Questions on: Hoya

Ron Smith, Horticulturist, NDSU Extension Service

Q: What does water sparingly mean regarding hoya plants? I have two plants. One never has bloomed, but I was told it takes seven years for it to bloom. I am not sure if that is true. The other plant, I believe, is a Bella. It has bloomed once, and for once, my husband was excited about flowers and their beauty. After it bloomed, the leaves began to wither, but only on the stems that bloomed. What am I doing wrong? (e-mail reference)

A: Water sparingly means to allow the soil to dry completely between waterings and then only apply enough water to wet the upper inch or so. Watering thoroughly means that when the soil dries, add enough water to have it flow out the bottom of the container and not allow the soil to dry completely, such as you would during the winter months. The plant probably needs more direct light, either sunlight or lights specific for flowering houseplants. Light is the determinant for a plant to produce flowers. Energy from light is stored in a plant’s vegetative tissue and used for reproductive purposes. Since the one plant has flowered, it is now in a rest period, so be patient and water sparingly through the winter.

Q: I have a heart hoya that I received a couple of months ago. It was a single branch about a foot long and leaning out of the pot horizontally, with several mature leaves and a flower stem. It sits in a south window and gets lots of indirect sunlight. Shortly after I got it, it started growing a new branch straight up from the horizontal piece. The new branch is at least 2 feet tall, with new leaves, flower stems and new growth nodes. Should I cut the top to force it to grow in new directions or let it continue to grow? (e-mail reference)

A: The plant apparently is in a strong vegetative stage of growth. Cutting it back to a node would help force it to branch more and eventually flower. You must have some very good potting soil to be getting that kind of response.

Q: I have a hoya plant that is doing very well, but I was told years ago that they are poisonous. I have a grandson who is now walking and into everything. Are hoya plants poisonous? If so, what parts? (e-mail reference)

A: Hoya is not listed in either of my texts on poisonous plants. However, it is a good idea to keep the plant out of your grandson’s reach in case there are compounds within the plant that may make him sick.

Q: I was given a plant a number of years ago. I was told it was a hoya. So far, it hasn’t done very well. It is supposed to have a perfect white star blossom with another star inside, which I haven’t seen. Is it a hoya and how should I care for this plant? My uncle and aunt gave the plant to me, but both now are deceased. (e-mail reference)

A: What you describe sounds very much like a hoya, but I can’t say for sure. Assuming it is a hoya, do not disturb the plant once the buds appear and don’t remove the dead flowers. Don’t repot until necessary. Keep it cool during the winter months (50 to 55 degrees). Give it bright light throughout the year, with some direct sunlight. Water sparingly in winter, but liberally during the summer months. Mist the leaves often, but not when in bloom, and fertilize only during periods of active growth. Good luck!

Q: I was given a heart shaped hoya leaf rooted in coconut husk. Could you tell me the proper name of this variety? Will it grow to become a plant or just stay a leaf? I have heard many conflicting answers. (E-mail reference)

A: I think the one you are referring to is known as hoya australis. If it is rooted, has sufficient bright light and other growth factors, it should grow into a climbing/trailing vine like the others.

Q: I have a hoya plant that is more than 20-years-old and very large. An aunt told me not to take starts from it because it would not bloom for years after that. Is this true? Can I take starts? And can I cut it back so it doesn't take over my dining room? (E-mail reference)

A: Go ahead and reduce the size of the plant but don’t take off any remaining spurs, as that is where the flowers originate each year. Take 3 to 4 inch cuttings, making the cut just below a pair of leaves. Dip the ends in a rooting hormone and stick two or three together in a pot containing a 50/50 mix of peat moss and coarse sand or perlite. Moisten the media then cover the entire pot in a plastic bag. Keep the pot in medium-room light until rooting is complete, which is about six weeks or more. Uncover and water sparingly until new growth appears, then begin regular fertilization schedules. After about 90 days, move them into new containers with a soil-based mixture and treat them as you would mature hoya plants.

Q: I received a very old, root-bound hoya and repotted it in a terra cotta pot. It is quite long and hanging along curtain rods in an east-facing room. It seems healthy and loses few leaves. I fertilizer it about every three weeks. It has developed a few bunches of blooms but they fall off before they open. Could I be watering too much? (E-mail reference)

A: You are likely watering either too much or too inconsistently. Water enough to soak the entire root mass, then allow the upper one third to one half to dry before watering again. Also, since it is an old, pot-bound plant, it might need topdressing with potting soil as well. Try these two adjustments and see if that improves things.

Q: Could you please tell me if hoya can be propagated from seed? Also, are there any hoya varieties that can climb a wall or a tree without any additional support such as chicken wire or a trellis? There must be a generic name for vines capable of doing that type of climbing but I'm not sure what that term is.

A: Yes, they can. Although most increases are done by cuttings being dipped in a rooting hormone powder (which stops the milky sap from flowing) which root in about 4 - 6 weeks. Seeds can be sown fresh and kept moist at about 70 degrees F. minimum. The seeds should sprout in about 5 - 7 days. The species of hoya that grows as a vine is known as the porcelain flower (H. australis). The H. carnosa, which is known as the wax or honey plant, is a vigorous climber that is more commonly on the market.

Q: I have been nurturing India rope hoyas for several years and now they have developed mealy bugs. I have tried spraying them with Orthene Systemic Insect Control and with Volck Oil Spray, but the bugs still come back. Is there some other way that I can get rid of these bugs? (Heindal, N.D.)

A: It sounds like you've made every reasonable attempt to control the mealy bug pest! The only suggestion I can come up with is to try and locate a fumigant card that gives off vapors that will eliminate them. Place the plant or plants in question in a sealed plastic bag or container, for a 24-hour period, and that should do it.

Another possible option is to dip the foliar part of the plant in insecticidal soap solution. Being soft-bodied, this relatively harmless insecticide should be quite effective on these persistent pests.

Q: Can you tell me what is wrong with my African violets and my hoya? Please help me. (Hosmer,S.D.)

A: It looks as if your African violets are suffering from a couple of possible maladies: dry air, too much sun, incorrect watering and overfeeding. I must say that those are some of the largest African violet leaves I've ever seen, so I suspect perhaps overfeeding. Starve it a little and see if it blooms for you.

Other than being undersized, I could not detect anything wrong with the hoya. You might try moving it to a location where it would receive more light from the sun.

Q: I have seen a lot of answers about the hoya plant in your column. Just to let you know my hoya has nine blooms on right now, so it will be in full bloom for Easter. It hangs in a west window in the dining room with a humidifier in the room also. Keep up the good work with your column; I enjoy reading it. (Westport, S.D., e-mail)

A: Thank you for the encouraging words and the news about your beautiful hoya! I bet it is a knockout. With the days getting longer and warmer, we will see a big reduction in the need for as much indoor heating compared to the last four months. This alone will wake-up many indoor plants with renewed growth and possible flowering.

Your vigilance in houseplant care is obviously paying off. You keep up the good work!

Q. Enclosed are two leaves from my hoya plant. Can you tell me what is wrong with them? Also, can you tell me what are the best keeper onions? (Braddock, N.D.)

A. The only thing I can figure is that a "do not" has been committed somewhere:

The only other possibility is a temperature fluctuation. Being native to tropical India, they do not take well to temperature exposure below 55 F to 60 F.

The best keeper onions are the long-day type, that are high in sulfur compounds and pungent in flavor. Try to get Autumn Spice, Spartan, Sweet Sandwich, Sleeper, Spartan Gem, and Fiesta. Try to get sets and plant early.

Q: I have had a hoya plant for 20 years that just finally bloomed this past year. Now the leaves are turning yellow and dropping off. I have looked for scale or mites, but I can't seem to find any. What is wrong with my plant, and how can I save it? (White Lake, S. D.)

A: It is amazing that you've had the same hoya plant for 20 years! I don't know what kind of care you've given it, but I'd say it is now time to cut it back and repot it. The plant may only be going through a post-blooming rest period, where you need to reduce the watering somewhat.

Q: I have had this hoya plant for 32 years, but the new leaves have a funny, leathery texture. The edges are curled under on some of them. What causes this? (Venturia, N.D.)  

A: It is difficult to pinpoint what could cause this problem. Here is a list of possibilities: insect damage, underwatering, poor light, potbound or low humidity. 

If it has been more than a year since you've repotted, I suggest starting there.

Q: Can you tell me what causes this condition on my hoya? Also, my cactus is in full bloom and is quite beautiful. (Detroit Lakes, Minn.)

A: Definitely salt or fertilizer burn, possibly combined with poor drainage. Congrats on the blooming of your cactus. It's rewarding to see it in flower anytime.

Q.I, like so many others, enjoy reading your articles, but somehow haven't seen my problem. I have a hoya plant that is quite large and old, but it never has any flowers. I have given slips from it that do have flowers. I give it Miracle-Gro and try to take good care of it, but no flowers. Does it need a different fertilizer or could it be too old? It didn't bloom even when I first got it. I would appreciate any information you can give me. (Hitchcock, S.D.)

A.Hoya needs about four hours of direct sunlight and high potassium fertilization in order to flower. I am willing to bet that your friends who are successful are providing either or both of these conditions.

Try moving it to a south-facing window and provide supplemental light of a Gro'-Lux quality.

Q. Please send me information on my hoya plant. I transplanted it a year ago but some of the leaves seem to fold up. A sample is enclosed. Thank you. (Roseau, Minn.)

A. It is most likely that your hoya is still responding to being transplanted, as it is not one of  their favorite things to happen to them.

Q. I have had my Hoya for 17 years and it was quite large when I received it. Over the past couple of years, the older leaves have lost their succulent quality. Enclosed is a sample of the shriveled leaf. The plant still produces new growth a few times a year. These leaves look healthy for a time, with the exception of one vine whose leaves have died out on the tip. I water the plant sparingly once every 1 to 2 weeks. I am unable to thoroughly soak the plant because it is root-bound and much over about half a cup of water runs right out the bottom of the pot. I have not repotted the plant in at least five years. The plant loses few leaves; an occasional leaf yellows and falls off. It has a western exposure which is the only option in my house. Any advice you have on how to improve the health of this plant, which has much sentimental value to me, would be appreciated. (Mandan, N.D.)

A. Here are a number of suggestions:

1. Take cuttings to root and start new plants. See enclosed publication, NCR #274, "Home Propagation Techniques," which other readers may obtain from any office of the NDSU Extension Service.
2. Repot at this time of year.3. Completely immerse container (assuming it is free-draining) in water about every two weeks to thoroughly soak rootball.
4. Mist foliage, except when in bloom, with distilled water during dry winter months.
5. Water sparingly in fall.

Back to Shrub/Hedge Menu
Back to the Hortiscope Table of Contents