Giant Reed — Plant Guide

🚫 Invasive / non-native weed

At a glance · What it is: A giant invasive grass that chokes creeks and washes · Tell-tale sign: Bamboo-like canes 15–30 ft tall in dense stands along water · Why it matters: One of California’s worst riparian invaders

How to identify

Looks like a massive bamboo or corn: thick, hollow, segmented canes 15–30 ft tall with broad blue-green leaves clasping the stem in two ranks, topped by large plume-like seed heads. Forms dense, monotypic thickets along streambanks. (Native Riparian plants like willows and Western Sycamore are woody and varied — arundo is a uniform wall of cane.)

How it got here

This plant has a real history where it comes from. Its canes have been cut into reeds for oboes, clarinets, and bagpipes for thousands of years, and used for thatching, fencing, and basketry across the Mediterranean, the Middle East, and Asia. None of that is why it’s here. It showed up in California in the 1820s doing a job. People planted it on purpose, along irrigation ditches and streambanks around Los Angeles, because it grows fast and dense and holds soil in place. That’s exactly the problem. The same growth that made it good at gripping a ditch bank makes it unstoppable in a real creek. It chokes the channel. When floods snap the canes apart, every broken piece washes downstream and takes root somewhere new. We planted this on purpose to stop erosion. Now it’s one of the reasons Southern California creeks flood.

Why it’s a problem

Crowds out native riparian vegetation and the wildlife that depends on it.
Guzzles water — far more than the natives it replaces.
Raises fire risk in normally fire-resistant creek corridors, and regrows fast after burning.
Worsens flooding by clogging channels; broken canes wash downstream and re-root. This is exactly why arundo removal is a centerpiece of local creek-restoration work.

How to remove it

Tough — it resprouts from rhizome fragments, so half-measures make it worse.

Small clumps: dig out the entire root mass; don’t leave rhizome pieces.
Large stands: typically cut-and-treat (cut canes, then apply herbicide to the cut stumps in late summer/fall) followed by repeat monitoring for regrowth. Often a multi-year, professional/organized effort.
Dispose of canes carefully — never dump near water, where fragments re-root.

Restoration alternative

These fill the same tall, water-hungry niche without wrecking the creek.

Western Sycamore — for canopy and shade.
Arroyo willow (Salix lasiolepis) & mulefat (Baccharis salicifolia) — fast streambank cover.
Deergrass (Muhlenbergia rigens) — a large native bunchgrass for the tall, vertical look without the invasion.