabgrass – Digitaria spp



Digitaria is a genus of plants in the grass family native to tropical and warm temperate regions. Crabgrass is considered lawn pest by most gardeners.

While it’s true some species are weeds, some are used as food in Africa. Their seeds are ground and the flour used to make porridge.

Both the hairy crabgrass and smooth crabgrass are specifically problematic weeds in lawns and gardens, growing especially well in thin lawns that are watered lightly, under-fertilized, and poorly drained.

One plant is capable of producing 150,000 seeds per season which makes them difficult to control.
When the plants die, they leave large voids in the lawn. The voids then become prime areas for the crabgrass seeds to germinate.

Biological control is preferable over herbicide use on lawns, as crabgrass emergence is not the cause of poor lawn health but a symptom, and it will return annually if the lawn is not restored with fertilization and proper watering.

6 Purslane – Portulaca oleracea



Clover or trefoil asre common names for plants of the genus Trifolium. They are small annual, biennial, or short-lived perennial herbaceous plants. Clover can be evergreen. Several species of clover are extensively cultivated as fodder plants.

The most widely cultivated clovers are white clover Trifolium repens and red clover Trifolium pratense.

The clover is palatable to and nutritious for livestock; it fixes nitrogen, reducing the need for synthetic fertilizers; it grows in a great range of soils and climates; and it is appropriate for either pasturage or green composting.

The seeds can survive high heat, low temperatures and can stay dormant for years before germinating.

7. Oxalis – Oxalis spp



Oxalis is a large genus of flowering plants in the wood-sorrel family Oxalidaceae. Many of the species are known as wood sorrels.

All Oxalis weeds are considered highly aggressive, and should be eliminated completely from your lawns and gardens in order to be controlled. An infestation can occur in almost any environment.

Some species for instant Bermuda-buttercup and creeping wood sorrel– are pernicious, invasive weeds when escaping from cultivation outside their native ranges; the ability of most wood-sorrels to store reserve energy in their tubers makes them quite resistant to most weed control techniques.