Are you battling shiny tall garden weeds in your backyard?
Before you are crying for help, have a look at these 11 tall garden weeds which can create massive headaches for gardeners, landscapers, horticulturalists and farmers.
11 Tall Garden Weeds
Its easy to miss these tall garden weed.
Each and everyone of the species profiled will reach over 1.5 metres high in a summer and are very effective at spreading themselves in the process.
Check out these mug shots and what we believe to be the best methods for elimination.
1. Paulownia Tomentosa
Also Known As: Paulownia Tree, Foxglove-Tree, Princess Tree, Empress Tree
Distribution: Native to China and the Korean peninsula, invasive in North America, introduced to Europe and South Africa.
Description:
You might think it’s ridiculous to call a fully grown tree a weed in your garden but this deciduous hardwood tree does have a record of explosive, invasive growth that has begun to wreak havoc across much of North America!
It’s difficult to envisage a taller garden weed since young growth can achieve over 2.5 metres of growth in a season.
The young growth has whorls of heart-shaped or multi-lobed leaves.
It has a large foxglove-like flower which produces fruit and very light seed that are easily dispersed by wind and water.
Eradication Options:
- Uprooting saplings
- Cutting into the tree
- Injecting (spraying) herbicide into the cuts
2. Pokeweed
Also Known As: Phytolacca Americana, American Pokeweed, Dragonberries, Poke Sallet, Inkberry, Poke Salad
Distribution: Native to eastern North America, but introduced to Europe and Asia.
Description:
This is a nasty poisonous plant and has a long record of killing people that ingest its roots, leaves and berries.
Pokeweed is a very tall herbaceous plant that can spread and reach heights of up to 2.5 meters in an average summer.
The toxins increase over time as pokeweed matures.
With its bright green leaves, purplish-stains stem and large black berries, it is difficult to avoid pokeweed, and it also poses a danger to children who may be tempted to eat its berries.
Eradication methods:
- Insecticides
- Digging out the whole plant including the taproot
3. Rhododendron
Alternate Names: Rhododendron Ponticum, Common Rhododendron, Pontic Rhododendron
Distribution: Indigenous to the Iberian peninsula and the Caucasus, but invasive in Western European and New Zealand.
Description:
Rhododendron has created issues for British horticulturists since it was introduced deliberately in the 18th Century.
Rhododendron is a spreading shrub which suckers excessively, and has high growth and propagation rates, making it extremely invasive. It is evergreen and generates purple blooms which become many-seed fruit.
It can easily grow 5 meters, and has the same excessively aggressive growth and horizontal spread.
Rhododendron is also toxic. Even honey from the pollen of Rhododendron flowers can cause poisoning!
Eradication methods:
- Stem injection control
- After the initial chemical insecticide treatment, and the shrub’s insect herbivore population has been exhausted, they can be dug up.
4. Ricinus
Also Known As: Ricinus Communis, Castor Bean
Distribution: Native to Mediterranean, Africa and Asia, invasiser in southwestern US
Description:
This invasive perennial flowering plant is known for its beans (seeds) and the oil derived from its beans.
It’s typically shrub-sized but has been reported reaching over 10 feet in height. The plant opportunistic spread fills in wasteland, fields and thrives on roadsides.
The foliage and seeds are toxic, which becomes problematic where the plant grows amongst crops and seeds unintentionally end up in animal feed.
Eradication Strategies:
- Mechanical methods (cutting, pulling, disking)
- Chemical control
5. Japanese Knotweed
Also Known As: Donkey Rhubarb, Polygonum Cuspidatum, Fallopia Japonica, Reynoutria Japonica and Asian Knotweed
Distribution: Native to East Asia including China, Japan and Korea. Invasive in the US and western Europe.
Description:
Japanese knotweed is a hollow-stemmed plant with raised nodes that can be between 3 to 4 metres tall every growing season.
It has large oval leaves and forms racemes of small cream flowers. It is very adaptable and produces an extensive root system which is why it can regrow two to three times after being cut down.
Interestingly, Japanese knotweed which has not been treated, or grown on contaminated land, is edible.
Japanese knotweed specimens must be disposed of at a licensed landfill site, or dried and burned.
Eradication techniques:
- Repeated applications of glyphosate
- Digging up
6. Wild Lettuce
Also Known As: Lactuca Virosa, Rakuten-Karyamu-So, Laitue Vireus, Tall Lettuce, Great Lettuce, Bitter Lettuce or Opium Lettuce
Distribution: coastal UK, Punjab, Australia, California, Washington DC.
Description:
This plant, in the lettuce and dandelion family, spreads rapidly and grows thick stalks of over 2 meters in a single growing season.
The long leaves are serrated, and it produces flowers that resemble those of a dandelion. Wild lettuce has sap that is effective for treatment of pain.
Eradication strategies:
- Herbicidal control
- Hand pulling weeds
- Continued grazing of animals.
7. Giant Hogweed
Also Known As: Heracleum Mantegazzianum, Giant Cow Parsley, Giant Cow Parsnip, Hogsbane
Distribution: Native to the Caucasus, spread to Western Europe, the US and Canada
Description
Giant hogweed is a noxious weed that can grow to 5 m or more.
It has giant, deeply lobed leaves which grow from its very thick green and purple stem.
At the tip of the stem there is an inflorescence of green-white flowers arranged in an umbrella shape.
The sap of this plant is phototoxic, which leads to severe blistering on skin that has made contact with this plant.
Do not handle it without wearing protective clothing, gloves and eye protectors!
Eradication strategies:
- Herbicidal control
- Uprooting of emerging plants
- Removal of flower spikes so it cannot produce seed
8. Creeping Thistle
Also Known As: Cirsium Arvense, Canada Thistle and Field Thistle
Distribution: This plant is native to the Caucasus and has spread to western Europe, the United States and Canada.
Description
This herbaceous perennial can quickly cover large tracts of land by developing a network of clonal colonies with multiple erect flowering shoots to 1.5 metres in height.
This weed is highly invasive, exploiting and spreading throughout any environment.
Its rapid turnover time means it evolves to establish itself quickly, and has the ability to avoid chemical means of control.
Eradication strategies:
- Weakening plants by continually cutting back the new growth
- Repeatedly digging
- Pesticides
9. Himalayan Balsam
Also Known As: Impatiens Glandulifera, Indian Balsam, Policeman’s Helmet, Jumping Jack
Distribution: This plant is native to Nepal and India and has spread to western Europe, the US and Canada.
Description:
Himalayan Balm is a large annual with purple-pink helmet-like flowers with edible nectar.
It was brought into the UK in the late 1930s and has become invasive.
The annual plant grows to about 2m in height and spread aggressively by exploding seed pods.
Eradication methods:
- Pulling or cutting off the plants before they flower and set seed
- Pesticides with products that include fatty acids and glyphosate
10. Common Mullein
Also Known As: Verbascum Thapsus, Greater Mullein, Aaron’s Rod or The Great Mullein
Distribution: Common in Europe, northern Africa and Asia, spread to the US, Canada and Australia.
Description
Common mullein forms tall (up to 3 metres) rod-like stems that bud and flower, similar to Aaron’s rod from the bible.
It produces rosettes of ovate leaves along its stem, followed by large light yellow flowers, in the second year of its growth.
Similar to many other weeds, it is aggressively invasive through the extensive dispersion of it’s seeds.
Medicinally it is utilized in an herbal tradition and in some cases has been planted as an ornamental.
Eradication strategies:
- Biological control by the figwort weevil and caterpillars
- Manual weeding can work
11. Giant Ragweed
Also Known As: Ambrosia Trifida
Distribution: Native to North America, spread to Europe and Asia.
Description
This invasive annual belongs to the sunflower family and produces tall stout stems that can exceed 4 metres tall, under the right conditions.
It possesses tough leaves and produces racemes of male and female flowers that efficiently pollinate.
The pollen produced by giant ragweed is highly allergenic and is a major contributor to experiencing hay fever.
Giant ragweed will spread and establish where ever there are fertile soils, including agricultural land and flood plains.
Giant ragweed is highly adaptive and several strains are resistant to herbicides.
Eradication strategies:
- Stem boring
- Injection with glyphosate
Rounding Up
We hope you have found this rogues’ gallery of tall garden weeds helpful.
Controlling invasive species like these requires persistence as even a small amount of root material that remains can regenerate a new plant.
With tall garden weeds, gardeners first tend to reach for the glyphosate, but most of these plants can be eradicated by manually uprooting them.
Sweaty work, but well worth it for clearing your weeds!