Giant reed (Arundo donax)
Arundo donax, the Giant reed, is a towering, bamboo-like ornamental grass native to the Mediterranean, growing 12-20 ft tall.
Complete Plant Information
Overview
Arundo donax, widely recognized as the Giant reed, provides an incredibly bold, tropical statement in the landscape, quickly reaching imposing heights. This rhizomatous, warm-season grass is native to the Mediterranean region and offers a dramatic architectural presence unmatched by many standard ornamental grasses. It is often used where vertical screening or a bamboo-like effect is desired without the aggressive root systems associated with true bamboo.
Growing to heights between 12 and 20 feet, the mature form of Arundo donax commands attention, featuring cane-like stems clothed in arching, gray-green leaves up to 2 feet long. While it is most striking in warmer, frost-free zones where it remains evergreen, even in cooler climates like St. Louis, it can establish significant height rapidly in a single season.
The versatility of the Giant reed makes it valuable for erosion control, water garden accents, and dramatic backdrop plantings. Gardeners should be mindful of its growth rate and potential for spreading, especially near water sources, balancing its striking beauty with appropriate placement management.
Fast Facts
- Plant Family: Poaceae
- Plant Type: Ornamental grass
- Native Range: Mediterranean
- Hardiness Zones: USDA Zones 6-10
- Size at Maturity:
- Height: 12-20 ft
- Spread: 5-8 ft
- Bloom Time: September to October
- Bloom Description: Purple
- Sun Exposure: Full sun to part shade
- Water Needs: Medium to wet
- Maintenance Level: Medium
How to Grow
Arundo donax is remarkably adaptable, performing well across a wide spectrum of soils—from light, sandy types to heavy clays—though it truly excels in moist to wet conditions, tolerating standing water. Planting should ideally occur in spring or early summer, ensuring the plant has plenty of room due to its mature spread of 5 to 8 feet. Full sun yields the best growth, but Giant reed tolerates light shade, though growth may be slightly suppressed.
In terms of hydration, maintain consistently moist soil; this plant performs excellently in rain gardens or near ponds where water supply is reliable. Water needs are medium to wet, making it a fantastic choice for damp areas of the landscape. Maintenance is considered medium; while it seldom suffers from major pest or disease issues, its sheer size means that vegetative clumps may lodge or flop over in heavy summer winds, sometimes necessitating staking for aesthetic integrity.
For gardeners in cooler zones (USDA 6-7), the plant will die back to the ground after a hard frost; cut the stems down to the base after this occurs. Applying a winter mulch can offer extra protection to the root system. In contrast, in frost-free zones (USDA 9-11), the Arundo donax remains evergreen and spreads aggressively via rhizomes, demanding management near natural waterways.
Propagation is straightforward; pieces of the rhizome or stem can be soaked in water until they sprout roots before being planted. Root balls can also be divided using a spade, providing easy multiplication of this impressive specimen.
Landscape Uses
The imposing vertical structure of Arundo donax makes it an exceptional specimen or accent plant, providing immediate visual impact near large water features or ponds. It is highly suitable for use as a natural screen or backdrop in border plantings where height is required immediately. This ornamental grass thrives in large containers, particularly when grown in 1 to 5 inches of standing water, making it perfect for augmenting larger water gardens.
Its architectural form lends itself well to tropical or contemporary landscape designs, contrasting beautifully with fine-textured or low-growing perennials. While primarily ornamental, the plant’s ability to thrive in wet areas makes it a prime candidate for stabilizing banks or thriving within a constructed rain garden, managing runoff effectively. Furthermore, the narrow inflorescences that appear in the fall are superb when cut for fresh use or dried for long-lasting arrangements.
Standout Features
Flower Qualities
- Showy
Noteworthy Characteristics
Arundo donax, commonly called giant reed, is a rhizomatous, perennial, warm season grass that sports a somewhat tropical appearance. In mature form, it can make a very bold ornamental statement in the landscape. It is a bamboo-like plant that is native to Europe (primarily the Mediterranean region).
Tolerances
- Black Walnut
- Air Pollution
Potential Problems
Giant reed generally exhibits no serious insect or disease problems, which contributes to its overall appeal. The primary concern revolves around its vigor, particularly in frost-free climates (USDA 9-11). Here, Arundo donax remains evergreen and can become highly aggressive, especially spreading along ditches, streams, or other water bodies where it will successfully outcompete many native species. In colder areas like St. Louis, it is not considered invasive because it dies back annually. Gardeners must manage lodging (the bending over of tall stems) during summer rains by occasionally staking the tallest clumps to maintain an appealing upright posture.
Frequently Asked Questions
What hardiness zones is Arundo donax suitable for?
Arundo donax is adaptable, growing successfully in USDA Zones 6 through 10.
How large does Giant reed grow?
This plant typically reaches heights between 12 to 20 feet tall, with a spread ranging from 5 to 8 feet at maturity.
What sun exposure does Giant reed need?
Arundo donax thrives best when given full sun conditions, though it exhibits good tolerance for part shade.
When does Arundo donax bloom?
The purple, narrow flower plumes appear relatively late in the season, typically from September into October. Flowering may be inconsistent in climates experiencing early frosts.
Conclusion
The magnificent scale and tropical texture of Arundo donax ensure it remains a favorite for creating dynamic, vertical interest in established landscapes. Whether you utilize the Giant reed for screening, water garden accents, or as a singular specimen, its rapid growth and substantial presence offer instant drama. Before planting this assertive ornamental grass, carefully check your local USDA hardiness zone and plan its final placement to accommodate its mature size and potential spreading habits.
Companion Planting
When positioning the towering Arundo donax, selecting appropriate companion plants that enjoy similar moisture levels is key. Since Giant reed prefers medium to wet soil, pair it with Bog Rosemary (Andromeda polifolia) or Swamp Milkweed (Asclepias incarnata) if planting near a pond edge or rain garden. For a bold, tropical grouping in a large bed, consider underplanting the base with large-leaved hostas or cannas, which appreciate the dappled shade the massive grass creates during the hottest part of the day. Avoid planting near delicate or sensitive drought-tolerant species, as the high water demands of Arundo donax may crowd out its neighbors.
Propagation Tips
Propagating Arundo donax is relatively simple, which aids in its use for erosion control or quick landscape filling. The most reliable method involves dividing the large root ball, which should be done carefully with a sharp spade, preferably in early spring before new top growth emerges aggressively. Alternatively, take cuttings of the cane-like stems or pieces of rhizome; these can be successfully rooted by placing them in moist soil or even soaking them directly in water until viable roots develop. This ease of propagation means a single established clump of Giant reed can quickly yield several new, substantial specimens.
