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Begonia Obliqua – A Complete Care Guide

Begonia Obliqua – A Complete Care Guide

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My favorite summer flowers are Begonias. Of the many varieties available, Begonia Obliqua is a perfect candidate to grow in those “bald” gaps and corners of the garden that need a quick green cover at the start of spring.

Their growing behavior is often considered rather weed-like with more and more plants automatically re-emerging every spring forming vast colonies.

But that’s the beauty of it! What goes in favor of growing Begonia Obliqua is that it’s a very hardy tropical with tubers that can survive under heavy mulch even in the colder zones.

Begonia Obliqua is a tuberous-rooted hardy perennial that typically forms a bushy mound of foliage up to 2 feet tall.

Unlike other tuberous begonias grown for the flowers, the main attraction to grow Begonia Obliqua is the foliage – somewhat large, obliquely ovate leaves of olive green.

They do grow white flowers in droopy pendent clusters from July to early fall. Altogether, the plant definitely fills out the backdrop and adds volume to the summer garden.

When I say hardy, I don’t mean that Begonia Obliqua care is “plant-and-forget”.

It has its own attention needs to keep healthy. Since the plants are native to dense tropical forests,

Begonia Obliqua care involves shade, warm temperatures, soil rich in organic matter, and plenty of moisture.

It’s in fact very easily spotted in its native regions during monsoon hikes forming a significant part of the green cover there.

According to Colorado State University Begonia Obliqua flowers are edible with a citrusy taste and can be used in the culinary arts for flavor and garnish provided they are grown without pesticides.





The main thing to remember about Begonia Obliqua care is that soil should have moisture retentiveness.

Grow Begonia Obliqua in a peat-based compost mixed with sandy soil in a raised part of your garden where water doesn’t collect. 

Heavy clay soil that becomes waterlogged is unsuitable as it can cause root and stem rot.

The ideal soil acidity level to grow Begonia Obliqua is in the range of pH 5.5 to 6.5. All your mulch, moss, bark, and other organic components will help improve the acidity of the soil but be mindful that acidity levels change over time.

I don’t recommend growing these plants in pots but you must, then use a light free-draining potting mix containing coco or sphagnum peat, perlite, or vermiculite.

Do make sure that the potting medium is sterile to avoid any fungus induced root rot problems.

You can prepare your peat moss mixture by soaking the moss in boiling water and allowing it to cool prior to planting.



Begonia Obliqua care requires that you provide it adequate sun protection. This plant can take filtered light and some sun in winters.

Although they are shade-loving plants, you can grow Begonia Obliqua quite healthy with a bit of morning or late afternoon sunlight.

That forgotten spot in your garden with dappled or filtered light works well, but remember that midday sun or heat is a no-no or they get burn marks and even the buds tend to fall off.



My Begonia Obliqua care hack for the moisture is to simply water the plant when the leaves look just a little lank.

This isn’t a suggestion to neglect them but more to exercise restraint to avoid overwatering. The mild wilting won’t damage them.

These are hardy tropicals and depend entirely on rainwater that doesn’t even reach them sometimes.

Remember that intermittent dryness is good to induce flowering. Besides, the fleshy stems hold a lot of water as well.

However, young Begonia Obliqua plants with delicate stems need a little more consistent watering. The peat, mulch, compost, etc. used in the soil have very good water retention properties and help in moisture management.

Pro tip: These plants are susceptible to fungal problems. Grow Begonia Obliqua away from sprinklers and sprays.

Water only at the roots or water in the mornings allowing the breeze to dry off the leaves during the day. This Begonia Obliqua care hack will ensure your plant stays disease-free.



These plants really flourish in hardy climes closer to the equator where you can grow Begonia Obliqua outdoors year-round.

That said, the plant can in fact take temperatures right down to 25°F (sub-zero Celsius). Once temperatures become cold the plant will automatically wilt and disintegrate for the winters.

You should ideally grow Begonia Obliqua in temperatures between  58 – 72°F (15 – 22°C) for the best results.



As with all tropicals and sub-tropicals Begonia Obliqua loves humidity. But due to its clump-forming behavior, the plant manages its own humidity needs to a great extent.

Some humidity enhancing Begonia Obliqua care hacks include mulching the area heavily and occasional misting. But mist only in the mornings, please.



You really don’t need to bother much with feeding if you want to grow Begonia Obliqua. Just scatter a layer of balanced organic manure all over the spot where you expect your begonia oblique colony to emerge.

Post that you can top it up with any balanced fertilizer like a 10-10-10, but make sure you dilute it three times its prescribed strength.

Be warned that too much nitrogen in the soil can cause Begonia Obliqua to grow excessively vegetative at the expense of flowering. Stop feeds before the onset of cold weather.



The best thing about Begonia Obliqua care is that the plant self-propagates by tiny bulblets or bulbils which form in the leaf axils in autumn and drop to the ground.

These tiny asexual formations about the size of a small pea fall to the ground and sprout the following spring. 

You can harvest these bulblets from the leaf axils and plant as desired. But I prefer letting nature take its own course and letting them fall wherever they would naturally.

I have observed that when they spring back next season, the cluster is surprisingly evenly spread out.

Eventually, this is how you get to grow Begonia Obliqua in beautiful bountiful bushes. You can even collect the tubers from the soil for storage during winters.



Begonia Obliqua has an upright growth habit with some branching. The bushy look comes when you have several plants growing together. 

You can grow Begonia Obliqua clusters to as tall as 2 feet. The best way to exploit this tendency is to grow Begonia Obliqua outdoors in shady corners of your garden.

From summer through early fall Begonia Obliqua displays loose floppy clusters of white blooms. As the days grow short, the plant goes dormant and the leaves turn yellow.

Although aggressive pruning isn’t required for these soft-stemmed herbaceous plants, deadheading the flowers is a good Begonia Obliqua care hack to induce flowering.

This also goes a long way in disease prevention.



The best potting advice to grow Begonia Obliqua is not to pot them at all! Yes, it’s true. They reach their highest glory when left to grow outdoors largely untended.

Their weedy colony-forming habit is their strong point. Potting them simply doesn’t deliver that aesthetic result.

The ideal planting location is a spot where the soil is very loose and full of organic matter, the ground level a bit raised for better drainage, and where there’s plenty of shade.



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Most people grow tuberous begonias as annuals just buying the baby plants in early spring until they die in late autumn.

Some gardeners collect seeds to germinate in the next season. You can grow Begonia Obliqua as annuals or perennials.

I find saving the tubers or corms a very effective way. Bulbils too are nature’s unique plan for Begonia Obliqua propagation.

Finally, begonia’s herbaceous stems take root very easily. Let’s examine each method in detail.


Begonia Obliqua propagation through corms or tubers

  • At the end of winter place the tubers an inch (2.5 cm) apart in a shallow tray filled with moist potting mix
  • Make sure to have the hollow side of the tubers facing up. The tubers should be visible above the soil and not buried deep.
  • The tray should be placed in a dark room maintaining at least 65°F (18°C) occasionally misting the soil.
  • In a month you’ll see each tuber to sprouting from the hollow.
  • Once the frost has passed 100% you can transfer the sprouted tubers in your garden 3 to 4 inches apart or in individual pots.
  • Again, the tubers have to be concave up and planted at the surface and not deep in the soil.
  • Adequate ventilation is needed throughout Begonia Obliqua propagation or it can catch mildew.
  • At the end of the season dig out the tubers when the foliage begins to turn yellow. Wrap them in soft paper or dry peat moss and store them in temperatures between 40 – 50°F (4 – 10°C), until next season.


Begonia Obliqua propagation through cuttings

  • You can grow Begonia Obliqua from stem cuttings if more than one sprout appears from a tuber.
  • Remove the extra sprouts when they are about 5 inches high and plant them in a well draining potting mix like 50-50 perlite and peat moss. Keep the soil just moist
  • Use a plastic bag to block out drafts and maintain high humidity levels. Humid conditions reduce wilting and promote faster rooting.
  • Keep this indoors in a somewhat dark spot, undisturbed until established.
  • When the roots are established you can transfer this to your Begonia Obliqua spot


Begonia Obliqua propagation through bulbils

  • Bulbils that form in the leaf axils and my favorite way to grow Begonia Obliqua.
  • At the end of summer, when the plants die away these bulbils fall around the area. At this point, I cover the entire patch with a thick layer of mulch for frost protection.
  • I mark the area so that I remember not to gather all the remains and tidy it all up at the start of spring.
  • These bulbils are actually nascent tubers that will produce new clones of the parent plant the following spring. Small little saplings pop through the debris once the frost goes away.
  • This is how I end up with a whole colony of Begonia Obliqua shrubbery every summer.



Spots or patches of white to greyish talcum-powder-like growth: This is powdery mildew, a fungal disease that shows on the top and underside of leaves.

It needs moisture and humidity to spread. Proper Begonia Obliqua care requires that you water the soil around the plant and avoid splashing the leaves.

Water in the morning so that droplets evaporate during the day. Immediately cut away affected leaves and do not compost infected debris.

There are commercially available sprays that are useful in treating this disease such as sulfur-based fungicides or neem oil.

Colorado State University research suggests the application of fungicides at 7- to 14-day intervals to provide continuous protection throughout the growing season.

They also recommend an alternative nontoxic control for mildew viz. baking soda combined with lightweight horticultural oil.

They have tested the fungicidal properties of this combination against powdery mildew on roses.

They advise that applications of 1 tablespoon baking soda plus 2.5 tablespoons of Sunspray oil in 1 gallon of water are still experimental. It may be worth a try if the situation demands it.

Burn marks: Dark brown, crisp looking marks on leaf edges are usually caused by low humidity or exposure to the midday sun. Cover the area with a shade cloth. Water deeply whenever you water.

Buds dropping off: Buds may dry, turn brown, and drop if the temperature is too high.  You should ideally grow Begonia Obliqua in temperatures between  58 – 72°F (15 – 22°C).

Neglect and dried-out soil can also result in bud loss too. Shade cloth and watering are usually solutions to this problem.

Poor drainage can also cause buds to drop. In this case, the center buds usually drop first.

Few flowers: This variety isn’t a heavy flowering type in the first place. That said, fewer flowers often result if plants are in too dark a spot.

Deadheading and pinching of the shoots can induce flowering as well. Overfeeding with Nitrogen-rich fertilizers can also result in a few flowers and makes the plant vegetative.

Plants rotting: Rotting can happen due to water-logging which can easily be avoided if you follow the Begonia Obliqua care instructions for soil.

The other reason is a fungal infection. Keeping the plant surroundings clean is important. Remove dead leaves, flowers, and any other decaying matter immediately.



  • Grow Begonia Obliqua in shade. Protect from midday sun or heat
  • Deadhead the flowers to extend bloom period
  • Feed established plants every two weeks from May to September with a high potassium plant food
  • Avoid late-summer applications of nitrogen fertilizer to limit the production of fleshy stems, which is more susceptible to infection
  • Do not allow soil compost to dry out but avoid overwatering
  • Avoid overhead watering to help reduce the relative humidity that can lead to mildew and other bacterial infections
  • Prune a few branches on overcrowded clusters if you feel air circulation is low
  • Save the tubers before winter
  • Save the same spot for the next growing season




Is the Begonia Obliqua annual or perennial?

You can grow Begonia Obliqua as a perennial, saving up the dormant tubers at the end of every season. The plants produce seeds and bulbs as well. Begonias propagated from seeds are like annuals.

Is Begonia Obliqua suitable for indoor growing?

Of all the begonias out there, this is one variety that I’d strongly recommend for outdoor growing. Use the same spot year after year to create a lush colony of these plants.


Is deadheading necessary to grow Begonia Obliqua?

Deadheading is not a necessary part of Begonia Obliqua care, rather a best practice often adopted by gardeners mainly for a tidy look and to induce flowering. It also helps to control diseases like mildew.



Begonia is a genus of over 1,000 species native to tropical and subtropical regions worldwide. Botanists often crossbreed and hybridize begonias to create a variety of colors, textures, and sizes we enjoy today.

There are three types of begonias based on their root structure – fibrous, rhizomatous, and tuberous. In general, fibrous and rhizomatous begonias make the best indoor plants.

Tuberous begonias like Begonia Obliqua do best as annual outdoor flowering plants rather than long-term indoor plants because their growth cycle includes a dormancy period when flowers and foliage both die back.

You should try to grow Begonia Obliqua along with Begonia Grandis, which has similar growth patterns but with pink flowers.

Try growing them in side by side patches to get a lovely mix of white and pink flowers.

I would strongly recommend that you try growing indoor succulent varieties like Begonia Amphioxus or the very unusual Begonia Darthvaderiana named after Darth Vader! I promise you, your Begonia journey will only get more interesting with time.

Happy growing!

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