I only know of two plants that go by the common name Oleander. One is Nerium and the other is Thevetia. Around here they are grown
in full sun, meaning from sun up till sun down. Further, both plants appreciate a fare amount of drainage material incorporated into the
soil. I would think completely back off on the fertilizer during the flowering period would be a real good idea.

Also, try letting the soil dry out 3/4 of the way down and flush the soil well with each and every watering. If this does not solve the problem
for you post again toward the end of summer with a photo of the plant, a close up pic of flowers and leaves.

{{gwi:8337}}

Thevetia has yellow flowers and much more delicate lighter green foliage so if yours had red, pink, peach or white flowers and strappy dark green leaves it is Nerium.

As advised, do not keep this plant moist! It is adapted to desert conditions and would not appreciate it and it isn't a heavy feeder, either.

Thanks for your replies which I just found. (For some reason, replies aren't being forwarded to me, despite my checking the box for that.) I never heard of Thevetia and am grateful for the education.

I have definitely not overwatered it~it's always dry to a depth of 3" before I give it a drink. And it's in a pot that's small relative to its height.

I don't believe I've ever fertilized it, either! Benign neglect is my watchword for gardening. I wonder if it could be reacting to the styrofoam material of the pot? Or maybe it just hasn't been hot enough~but that should be cured almost immediately now that we've entered Washington's hottest months.

If it hasn't been cured in a month, I will break down and buy a digital camera.

Happy Fourth of July!
Ginny

Here is a pic of Thevetia

Here is a link that might be useful: Thevetia

Here is the more common Nerium oleander. The foliage is similar but the blooms differ.

Here is a link that might be useful: Nerium oleander

I have a red nerium oleander and the blooms never fully mature but shrivle and die. has been planted 6mos or so in well drained soil. have tried permethrin in case of pests but that's doesn't seems to work. any suggestions would be helpful.

As well as Nerium oleander, I have yellow, peach and white Thevetia peruviana trees AKA Lucky nut . All are very each to grow and enjoy full sun. I also have Thevetia ovata which looks totally different from it relations.Locally it is called 'The Christmas tree' due to the red seed pods that decorate the tree year round and the blooms resemble Papaya blooms.. Not a common plant.