Monday, June 18, 2018
Home and Garden

Ask Dr. Hort: the paw-paw plant, palm tree scale and yellowing hibiscus leaves

Mystery tree produces bananalike fruit

Q: Please let me know what type of tree this is. I think it is a fruit tree. Laura Manfredi, Spring Hill

A: The mystery plant in the picture appears to be a native paw-paw, Asimin obovata. It is a deciduous, (loses its leaves) slow-growing shrub to a small tree with large white flowers followed by 4- to 6-inch green fruits. As the fruits ripen the skin will get a yellowish cast and soften and when opened has flat brown seeds scattered throughout the soft edible, banana-flavored flesh. The paw-paw is in the Annonaceae or custard apple family, a cold hardy relative of the mostly tropical atemoya, cherimoya, sugar apple, sour sop and others.

How to combat scale on a palm tree

Q: We have scale on our palm tree in the atrium. I have had the palm for several years. It has almost reached the top of the walls. I would hate to have to replace it. What is the best to spray on it? Dolores Hunter, Palm Harbor

A: The first step in controlling the scale is to prune off heavily infested fronds (to reduce the population).

Next would be to completely spray the palm, high and low, with Neem Oil on a weekly basis, following label directions, for three weeks. The oil should smother the adults and the repeated sprays should kill the crawlers (newly hatched out mobile scales), which are very easy to kill.

As a new spear leaf arises on your palm, keep a vigilant eye out for any sign of scale as the frond unfurls. Any dead adult scales left behind won't fall off, the scale is dead, the waxy covering remains.

For proof, scratch the covering off with your fingernail. If it is white and powdery underneath, it is dead. If it oozes, it was still alive. Treat again with three more applications of Neem Oil.

Don't worry about yellowing hibiscus leaves

Q: I have been noticing a lot of yellowing leaves on my hibiscus bushes. Could you please help me out so I can take on this problem? Bill Beck

A: Yellowing leaves on your hibiscus, Hibiscus rosa-sinensis, is not a problem.

Many plants didn't get any rest with the mild winter, so are a bit late putting on their spring flush. As this happens, older leaves will yellow and fall.

Fertilize, following label directions, with a granular balanced product, with 50 percent slow-release nitrogen, such as a 6-0-6, or 10-0-10. Phosphorus will be taken out of granular fertilizers by 2014, when the new State Fertilizer Law takes affect, so get used to a zero in the middle.

A few culture changes could affect flowering

Q: Have a problem with my amaryllis that won't bloom. I have about 12 to 14 plants (in big pots) that I've had for about 5 to 6 years. They bloomed great until our very cold winter two years ago and then last spring only one bloomed.

So last winter I decided that maybe they needed a rest, so dug them up, put in brown paper bag and stored in the closet. About first of April, I planted them, new soil, and within two weeks, they all were growing leaves. Now they are so full of nice shiny leaves but no flowers or even a stalk telling me they are coming. However, one of them recently opened up (three flowers), and that's it.

Why is this happening? No, I have never fertilized and they did fine. Marilyn Underwood, Clearwater

A: A few problems could have occurred, but first and foremost, amaryllis, Hippeastrum spp., bulbs should be dug and/or transplanted from October-January, during their dormant period, not April. When planting, the bulb should be sticking out of the soil half way (planted too low, no flowers) and placed in a sunny location (not enough sunshine, no flowers). Lastly, when fertilizing, use a soluble fertilizer lower in nitrogen (the first number) and higher in potassium (the last number) such as a 5-10-10 or equivalent, and begin in January and continue bimonthly applications through August to promote leafy growth to support larger flowers next season.

Identify which cultural practices were wrong and make changes for next year.