The below plumeria I received from my mother. When I received it it was green as shown in the third picture. Over the course of ten days the leaves are turning a pale green to yellow color, see first and second pictures. Why are the leaves turning color? Thank you for all information.
Yes, they were in full sun at my mom's.
No, I did not re-pot them.
Not sure of the potting media.
She likely fertilized them. What kind should I use?
(My mom passed away last week and I took this plant with me. She could grow everything and I badly want to see this plant bloom. Lived in zone 4b and had blooms the past two summers.).
I so appreciate your help. Thank you.
I'm assuming your Mom also lived up north in zone 4b, so I guess you know to bring it indoors in winter. When warm, full sun will be best for your plant. The pot from your pic looks a little small, so I think it would benefit from being transplanted to a slightly bigger pot. As for potting soil, that miracle grow soil that comes in a bag and is sold at HD or Lowes, will work nicely.
For fertilizer, it would be best if you use something that says "plumeria fertilizer" but a formula for blooming tropicals will work too. Since you will probably benefit from repotting, it is doubtful that it will bloom this year or even the following year. However, fertilizing will ensure blooms in subsequent years. Who knows, being that it has bloomed in the past, maybe by just stepping up with fertilizer, it might produce an inflo (flower) this year.
Plumeria are both heavy feeders and water-hogs. That being said, they don't like to sit in water! The potting media should be well-draining and the pots as well. Don't let it sit in a saucer filled with water. The media that I see looks like it is simply peat. If so, it is highly water-retentive, not a good thing. Un-pot your plants and see if they are root-bound. Regardless, if the potting media is in fact water-retentive rather than well-draining, make up a good media for them. You can start off with typical Miracle-Gro potting soil and to that I would add 1/4 medium Douglas fir bark and 1/4 coarse perlite. You can just purchase a large bag of "orchid mix" and that will do. The ratio then would be 1/2 potting soil and 1/2 orchid mix.
I doubt you will see a bloom this year so don't bother with "blooming" fertilizer. Your main goal should be to get them healthy before dormancy. Just use a general purpose fertilizer, 20-20-20 is fine but use it at half strength. Fertilize one week, water thoroughly the next week, and then fertilize again. Repeat this through August. Don't fertilize after that, just water. I don't care whether you force the plants into full dormancy or keep them growing in pots inside during the fall/winter. Don't fertilize after August.
If your mom had these plants in full sun, you want to give them as much sun as possible. I would suggest that they get a minimum of six hours of full sun every day.