There is a lot of new material on this page but it is still under contruction so not all links and pictures are done yet
should be done in a few days



Tuberous Begonias
by Brad Thompson


   Tuberous Begonias are probably the most commonly grown begonias worldwide.  The tuberhybrida types are always popular and are commercially grown in many countries.  Unlike the other types of begonias, tuberous begonias grow from achrist Church Arboretum bulb like structure and most go dormant part of the year.  These die back completely, leaving only the tuber, which requires special storage.  There are a few begonias placed in the tuberous class, which don’t have tubers but form a caudex.  There is some debate as to whether these should be in this class but currently they are commonly called semi-tuberous.  More correctly they should be called caudex forming begonias. 

   Tuberous begonias were one of the first types of begonias to be hybridized.  Combining aspects of the various species, hybridizers have developed types with large double flowers.  This type is called tuberhybrida.  There are also a few dozen well known species with various unique qualities.  There are just as many other species that have been newly discovered or are not in wide circulation. There are also various hybrids between tuberous and other types such as Riegers, which don’t have tubers but have some tuberous qualities. For purposes of this article, the tuberous types are divided into five main types, tuberhybrida, species, caudex forming, hiemalis and cheimantha.
mike stevens collection


Tuberhybrida Type Tuberous

   This is by the far the most widely grown type of tuberous begonias.  This is also probably the most popular type of begonia worldwide.  Over many decades of hybridizing work,
various species traits were combined to create what we know as the tuberhybrida type today.  Much work continues today in Europe, Australia, New Zealand and North America to come up with even more improved varieties. 

   The most attractive characteristics of the tuberhybrida are their double flowers.  The flowers come in every color but blues.  There are also various styles of flowers from ruffled mike stevens collectionpetals to rose forms.  There are even picotee type tuberhybrida that have petals with edgings of different colors.  Most are upright growing but there are also hanging types with trailing stems called pendula tuberhybrida.  The flowers range in size from a couple inches as in the commercial Nonstop(TM) varieties to named varieties that can have dinner plate sized blooms with proper culture.  There are also scented varieties available.  Not all tuberhybrida have double flowers, there are many with single and semi-double flowers but these are less well known or new introductions.  An example of this is the Mission Bells series which resulted from crossing tuberhybrida back to tuberous species to gain new traits.

   All tuberhybrida go dormant for the winter.  All upright varieties
usually require staking to support the flowers.  Unstaked plants can break off at the tuber easily.  I learned this the hard way.  I had a garden party and a friend was admiring a perfect specimen that was a foot tall with a beautiful six inch picotee flower.  My friend said "You really should stake that, a breeze could break it off".  15 minutes later a gentle breeze broke it right off at the soil line.  I've staked mine ever since.  There are probably more books available on this type of begonia than any other type.  Since this is a specialized type of begonia, further reading is recommended.  An especially great book on tuberous begonias is by Mike Stevens, available from many sources, including ABS and Amazon.
  
I found this site that has great pictures, unfortunately the page is written in Japanese but still worth a look, Japanese Site with great tuberous pictures


A great source for tubers and picture, Blackmore & Langdon Tuberous
Begonias
Really nice pictures of tuberous begonias, Australian Begonia Company, Candybell

Pictures,links, and info on tuberous begonias, Scottish Begonia Society (UK)

Pictures,links, and info on tuberous begonias, East of Scotland Begonia Society (UK)

Small but excellent gallery of tuberous begonia pictures, Julie Vanderwilt pictures of tuberous begonias


yellow tuberousSpecies Tuberous (and first generation hybrids)

   There are a few dozen types of species tuberous begonias.  There are also as many first generation hybrids between the various species.  Many require specialized care or are unique so may require more research into the care for specific species.  All grow from a tuber or similar root structure.  They come in a wide range of sizes, flower colors and sizes, and leaves.  Several species types form bulbils in the leaf axils that can be collected and grown into new plants the next year.  At least one variety, B. grandis variety evansiana, is win
ter hardy even in cold climates.  Most require similar care to the tuberhybrida but may be more tender or difficult to grow.  Examples of this type are B. sutherlandii and B. boliviensis. For a list of tuberous begonia species follow this link to the list Tuberous Species List   Examples of first generation hybrids are B. 'Airy Fairy', B. 'Bumble Bee' and B. 'Santa Barbara'



Caudex Forming Tuberous

   This type is commonly called semi-tuberous but caudex forming or caudiciform is more proper.  Nearly all are variations or
hybrids of B. dregei.  There are a couple that aren’t but all need similar care.  The caudex is a unique root structure that looks like a large tuber (which is how they got lumped in this group).  It is usually half out of the soil.  From this caudex small stems arise.  During stressful times or bad weather this type can lose all their foliage down to the caudex.  Unless the caudex is rotted by overwatering, new stems will come back from the caudex when conditions improve.  This type does best in clay pots to avoiding keeping them too wet.  The caudex forming are commonly grown as a natural bonsai and do well in the shallow bonsai pots.  This type is very mildew prone, especially during cool wet times of the year, but also nearly any time of year.  They may require routine spraying with a fungicide to be successful with them.  Examples of this type are B. dregei var partita and B. dregei var glasgow.  All have small leaves and most have white flowers like B. suffruiticosa pictured to the left.




Hiemalis Type Tuberous

   Most of this type are not truly tuberous but have tuberous parentage and some tuberous qualities.  They are hybrids between various tuberous types and other types such as rhizomatous.  There are some red reiger begoniawith tubers but these are not commonly grown anymore and may not exist.  Most have tuberous qualities such as double flowers but don’t have a tuber so grow all year.  The most common of this type grown are the Riegers.  The Riegers are ever blooming if given enough light.  They can be trimmed any time of year to keep them compact, if grown indoors.  Outdoors, grow and prune as you would shrubs. The Riegers may require winter protection or additional light during short days.  They are common florist plants and are most commonly grown indoors or in greenhouses.  New varieties will do well outdoors however and some recent developments have created some that will grow in full sun in some areas. 





Cheimantha Type Tuberous

   This type of tuberous is not commonly grown, at least in the US.  They are hybrids between B. socotrana and B. dregei or other types.  They are winter blooming.



Marty Korobkin and Bob Golden at the Gazebo Begonia Show
Picture by Mike Flaherty

Mike Flaherty next to B. 'Big Red'
photo by Mike Flaherty


Gary Hunt at Chrischurch Arboretum in New Zealand, standing next
to large B. pearcei Display, photo by Mike Flaherty

Tuberous Culture


Potting

   Tuberous begonias will grow in a variety of pot types.  The most commonly used pots for tuberous are plastic.  Some species such as B. boliviensis, which has a very large tuber, may do better in a clay pot to avoid any chance of overwatering.
 Although tuberous begonias can be started directly in the pots they are to grow in, they usually are started in flats or smaller pots first.  Most will require at least an eight inch pot but starting them directly in that size is more risky than starting them first and transplanting.  Large numbers of tubers are usually started in shallow nursery flats filled with mix or oak leaf mold.  If you’re starting a small number of tubers, you can substitute four inch pots.  The tubers shouldn’t be placed into flats or pots for starting until the eyes on the tubers have started to sprout.  This is a sure sign they are ready to grow.  Planting sooner runs the risk of rotting tubers.  The top of the tuber is the side with the depression in it.  When starting them, cover them shallowly and keep slightly moist until you have shoots a few inches tall.  Once you have shoots, they can be transplanted directly into eight inch pots.  When transplanting, plant them an inch or so deeper than you started them at.  This will cause more roots to form above the tuber and make for a sturdier plant.

   If planting the pendula hanging type tuberhybrida, it’s best to use at least three tubers per basket to make a full plant.  Tuberous begonias can be grown easily in beds but the tubers should be started first before planting in the beds.  They should have soaker type watering or carefully watered with a wand to avoid wetting the foliage.  Overhead or spray watering may cause mildew problems or damage the blooms, at least in many growing conditions.  

 

Pruning and Staking

   Tuberous begonias don’t require pruning.  Some of the species and pendula type tuberhybrida should have the tips pinched out when they are a few inches tall to promote fuller growth. The tuberhybrida are not usually pinched.  Pinching these will force branching but reduce the flower size.   Most of the upright growing tuberous  require staking to keep the stems from breaking off at the tuber.  It is best to insert a stake when planting the tuber so you can place the stake next to the tuber.  If you wait to stake later, make sure you insert the stake or stakes for multiple stems, far enough away from the stem that you don't push it down through the tuber.  It is best to use the plastic stretch type tie since the stems are soft and can be damaged if wire ties are used.  For some very full growing tuberous varieties I cut down round tomato cages and put them into the pot when the plant is young.  As the plant grows up it will fill in and be supported by the cage so doesn't usually need ties.  If growing for a show however, you need to use proper stakes.  

Watering and Fertilizing

   Tuberous begonias usually require more water than some other types but should be allowed to dry slightly before watering.  They will let you know if they are improperly watered by dropping flowers or wilting.  They should be fertilized weekly with quarter strength fertilizer all during their active growing period.  Stop fertilizing when plants shows signs of winding down or a month or so before you expect them to do dormant.  Double flowered tuberhybrida will put out single or undersized flowers if not fed properly.  Avoid getting water on leaves and flowers except for occasional necessary rinsing for grooming purposes.

Light and Heat
 
   Tuberous begonias require good light in order to grow or bloom properly.  Morning sun or filtered light all day is preferred.  They won’t grow in extremely hot or dry areas.  They grow best in coastal areas of California and northern climates.  They either won’t grow or won’t grow well in most areas of Florida and Texas where other types of begonias are commonly grown because they can't tolerate the high temperatures. 

Pests and Diseases

   Since tuberous begonias go dormant part of the year, they shed most of their pests at that time so aren’t usually pest prone.  The only pest that is a common problem are thrips.  Any time you see distorted new leaves or flowers you should suspect thrips.  They can sometimes be seen moving quickly if you pull flowers apart but are extremely small.  Thrips can only be controlled with an insecticide.  Routinely spraying tuberous begonias is recommended to avoid a thrips problem.  Waiting till you see damage will usually result in having bad looking plants for the rest of the season.  They will survive but once the damage is done they probably won’t look pretty again that season unless caught early.  Since thrips hide in the buds and flowers, a systemic insecticide works best since it’s nearly impossible to hit them directly with any other type spray.  The tubers can sometimes have mealy bugs or borers on them so should be sprayed or dusted before storage.

   Tuberous begonias can be mildew prone in various locations or during poor weather conditions.  Some may require a fungicide to keep mildew in check.  Some fungicides may discolor or damage flowers so should be tested on one plant first. If you notice stem rot or rotting leaves this is a more serious fungal disease.  Remove damaged stems and leaves and start routinely spraying with a fungicide that specifically says it treats other fungal diseases than powdery mildew.  Mildew spray don't usually treat this type of fungus disease.  Also try to start watering in the morning so the inside of the plant and the leaves have time to dry before night time, and make sure to let plant dry out before watering.
 

Propagation


   Tuberous begonias can be started various ways.  They can be grown from seed, from stem cuttings, from tuber sections or from leaf cuttings.  Some that form bulbils from leaf nodes can also be started from those.  Seed should be started early enough in the season so plants have time to get some size before moving outside.  Plants grown from seed started early enough will perform nearly as well as plants grown from tubers but usually aren’t their best till their second year.  After the first year, the tuber may only be pea sized so you may have to look carefully after they go dormant to find the little tuber.  The tuber will increase in size every year.

    Tubers can be sectioned like potatoes with at least one eye per section.  These sections should be allowed to heal before planting and dusted with a fungicide.  Since many tubers are very expensive I don’t recommend sectioning the tubers.  If you’d like to try that method of propagation, practice with cheaper tubers before trying it on any expensive tubers.  Most experts advise against sectioning tubers as the cuts never really form a thick skin so can rot at that point, even years later.  This method should really only be used to save tubers that have rotted sections and even them you should take stem cuttings later to start a new tuber.  Some species such as B. sutherlandii form clusters of small tubers.  These can be separated into individual plants each year.

   Tuberous begonias grow easily from stem or leaf cuttings.  Young growth works best and cuttings should be taken early in the year.  The plant grown from the cutting needs time to grow it’s own tuber before it goes dormant the next fall, so the earlier the better.  Tuberous begonias don’t root well in water, except for the smaller stemmed types like the caudex forming types and B. sutherlandii.  Most tuberous stem cuttings will start directly in potting mix.  They may look wilted initially but most will eventually root and recover.  It’s best to keep them in shade until they have rooted.  Leaf cuttings should be started as you would rhizomatous begonias.  In my experience leaf cuttings will look funny the first year as they usually just spend their energy making a tuber.  The second year the tuber will usually put up stems.  


 Special Uses, Tips, and Winter Storage

   You can find tuberous begonias to fill nearly every niche except full sun or deep shade areas as long as you have a climate where tuberous begonias will grow.  Some begonia growers have collections exclusively of tuberous begonias.  They put on a magnificent show during the summer and fall and since they are dormant for the winter, the grower gets a rest too.  In Southern California tuberous begonias aren’t commonly entered in shows so this is a good category for new growers to try in those areas.

   A few varieties such as B. sutherlandii, it’s hybrids and also B. dregei varieties can be kept growing through the winter by growing in terrariums or under lights.  Most tuberous varieties however will go dormant and must be stored for the winter.  In late fall your plants will start to wind down and foliage become yellow.  Once it’s apparent they are stopping growing for the season, stop all watering and put in a location where they won’t get rained on.  Eventually the plant will die back completely. 

   You can store the tubers in the pots they grew in but it’s better to remove all the soil mix and dry the tubers further in open flats or boxes.  Tubers planted in beds should also be dug up and dried.  Many growers dust the tubers with a fungicide or insecticide powder at this time to eliminate any pests or diseases before storing the tubers.  They can be stored in cardboard boxes or paper bags.  Some growers store them in sawdust, vermiculite or peat but that isn’t necessary.  Whatever they are stored in should be dry and be able to breathe.  Plastic bags aren’t recommended since they hold moisture and cause diseases that can do damage to the tubers. 

   Tubers should be stored in a cool dry location.  Storing them in overly warm areas may cause them to sprout prematurely, too cold may cause rotting.  Tubers should be inspected routinely over the winter to check for rotting or insect damage.  Prompt attention may save tubers with problems if caught early.  Rotted parts can be cut out and the remaining tuber treated with a fungicide.   Storing each tuber in it’s own paper bag will keep potential problems from spreading to other tubers.  When you’re almost ready to plant the tubers, you might move them to a warmer place to help them sprout out sooner. 

   If you’re really lazy and live in a temperate climate like southern California, you can leave the tubers in the pots they were growing in and just tip them on their sides for the winter to keep them dry.  In the spring when they should be starting to sprout, turn the pots up again and start watering.  This method isn’t as good as proper storage but better than doing nothing and most tubers will usually come back though you will lose a few.  See tuberous page one for more info on winter storage and restarting the tubers in the Spring.

Growing tuberous link

University of Minnesota article on tuberous
GardenHive article on starting tubers

Many thanks to my friend Mike Flaherty for his great photos and to the other photo contributers.  If you live in CA and especially if you live in the Santa Barbara area it is worth a trip to the Annual Gazebo Begonia Show to see the many spectacular tuberous begonias grown by Paul Carlisle and Mike Flaherty.  Many of the photos on this page were taken at the display. Click on pictures below to see larger version (links coming soon)  The larger version has much more than the thumbnail versions show, so you really should look at them all.  If you were the photographer of the photos with no author, please let me know and you will get full credit or I will of course remove them at your request.

B. "Airy Elf'
photo by Brad Thompson

B. 'Cinnamon Bells'
photo by Brad Thompson

tuberous group
photo by Mike Flaherty

Pink Tuberous
photo by Ed Bates

White Tuberous
photo by Ed Bates

Picotee Tuberous
photo by Ed Bates

B. 'Bellbridge'
unknow photographer

B. 'Butter Bells'
photo by Brad Thompson

B. 'Can Can'
unknown photographer

caudiciform begonias
photo by Michael Kartuz

caudiciform begonias
photo by Michael Kartuz

B. davisii hybrid
photo by Mike Flaherty

Orange Tuberous
photo by Ed Bates

B. 'Mission Bells' series
photo  Brad Thompson


B. 'Tessa'
unknown photographer

B. grandis var evansiana
photo by Mike Flaherty

B. grandis var evansiana
photo by Mike Flaherty

B. 'Firedance'
unknown photographer

Gazebo Begonia Show
photo by Mike Flaherty

Gazebo Begonia Show
photo by Mike Flaherty

Gazebo Begonia Show
photo by Mike Flaherty


Gazebo Begonia Show
photo by Mike Flaherty

Gazebo Begonia Show
photo by Mike Flaherty

Paul Carlisle Display
photo by Mike Flaherty

Orange Tuberous
photo by Mike Flaherty

Orange Tuberous
photo by Mike Flaherty


White Tuberous
photo by Mike Flaherty

B. 'Isabel'
unknown photographer

Mike and Big Red
phot from Mike Flaherty

B. 'Mission Bells' series
photo by Brad Thompson

B. 'Mission Bells' series
photo by Brad Thompson

B. 'Cracker Jacks' series
photo by Brad Thompson

B. 'Cracker Jacks' series
photo by Brad Thompson

B. 'Cracker Jacks' yellow
photo by Brad Thompson

B. 'Lady'
unknown photographer

B. 'Mission Bells' series
photo by Brad Thompson

B. 'Mission Bells' series
photo by Brad Thompson

B. 'Mission Bells' seedling
photo by Mike Flaherty

B. 'Mission Bells' series
photo by Brad Thompson

B. 'Mission Bells' series
photo by Brad Thompson

B. 'Mission Bells' series
photo by Brad Thompson

tuberous seedling
photo Brad Thompson

Paul Carlisle tuberous
photo by Mike Flaherty

B. pearcei
photo by Mike Flaherty

B. pearcei and Gary Hunt
photo by Mike Flaherty

B. 'Party Dress'
unknown photographer

orange pendula tuberous
unknown photographer

pink picotee tuberous
unknown photographer

orange picotee tuberous
unknown photographer

Two toned pink tuberous
unknown photographer

B. 'Roses for Ruthie'
photo by Brad Thompson

B. 'Roses for Ruthie'
photo by Brad Thompson

B. 'Rudy Tuttie'
photo by Mike  Flaherty

ruffled tuberous
unknown photographer

unnamed tuberous seedling
photo by Brad Thompson

B. suffruiticosa
photo by Micheal Kartuz

B. sutherlandii
unknown photographer

Taffeta Series
photo by Brad Thompson

orange picotee
unknown photographer

pink picotee
unknown photographer

pink tuberous
unknown photographer

pink ruffled tubouers
unknown photographer

B. 'Summer Dawn'
unknown photographer

Gazebo show
photo by Mike Flaherty

ruffled picotee
photo by Mike Flaherty

B. partita
photo by Brad Thompson

B. 'Linda Jackson'
unknown photographer

B. 'Cracker Jacks' series
photo by Brad Thompson

Gazebo Show
photo by Mike Flaherty

Marty, Bob, and Display at Gazebo Show, photo by Mke Flaherty
 Tuberous Gallery Two, coming soon, I am receiving many new additions and am in the process of editing

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