Yellow leaves on mandevilla

Q Our mandevilla plant is starting to develop yellow to orange leaves that then drop. Isn’t it a bit early for the plant to lose its leaves?

A Perhaps the leaf drop is a month or two early. Most likely, the late-season rains affected the root system and caused some minor damage. This often shows up as the premature loss of leaves. It may stop as the weather becomes drier, but make sure the plant has adequate water. Also, a light fall feeding may help the mandevilla hold its foliage a while longer.

Try manganese, not magnesium

Q: Our sago has dark green leaves at first, but they then turn brown. We have applied palm food and magnesium. What else can we do?

A: Browning of new sago leaves does suggest a nutrient deficiency. But it’s usually a lack of manganese that causes the plant to decline. You have applied a general palm fertilizer that might contain some manganese — but probably not enough to correct a deficiency. You have also applied magnesium, which is often confused with manganese.

Give the plant a manganese-sulfate application, following label instructions. One application is all that is needed. New growth produced a month or more after treatment normally continues the good green color.

It’s OK to keep or remove baby sagos

Q: I have a mature sago that has sprouted baby plants around the base. Do these have to be removed?

A: Create the sago look you like. Some prefer to keep a clear single trunk by removing the off shoots from the base. Others like multiple trunks and allow some of the shoots to continue growth. It is probably best not to grow a too-congested plant that harbors pests and often has a contorted look. You can remove the young plants as needed by cutting or prying them loose from the parent plant. These can then be rooted in containers of potting soil to grow more plants for your collection or to share with friends.

Frangipani might be thirsty

Q: I have several frangipani with leaves that are turning yellow and dropping off. I see some spots on them but no insects. What should I do?

A: First, check to make sure they have adequate water. Frangipani, also know as plumeria, yellow and drop their leaves during periods of drought. If the plants are in containers or a dry location in the landscape, the cure could be as easy as keeping the soil moist.

Also, examine the leaves for small yellow to orange spots that are caused by a rust fungus. The spots are the spores being released by the fungus. A heavy infection can cause an entire leaf to turn yellow and drop. Where needed, the Fertilome Systemic Fungicide or Immunox Fungicide can help control this leaf disease. Follow label instructions for safe and effective control.

Mandevilla yellowing and dropping leaves and all flowers – Knowledgebase Question

Unfortunately, based on your description I am not certain what is happening. If the yellowing and wilting coincided with applying the fertilizer then I would suspect an overdose of that. If it was a foliar application you could try rinsing off the leaves; if it was a granular application you can try to scrape it off the soil surface or you might try leaching it out of the soil by watering heavily and letting it drain, repeat several times in quick succession. Too, you would not want to be fertilizing much this late in the season as they need to begin slowing down in preparation for being brought indoors.
Another possibility since the symptoms were sudden, is that something affected the tuber beneath the soil and damaged it or caused it to rot. You might dig down carefully and take a look. Sometimes a bacterial or fungal infection can do this, and also make sure that the drain holes in the ottom of the container are functioning — overwatering can cause damage signaled by yellowing and wilting.
I am not sure how your nighttime temperatures have been but if the yellowing plants are in a more exposed location and you have suddenly had nights under 50 degrees, it may be related to cold exposure.
Since I am only able to make guesses from a distance, and you have a lot of these plants, I would strongly suggest you work with your county extension to try to identify the cause. Once you know that, you can determine how to proceed. I hope it is nothing too serious.

Q: I bought a mandevilla vine last spring, and I have brought it into my southeast-facing apartment, where it is doing well. I have five cuttings from it that are all growing nicely, but some of the leaves seem to develop spots, and then after a day or so they turn yellow and fall off. I can’t see anything on the leaves, even with a magnifying glass, although when I rub the top of the leaves my fingers get a little bit sticky. What could the problem be, and what should I do about it?

Also, last winter I kept an alstromeria plant indoors, and it bloomed beautifully all summer. It seems to be doing well this winter as well. My question is, as this will be the plant’s third year, should I change the soil? Also, will any type of potting soil work, or does it require something special? I have just fertilized it during the growing season. Also, will the soil surrounding the mandevilla vine need to be changed too, or should I just leave it and fertilize it during the growing season?

A: Mandevilla leaves typically turn yellow and drop off near the base of the plant. This is quite common with many vines, which lose their older leaves as they grow. However, if your plant is losing leaves in other areas then there is cause for concern. The first thing to check is the amount of water the plant is getting. Too much water can cause a problem, especially if the water is not draining away quickly. Check to make sure the roots of the plant are not sitting in soggy soil. If they are, you might want to look at a pot that offers better drainage. When you water, do so in the sink, allowing the water to run out of the pot and down the drain.

A lack of water, or allowing the plant to dry out too much between waterings, can also cause problems. Mandevilla likes to have a moist soil, but never wet. Use your index finger to check. Insert the finger up to the first knuckle. If the soil feels dry it is time to water. I have had a few readers tell me that their finger is not sensitive enough to detect the moisture, so I ran across another technique that you can try that involves using a chopstick.

The chopstick should be plain wood and not be treated in any way. Insert the chopstick into the soil, avoiding the roots. Leave the chopstick in place for 10 minutes and then examine it. If it has changed colour or has a watermark, the soil is moist. If it has only slightly changed colour you will need to check the soil again in a few days. You can rinse and dry the chopstick to use again, or you can also use a popsicle stick.

The spots you are describing may be a fungal infection called leaf spot. You can treat leaf spot with a garden sulfur spray or a garden fungicide such as Serenade. Mealybugs or whitefly can cause the stickiness that you are describing, but since you examined the leaves closely I think we can rule those out.

As for the alstromeria and mandevilla soil, I would change the soil for both plants. You should also consider moving them into to a bigger pot. They do not require any special potting mix, just a good quality one. One tip I would offer when repotting is to moisten the potting mix before using it. Place a layer of the moistened soil in the bottom of the new pot, place the rootball of the plant into the new pot, and then add more moistened potting mix around the sides of the rootball. This method keeps the transplant shock to a minimum.

Q: I have a calamondin orange tree. My cat was sharpening his nails on it and stripped the tree of leaves, and I am wondering if the cat has killed the tree. I put the tree in my west-facing window, then in the basement in the dark for four weeks. If I bring it back to the west-facing window, what are the odds of it growing again? I am hoping that it will come back, so if you have any suggestions I would appreciate it.

A: The best answer I can give you is that if it were me I would certainly try it. You won’t know unless you do it. I would keep the soil moist but not wet, and be patient. If you see signs of life I would even consider putting it outside when all danger of frost is gone.

Gerald Filipski is a member of the Garden Writers Association of America. He is the author of Just Ask Jerry. E-mail your questions to [email protected] To read previous columns, go to edmontonjournal.com/filipski

Mandevilla Vine – Knowledgebase Question

Mandevilla
Posted by piksihk
Excessive rain and poorly draining soils can cause the leaves of your mandevilla to turn yellow. Typically you’ll see completely yellow leaves rather than yellowing leaves with spots if your plant is reacting to being overwatered. If the spots develop after the leaves have turned yellow, it’s a secondary infection. In this case, the best treatment is to pull off the affected leaves or prune your plant back to remove the damaged leaves.
If the yellowing and spotting are occurring simultaneously, I’d be more inclined to think a fungal disease has attacked your plant. You can control fungal diseases with a fungicide such as Daconil, Cleary?s, Dithane, or Kocide. Be sure to apply according to label directions. A fungicide will protect the uninfected plant parts but won’t restore the affected leaves to their former green color so, depending upon the extent of the infection, you might want to prune the plant back to remove the diseased leaves, stems and flowers, and then spray with a fungicide. I know it will be hard to prune your plant back but this is the time of year that mandevillas put out tons of new growth so your pruning cuts should not be noticeable after a few weeks of healthy growth.

How to Over-Winter a Mandevilla Vine: Following Up

Posted in Gardening Tips on October 29 2013, by Sonia Uyterhoeven

Sonia Uyterhoeven is the NYBG‘s Gardener for Public Education.

Back in October of 2011, I answered a question a follower asked us on Twitter: “How do I overwinter a mandevilla vine?” It was simple enough to come up with an explanation at the time, but little did I know I would be receiving so many additional questions after the fact. Over the last two years, a number of Plant Talk visitors have stopped in to leave their comments and requests, which I’ll answer here.

For those who are not familiar with it, the mandevilla (Mandevilla splendens) is a Brazilian native with glossy leaves and bright, trumpet-shaped flowers. It is normally grown as a vine but occasionally pruned into an upright shrub shape. A hybrid, Mandevilla x amabilis, forms a tall vine perfect for growing on a trellis. But because these plants are not hardy in our zone, they require some special care in the cooler months. You can read all about it in my original post. In the meantime, I’ll answer the more specific questions our visitors have posed in hopes of helping your mandevilla survive the coming winter.

If you have a question that I haven’t answered here, feel free to leave it in the comments below!

Q: “I was wondering if I can put the mandevillas in a greenhouse, because I have eight of them, all in very large pots.” — Jay

A: The answer is yes, your mandevillas will be very happy in a greenhouse. Depending on the temperature and the light level, your mandevillas will either continue to grow slowly through the winter or they will go dormant, the latter of which should only happen if the temperature in the greenhouse is less than 60 degrees Fahrenheit. Keep the plants on the dry side, making sure that they do not completely dry out. The foliage will drop off and it is best to cut the vines down to about 8-12 inches. They will start to grow in spring as the weather warms.

If the greenhouse is kept at 65 degrees Fahrenheit or higher, then your mandevillas will continue to grow through the winter. If they get enough light, they will flower.

Q: “If I am removing my mandevilla from the earth to a container, what size container is a good size?” — Jennifer

A: When digging it up from the garden, place the root ball in a container that is slightly larger than the root ball. The goal is to give the roots some room to settle in but not too much. When you move a container plant and increase the pot size you can bump it up one size larger. Pot sizes usually increase by two-inch increments.

Q: “How often is ‘occasionally’ for dormant watering?” — Linda

A: You want the soil to be on the dry side but not completely dried out. The plant is dormant (inactive) but still alive, so you need to make sure that it doesn’t dry out and desiccate. Water it before you store it in the garage (or the chosen location) and check on the container once every three weeks to a month to see how it is doing. If it is being stored in a cool location, there is a good chance that it will require no or low watering (maybe once or twice during the winter).

The frequency of the watering will be determined by the light and the temperature. A container in a sunny, cool greenhouse will require a different watering regime than a garage. In that case, you will need to check more frequently.

Q: “I am losing leaves fast. What should I do?” — Fay

A: At this time of year, I am assuming that your mandevilla is going dormant and the loss of foliage is due to the seasonal change (lower temperature and light levels). If you are growing your mandevilla in a container in your home and it is losing foliage, then one option is to move it to a brighter location to see if that helps. If the plant has decided to go dormant, then it might be best to just let it do its thing (see above). If your mandevilla is losing its foliage and it is not due to the seasonal change then there could be a few possibilities.

In general, if house plants start losing foliage, check first on light level. Also look at your watering practices. Yellow leaves could be from over-watering or under-watering. Stick your finger into the potting mix and check to see if it is dry or wet. Checking an inch or two below the surface level is always wise to get a sense of the moisture level in the pot. Another reason for foliage yellowing and falling off could be a pest problem. Inspect the foliage for signs of scale, mealybugs or any common household pests. Given the time of the year, I am guessing that your mandevilla just wants to go dormant for the season.

Q: “Pruning seems to present one problem—milky sap dripping from cut ends. How do I deal with that, or can I just ignore it? Also, how do I propagate the plant?” — Ian

A: Mandevilla is in the Apocynaceae Family—the Dogbane Family. Many members of this family have a milky latex sap. The sap can be a skin irritant, so wear gloves when you are pruning your mandevilla.

There are a number of ways to propagate the vine. You can propagate it from seed—it’s best to soak the seeds for 12 hours before planting. You can also take cuttings in the spring or in the late summer from the new growth. The cuttings should be about 2-3 inches long and have two sets of leaves—remove the bottom set. Dip in rooting hormone. Use 2 parts sand to 1 part peat for your mix, or a sterile, soilless potting medium. Mist cuttings and cover. Place in indirect light with temperatures around 70 degrees Farhenheit. They will root somewhere between 1-2 months after.

You can also layer the mandevilla by taking a low lying branch and layering it in another pot. Make sure the stem has good contact with the potting soil. It will take several months for it to root. There are many excellent videos on YouTube that will show you how to take cuttings and layer.

Varieties

The plant genus Mandevilla includes countless species and hybrids, but only a few of them are cultivated. About 120 species are known worldwide. When buying a Mandevilla, you can choose between upright or hanging varieties and different heights.

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They range between 30 and 500 cm. The only feature that all varieties have in common is the shape of the flowers. Mandevilla sanderi, Mandevilla boliviensis, Mandevilla x amabilis and Mandevilla laxa are the four species that are most common.

Mandevilla sanderi

  • Mandevilla sanderi is the most famous and popular species
  • it has white, pink or red funnel-shaped flowers, with diameters of 4-7 cm
  • multiple flowers sit on one panicle
  • their densely arranged leaves are thick, smooth and rich green
  • this species can reach heights of 50 – 200 cm

Mandevilla boliviensis

  • the semi-evergreen Mandevilla boliviensis is considered to be particularly rich flowering
  • the large white flowers have a bright yellow throat
  • their leaves are solid, shiny, all-round and smooth
  • this species forms between 50 and 200 cm long tendrils

Mandevilla x amabilis

  • the slightly fragrant pink flowers of these strong climbers belong to the largest among the Mandevilla species with a size of up to 10 cm – as well as their leaves
  • in addition, the leaves are dark green and strongly textured
  • the Mandevilla x amabilis can grow up to 500 cm

Mandevilla laxa

  • the last of these four species is Mandevilla laxa with its snow-white flowers
  • this fast-growing climber can grow about 500 cm in height
  • its highly fragrant, white or creamy flowers adorn the plant from July to September in dense grapes
  • the dark green leaves are long, elliptical and heart-shaped at the base

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