- About author
- All About Begonias
- Ornamental Features
- Landscape Use
- Species & Cultivars
- Tuberous Begonia Care – How To Grow Tuberous Begonias
- What is a Tuberous Begonia?
- How to Grow Tuberous Begonias
- Tuberous Begonia Care
- Where to Buy Tuberous Begonias
- Cheat Sheet
- Keep It Alive
- Tuberous begonia growing guide
- Begonia (Tuberous Begonias)
There are very few places in this world where Begonias can be grown outdoors throughout the year. In many cases, growers will place the plants outdoors during the warmer months and bring them inside during the winter. Others prefer to keep their potted Begonias indoors throughout the year. When caring for any house plant, it is very important to understand its nature and needs if you want it to flourish. If you are planning on buying somebody a potted plant for Mother’s Day, as a house warming gift or any other occasion, it is also important to make sure that they are aware of these conditions. Continue reading to find out just how to care for potted Begonias.
A vital part of any plant’s life is the proper lighting. In terms of natural light, you will find that Begonias tend to do well in just about any window apart from north-facing windows. When experimenting with natural light, you need to monitor the plant’s progress quite closely. If you see the plant begin to branch out, this is an indication that they need more light. If you notice stunted growth or burning, then you need to reduce the amount of light.
As for artificial light, there are a number of options and they all vary in price. If you have a wide selection of plants, then you may want to invest in something more elaborate in order to care for them all. If not, you can choose a cheaper option like cool white fluorescent tubes in a regular lamp will do. You should also keep these lights on for approximately 14 hours each day.
Choosing a pot
When you order your Begonia from your florist or nursery, you will notice that it is already potted according to the size of the plant’s roots. In time, as the plant grows, you may need to transfer the plant to a larger pot. However, do not overcompensate by placing the small Begonia in a huge pot. The do not thrive in such conditions and you will be doing more harm than good. If the plant never appears to dry out, then this could be a clear indication that the pot is too large for the plant. Remove the plant immediately and place it in a smaller pot with fresh potting soil. Do not use the soggy potting soil from the larger pot!
Begonias that are grown indoors should be potted in a soil-less potting mix. This mix consists of mainly peat moss and perlite and / or vermiculite. Using regular soil, manure or anything similar tends to hold water for too long. This is no good for your Begonia’s roots since it attracts disease.
It’s very important not to over water. Let the potting mix to dry slightly before watering and, when you do, do so with care. As soon as you see the water start to run out the bottom, stop watering. If you place a saucer beneath the pot, make sure that you place pebbles in the saucer. Begonias don’t particularly like an abundance of water. You can use a bottom watering method, if you prefer, but you will need to empty any remaining water out of the saucer after a few hours. Wick watering (used with African Violets) and self-watering pots are other options that work well with Begonias.
While Begonias don’t like swimming in wet soil, they do enjoy a particularly humid environment. In order to achieve the kind of humidity that makes these potted plants thrive, you can mist them regularly or purchase a humidifier. If you choose to use fluorescent lighting, you can place your Begonias in (non-flammable) plastic tents to help create a localised humid climate for them.
If you are growing your Begonias indoors, you are able to prune them any time the need arises. These shoots are great for growing more Begonias as back up plants or as gifts for friends and family members. Mealy bugs are probably the biggest issue when it comes to growing Begonias indoors. To keep them at bay, use some rubbing alcohol and small brush to directly target the bugs or carefully spray the plant lightly with the rubbing alcohol. The alcohol will not harm the plant but you should avoid spraying the soil, just in case.
Begonias are also one of the safest plants to keep in your home. Any toxins in the plant are found below soil level and the toxin is fairly harmless all the same. That’s what makes them such a popular house plant and alternative gift to the usual Mother’s Day arrangement.
Begonia, (genus Begonia), any of about 1,000 species of mostly rather succulent plants in the family Begoniaceae, many with colourful flowers or leaves and used as pot plants indoors or as garden plants. They are from the tropics and subtropics. Prominent features are their usually four-coloured tepals (petals and sepals together) in two pairs of different sizes and the three wings on the ovaries of the female flowers. Flower colours are pink, red, yellow, or white, with the ovary below of the same colour. The usually lopsided, alternate leaves are variable in shape and in colour on different forms.
The more than 10,000 recorded cultivated varieties of begonias—mostly of hybrid origin—present a bewildering array of forms. Most varieties are included in one of three large groups: fibrous-rooted, rhizomatous, or tuberous-rooted.
Fibrous-rooted begonias can be further divided into the wax, or bedding, begonias (Semperflorens-Cultorum group), including the offshoots of B. semperflorens used most often as summer bedding plants; the so-called cane stem types (angelwing begonias), characterized by their tall stems; and the hairy begonias, which have feltlike leaves.
Rhizomatous begonias include the rex, or beefsteak, begonias (Rex-Cultorum group), including offshoots of B. rex and allied species, prized for their brightly coloured and patterned leaves.
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Tuberous-rooted begonias include the Tuberhybrida group, grown outdoors for their large and colourful flowers from early summer to first frost, and the greenhouse begonias that bloom during the winter. The latter are subdivided into the Cheimantha group, derived from crosses between B. socotrana and B. dregei, and the Elatior group, derived from crosses between B. socotrana and tuberous Andean species.
The Tuberhybrida group includes the following types based on flower characteristics or growth habit: single (single-flowered); crispa, with frilled tepals; cristata, with crested tepals; narcissiflora (daffodil-flowered); camellia (camellia-flowered); ruffled camellia; rosebud, with a raised rosebudlike centre; fimbriata plena (carnation-flowered); picotee, camellia-form with tepals showing colour shading; marginata, tepals edged in colour different from the dominant; marmorata, camellia-form, rose-coloured, and blotched with white; pendula, hanging-basket plants; and multiflora, compact bushy plants with many small flowers.
Most begonias are tender plants, intolerant of dry conditions and requiring protection from strong sunlight.
The genus was named for Michel Bégon (1638–1710), governor of Santo Domingo and a patron of botany.
All About Begonias
Begonias are one of our most popular plants and there are so many to choose from! Each has unique characteristic and therefore, different purposes in the landscape (or home). As we approach the spring planting season, we thought you might want to learn more about these versatile, eye-catching and easy to grow plants. This post and the personal growing notes included were provided by Jen M., our perennial grower.
Begonia semperflorens are probably one of the most popular of all the Begonias. They are commonly called wax begonias and they have many different varieties such as ‘Prelude’, ‘Encore’ and ‘Cocktail’. Some of them have green leaves, and here in Little Rock they do best in afternoon shade. Others with bronze leaves can be grown in 1/2 day sun or more. In full sun, these bronze leaves turn brilliantly red.
Wax begonias are easy care, warm season annuals that bloom from spring to fall. Grown in pots, or in landscape beds, these begonias bloom all summer providing lots of color, especially when grown en masse. You can find these bedding plants here in 6 pack flats, making them a low cost option for spring color plantings.
Hybrid Wax Begonia
Begonia benariensis are hybrid wax begonias. Think of them as wax begonias on steroids. ‘Whopper’ and ‘Big’ are readily available here during the spring season. Both of these varieties share the designation of being 50 mile-per-hour plants, which means they are eye-catching when viewed from a vehicle driving 50 MPH… pretty amazing! While regular wax begonias grow to 10 inches or so, these hybrids can reach up to 20-34 inches in height. Everything on these begonias is bigger- leaves, flowers and overall height. Why choose these over the standard smaller wax begonia? Versatility. ‘Whopper’ and ‘Big’ can be used in the middle or back of a landscape bed while their smaller cousins are used as edgers. Because they grow larger, they can be used in oversize pots as a centerpiece, and in beds, they make a bit more of a statement.
Tuberous Begonias have large, bright flowers; one popular series is called Non-Stop due to the consistent blooming. Boliviensis begonias are also tuberous and have very different look, with long narrow leaves and long blooms. These begonias do best in containers where it is easier to control watering. They need to grow on the dry side, and they tend to rot in the ground. Be mindful of the sun on these, they truly do not tolerate direct sun.
Begonia x hiemalis is the scientific name for the Rieger begonia, which is a cross between tuberous and wax begonias. The result is beautiful glossy foliage with an abundance of dainty, flowers in bright colors. These begonias are typically grown as indoor plants, although they also do well in containers located in shady spots.
Cane Begonias are usually grown for their upright tall habit and beautiful leaves. By my front door, I wanted a monochromatic color scheme (shades of all the same color) and I chose silver/white (above image). The cane begonia ‘Looking Glass’ has the most intense silver leaf and was a showstopper all season long. The key to success was no harsh sunlight and moist but not wet soil. Done and done! Look for other cane begonias readily available such as ‘Sophie Cecile’, ‘Sinbad’, ‘Lady Vanderwilt’, and ‘Louis Burke’. Other plants in this container are White Polka Dot plant and ‘Silver Falls’ Dichondra (a 2019 Arkansas Diamonds plant selection).
Rex Begonias do bloom but the flowers pale in comparison to the amazing leaves which seem to glisten and sparkle in the light. Grow these babes in shade or bright, indirect light. In 2017, we offered a Rex begonia called ‘Jurassic Silver Swirl’ for the first time. Pretty new to the market, they have been bred for better vigor and seem to have a bit better heat tolerance. I grew them under my porch that had very little direct sun but bright light. They did great. I put 3 in a blue 12″x12″ pot and as you can see in the image above, they filled it out nicely.
Dragonwing Begonias compete with wax begonias in a popularity contest. This is why they get their own category and both are winners in my book, just depends on where and how you want to grow them. Sometimes called Angelwings due to the shape of the leaf, this begonia does it all. It performs in pots, in the ground and also looks fantastic in hanging baskets. It can and will take some sun, although it looks the best when grown in morning sun and afternoon shade. Growing 15-24 inches tall and wide, Dragonwings are versatile, and a great beginner option for someone looking to green up their thumb. Dragonwing begonias were a 2015 Arkansas Diamond plant selection for good reason!
For beautiful foliage and a constant display of color throughout the season, grow begonias.
Most begonias that we grow outside will be between 8 inches and 2 feet tall.
Begonias are grown for their foliage and/or for their attractive flowers. Begonias flower throughout the summer and up to the first frost. They can be used as bedding plants, in window boxes and in baskets and other containers.
Disease problems associated with begonias include Botrytis blight and stem rot, powdery mildew, and Pythium root and stem rot. The major pests of begonias are mealy bugs, spider mites, scales, snails and slugs.
Begonias will not grow out of bounds and are ideal for small flowerbeds. Plants should be placed 12 inches apart for the best effect in the garden and somewhat closer in containers. Begonias look best when used in mass.
Most begonias grow well in partial shade and in a moist, well-drained soil with plenty of organic matter. In general, begonias need bright light to flower well. Some will burn if the light is too intense. Bronze-leaved wax begonias grow better with full sun than other types.
Begonias are not “heavy feeders,” so fertilizer should be applied in moderation.
Species & Cultivars
The most common types of begonias for growing outside are the fibrous rooted begonias (or wax begonias) and tuberous begonias. These are tender in South Carolina, but the beautiful and perennial hardy begonia will grow throughout the state.
‘Pizzazz White’ Wax Begonia
Photo by Karen Russ, ©2007 HGIC, Clemson Extension
Wax Begonias (Begonia x semperflorens-cultorum): Few other annuals can beat the wax begonias for hardiness and continuous flowering throughout the summer. These begonias are not restricted to a partial shade; they can be grown in full sun as well. Wax begonias with bronze foliage do better in the sun than green varieties. Wax begonias withstand drought and heat better than other begonias, although they definitely prefer moist, well-drained, fertile soil.
Bushy plants, with shiny heart-shaped leaves of green, bronze-red or mahogany are covered with small white, pink, rose or red flowers.
Set plants 6 to 8 inches apart in the garden after the danger of frost is past. Plants may also be started indoors from stem cuttings taken in the spring or fall.
- ‘Victory’ is a series with bronze leaves. They grow 8 to 10 inches in the garden and sport large, showy flowers.
- ‘Challenger’ comes in a mixture, where the red, rose, pink or white flowers contrast with its green-and-bronze foliage.
- ‘Ambassador’ series has large flowers on compact, green-leafed plants.
- ‘Cocktail’ series is 6 to 8 inches tall with bronze foliage. The flower colors are ‘Brandy’ (pink), ‘Gin’ (rose-pink), ‘Rum’ (white with a rose red edge), ‘Vodka’ (flowers) and ‘Whiskey’ (white).
- ‘Prelude Series’ hold up well through rain and heat. The compact plants have bright green foliage.
- ‘Pizzazz Series’ includes white, red, and pink cultivars. They are heavy blooming and grow 8 to 10 inches tall.
‘Dragon Wings’ Begonia in part shade
Photo by Joey Williamson, ©2007 HGIC, Clemson Extension
Dragon Wings Begonia (Begonia x argenteoguttata ‘Dragon Wings’): This begonia is known for its long blooming period – from spring through until frost without pause. It reblooms reliably because it is sterile and does not expend energy on producing seeds. The plant grows 2 to 3 feet tall, with tall arching canes and 5 inch long, glossy, deep green leaves. It will grow well in either sun or shade, and prefers fertile, moist but well-drained organic soil.
Hardy Begonia (B. evansiana syn. B. grandis): This is a superb southern heirloom perennial that is passed from gardener to gardener. They grow best with rich, moist soils in partial shade.
The hardy begonia reaches 2 to 3 feet in height. Small, pink flowers bloom in drooping clusters above the leaves in late summer. The large angel wing-shaped leaves are backed in glowing red. They are especially lovely when planted where late, low afternoon sun will shine through the leaves. Tiny bulb-like tubers that appear at the leaf joints in late summer can be used to increase your stock or to share with a neighbor.
Hardy Begonia is known for its beautiful foliage.
Photo by Karen Russ, ©2007 HGIC, Clemson Extension
Tuberous Begonias (B. x tuberhybrida): Tuberous begonias grow best in partial shade. The plants need frequent watering and light fertilization, but excess of either causes flower bud drop. Tuberous begonias will grow best in the upper Piedmont and mountain areas of South Carolina. They do poorly in very hot and humid parts of the state.
Tuberous begonias have 2-to 4-inch wide flowers in white, yellow, orange, rose, red and pink. They are available either in upright varieties or with trailing stems 12 to 18 inches long. The trailing types are nice to plant in hanging baskets.
Remove the first flower buds that appear so that the strength goes into the young plant. Remove the single female flowers before seed forms to keep the plant blooming. The female flowers are smaller and are on either side of the showy, double male flowers.
Tuberous begonias must be dug up and replanted each year because they will not survive winter cold. Dig tubers before frost. Cut tops back to within a couple inches of the tubers. After drying, pack the tubers in cardboard boxes between layers of vermiculite, peat moss, or wood shavings and store at 45 to 55 °F.
Start tuberous begonias in early spring by setting tubers into shallow flats. Keep out of direct sunlight. When the roots are established and shoots are about 1 or 2 inches high, move them to pots 4 to 6 inches wide. When all danger of frost has passed, move them outdoors.
‘Non-stop Mocca Orange’ Tuberous Begonia
Photo by Karen Russ, ©2007 HGIC, Clemson Extension
- ‘Non-stop Series’ are compact and small- flowered multiflora types. They are more heat-tolerant than other tuberous begonias and will flower longer. This type is best suited to growing in the South.
Rex Begonias (B. rex): Rex begonias are not grown for their flowers, but for their beautiful leaves. The leaves can be a kaleidoscope of colors – green, red, pink, silver, gray, lavender and a maroon, so deep that it appears black. These spectacular begonias grow best in part-shade in rich, moist, well-drained soil. They grow well in hanging baskets and other containers.
- ‘Merry Christmas’ grows 10 to 12 inches tall with smooth red and green leaves shaped like lopsided hearts.
- ‘Silver Sweet’ is an especially easy-to-grow 12 to 18 inch tall cultivar. Its leaves are like those of ‘Merry Christmas’ but are silver with green veins.
- ‘Helen Teupel’ grows to 12 inches tall with pointed, sharply lobed leaves that are purplish red brushed with pink and silver.
Tuberous Begonia Care – How To Grow Tuberous Begonias
If you can’t decide what to plant in that protected, semi-shady corner, you can’t go wrong with tuberous begonia. However, tuberous begonia isn’t a plant-it-and-forget-it plant. Keeping the plant alive and healthy requires a bit of extra attention. Read on for some tuberous begonia growing tips.
What is a Tuberous Begonia?
Types of tuberous begonias include upright or trailing varieties with single, double or ruffled blooms in tropical shades of pink, yellow, orange, red and white. The gold, purple, green or burgundy leaves are nearly as attractive as the flowers.
Tuberous begonias are frost-tender. If you live in USDA plant hardiness zone 10 and above, you can grow tuberous begonias outdoors year-round. Otherwise, you’ll need to dig the tubers and store them during the winter.
How to Grow Tuberous Begonias
Although tuberous begonias are shade-loving plants, they also require a bit of morning or late afternoon sunlight. A location in dappled or filtered light also works well, but the plants won’t survive midday sun or heat. Begonias need moist, well-drained soil and are likely to rot in soggy conditions.
Tuberous begonias are available at most garden centers at spring planting time. However, you can also purchase tubers and plant them indoors six to eight weeks before the last expected frost date in your area.
Place the tubers an inch (2.5 cm.) apart, hollow side up, in a shallow tray filled with moist potting mix and sand. Store the tray in a dark room where the temperature is about 65 degrees F. (18 C.). Water just enough to keep the potting mix moist. Watch for the tubers to sprout in about a month.
Plant each tuber into a pot when the shoots are about an inch (2.5 cm.) long, then move the pots to bright light. You may need supplemental light to prevent the plants from becoming spindly.
Plant the begonias outdoors when you’re sure all danger of frost has passed.
Tuberous Begonia Care
Water the plants regularly to keep the potting soil slightly moist. Provide a balanced, water-soluble fertilizer monthly during the growing season. Be sure to provide plenty of air circulation to prevent powdery mildew.
Use a sharp knife to cut spent blooms as soon as they fade.
Cut back on water in late summer, then dig the tubers when the foliage begins to turn yellow. Place each tuber in a small paper bag and store the bags in a cardboard box. Room temperatures for storage should be between 40 and 50 degrees F. (4-10 C.).
Check the tubers occasionally and discard any that are soft or rotten. Replant the tuberous begonias in spring.
How to propagate tuberous begonias is a question often asked by gardeners who have fallen in love with the ruffled flowers of a favorite potted plant. The short answer: it’s easy to propagate tuberous begonias. The best way to do it is from cuttings–and either stem or leaf cuttings will work. If you’re wondering how to grow tuberous begonias from cuttings, see step-by-step instructions at Propagation Tips by the American Begonia Society.
Above: For a similar deep pink tuberous begonia, consider Begonia ‘Helena’ bred by UK-based Blackmore & Langdon. A bare root tuber is $69 and will ship in the spring from White Flower Farm. For UK readers, a Helena tuber is £18 from Blackmore & Langdon. To grow tuberous begonias, you can plant tubers (they can be potted in March) or you can wait until the weather warms up and then buy potted plants from a plant nursery. For tips to plant tubers, see White Flower Farm’s How to Grow Tuberous Begonias video.
Where to Buy Tuberous Begonias
One reason to buy tubers is you will find a greater selection available by mail order than in plant nursery. In the UK, in addition to Blackmore & Langdon’s (which has been breeding begonias since 1901), you can find a good selection of tuberous begonia tubers at Thompson & Morgan and Crocus.
For US gardens, sources for begonia tubers include Longfield Gardens, Eden Brothers, and American Meadows.
Above: Photograph by Maja Dumat via Flickr.
- Tuberous begonias are showy container plants; flank an entryway with pots planted with begonias that complement the paint color of a front door.
- If tuberous begonias get leggy or spindly, cut them back to a height of 3 inches to encourage new, bushier growth.
- Tuberous begonias need sun protection; find a shady spot for them where their flowers can glow.
- Flower size can vary, fro, 2 to 8 inches, depending on the variety.
Above: Apricot flowers are common among tuberous begonias.
Keep It Alive
- Remember that tuberous begonias are tropical plants and will balk at cold weather; don’t leave them outdoors overnight when temperatures dip below 50 degrees.
- Begonias are heavy feeders; fertilize weekly to encourage flower production.
- Tuberous begonias require well-drained soil and regular watering. (If the top inch of soil is dry, it’s time to water a potted tuberous begonia.
- Humidity and bright shade will make a tuberous begonia very happy.
Read more growing tips in Begonias 101: A Field Guide to Planting, Care & Design in our curated guides to Tropical Plants 101. For more ideas for colorful container planting schemes, see:
- Container Gardening: Sarah Raven’s 7 Tips for Perfect Flower Pots
- Gardening 101: Petunias
- Container Gardening: A DIY Planter on Wheels
- Fuchsia: A Field Guide to Planting, Care & Design
- Container Gardens: 5 Tips for a Perfect Window Box
Tuberous begonia growing guide
Plant the tubers in trays with the buds upwards. Just have the eye buds showing. Use a good seed-raising mix and mix in about 50 per cent coarse sand, pumice or perlite or vermiculite which gives very good drainage. This is important as it does not pay to get the tubers too wet. Place the tray on a bottom heat if you have a heat pad; if not, then in a warm sunny spot. The seed-raising mix should have some fertiliser in it, so no need to add any more at this stage.
When the tubers send up a couple of leaves, pot them up into plastic pots. Plastic pots hold moisture better than clay ones, which tend to dry out more easily. Go for a five-litre pot with a wide base as this will ensure that when they are fully grown, they don’t topple over. During the season, as they grow, put a small stake in and tie them with a soft type tie.
* Salvias for every garden
* Sweet peas from real gardeners
* Is this the easiest colourful cut-flower for summer?
ALAN TROTT / NZ GARDENER Grow begonias in a shade house or in a shaded part of the garden as full sun can burn the leaves and flowers.
By early December, the plant is starting to send up flower buds. You will see small flowers on each side of the main flower. Nip these out at an early stage.
Begonias do not need a glasshouse when they start to bud up. However, a glasshouse is great to start the tubers off. A shade house or a shaded spot is best for later in the season, as in full sun you can burn both the foliage and flower. Folks often think you need to have a glasshouse for them but begonias perform better in a shade house. Or use corrugated polycarbonate which is tinted – this helps with shade as well.
Hanging basket tuberous begonias are spectacular when in full bloom. They flower for many months, and some are even scented. So if you have a shady terrace, begonias are a must. You don’t even have to disbud them.
ALAN TROTT / NZ GARDENER Begonia display at Hampton Court Flower Show.
Tuberous begonias have few issues in the way of disease. The vine weevil can sometimes be a problem, so watch out for them nearer the end of the season. They lay their eggs in December to March and later, little white grubs appear to bore into the tuber. If left, they will kill the plant. Buy a powder that controls grass grub, and dust the pot early in December. Powdery mildew can be a problem later in the season when the days shorten and become more humid. Often, grey white spots appear on the leaves of overcrowded plants, but a good fungus spray will clean this up pronto.
Begonias are often thought of as delicate plants that only grow in a warm climate but this is not the case as some South Island gardeners have amazing displays until the frosts arrive.
As autumn approaches and the days become shorter, slow down your watering. Do this gradually until you don’t water them at all. Leaves will start to yellow. Just leave the plant now until the growth above breaks off from the tuber naturally and then dig the tuber out of its pots. Cut the old roots off them and inspect each tuber for blemishes or pests and store in a dry spot. As long as the tubers are kept dry and free from pests and diseases, they will be ready for next year’s planting. Do watch out for mice as they can clean out tubers very quickly.
ALAN TROTT / NZ GARDENER A hanging basket of tuberous begonias is spectacular in full bloom.
Tuberous begonias can also be grown in the garden and they put on a grand display, but are better in a little shade. You can buy seedlings for these plantings. Buy them in trays in spring from a local nursery. They too are best dug out in late autumn and stored for the following year.
Do try to grow begonias as most places in New Zealand can grow them with ease.
Go to the Begonia House in Wellington’s Botanic Garden for an amazing display, and of course many public gardens have displays, so check your local area out.
Both Auckland and Christchurch have great begonia societies which you can join too, and they’d be a great resource.
Auckland Begonia Circle: 09 537 4557
Canterbury Begonia Society: 03 3295950
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Begonia (Tuberous Begonias)
Latin Name Pronunciation: beg-own’ee-uh
Tuberous Begonias are frost-tender plants that thrive where they receive bright light but little or no direct sun. Given an early start, they put on a glorious display all summer long. We grow our Begonias in pots and hanging baskets, but they can also be planted in the ground (once the danger of frost has passed). Either way, unless you live in a frost-free climate, you must lift and store the tuberous roots in fall to carry the plants through winter.
Starting Tubers in Flats or Pots
- To get a jump on a short season, plant tubers on arrival in flats (shallow containers with drainage holes) or 4–5″ pots.
- The potting mix should have a light texture and be well drained; a soilless mix, mixed 3 to 1 with builder’s sand, meets both requirements. Begin by placing potting mix and sand in a plastic tub or bucket. Slowly add water and stir until the mix is moist but not soggy. Put moistened mix in the container, stopping about 1½″ shy of the rim.
- Handling the tubers with care (especially if they have begun to produce new growth, which is very fragile), place them, hollow side up, on top of the potting mix. Space the tubers 2–4″ apart in a flat (one tuber per 4–5″ pot) and cover them with ½″ of potting mix. Then water sparingly and place the container in a window that provides bright but indirect light.
- Keep the potting mix moist but not soggy.
- To hasten growth, set the container on a heating mat or a radiator (with a few magazines between container and radiator to prevent overheating). Tubers that have not already begun to sprout when you receive them will generally show signs of growth within 2–6 weeks after planting.
- After the first 2 leaves have emerged, transplant tubers started in flats into 4–5″ pots or, provided the danger of frost has passed, into a lightly shaded outdoor bed that has been amended with organic matter such as compost or peat moss.
- Lift and move the tubers carefully to avoid damaging the roots, and set the top of each tuber 1–2″ below the surface of the potting mix or garden soil. Begonias planted in the ground should be positioned so that the points of the leaves aim at the viewer, because the blooms will face the same direction.
- Plants in 4–5″ pots should be moved into 7–10″ pots when the roots fill the pots. If time and energy permit, a final move to 12″ pots will yield especially spectacular plants.
- Set pots outdoors in a bright but not sunny location when the threat of frost has passed. Tuberous Begonias will not grow well in deep shade.
- When upright varieties are 4–6″ tall, push a heavy, 18–20″ long bamboo stake (or one of our cushioned, steel Begonia Stakes – Set of 5) into the potting mix or garden soil on the side of the plant opposite the points of the leaves. Place the stake a few inches away from the main stem to avoid injuring the tuber.
- Fasten the plant to the stake with garden twine or soft plastic tape looped in a figure-8 around stem and stake. As the plant grows, you may need more ties to provide additional support.
- Tuberous Begonias thrive in soil that is evenly moist but well drained. Soggy soil can cause the stems to snap off at the base.
- Fertilize plants once a month with a balanced (20-20-20), water-soluble fertilizer mixed as directed.
- Keep plants tidy by removing spent flowers; cut the flowers off close to the stem using a sharp knife.
- The only disease that may trouble your plants is powdery mildew, a fungus that appears as white powder on the leaves. Powdery mildew is easier to prevent than it is to cure, and placing your plants in a location where air can circulate freely around them is the best prevention. If you’ve had trouble with powdery mildew on Tuberous Begonias in the past, you can prevent future outbreaks by spraying with a mild fungicide that you can prepare yourself by mixing one tablespoon of baking soda and 2 or 3 drops of insecticidal soap in a gallon of tepid water. Spray this solution every 10 days during hot, humid weather. Once mildew appears, the only effective remedy is to spray promptly with a commercial fungicide. Follow the directions on the label carefully.
- Allow plants to grow through November (or until frost) to store energy for the next season.
- Force container-grown plants into dormancy by gradually withholding water.
- Dig plants grown in the ground with a ball of soil and let them dry out in a shed or on the garage floor.
- When the stems break free from the tubers, shake off excess soil and allow the tubers to cure in the sun for about 4 days. Then store them in dry peat moss or sand in open flats in a cool (45°–50°F), dry place.
- Replant the tubers as suggested above in late winter.
Growing Hanging Basket Begonias
- Hanging Basket Begonias—varieties with trailing stems—require much the same care as upright Begonias, except that they look their best in a shallow container that can be suspended from the eaves of a house or from an arbor.
- One Hanging Basket Begonia tuber in a 12″ container makes for a spectacular and long-lasting display.
- Please note: If the stems of a Hanging Basket Begonia grow upright and refuse to trail over the edge of the container, plants are not receiving enough light.