Oleanders: A Guide to Winter Hardiness
Introduction
Oleander shrubs (Nerium oleander) are known for their showy flowers and adaptability to various soil conditions. They thrive in hot and sunny climates and are drought tolerant. However, their cold tolerance can be a concern for gardeners in colder regions. This article will explore the winter hardiness of oleanders, providing tips for protecting them from cold damage.
Cold Tolerance
Most oleanders can tolerate temperatures down to 15-20 degrees Fahrenheit (-10 to -6 degrees Celsius) in their perennial range (hardiness zones 8 to 10). Exposure to lower temperatures for extended periods can damage plants and inhibit flowering. Planting oleanders in full sun helps melt frost more quickly, reducing the risk of damage.
Effects of Cold on Oleanders
Even a light frost can burn developing leaf and flower buds on oleanders. Severe frosts and freezes can cause plants to die back to the ground. However, in their hardiness range, oleanders that die back to the ground typically don’t die all the way to the roots. In spring, they will likely re-sprout from the roots.
The most common way that cold affects oleanders is during early spring cold snaps after plants have begun warming up in late winter. This sudden reversal of temperature can prevent oleanders from producing flowers in the summer.
Protecting Oleanders from Cold
- Mulching: Apply a 2 to 3 inch layer of mulch around oleander shrubs to insulate the roots in regions where they are less hardy. This helps protect the roots even if the top growth dies back to the ground.
- Pruning: If cold-damaged limbs occur, prune them away to remove unsightly dead branches.
- Avoid Burning: Do not burn cold-damaged limbs, as the fumes from oleander are toxic.
Winter Hardy Oleander Varieties
Oleander winter hardiness can vary depending on the cultivar. Some winter hardy oleander plants include:
- Calypso: A vigorous bloomer with single cherry-red flowers.
- Hardy Pink and Hardy Red: Two of the most winter hardy oleander plants, hardy to zone 7b.
Toxicity
All parts of the oleander plant are toxic. Wear gloves when handling oleanders and avoid burning pruned limbs.
Additional Tips
- Plant oleanders in well-drained soil.
- Water oleanders deeply and infrequently, especially during hot, dry weather.
- Fertilize oleanders regularly during the growing season.
- Prune oleanders in late winter or early spring to remove dead or damaged branches and encourage new growth.
By following these tips, you can help your oleander shrubs survive the winter and continue to enjoy their beautiful flowers for years to come.
