What you absolutely need to know about oleanders!
Location: As much sun and as little rain as possible – especially for double-flowered varieties.
Care: Oleanders like alkaline (i.e. calcium-containing) soils, corresponding to their native habitat in Mediterranean river valleys. Therefore they should never be watered with rainwater; the harder your tap water, the better. Oleanders are among the few plants which enjoy constant „wet feet“, that is, standing water in the saucer. NOTE: this applies only during the summer. In winter, in a cool location, they should be watered according to the old rule of thumb: "when the soil separates from the edge of the pot".
Oleanders are pruned only when the lower portions of the stems start to get bare. With white, yellow, and salmon cultivars, this will seldom be necessary; they voluntarily send up new shoots from the base. However, many pink and red varieties become bare at the bottom more quickly.
Overwintering: Oleanders tolerate a fair amount of frost. However, in order to protect next spring's flower buds (which have already formed in a latent state by autumn), they should be brought indoors as soon as temperatures threaten to fall below -5 C (23 F). If necessary, they can be kept in a cold dark cellar; however, a cool, brightly-lit stairwell or similar location is preferable.
Trimming inflorescences: The answer to the standard question "Should I remove the spent flower clusters before bringing the plants inside?" is NO. The first blossoms of the following spring will develop from these old inflorescences. Otherwise, one might have to wait until as late as August for the first flowers.
Yellow leaves: The oleander is indeed an evergreen plant; this doesn't mean, however, that it doesn't lose and/or shed its leaves and grow new ones. It absorbs all possible nutrients from the old leaves, and they then become yellow "overnight" - this is normal. This happens faster with some cultivars, more slowly with others. The result is the development of unattractive bare stems or "aging", which is countered by pruning.
Excerpt from a description by
Flora Mediterranea, Königsgütler 5, 84072 Au i.d. Hallertau
© Flora Mediterranea www.floramediterranea.de