Yellow Leaves on Hibiscus

“Help! The leaves on my hibiscus plant are turning yellow. What’s wrong with it?”

Don’t panic, yellow leaves on hibiscus are normal. They look like something is wrong, but they are usually just a warning, a call for help, and not a sign of impending death.

Hibiscus leaves turn yellow and drop from the plant due to stress. The stress can be of any type and figure out what kind of stress is the challenge for the gardener. We cannot tell you exactly what is wrong with the plant without knowing a lot more than you are likely to be able to tell us. YOU have to think about it, and when you are pretty sure you have determined the cause, then you can take action to relieve the stress on your hibiscus. This article is intended to help you figure it out what is wrong.

Stresses that can cause yellow leaves on hibiscus include:

1. Not Enough Water
In warm conditions, hibiscus needs a lot of water, even every day or more than once a day if it’s really hot or windy. Self-watering pots can be an excellent way to avoid this type of stress. A watering system controlled by a timer is another way for gardens with large numbers of plants.

2. Too Much Water
Yes, hibiscus can also be given too much water when the weather is cool or overcast. Hibiscus like to be moist but not sopping wet and if they don’t need the water due to cold or dark conditions then too much will stress the root system.

3. Too Hot
This is related to water but please take note on super hot summer days that hibiscus will need lots of water to keep all the big lush leaves well supplied. If they don’t get enough they react by dropping leaves (that turn yellow first) so that they don’t need as much water.

4. Too Cold
Hibiscus are tropical plants that thrive in the same temperatures that people like, 65-85°F (18-29°C). Like us, they will survive, but they will not like temperatures down to freezing and up to 110°F (38°C). If they get too cold or are placed in a cold drafty window, they can react with yellow leaves.

5. Too Much Direct Sunlight
Hibiscus like sunlight but just as most people like moderate amounts of it so do hibiscus. Too much sun places stress on hibiscus that is not used to it and they can react with yellow leaves or big white spots on leaves. The white spots are similar to sunburn on us. They won’t kill the plant but will cause it to shed leaves.

6. Too Little Sunlight
Light is the source of life for plants such as hibiscus. If they do not get enough to support all the big lush leaves they will drop some of their leaves (which turn yellow first) so that they don’t need to support so many. However, that means that there is less green chlorophyll left to support the needs of the rest of the plant so it may continue to decline until there are only a few leaves left on the plant.

7. Insects, Particularly Spider Mites
Spider mites are tiny spiders that look like little crabs under magnification. Usually, you cannot see spider mites with the naked eye but do they ever leave a mark on hibiscus leaves! First, you may see mottling of the leaves which begin to look dirty and then tired. The underside of leaves will show marks made when the mites suck the juices from the leaves. As the infestation gets worse you will see small spider webs under the leaves and at the top of stems. Leaves will yellow and fall off the plant and the entire plant will look stressed. If left untreated, spider mites can cause every leaf on the plant to fall. It takes hibiscus weeks to recover from a bad spider mite infestation so it is best to take action as soon as possible.

8. Too Windy
Most of us do not realize the stress that the wind places on plants. The Wind dries them out and the result is yellow leaves.

9. Improper Nutrition or pH ~ Chlorosis
This is a different condition, called Chlorosis and the yellow is a different yellow. The leaves will remain partly green and partly yellow when there is a nutrition problem. Leaves almost always fall off the plant after turning solid yellow. If they do not turn completely yellow nor fall off, then it is likely that the problem is a lack of essential nutrients. This can be due to no fertilizer applied or due to a pH level of the soil that is too high or too low. The leaves do not turn a bright yellow all over if this is the case nor do they drop off. Such problems can be corrected by using fertilizer and/or amending the soil with substances that will neutralize the pH. Consult a nursery professional at a local garden center if this is the case.

10. Pesticide Use
This is not a common problem but overuse of pesticide or using the wrong pesticide or too strong a pesticide or spraying in the hot sun of mid day can also cause leaf problems. If you have applied pesticide recently this may be the problem but if you used the same type at the same strength and done so in morning or evening then it is most likely one of the other stress problems above.

Once you have reviewed all the possible problems and decided on a likely source of the stress the cure is to remove the stress. Sometimes it is already done, as when you have watered thoroughly after neglecting to do so during a heat wave. There is no saving the yellow leaves that WILL fall off but the good news is that hibiscus will quickly grow back new green leaves when the stress is removed. Sometimes it becomes necessary to prune back a stem that has lost all of its leaves except for a few at the top. Pruning causes a cascade of plant growth hormones to enter the bare stem and stimulates new growth on the remaining part of the stem after pruning. This is a final solution if all else fails but it is best to remove the cause of stress first and to feed and water the plant well since that may be all it will take to get new growth on your hibiscus.

Yellow leaves are not the worst thing in the world. Sometimes the situation will correct itself, other times you need to correct the stressful condition. The hibiscus will do its part by reacting to the improved condition by no longer dropping leaves and often by regrowing new ones to replace any that were lost. Good luck with your growing and gardening and by all means have fun with it!

Spider Mites

My Hibiscus Leaves are Turning Yellow!


Yellow Leaves on an Otherwise-Healthy Plant
The First Sign of Spider Mites

Spider mites are a warm weather problem for many hibiscus growers. They prefer hot, sunny, dry conditions and their levels can soar when the temperatures rise. If not dealt with they can cause all the leaves of a hibiscus to fall off and seriously damage the overall health of the plant.

How Can I Tell if My Hibiscus Have Spider Mites?

The first sign of spider mites is yellow leaves. A leaf or two first gets yellow mottling mixed in its normal green, then slowly the entire leaf turns bright yellow. At first, you just see a few yellow leaves, here and there, and don’t think anything of them. But very soon the spider mite population explodes and more and more leaves turn yellow at an increasing rate of destruction.


Spider Mite Webs in Bright Sunlight

As the spider mites spread, they become visible to the naked eye only in the brightest light with the closest inspection. A magnifying glass helps immensely at this stage. Look at the tips of the branches with yellow leaves, and you will see very fine webbing. These are the spider mites’ webs. You can sometimes see little dots on the webs – the spider mites themselves. At this point, you have a severe infestation that must be dealt with quickly or these little pests will make every leaf on your plants turn yellow and fall off, which can eventually kill the hibiscus.

Tell-Tale Signs of Spider Mites


An Advanced Case of Spider Mites
Look Closely to See the Webs & Mites on Growing Tips
Leaves Show the Typical “Mottling” of Green & Yellow

Tiny Spider Webs: Look for tiny spider webs on the growing tips of your plants. You will need to look very closely, in bright sunlight, for very fine, tiny webs on the smallest growing tips or developing buds. If you have good eyes and bright light, you may see tiny dots along the webs. These are the spider mites. With a magnifying glass, you can see that the dots actually look like tiny crabs scuttling along the web.

Growing hibiscus in the house or in a greenhouse offers a lot of protection from many forces of nature, including pests like thrips, ants, slugs, and even aphids much of the time. However, there is one bug that thrives in the warm conditions of the greenhouse and positively flourishes in the warm, dry environment of a house – the spider mite. The warmer and drier the environment, the more these little critters reproduce! So if your hibiscus is still indoors, watch carefully for signs of them.

Stippled Leaves: Leaves become stippled as the mites pierce the leaves and draw out chlorophyll from them, leaving colorless leaf spots behind. If you start to see leaves that look like this, with yellow stippling, search for spider mite webs on the stem tips.


Leaf Stippled by Spider Mites

Yellow Leaves: If the infestation continues, leaves that are badly infested will turn yellow and fall off. For many people, yellow leaves that fall off their hibiscus is the first clue that something is wrong. But by the time the infestation reaches this stage, it is already quite advanced. It’s best to learn how to detect spider mites in the earlier stages.

Sick Plant: If the spider mite infestation continues unchecked, the whole plant begins to look tired, with the leaves slightly drooping despite being well watered.

Defoliation: If left untreated the mites can create a mass of webbing over the plants, and most or all of the leaves will become damaged, turn yellow, and fall off.

How Do I Get Rid of Spider Mites?


Plant Defoliated by Spider Mites

Over the years, we have written many articles on how to control spider mites. The methods below are the ones we have found to be most effective at killing spider mites with the least amount of harm to the hibiscus plants. The method each of us chooses depends on the circumstances – how many hibiscus plants we have, how big the plants are, whether they are indoors or outdoors, in a house or greenhouse, in pots or in the ground, etc. At HVH we have hibiscus growing in the greenhouse, on the ground in an outside garden, indoors in a house environment, and outside on porches and decks in pots. We use different pest control methods for each of these different sets of hibiscus. Very few of us have extra time to waste, so efficiency matters! All of these methods work. It’s just a matter of finding the method that is quickest, easiest, and most efficient for you hibiscus and their growing circumstances.

DROWNING SPIDER MITES

This is our favorite method for all hibiscus growing in small-medium pots and for houseplant hibiscus. You only have to do it ONCE to kill all spider mites and their eggs. It kills every kind of spider mite, even the most microscopic ones that can hide in cracks in the bark. This method does require precision and care. You’ll need a timer and a thermometer – a kitchen “candy” thermometer is perfect. If the water is too hot or you leave the plants too long, you can damage the leaves and they will all fall off after treatment. If the water is much too hot and you leave the plants much too long, you could actually kill a very young plant. But if the water is too cool or if you don’t leave the plants in the water long enough, you won’t dissolve the covers of the eggs and kill the growing larvae, which means the infestation will come right back.


A Large Sock on a Small Pot
  1. Wrap the hibiscus plant pots in some kind of fabric and use a twist tie to secure the fabric around the base of the plant. The fabric must let water through, so don’t use plastic bags, or you will carefully protect any pests that are living in the pot and soil. Large socks or pantyhose work well to wrap up small pots, and pillow cases work well for large pots.
  2. Lay several hibiscus plants on their sides, pots and all, in a bathtub. You can put many of them close together in a single layer in the bottom of the tub.
  3. Fill the tub with water that is bath water temperature – about 90°F (32°C). It should not be so hot that you can’t comfortably keep your skin in it. What feels too hot to the skin will risk damaging your plants’ leaves.
  4. Fill the tub until all the plants are covered, and weight the plants down to make sure all parts of all plants are submerged in the water. (An easy way to weight them is to cover the plants with two large towels, then to pull the two shelf racks out of your oven and lay those carefully over the top of the towels.)
  5. Leave the plants submerged in the water for 45-60 minutes.
  6. Drain out the water and stand the plants up in the tub until the excess water drains out of the pots.
  7. Remove the fabric covers, and scoop any loose soil in the fabric back into the plant pots.
  8. Leave the plants out of bright light for a few hours to rest, then put them back where they belong. Be careful not to water the plants again until the soil dries out after this thorough soaking.

Unless plants are recontaminated by exposure to another infected plant, plants should remain free of spider mites, aphids, and other pests for 4-6 months or more. This method has the added advantage of leaching out any build-up of fertilizer salts in potted plants, which needs to be done once or twice a year. So it is two plant-care activities in one.

WASHING OFF SPIDER MITES


BugBlaster

If your hibiscus is too big to put in a sink or bathtub, an alternative method is to wash your plants in a shower, under a faucet, or with a hose or BugBlaster. If done carefully and conscientiously, this method will wash off and drown adult spider mites, but it will not wash off or drown all eggs and nymphs. So you will have to repeat it 3-4 times, every 5-7 days, to get rid of all the spider mites as soon as they hatch out and grow into adults.

This method works for large hibiscus in pots or for hibiscus planted in the ground. It’s especially good for people with smaller hibiscus collections, because it is very effective, and it is the least damaging to plants and to the environment. It is time-consuming though; each plant must be washed slowly and carefully.

  1. If plants are in pots, lay them on their side where the pots can be rolled over to all sides. If plants are in the ground, get a long enough hose that you can walk all around each plant.
  2. Using a hard stream of water, wash every single millimeter of each plant – the top and bottom of every single leaf, branch, stem, and twig. Spray systematically, making sure you don’t miss one spot on the plant where spider mites could be lurking. Spider mites live mostly on the bottoms of leaves, so spraying the bottom of each leaf carefully is crucial.
  3. When finished, wash the ground with a very strong stream of water and enough water to drown any spider mites that fell off the plants.
  4. Repeat this washing process 2-3 more times every 5-7 days.

TREATING SPIDER MITES WITH SPRAYS

Another alternative method is to treat with either a miticide, such as Bayer Advanced 3-in-1 or with Horticultural Oil or Neem Oil. All three treatments work equally well, in our opinion, and we sometimes alternate between them, using one one week and the other the next week. Just like the washing method, sprays are effective at zapping adult spider mites, but in our experience, they don’t kill all the eggs or nymphs. So you have to repeat the spraying every 5-7 days for 3-4 egg-hatching cycles to make sure you get every emerging adult spider mite.

Breathing any of these products is very bad for you, so if you decide to spray, you should absolutely use a respirator mask. Oil droplets aren’t poisonous, but breathing oil into your lungs is very harmful to your body. You can feel it in your lungs for quite a while afterward if you make this mistake! It takes a lot of spraying to kill all the spider mites, and that amount of spraying without a mask is definitely bad for lungs.

One more note about spraying: All these products are best sprayed in the evening when the plant can be protected from the sun for the hours that the products are doing their work. If you spray in the evening, the products have 8-12 hours to work, and the sun won’t burn the products into plant leaves and burn them or harm them in any other way.

  1. Put your hibiscus in a protected place outside with enough space to walk all around each plant.
  2. Put on your respirator mask.
  3. Carefully and systematically spray every millimeter of the plant: tops and bottoms of every single leaf, stem, branch, and twig, as well as the surface of the pot and soil. It takes the time to spray this carefully, but you may as well not bother spraying at all if you don’t do it this carefully! Spider mites living mostly on the bottoms of leaves, so spraying the bottom of each leaf carefully is crucial.
  4. Let the spray product dry for several hours before bringing the plants back into a house.
  5. Repeat this spraying process 2-3 more times at intervals of 5-7 days.

The trick with pest control is conscientiousness. Any one of these methods will work if applied conscientiously following the directions exactly. So find the method that’s easiest and most comfortable for you to follow!

Chlorosis

Yellow Leaves ~ Is it Chlorosis?


‘Chlorotic Hibiscus Leaves’

What is Chlorosis?

The green we see in the leaves and stems of plants is a green pigment called “chlorophyll.” Chlorophyll is much more than a pretty color. It is the essential substance that a plant uses to produce food and energy from sunlight, fertilizing nutrients, and water. When all of a plant’s leaves begin to lose their green color, this means they are losing their chlorophyll, or the ability to produce food and energy for growth and flowering. “Chlorosis” is a special situation where plants have some kind of condition, such as a disease or nutritional deficiency, that causes them to produce less chlorophyll than normal.

How Can I Tell Chlorosis from other Causes of Yellow Leaves?

For our purposes, chlorotic leaves on hibiscus are those that turn yellow but do not fall off right away. Most other causes of yellow leaves result in the leaf falling off shortly after it turns yellow (spider mites, normal replacement of aging leaves with new leaves, extreme weather conditions, etc). When hibiscus leaves become chlorotic, they usually turn yellow between the veins that are visible on the leaf, while the veins themselves remain green. This gives a more mottled impression than a leaf which quickly turns yellow all over and then falls off. Chlorotic leaves will eventually turn brown along their edges, then the whole leaf may yellow and fall off, but this is a very slow process.

What Causes Leaf Chlorosis?

There are many possible causes of chlorosis. These are the causes we most commonly see:

  • Iron deficiency in the soil or potting mix
  • Magnesium deficiency in the soil or potting mix
  • High pH (above 7.2) of the soil or potting mix – or an “alkaline” soil
  • Overly wet and poorly drained soil that damages the roots’ ability to absorb minerals
  • Fungus or other pathogens that damage the roots’ ability to absorb minerals or the plant’s ability to use them

What Do I Do about Chlorosis?

First, determine the cause of your plant’s chlorosis.

  • If your plant’s soil is overly wet or poorly drained, start by correcting this and see if that solves the problem.
  • If the chlorotic leaves are at the ends of the stems, in the newest and youngest growth, then the problem is usually an iron deficiency.
  • If the chlorosis shows up in the lower leaves, the older growth, it is most likely a magnesium deficiency.

Chlorosis at the tips of branches in the youngest leaves
is usually caused by a deficiency of iron

Apply the appropriate treatment to fix the problem.

  • If the problem appears to be overly wet or poorly drained soil, then stop and correct this before trying anything else.
  • If the soil is not overly wet and it drains well, then try correcting for mineral deficiency.

How Do I Correct for Mineral Deficiencies?

Treatment involves making more iron or magnesium available to the plant. Both are used by the hibiscus to make chlorophyll, which is what makes the leaves green.

  • A quick but temporary fix can be achieved by spraying the leaves of the chlorotic plant with either iron chelate or magnesium sulfate, depending on which mineral appears to be deficient.
  • A longer lasting fix is achieved by applying iron chelate or magnesium sulfate to the soil or potting mix that the hibiscus is growing in.

Iron Chelate made with FeEDDHA

Both iron chelate and magnesium sulfate can be found in many nursery supply stores, but be careful when you look for them. Only iron chelates made with FeEDDHA are effective in all kinds of soil and potting mix. For your convenience, we have both these products in their optimum form for hibiscus available now in our HVH Online Store. Specific directions are included with the products about amounts to use and how to apply them.

What If These Treatments Don’t Work?


Magnesium Sulfate

1. Check the pH of the Soil: Testing soil pH accurately is actually a rather difficult task, best done by a lab experienced in doing so. You can check with the agriculture extension office in your county to see if they will check the pH for you, or we can recommend a lab where you can send a soil sample. Alternatively, you can purchase a pH meter, but be aware that the cheapest ones are notoriously inaccurate, and even the reliable ones require regular maintenance and the knowledge of how to use them properly.

2. If the pH of your Soil or Potting Mix is above 7.2, Treat to Lower the pH: The classic way to lower pH of soil or potting mix is to mix elemental sulfur and iron sulfate (ferrous sulfate) into it. This provides a long lasting fix for the problem and should eliminate iron-based chlorosis for 2 years or longer. The recommendation is to mix the two minerals together, half and half, then introduce them into the soil before watering them in. This lowers the pH and adds iron to the soil. Results are slower to see, but longer lasting and a more complete fix for the problem.

Lab Work – Is It Useful?

An agricultural lab will do a complete soil analysis for you that will reveal the amount of all the important nutrients contained in your soil, as well as the pH. A soil analysis usually costs less than $100 and can be helpful if you are not confident about the quality of the soil you are planting in. Another useful test that you can have done at the same time is a water analysis for agricultural purposes. This will tell you the water pH and a number of minerals in your water. The most complete picture of the growing situation can be obtained by sending some leaf samples to the lab where they will be analyzed to see if all the needed minerals are present in the leaf. This is how large commercial operations keep their plants growing on schedule, and obtaining this information can also be useful to the home gardener.

OK, so this sounds like a lot of trouble and expense to go to! We agree! We only recommend lab analysis of soil, water, or plant leaves for those with stubborn chlorosis problems, or for those with enough money, time, and interest to make the experience of working with an agriculture lab enjoyable.

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