Updated: Oct 23, 2021
Does the world need another oleander? When I ask myself this question, I immediately think of my time attending Monticello's Historic Landscape Institute in Charlottesville, Virginia. There, at Thomas Jefferson's home, a rare, variegated oleander topiary stood in a collection of exotic plants, including others that thrive in California, elegantly clipped lantana and hibiscus. This oleander was cared for as a prized possession, a rarity in other parts of the country. In such climes, oleanders are tender, but here in California, they line our state highways for miles on end. So the question is better directed to our California's designers. The answer depends on the design requirements that may merit another oleander in the landscape.
Oleanders are tough. Once they are established, their removal is challenging unless one hires a tree service or qualified landscape contractor that will grind out its stump so it does not regrow. Drought tolerant, too. Just a few good, deep watering sessions through the summer will satisfy its thirst while still producing prolific blooms. Their sizes and colors vary. A full size oleander can reach 20' tall, whereas dwarf cultivars could reach 6' but are often less. The more common available colors are red, pink, and white, but a careful search will find various shades of pink, salmon, purple, or even yellow. The pink shown above is a clear, clean shade, while others might be more harsh or faded. Flowers can be simple or double, so the best recommendation is to identify N. oleander by specific cultivar name or search in nurseries over the summer when inventory is in bloom. Which brings me to another reason why it is best to inspect plants while in bloom; nurseries can mix up colors, surprising designers if the intent was for a specific color.
Now a few words about design and I will be blunt. Firstly, all parts of the oleander are toxic. I refrain from saying "poisonous," simply because the implication is death (which can occur although rare). If death were more common, I find it hard to believe we would collectively want to plant it as much as we have. Rather, there are many plants with levels of toxicity depending upon how much is ingested, and for oleanders, I hardly recommend placing them where curious pets or small children might be vulnerable. While toxicity is a concern, I recall deer eating oleander in Sonoma County, especially if drought and hunger has led to few alternatives. What likely occurred is a really bad stomach ache along with further avoidance.
Secondly, do not mimic freeway landscapes (unless you are a freeway landscape architect, then that is another conversation). I will hazard a guess that when oleanders were planted, the multi-colored layout was based purely on volume and not "design." Whatever was available in whatever order seemed to be the intent. Designers can do better, selecting specific color(s) for a cohesive palette with other plants. I vote for maintaining each mass as one color, which is less busy in the landscape. Use other colors in different locations if that satisfies the need for variety.
Finally, there are a few things to understand when specifying shrubs trained as trees, particularly with oleanders. Namely, they prefer to be multi-stemmed shrubs, so they will persist with producing side limbs on their trunks as well as suckers from below the soil line. This means that maintenance should include regularly removing side sprouts as they grow. Leaving them ignored and the tree will revert to shrub form.
Botanical Name: Nerium oleander
Nerium: Greek vernacular name for this species
Oleander: Italian, oleandro, olive-like leaf shape
Common Name: oleander
Family Name: Apocynaceae
Positioning: Patio (trained as standard), background or barrier (large sizes)
Garden Themes: Mediterranean/drought tolerant, cottage, rain
Uses: Border, foundation (size appropriate), topiary, screen, informal hedge, container, green stormwater infrastructure (elevated uplands only)
Type: Evergreen shrub (may be trained as standard)
Form: Round, upright
Size: 20' wide x 12' tall (cultivars may vary)
Outstanding Feature(s): Flowers, foliage, hardiness
Bark: Dark brown (may become furrowed); young stems green, fleshy
Arrangement: Opposite to whorled
Shape: Lanceolate, linear
Color: Dark green above, light underneath (some cultivars are variegated)
Flower: Summer into autumn. Cyme, or cluster, tubular, single or double, in white, shades of pink, red, purple, or yellow; scented or unscented
Fruit: Autumn into winter. Brown follicle opens to reveal fuzzy seeds that can be carried by wind and reseed.
cultural requirements, tolerances & problems
Sunset Zones: 8-16, 18-24; H1, H2
USDA Zones: 8-10
Light: Full sun to part shade
WUCOLS SF Bay Area Hydro Zone: Low
Texture: Sand, loam, clay, (rocky, well-drained, responds to high-organic matter)
Moisture Retention: May dry between watering
pH: Slightly acidic to highly alkaline
Tolerances: Drought, heat, pollutants, poor soils; deer; resistant to Texas root rot and verticillium
Problems: All parts are toxic; sap is a skin irritant
Branch Strength: Medium to weak
Insects: Aphids, scale
Disease: Sooty mold, armillaria
citations & attributions
Bayton, R. (2019). The Royal Horticultural Society's the Gardener's Botanical: An Encyclopedia of Latin Plant Names. London: Mitchell Beazley.
Missouri Botanical Garden. "Nerium oleander." Accessed on July 6, 2021 from https://www.missouribotanicalgarden.org/PlantFinder/PlantFinderDetails.aspx?kempercode=a532.
Norris Brenzel, K. (Ed.). (2012). The New Sunset Western Garden Book. New York: Time Home Entertainment, Inc.
NC State Extension. "Nerium oleander." North Carolina State University, Raleigh. Accessed on July 6, 2021 from https://plants.ces.ncsu.edu/plants/nerium-oleander/.
Urban Forest Ecosystems Institute SelecTree. "Nerium oleander Tree Record." 1995-2021. Cal Poly State University, San Luis Obispo. Accessed on July 6, 2021 from https://selectree.calpoly.edu/tree-detail/955.
Water Use Classification of Landscape Species. "WUCOLS IV Plant List." University of California, Division of Agriculture and Natural Resources, Davis. Accessed on June 28, 2021 from https://ucanr.edu/sites/WUCOLS/Download_WUCOLS_IV_List/.