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