By: Raffaele Di Lallo, Author and founder of Ohio Tropics houseplant care blog
Many people might be shocked to know that certain begonias are grown for their leaves rather than their flowers. The rex begonia plant is one of those! Although they do flower, the main attraction is the beautiful and ornate foliage that it produces. Rex begonia care indoors can be a little tricky, but it is certainly possible to grow beautiful specimens if you understand the plant’s needs.
Let’s take a look at the most critical elements of growing the rex begonia as houseplants.
Rex begonias are rhizomatous begonias. A rhizome is basically a thickened stem, and the leaves emerge from the rhizome.
Generally, the rex begonia indoors prefers relatively cool temperatures, moist soil and humid conditions.
Rex begonias do well in bright indirect light. Some directsun is okay for short times, especially if it is from an eastern window thathas morning sun, which is gentler. For periods of the year where the sun isstrongest, or if you live in an area that has strong sun, you will want toavoid too much direct sun. You can easily use sheer curtains to diffuse directsun, or set the plant a few feet back from a very sunny window. Too much directsun can burn the foliage.
Rex begonias prefer to grow in a fairly evenly moist soil.However, you must have a good balance because these plants can easily be proneto root rot. A good rule of thumb is to allow the top inch or so (2.5 cm.) todry out, and then water again. It is better to keep the soil on the slightlydrier side, but never let the soil completely dry out, as this can quicklyspell death for your rex begonia. If you let the soil get too dry, your plantwill quickly wilt.
As far as fertilizing goes, you can fertilize with a dilutesolution about twice a month during the active growing season. Avoidfertilizing during the winter months when plant growth can come to a halt.
Also, avoid allowing your rex begonia’s leaves to be wet forextended periods of time, especially at night, since this can encourage powderymildew as well as bacterialeaf spot.
As far as soil goes, rex begonias like a light and airysoil. Avoid any heavy potting mixes. Pottingmixes designed for African violets are a good choice for rex begonias.
Rex begonias like conditions with high humidity. In fact,the foliage will grow larger when the humidity is higher. Aim to increase thehumidity, especially during the winter months, by a few different methods. Youcan place a plant on a tray with wet pebbles, use a humidifier, or place themin naturally humid areas such as a bathroom. You can also group plants togetherto increase humidity through plants’ natural process of transpiration.
Finally, choose a pot that is wider than it is deep sincethis is more appropriate for rhizomatous plants like rex begonias. If you’dlike to propagate them, you can do so by leaf cuttings or by cutting sectionsof the rhizome and repotting.
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When I first started going to garden events like RHS Chelsea Flower Show, the first thing I was drawn to was the begonia display on Dibley’s stand. Their giant leaves in all manner of swirls and markings of Day-Glo technicolour. I wanted to grow them all so I placed an order immediately.
It’s been over four years since that first order and I’ve since learnt the hard way (RIP begonias) that they can be pernickety customers when it comes to growing them as houseplants. With some trial and error, I’m gradually cracking the code however and I wanted to share some of my findings so far with you all.
Last Updated: March 28, 2021 References Approved
This article was co-authored by Melinda Meservy. Melinda Meservy is a Plant Specialist and the Owner of Thyme and Place, a botanical boutique offering plants and gifts in Salt Lake City, Utah. Before starting her own business, Melinda worked in process and business improvement and data analytics. Melinda earned a BA in History from the University of Utah, is trained in lean and agile methodologies, and completed her Certified Professional Facilitator certification. Thyme and Place offers indoor plants and containers, a fully stocked potting bench, and tips on plants to suit your space and lifestyle.
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You know you've hit the flower jackpot when your plant is known for its brilliant flowers and its fancy foliage. The begonia has both of these lovely features. Begonias can be high-maintenance at times, but the end result of having a beautiful, flowering plant is well worth it.  X Expert Source
Plant Specialist Expert Interview. 18 August 2020. In summary, the begonia is an awesome plant. Follow these steps to learn how to care for this perfect plant.
The painted-leaf begonia needs a lot of bright, indirect light to thrive. Just as importantly,, you want to keep it away from direct sunlight which can scorch its leaves.
Alternatively, because the plant does not produce flowers often like other begonias, it is more tolerant of low light conditions. You can likewise use fluorescent lights. Although, they’ll need longer hours of exposure because indoor lighting doesn’t offer the full spectrum of colors the sun does.
This makes an east facing window the best place to grow your begonia if you want to keep it closer to the window. Here, because of the gentler morning sun, it can take short periods of direct sunlight. But, you still want to keep it away from the sun’s rays most of the time.
In the west and south facing windows, it needs protection from the afternoon and summer sun, especially if you live in a warm climate area. in this location, you’ll want to keep the plant at least 3 to 6 feet away from the window opening, depending on the angle at which the sun comes in at different times of the day. Or, you can cover the window with sheer curtains to filter the light.
North facing windows can likewise work if there’s enough light. This is probably not a good option if you live in a cool climate location since there will be less light here. If that’s the case, you can supplement with grow lights.
Your painted-leaf begonia enjoys moderate temperatures. Thus, as long as you keep things between 65 to 75 degrees it will be happy. This makes them hardy to USDA zones 10 and 11.
If you live outside of these zones, they’re best grown as houseplants. This will allow you to take them outside during the summer and bring them back indoors once it starts to near 60 degrees in the fall.
You do not want it staying in temperatures under 60 degrees for long periods of time. Otherwise, its leaves, which are its main attraction will get damages.
Similarly, the small temperature range also tells you that it is not a fan of fluctuating climates. As such, you want to keep it somewhere that’s consistent. This also means avoiding areas where cold breezes can in or heaters, fireplaces and air conditioning will suddenly make it much hotter or colder.
On the other hand, if you live in USDA zones 10 and 11, you can keep the plant outdoors, in the ground or a container. Because of its love of light, and need for protection from the sun’s rays, a bright, partially shaded location is best.
Humidity is another areas where the plant needs attention. Your painted-leaf begonia needs at least 50% or higher to thrive. Having enough moisture in the air allows it to grow large leaves.
As such, it will do well in some homes that are a little bit more humid. But, if you find that your home’s humidity is between 30% and 40% if it is a good idea to take some action. You’ll likewise want to watch out for winter when the air tends to get dry.
In any of these scenarios, you pick one of the following humidity raising strategies.
I’ve found that the easiest way to maintain enough humidity it to get a digital hygrometer. This inexpensive device quickly tells you the humidity in a given room. So, you always know what it is and can easily adjust as needed.
The painted-leaf begonia likes moist soil. But, it hates having wet feet. More importantly, leaving it to sit in water for prolonged periods of time will cause root rot which it is susceptible to. Thus, overwatering is a sure way of damaging your plant and eventually killing it.
That said, you also don’t want the plant to go dry, which has its own negative effects. But, between the two too much water is what you want to avoid since it will kill your plant fairly quickly.
Because the painted-leaf begonia likes moist conditions, you’ll need to water it regularly during summer when the weather is hottest. Summer, along with spring is also when its growing season occurs.
As such, it needs enough sustenance, plant food and water to grow optimally.
However, it is important to cut back on watering come fall and winter. During this time, it goes into dormancy which means it doesn’t need as such sustenance. The weather is likewise colder which keeps soil moist or wet longer.
Since your watering routine will shift throughout the year, using a fixed schedule when you water every few days isn’t a good idea. Instead, it is a better idea to check the soil before watering. The two easiest ways to do this are:
Finally, when it comes to watering, morning is the best time to do it. In contrast, late afternoon and evenings are the worst times.
That’s because morning gives you a lot of time through the day of sunlight. This lets water evaporate so it doesn’t sit for too long. But, the sun and heat aren’t overly intense like mid-afternoons where a lot of the water evaporates.
On the other hand, evenings are cooler. There is also no sun. This means water is likely to sit longer and possibly through the night. By allowing this to happen, you put the plant at higher risk of root rot.
This also opens the door for powdery mildew and bacterial leaf spot. Both of which are moisture-related problems.
Since your painted-leaf begonia is prone to these issues, soil plays an important role in keeping it healthy. With the proper soil, you can decrease the risk of waterlogging.
As such, the plant does well in loose, airy soil that allows for good drainage. This allows excess moisture to drain faster. In doing so, it doesn’t let your plants sit in water for long periods of time.
This makes African potting soil a good option if you don’t want to make your own mix.
Alternatively, you do not want to keep in heavy potting soil which are designed to retain water.
Another thing to keep in mind is that painted-leaf begonias are rhizomatous plants. This means they like having a lot of room to grow outward (and less down downward).
As such, using a wider, shallower container works well.
Feed your painted-leaf begonia every 2 weeks during the spring and summer. You can use any houseplant fertilizer since they aren’t picky about it.
You can use a balanced liquid fertilizer diluted to half or quarter strength during this time when it is actively growing.
Like water, be careful not to feed it too much. While giving it more fertilizer may seem like it will help the plant grow bigger and faster, the opposite is often the case. That’s because too much fertilizer causes root burn as it leaves salt residue in the soil that can damage your plant when it accumulates.
Similarly, painted-leaf begonias tend to grow longer and thinner when give more plant food. This is not a good look for your begonia (or other plants).
Once fall arrives, it is time to scale back on feeding as the plant winds down. In the winter, you don’t need to feed it as it goes into dormancy.
Painted-leaf begonia are known for their foliage rather than their flowers. As such, you’ll likely want to trim off flowers when they bloom.
While they do add to the plant’s looks, its blooms aren’t its main attraction. More importantly, allowing its blossoms to grow will make the plant expend nutrients and resources on its flowers instead of the leaves.
On the other hand, removing them allows your painted-leaf begonia to focus all its energy on growing foliage, making your plant look better.
Additionally, you’ll also want to prune any stems that have become leggy. Again, this is never a good look for any houseplant. By cutting these back, you’ll promote new growth that will help make the plant look fuller and bushier.
If you see any dead, discolored or damaged leaves, remove them a well.
Painted-leaf begonia can be propagated in different ways, including:
Of the three, the most common is leaf cutting because it requires less work to set up. On the other hand separating the rhizome takes the most work since you need to get the plant out of its container. However, it also gives you a head start compared to the other two.
The best time to propagate is early spring. Although, you can likewise do it in the summer provided it doesn’t get too hot in your area.
Stem cuttings is very similar to leaf cuttings. But this time, instead of taking a leaf, you’ll be taking a stem.
Here you’ll divide the rhizome. As such, you’ll need to do a little digging to expose it. Then separate a section of the rhizome and plant it in its own container.
Painted-leaf begonia don’t mind being a little pot bound. As such, you only need to repot them once they’ve outgrown their current container. A good sign of this is when its rhizome reaches the edges of the container.
If it hasn’t outgrown its pot, you can refresh the top soil once a year. This will help keep it loose and airy why adding fresh nutrients as well.
When choosing a container, go with something that is wider and shallower. The plant’s leaves grow outward from its rhizome. This means it likes more room for the rhizomes to spread horizontally than vertically.
Spring is the best time to repot. If you’re planning to propagate the plant, this is likewise a good time to do so because you’re taking out of its container anyways.
Similarly, you can reduce the size of the plant by division. This will allow you to keep the plant in its container and grow a new plant as well.
Painted-leaf begonia are toxic to people and animals. Keep young children, dogs and cats away from these plants at they may get curious enough to ingest it.
Painted-leaf begonias are susceptible to some pests and diseases.
Among its biggest problems are moisture-related issues, which can damage its leaves and roots. It is susceptible to root rot, which is why it is important not to overwater the plant.
Similarly, powdery milder, gray mold (botrytis) and bacterial leaf spot are potential problems because it likes moist conditions and high humidity.
This makes it imperative not to water the plant overheat where you wet the leaves. It is also a reason why misting isn’t the best way to increase humidity since you’re spraying water on foliage. Finally, avoid watering the plant late in the day because water doesn’t dry as well with no sun and cooler temperature.
In addition to these problems, you’ll also want to be on the lookout for pests. Here, mealybugs, aphids and caterpillars can potentially attack its leaves and stems.
Regular inspection lets you spot them early so treatment is faster.