The following are some of the most common questions and concerns related to cold-hardy oleanders:
What’s the difference between winter hardy and non-winter hardy?
A. Winter hardiness refers to whether or not a plant can survive extreme cold conditions. Non-winter hardiness refers to how well a plant grows in hot weather, such as summer heat or even drought.
Winter hardiness is determined by two factors: the temperature at which the plant was grown and its exposure to frost. Plants that were grown under cold conditions may not survive freezing temperatures, while plants exposed to frost may die if they don’t get water quickly enough.
Non-winter hardiness is determined by three things: soil type, amount of sun it gets, and species. Species have different needs than other types of plants. For example, some species need lots of sunlight, while others like desert-like environments.
Some oaks (especially red) are considered “cold-hardy” because they grow best in colder climates. Other oaks aren’t considered cold-hardy because they’re too tolerant of high temperatures and lack adequate shade from trees or buildings.
What’s the best way to protect oleanders from the cold?
A. One of the best ways to protect oleanders from freezing temperatures is to grow them against a wall or fence. Oleanders growing against a house or other solid surface will remain warmer than oleanders in the open. Sun exposure should be limited during freezing temperatures, as sunburn can damage sensitive foliage.
What is the most important thing to know about oleanders and water in freezing conditions?
A. When water freezes, it expands–which can cause pipes to burst. So don’t be fooled into thinking that because the temperature isn’t that cold outside, your oleanders won’t need water. If you have any concerns at all, it’s best to keep watering throughout the winter.
What’s the best way to protect oleanders from frost?
A. There are several ways to protect your plants from frost, including:
Bags of sand or mulch . Spread a layer of sand or mulch around the base of the plant (the thicker the layer, the better). This acts as an insulation barrier, protecting the roots and stems.
Burlap wrap. Drape a thick layer of burlap around the base of the plant. This creates a barrier between the frost and the plant.
What’s the best way to keep oleanders hydrated in freezing conditions?
A. The best way to keep your oleanders hydrated is to water them before the temperature drops. If this isn’t possible, however, never hesitate to break the ice covering the top of the soil (just be careful not to get any plants–or yourself–too wet). As mentioned above, water expands when it freezes. This can cause the ice to crack and break away from the sides of the pot. However, this isn’t a foolproof method, so check your plants often during freezing conditions just to make sure they’re not drying out.
Why do my oleanders have brown tips?
A. The most common cause of browning foliage is due to a lack of water. Remember that the first sign of drying is not dead, it’s dying. Brown tips can also be caused by sunburning (which may lead to dieback), extreme temperatures, and nutrient deficiencies.
How can I prevent sunburned oleander leaves?
A. If your oleanders are experiencing sunburned tips and edges, chances are they need more shade. If the sunburn continues, dieback is likely. You may want to try adding a bit of burlap on the southwest side of the plant (the side that’s mostly in the sun). This acts as an insulation barrier, protecting the plant from too much sun and heat.
What can I do to help my oleander get rid of aphids?
A. If you find a lot of aphids on your oleander, there are several ways to get rid of them. To keep them off in the future, try washing the leaves with a strong blast of water every few days. You might also try applying gibberellic acid (sold at garden centers for use on plants) or crushing garlic to a fine paste and mixing it with a little water. Be sure to apply this mixture only where the aphids are located.
How can I get rid of leaf miners on my oleanders?
A. Leaf miners are moth caterpillars that eat the leaves of plants (they look like little black lines on the leaves). The best way to get rid of these pests is to pick them off by hand and destroy them (or at least be sure to pick them up before they turn into moths and continue the cycle). You might also try spraying with an insecticidal soap.
How can I get rid of mealybugs on my oleander?
A. Try one or a combination of the following solutions:
Wash the plant with a strong blast of water every few days (be sure to hit all sides of the leaves so the bugs can’t take shelter in any nooks and crannies).
Apply a little cooking oil to the base of the stems and beneath the leaves. After a day or so, you can try wiping this away with a tissue. The mealybugs are likely to stick to the tissue.
What should I do about fungal infections on my oleander?
A. Fungal diseases such as leaf spot or gray mold can occur when plants are over-watered, kept too damp for too long, or have been exposed to high levels of moisture (such as in a rainy/snowy climate). If the infection is minor, you can wipe the leaves clean and try to keep the plant more dry (even allowing for a little dampness in the soil). Do not water unless the top layer of soil is dry. If the infection is severe, try cutting away all the infected leaves and wash off the rest of the plant, keeping the soil dry until it’s healthy again.
What should I do about black spots on my oleander?
A. Black spots are likely to be a sign of fungi or virus. While fungicides may help with the fungus, there isn’t much you can do for a viral infection. You’ll need to cut away all infected material and try to keep the rest of the plant healthy.
How can I get rid of scale insects on my oleander?
A. Try using a cotton swab dipped in alcohol, coating the insect with a thin layer of oil, or spraying with a little soapy water.
What can I do about slugs and snails?
A. You could try using a copper barrier around the base of the plant. Slugs and snails are reluctant to cross copper, so they’ll be blocked from getting to your oleander (or any other plants you choose to protect).
How do I get rid of mold on my oleander?
A. For black spots, see the answer above this one. For gray mold, you can try wiping down the leaves with a cloth moistened in milk. Be sure to remove all the dead and infected material first.
Sources & references used in this article:
Protein, leucine aminopeptidase, esterase, acid phosphatase and photosynthetic responses of oleander (Nerium oleander L.) during cold acclimation and freezing … by T Syros, T Yupsanis, D Petkou, AS Economou – Journal of plant physiology, 2005 – Elsevier
The effects of enhanced UV-B radiation on the Mediterranean evergreen sclerophyll Nerium oleander depend on the extent of summer precipitation by P Drilias, G Karabourniotis, E Levizou… – Functional Plant …, 1997 – CSIRO
Nerium oleander L.Cranberry Cooler’,Grenadine Glace’,Pink Lemonade’,Peppermint Parfait’,Raspberry Sherbet’andPetite Peaches and Cream’ by WA Mackay, MA Arnold, JM Parsons – HortScience, 2005 – journals.ashs.org
Anatomical changes in leaves of Puma rye in response to growth at cold-hardening temperatures by NPA Huner, JP Palta, PH Li, JV Carter – Botanical Gazette, 1981 – journals.uchicago.edu
NEW COLD-HARDIER OLEANDERS FOR NORTH TEXAS HORTSCIENCE 40 (1): 265-268.2005. by WA Mackay, MA Arnold, JM Parsons – HORTSCIENCE – plantanswers.com
Agronomic and pharmacological aspects of Nerium oleander: an important medicinal plant by F Ebrahimi, M Ghorbani Nohooji… – … Fair of Medicinal Plants …, 2018 – researchgate.net
[EP574] Key Plant, Key Pest: Oleander (Nerium oleander) by J Popenoe, CR Warwick, J Bourdon, J Chen – EDIS, 2019 – journals.flvc.org
Improving biological and physiological parameters of Nerium oleander L. cuttings by using biostimulating substances. by D VÂȘCĂ-ZAMFIR, E Delian… – … Papers-Series B …, 2018 – horticulturejournal.usamv.ro