Hoya tips, tricks and trouble-shooting
If there was a competition for the most addictive plant family, Hoyas would win first prize. This gorgeous genus is thought to combine around 900 known species, cultivars and hybrids, with over 500 scientific names published. However new species are being discovered all the time. Lucky us!
Hoya are NOT your run-of-the-mill indoor plants and do have some unique requirements, as well as some unique ailments. Whether you're a hoya newbie or have some Hoya experience but always keen to learn more, this collection of hoya tips and tricks, FAQ's, what to do's (and what NOT to do's), is made for you. Let the trouble-shooting begin!
Why is my hoya putting out long vines with no leaves or only tiny leaves?
This is most often a sign your hoya wants to climb. Once a location is found that better provides the conditions they want, they will usually shift their focus back to growing leaves again. Some hoya start off with lovely big leaves, one after the other, dense and bushy, then suddenly shoot out long, leafless vines. A sign they are starting to mature to the point they want to climb. Totally normal.
TRELLIS TIME Take the hint. It's time to give your hoya a trellis. If you're in New Zealand, I love both the Arka and Botanopia trellises for my Hoya (or for my overseas plant friends, these trellises are great for Hoya too).
MORE LIGHT can also help your hoya shift its energy back to foliage. Once in better conditions and supported, leaves will grow along those vines, so don't cut them off! Treat the vines with care, as they will be more delicate than the older, hardened stems. The tiny nodes (the little bumps you see along the length of the vines), are where leaves (and hopefully peduncles), will later grow from, so take care not to damage them.
Why has the end of my hoya vine dried out and stopped growing?
The most common reason is gravity, sort-of. Hoyas love to climb. Even without a support, most hoya do their best to head on up. A trellis is a big help to give your plant the signal it's climbing and that it should keep growing.
If a vine is dangling down, or you've attached it to your trellis growth-tip-down, they'll often get the signal they're growing in the wrong direction, and thinking that there's nothing to climb in that direction, respond by killing off that growth tip. Normally a new growth tip will then activate somewhere else higher up on the plant and try for better chances of climbing.
So do give those long vines something to climb, but keep the tip pointing up! If you want to loop it around a trellis, wait until the vine is long enough to loop fully around, and let the top few inches point up, ideally with the tip kept at least above the middle of the plant. Only attach the growth tip loosely to the trellis, so it can move around freely. And boy do they move!
How can I make my hoya flower?
The short answer is you can't force your hoya to flower. But nor is flowering a totally random occurrence you have no control over either. You absolutely can provide the right conditions for blooming and - as you can probably guess by the many bloom boosters and flower fertilisers on the market - nutrition matters too.
In fact the care you give your hoya when it is NOT flowering, including what you feed, can be the key to unlock successful flowering next season.
However, keep in mind most hoya will take their time maturing, and may not flower until they have a few years behind them. Yet some flower as cuttings! Like most things in life, and certainly in our hobby, there are always exceptions. However if the stars are aligned, and your hoya is old enough to get it's bloom on, there are a few things you can do to help it along.
Often a reluctant bloomer is simply due to not enough light, however some hoyas shift into reproductive mode (ie: flowering), in response to 'stress' which encourages blooms, such as a cold period or dry patch. If you research the habitat your particular hoya comes from it can give you clues to what the required stress might be that you can emulate.
Leaf type can also offer some clues. Thicker, more semi-succulent leaves - like the popular Hoya carnosa - often require a short dry period to trigger flowering, such as a month of drying out.
Hoya also have times of year they typically bloom, and once you know what that is for your particular hoya, shifting from a grow fertiliser to a bloom fertiliser can help. Shift BEFORE peduncles or buds form, as well as creating a change in conditions (especially light).
Keep in mind if your hoya isn't growing leaves, it likely won't grow flowers either. Improving the substrate is often recommended if your hoya isn't doing much of anything despite conditions being ideal. Plus make sure you're feeding a good fertiliser to rule out mineral deficiencies.
A proper soil-less hoya mix, or fern fibre, are two popular options (I use both, but currently love the Bio Leaf Hoya blend). As far as Fern Fibre, we're spoiled here in New Zealand as being the home of NZ Fernwood Fern Fibre the price is awesome here, but although it's pricier overseas, (this one's for my international plant friends), you can get Fernwood Fern Fibre on Amazon.
Should you remove hoya flowers after blooming?
No! The blooms themselves will drop off when finished flowering, however it's important to leave the peduncle on (that's the stalk the flowers were attached to), because most hoyas will repeat bloom from that same spur year after year, sometimes multiple times in one season. The spur is the end of the peduncle, where the flowers will appear.
Why do my hoya's buds dry up or die without flowering?
Also called 'bud blast', this is relatively common and there are lots of possible causes so there are lots of possible solutions. Let's run through the most common fixes:
DON'T change conditions. In the same way a change in position or conditions can trigger flowering, once buds have formed, now's the time to avoid any changes until buds flower.
DO change fertiliser. The shift from a nitrogen-rich foliage fertiliser, to a bloom fertiliser is recommended at the first sign of a new peduncle, or new buds on a spur that has flowered before. Ideally you want to shift before flowering, that's around early Spring for many Hoyas.
A lot of fertilisers provide plants with what they need to grow foliage, but the mineral requirements for flowering is very different. Staying on a foliage fertiliser when a plant is trying to flower can interrupt or inhibit flowering. My favourite is GT Flower Focus as it's complete and balanced, lower in nitrogen, higher in calcium, and low in salt to help avoid fertiliser burn. Another excellent option is Dyna-Gro Bloom.
FOLIAR FEEDING. Speaking of fertiliser, some collectors report good results using their bloom fertiliser as a foliar spray to encourage blooming, however check first that your choice of fertiliser is formulated for foliar feeding (both GT and Dyna-Gro are). Also make sure to check the dilution rate for foliar feeding as it is often less (ie: more diluted), than for root feeding. You also always want to avoid fertiliser getting on the blooms themselves as they tend to be more sensitive to fertiliser salts.
CALCIUM. Another fertiliser-related cause of bud blast is a calcium deficiency. Check your fertiliser label! Most do NOT include calcium, even though it's an essential nutrient for hoyas. I look for around 50 to 130ppm calcium for flowering (that's the rate once diluted). The fertiliser label sometimes tells you calcium in ppm, otherwise you can work it out using a ppm calculator online or ask your retailer before you buy to check it includes calcium, and what the ppm level is. And yes, another reason I like GT and Dyna-Gro for Hoyas is because both include calcium.
WATER. Increase watering (slightly). Getting too dry, or staying dry too long, can spell the death of buds. Thinner-leafed hoya retain less water than thicker leaf varieties also, so tend to be more sensitive to drying out. Keep a closer eye than usual on watering when due to flower as bud blast can also be caused by over-watering.
HUMIDITY. If your particular hoya prefers higher humidity, when buds are forming is not the time for low humidity! Research more about your hoya's natural habitat and do your best to emulate those conditions. Grab yourself a hygrometer as well to check temperature and humidity. For those in NZ I use the H2O cordless humidifiers but for those overseas you can get the Levoit brand from Amazon.
TIME. Give it time. Some hoya can take months to go from blooms to flowering. I've heard of one that took over a year! Some find younger hoya are more likely to experience bud blast and maturity sorts it out. Think of it like a practice run ;)
TEMPERATURE. Watch temperature highs and lows. A big temperature change can cause buds to abort their mission. Look up what your hoyas ideal temperature range is and grab a thermometer to keep an eye on conditions. Some prefer it on the cooler side so getting too toasty can zap those buds. Hoya Bella and Serpens are two that prefer cooler conditions.
Why are my hoya's leaves coming out curled and deformed?
For some hoya this is normal and they will sort themselves out as they mature, but if that's not normal for your particular hoya, the next common causes are either a calcium deficiency (or nutrient deficiency in general), damage when forming, or bugs.
Isolate and inspect for pests, treat if needed, and also start feeding. One or both normally get growth back to normal (if that's not normal for your particular hoya of course). Keep in mind very few fertilisers include calcium, so if yours doesn't, either find one that does, or supplement with dolomite lime or cal mag (don't waste your time with eggshells or milk!). Two fertilisers that do are Growth Technology and Dyna-Gro.
Why are leaves on my hoya turning yellow and dying?
The causes of yellowing in old growth are pretty universal across all plants. This guide to why leaves turn yellow runs you through the most common causes and the solutions for each. If you don't already, go grab that fertiliser, as a simple nutrient deficiency is a common cause, and easily fixed before you lose too many leaves.
Until you find the cause and fix it, don't cut off those yellowing leaves. Your plant is using them for 'life support' right now, so if you remove them without fixing the cause, your plant will likely sacrifice one leaf after another to try and stay alive.
If yellowing leaves is happening in conjunction with growing peduncles or new buds on old spurs, that points towards a nutrient deficiency also, as what you're not giving the plant, it's taking from itself to fuel new growth. However to help fix yellowing in that situation, pick up a bloom fertiliser like GT Flower Focus or Dyna-Gro Bloom NOT a foliage fertiliser or grow fertiliser.
Can hoyas bloom indoors?
Yes, despite the more consistent conditions indoors, which don't provide as obvious changes in light and temperature as outdoors to trigger flowering, hoya absolutely can flower indoors. However some hoya do have a reputation of being more difficult to flower inside than others (Eriostemmas are one example).
Why are the spaces between my hoya's leaves getting long and leggy?
Called internodes (the stem between the nodes where leaves grow from). If your hoya's internodal space is increasing and it's getting 'leggy' and sparse, this is most often a sign of needing to be closer to a light source, or needing brighter light. Some also stretch out in search of something to climb, so a trellis may help also.
What causes sticky sap when my hoya isn't flowering?
Finding sticky sap on leaves when your hoya is not in flower is a sign of pests, usually aphids or mealybugs. Some hoya produce more of this sticky sap than others, which can stain. Best to isolate, clean the sap off the leaves, and treat if you find pests.
What causes spots on hoya leaves?
Spots can be due to a few reasons. The colour and location are helpful to know for reducing the list of possible causes. Here are the most common causes and fixes...
Dark spots underneath hoya leaves (edema)
One of the most common is related to water use by the plant, called edema, also spelled oedema. This happens when more water is held in the leaves that the plant can 'breathe out' (or transpire), causing leaf cells to collapse. If water-related it will usually be seen under the leaves, but may also show little 'dimples' above each spot on the top of leaves. Caught early, and if conditions are improved, this should resolve pretty quickly, however can lead to more damage or even leaf loss over time. How to fix edema depends on the cause.
One cause of edema is not enough airflow, reducing the plant's ability to 'breathe' (or transpire). Also related is the combination of high humidity without enough air flow. Another cause is the combination of warm substrate and cooler air temperatures.
If your substrate doesn't dry out fast enough and retains too much water, this can also cause edema. Plants transpire differently at night vs during the day, so watering too late in the day can also increase the chances of edema overnight.
Over time edema can damage leaves and the spots can become bumpy, corky, pitted or raised. Improving airflow, temperature and monitoring humidity is recommended if you can't pinpoint just one cause, along with watering at the start of the day.
White or yellow spots on hoya leaves
White or yellow spots are more likely to be a nutrient deficiency (often nitrogen or manganese). A higher-nitrogen grow or foliage fertiliser can quickly resolve this (make sure it's a complete fertiliser that also includes manganese with all 12 essential minerals).
If you can find one, ideally look for a fertiliser that avoids urea as the nitrogen source, as hoya can have a hard time turning urea in to nitrogen, causing a deficiency even when you are fertilising. A growing number of foliage fertilisers (which are traditionally the highest in urea) are now urea-free, such as GT Foliage Focus (that one's also available on Amazon if you're based overseas).
Small, pinprick, black spots on the top of hoya leaves
Small, pin-prick, black spots on the top of the leaves is usually from too much sun as a stress response, usually only where direct the sun hits. If the spots are reddish this can often be sun stress also, from too intense light. Similar to paler skin forming freckles with too much sun exposure.
Insect-feeding damage can also leave behind reddish-pigmented spots at the feeding site. This is because hoya can produce anthocyanin (a red pigment), at damage sites, whether from insects or sun. Isolate and check for pests. Treat if needed.
White spotting on hoya leaves
If the spots are white, and disappear when the leaf is wet and reappear when dry, or can be rubbed off, this is more likely from excess salt minerals from your water or fertiliser. You can try shifting to rainwater if your tap water is on the hard side, or change to a lower-salt fertiliser that avoids high-salt ingredients like chlorides.
Leaf spot and ring spot on hoya leaves
If the spots start out small and black but then slowly spread across the plant, it could be leaf spot, a disease caused by bacteria and fungi.
Spots that look like concentric rings may be a condition called ring spot, a virus that appears when the plant is stressed, won't typically kill plants, appears on old growth rather than new growth (seeing it on new growth can be a sign it's a harmful virus), and should stop happening when your plant is happier.
And if that wasn't a long enough list, some hoya just tend to naturally have darker spots on the back of their leaves!
Do all hoya need to climb?
No, there are a few differences in the way hoya grow. Most send out vines and want to climb, but some have a more hanging growth habit, like Hoya bella. Although not as common, some grow bushy like a shrub, and some are combinations of these growth habits.
Can all hoya go in hanging baskets?
Some hoya are better suited to hanging baskets than others. That's not to say you can't keep a vining hoya hanging, or hanging hoya climbing, but it can impact their growth, leaf size and potential to flower if left to trail when they want to climb, and vice versa. Some heavier or larger leafed hoya get too big and heavy to climb, like compacta. Some start off growing up, then later hanging down, like Hoya linearis.
Most of the more common, commercially available hoya are pretty hardy and will cope with both vining or climbing, but with so many species of hoya, it's best to research what your particular hoya prefers.
When should you start a hoya on a trellis?
The general rule if you plan to give your hoya something to climb, is to start young. Train it up a trellis from small. A hoya that starts off hanging means the leaves will have ended up orienting themselves 'upside down' when you later convert it to climbing. If it starts off climbing from young, the leaves will grow 'facing up' towards the direction of the light.
Leaving a hoya to hang when it wants to climb, can also result in long vines with no leaves. Wrap hoya vines around the trellis anti-clockwise, not clockwise. The hoya genus twines anti-clockwise (others like honeysuckle spiral clockwise).
Keep the last few inches of the growth tip facing up, not down. Wait until the vine is long enough to fully loop around the trellis, so the grow tip ends up facing up. Tie the growth tip very loosely and not too close to the tip, so it can still move around (they can move a lot!). Too tight, or too close to the tip, or facing down, can all stunt or stop growth, and the tip can dry and die off.
Why are my hoya's leaves wrinkled?
Soft and wrinkled, even when watered properly, can be a sign of root rot. The roots may be damaged or rotting, and unable to take up water. Check the roots and if it's not looking good, treat for root rot and also take an 'insurance cutting' to propagate just in case.
Shrivelling or wrinkled leaves, combined with under-watering (such as watering too lightly or not often enough), can be caused by not enough water or low humidity. Check the roots. Staying dry too long, or not watering thoroughly enough when you do water so the substrate is fully saturated, can cause some roots to die. When you water again those dead roots can't absorb the water, which is how you can end up with root rot from underwatering (even though over-watering often gets blamed).
Wrinkled leaves can also be a sign of pests (especially mealybug), so if the roots are fine and you've ruled out watering or humidity as an issue, it can pay to be cautious and isolate, even if you don't spot any pests, keep an eye out and treat if needed. Check for root mealy also.
Why is my hoya limp even after watering?
Weak, limp leaves is usually water or root related (normally both). The roots may have died back completely, often due to a lack of watering, or watering too often without letting your plant dry out enough in-between. Check the roots right away and if it's looking too late, get out those snips and take an 'insurance cutting' in case you lose the plant, so you can start again. Also check for pests.
Why are my hoya's leaves falling off?
Although this can have a few causes, the most common reason for sudden leaf drop is temperature-related. This can be a common hoya response to 'catching a chill' from a sudden temperature drop or being in the path of a cold draft.
Can I shift my hoya outdoors for summer? Or grow my hoya outdoors all year-round?
Most hoya can be grown outdoors in zones 9 to 11. New Zealand's extremes vary from zone 5a to zone 12a. It's best to check the conditions your particular hoya prefers to grow in it's natural habitat, before you put your hoya outdoors.
In general, Auckland and north is in zone 10, with zone 11 in the Far North. Most of the rest of the North Island averages zone 9, although can be zone 8 as you go more in-land. Most of the South Island averages zone 8, with coastal regions zone 9. However these are generalisations. You may be in zone 10 in a hoya sweet spot, but if your home is exposed to cold drafts or offers no shade from the sun, that doesn't mean your zone 10 hardy hoya should be in that exact location. Make sure to take your local conditions into account and compare them with your hoya's preferred conditions.
What causes new growth on hoya to come out red or pink?
Some hoya's new growth comes out a lovely shade of red and pink in response to too much light, called sun stress. As pretty as it can look, it is also a sign it's getting more light than the plant can handle, so consider the move out of direct light or further away from the window or light source.
As my own experience grows (and undoubtedly as more things go wrong), I'll keep on adding to this list to share the tips, tricks, do's and don'ts I learn along the way :)
Before you go, I wanted to say a big thank you to Carol Noel in particular. I'm a bit of a sponge when it comes to learning, but as I (unsuccessfully) try to resist the hoya addiction and my own hoya collection expands, I've learned so much from Carol in particular, who is very generous in sharing her experience freely and publicly to benefit all hoya hobbyists.
I wouldn't call myself an expert. I love that about our hobby. You never stop learning. It is experts like Carol that allow me to keep learning, and to share that learning with you in free care articles like this, shared in the same spirit as Carol inspires. Possibly a weird thing to say, but I also want to give a shout out to the many hobbyists who ask for help. We all learn together when you share photos and ask for help trouble-shooting Hoya problems, thank you :)