Discovering Native Willow Trees: A Riparian Staple in Southern Arizona

Written by Justin Tornatore, ISA Certified Arborist | TIMBERx

Abstract

In the arid expanses of southern Arizona, where the Sonoran Desert meets intermittent waterways and seasonal washes, native willows (Salix, family Salicaceae) are vital parts of riparian ecosystems. These deciduous trees and shrubs thrive in the region's limited moisture corridors, a striking contrast to the surrounding drought-adapted flora. For homeowners and landscapers, the prominent Goodding's willow (Salix gooddingii) offers shade, wildlife value, and erosion control [1]. It's also one of the thirstiest trees you can plant here [2][3][4]. This article covers the key native willow species in southern Arizona, their ecological role [1][2][5][6], their benefits and limits in designed landscapes, growing conditions and planning numbers, and planting and care.

Background: Principal Native Species in Southern Arizona

Southern Arizona's riparian zones host several native willows, adapted to the region's two rainy seasons and fluctuating water tables.

• Goodding's willow (Salix gooddingii) is the most widespread and tree-like. The USDA Forest Service describes it as a fast-growing, deciduous, dioecious (separate male and female plants) shrub or tree reaching 20 to 60 feet [1]. Its lance-shaped leaves are bright green with finely serrated margins, and the bark becomes thick, furrowed, and gray-brown with age. Catkins appear in early March [1].
• Bonpland willow (Salix bonplandiana), sometimes called red willow, complements it in southeastern Arizona and mid-elevation streams. Its leaves are dark green above and paler below, and it can reach similar heights, though it's less common in the low desert.
• Coyote or narrowleaf willow (Salix exigua) is a shrubby associate that forms dense thickets along gravel bars and ditches.
• Arizona willow (Salix arizonica) is a rarer high-elevation, mat-forming shrub largely absent from the southern lowlands.

Goodding's willow frequently codominates with Fremont cottonwood (Populus fremontii) in riparian communities of the West [1], the classic "cottonwood-willow" galleries along the Santa Cruz, San Pedro, Salt, and Verde rivers.

What the Research Shows

Riparian areas punch far above their weight. UA Cooperative Extension reports riparian areas make up only about 0.4% of Arizona's total area, yet 80% of the state's vertebrates spend some part of their life cycle in them [2]. The Arizona Game and Fish Department similarly notes these systems cover about 0.4% of the state's landscapes while up to 80% of Arizona wildlife species depend on them [5][6].

Wildlife and restoration value. The Forest Service notes willows provide excellent browse and cover for wildlife, are a preferred food and building material for beavers, and that Goodding's willow provides shade for fish and other wildlife [1]. It tolerates flooding and long, hot growing seasons, making it ideal for rehabilitating riparian zones of the Southwest [1]. Roots have been noted down to 7 feet in Arizona [1].

Water dependence. UA classifies Goodding's willow as an obligate wetland species, the most dependent on wetland conditions and the least drought-tolerant of the riparian trees compared [2]. UA's watering guide puts willows and cottonwoods among the high-water-use plants that need much more water than established arid-region plants [3]. UA also warns that landscape cottonwoods and willows often do well for three to five years, then slow and decline, because sprinkler or drip systems can't supply what large riparian trees need. Those stressed trees are then colonized by wood borers [4].

Propagation. Willows are usually planted from stem cuttings, and seed remains viable for only a few days [1]. Goodding's willow grows well in a pH range of about 6 to 7 and tolerates alkaline desert soils, with very low shade tolerance and high flood tolerance [1].

Field Observations

Ecological anchors. Native willows are foundational to southern Arizona's biodiversity hotspots. Their extensive fibrous root systems stabilize streambanks and prevent erosion, particularly during monsoon floods and winter flows. By anchoring fine-grained alluvial soils, they reduce sedimentation and help maintain water quality. Dense thickets and overhanging branches provide thermal refuge and cover for fish, amphibians, and aquatic invertebrates. Catkins supply early-season nectar and pollen for native bees, butterflies, and other pollinators; foliage and twigs serve as browse for mule deer, javelina, and small mammals; and willows host larvae of butterflies such as the mourning cloak (Nymphalis antiopa) and western tiger swallowtail (Papilio rutulus). In restoration, Goodding's willow is a keystone species that helps degraded riparian zones succeed toward mature cottonwood galleries. Willows also contribute carbon storage, nutrient and contaminant filtering, and resilience in an era of drought and urbanization.

Benefits for homeowners and landscapers. Their fast growth [1] provides quick shade and privacy screening, cooling nearby structures. The graceful, pendulous branches and silvery-green foliage add visual interest, with spring catkins adding texture and autumn yellowing offering seasonal color. Willows attract birds, butterflies, and pollinators, and their root networks excel at erosion control on slopes and near retention basins, making them useful in bioswales, rain gardens, and stormwater features. They need little fertilizer or pesticide, but they are not low-maintenance trees: they're high water users that need much more water than arid-region plants [3], and they only fit a water-conscious landscape when sited where water naturally collects. Compared with non-native ornamentals, native willows support local food webs more effectively and avoid the invasiveness of some exotic Salix species. Landscapers use them as "living fences" or windbreaks, and their tolerance for periodic inundation suits properties with seasonal water features or effluent-irrigated areas.

Growing conditions for Goodding's willow:

• Sun and soil: full sun (it has very low shade tolerance) and moist to seasonally wet soils, including clay, loam, silt, sand, or gravel mixtures; it grows well at a pH of about 6 to 7 and tolerates alkaline desert soils [1]. Fine-grained alluvium is ideal; avoid compacted or heavily saline sites.
• Drought tolerance: low. It's an obligate wetland species and the least drought-tolerant of the common riparian trees [2], so it needs permanent access to water, whether a shallow water table or reliable irrigation.
• Mature size: 20 to 60 feet, depending on how much water the site provides [1].
• Lifespan in landscapes: without a reliable water source, landscape willows often decline after a few years and are then attacked by wood borers [4].
• Water needs: high during establishment and high afterward unless the roots reach a water table [2][3]. It tolerates flooding but not drought [1][2].
• Propagation: dormant stem cuttings taken in late winter root readily; willows are usually planted from cuttings because seed stays viable for only a few days [1]. If you use seed, sow it immediately on moist, bare soil.

Practical Recommendations

1. Site it where water is. Plant near a wash, basin, pond edge, or other reliable water. A dry-yard drip system usually isn't enough [3][4].
2. Plant in the cool season. Late fall through early spring lets you take advantage of winter rains.
3. Space and backfill thoughtfully. Give each tree room for its mature canopy, and backfill with native soil rather than rich compost to encourage deep rooting.
4. Mulch heavily to hold moisture and suppress weeds, keeping mulch away from the trunk.
5. Prune in dormancy to shape or remove damaged branches, and never top a landscape willow. Topping leaves large wounds open to decay and forces weakly attached sprouts [7]. For a screen, plant several willows or let the tree keep its natural multi-stemmed form instead.
6. Watch for pests. They're usually minimal; occasional aphids or borers rarely need intervention, and borers mostly signal water stress [4]. Monitor for cottonwood leaf beetle in dense plantings.
7. Respect the roots. Aggressive surface roots can lift pavement or clog drainage if planted too close to structures; keep them well away from pipes and foundations.
8. Plan for the extras. Pollen may trigger seasonal allergies, and female trees produce cottony seed fluff. In urban settings away from natural water, plan on regular deep irrigation for the life of the tree [3][4].

Key Takeaways

• Riparian areas cover about 0.4% of Arizona but support most of its wildlife [2][5][6].
• Goodding's willow is a fast-growing, flood-tolerant native that's ideal for riparian restoration [1].
• It's a high-water-use, obligate wetland tree; plant it where water naturally collects [2][3].
• In dry yards, stressed willows decline and attract borers [4].

Native willows, led by Goodding's willow, sit at the intersection of ecological integrity and practical landscaping in southern Arizona. By stabilizing soils, sustaining wildlife, and delivering fast shade, they're a resilient choice when sited where water naturally collects. Planting native willows today helps ensure southern Arizona's riparian legacy endures for future generations.

Talk to an Arborist

Wondering whether a willow fits your site? Text Justin at (520) 451-8790 (texting is preferred over calling) or email Justin@TimberxTrees.com. TIMBERx is a veteran-owned tree care company led by Justin Tornatore, ISA Certified Arborist, serving Tucson, Oro Valley, Marana, Vail, Sahuarita, Green Valley, and Benson.

References

1. Reed, W. R. (1993). Salix gooddingii. In Fire Effects Information System. USDA Forest Service, Rocky Mountain Research Station. https://www.fs.usda.gov/database/feis/plants/tree/salgoo/all.html
2. Zaimes, G. (2007). Understanding Arizona's Riparian Areas (AZ1432). University of Arizona Cooperative Extension. https://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1432.pdf
3. Call, R., & Daily, C. (2017). Watering Trees and Shrubs (AZ1298). University of Arizona Cooperative Extension. https://www.extension.arizona.edu/publication/watering-trees-and-shrubs
4. Schalau, J. (adapted 2023). Borers in Landscape Trees (Backyard Gardener #52). University of Arizona Cooperative Extension, Yavapai County. https://extension.arizona.edu/sites/extension.arizona.edu/files/attachment/Borers_0.pdf
5. Arizona Game and Fish Department. (n.d.; accessed October 2026). Arizona's Extraordinary Landscapes. Arizona Wildlife Conservation Strategy. https://awcs.azgfd.com/arizonas-extraordinary-landscapes
6. Arizona Game and Fish Department. (n.d.; accessed October 2026). Aquatic and Riparian Ecosystem Group (Chapter 7: Habitat Profiles). Arizona Wildlife Conservation Strategy. https://awcs.azgfd.com/chapter-7-habitat-profiles/aquatic-and-riparian-ecosystem-group
7. International Society of Arboriculture. (2021). Why Topping Hurts Trees (TreesAreGood consumer brochure). https://www.treesaregood.org/Portals/0/siteContent/pdf/Web%20TAG%20brochures/TAG_CBweb_Why%20Topping%20Hurts_v2.pdf