Weed of the Month
Learn about noxious weeds and steps you can take to manage or eradicate. Each month we will bring you a new profile and helpful resources.
December Weed Profile
Giant Reed
(Arundo Donax)
Giant reed is a perennial grass that can grow to 25+ feet tall. Originally imported to the US as an erosion control and horticultural plant in the 1800s, it has escaped and moved into many riparian areas in the west. It is native to the Mediterranean region and eastern Asia.
It spreads by rhizomes and stem nodes and can form large clumps resembling bamboo. It grows in full sun and in lightly shaded areas and is very drought tolerant.
The leaves can be 2 inches wide and up to 36 inches long. Stems are ¼ -2 inches wide.
Its distinctive auricles clasp the stem. The ligules are large and papery with small hairs along the margin.
The flowers are arranged in a large plume 1-2 feet long. Within North America, it is not believed that the seeds are viable.
Giant reed forms huge colonies along waterways. It disrupts the water flow, increases sedimentation, and changes the structure of water channels that can lead to erosion. Dead and dry stands can pose a fire hazard.
Colorado has less than 500 known locations and this List A noxious weed needs to be completely eliminated. Because it easily spreads by plant fragments removal is not an option. Use of a systemic herbicide will give the best control.
RESOURCES
Noxious Weeds of Colorado 14th Addition
Colorado Weed Management Association
https://cwma.org/weed-information/publications/
Items of Interest
Weed of the Month
2023
January Weed Profile – Common Mullein
February Weed Profile – Cypress Spurge
March Weed Profile – Dames Rocket
April Weed Profile – Sulfur Cinquefoil
May Weed Profile – Poison Hemlock
June Weed Profile – Plumeless Thistle
July Weed Profile – Puncturevine
August Weed Profile – Common Tansy
September Weed Profile – Bull Thistle
October Weed Profile – Bounchingbet
November Weed Profile – Common Burdock
December Weed Profile – Giant Reed
2022
January Weed Profile – Knotweed
February Weed Profile – Rush Skeletonweed
March Weed Profile – Black Henbane
April Weed Profile – Chinese clematis
May Weed Profile – Houndstongue
June Weed Profile – Milk Thistle
July Weed Profile – Oxeye Daisy
August Weed Profile – Spotted Knapweed
September Weed Profile – Perennial Pepperweed
October Weed Profile – Yellow Flag Iris
November Weed Profile – Common St. Johns Wart
December Weed Profile – Field Bindweed
2021
January Weed Profile – Dalmatian Toadflax
February Weed Profile – Common Mulllein
March Weed Profile – Mediterranean Sage
April Weed Profile – Saltcedar
May Weed Profile – Absinth Wormwood
June Weed Profile – Eurasian watermilfoil
July Weed Profile – Yellow starthistle
August Weed Profile – Hairy willowherb
September Weed Profile – Yellow toadflax
October Weed Profile – Chamomile
November Weed Profile – Diffuse knapweed
December Weed Profile – Poison hemlock
2020
January Weed Profile – Cheatgrass
February Weed Profile – Myrtle Spurge
March Weed Profile – Hoary Cress
April Weed Profile – Leafy Spurge
May Weed Profile – Scotch Thistle
June Weed Profile – Dyer’s Woad
July Weed Profile – Orange Hawkweed
August Weed Profile – Purple Loosestrife
September Weed Profile – Teasel
October Weed Profile – Canada Thistle
November Weed Profile – Russian Knapweed
December Weed Profile – Russian Olive