At the same time, hybridizers have been making tuberous begonias more adaptable to your garden, and they have brought new colors and shapes to the flowers.
Such classic forms as that are mimicked by these spectacular begonias are the following:
- rose
- poppy
- carnation
- camellia
- gardenia
- daffodil
At the 1939 World’s Fair in San Francisco, huge beds of tuberous begonias enlivened the grounds, and the masses of color led to hundreds of new enthusiasts for these plants.
Up to that time, it was believed that the world’s finest begonias came from the English seed house of Blackmore and Langdon.
However, a gifted young Bohemian gardener, Frank Reinelt, had been quietly developing his Pacific strain of tuberous begonia hybrids in America, not far from San Francisco.
His giant blooms, perfect forms, and wide color range easily beat the English hybrids.
Soon, other pioneers ventured into the begonia field—notably the Antonelli Brothers and Worth Brown.
Five Million Begonias In Full Bloom
The grounds of these growers are pretty close together at Capitola, California.
In September, at the annual begonia festival, visitors could view about 5,000,000 plants in full bloom.
Soon, excellent begonias have been arriving from Belgium and Holland.
A collection of 5,000 Belgian hybrids was planted at the Seattle World’s Fair.
Right now is an excellent time to start begonia tubers into growth.
Which size do you buy?
Large tubers (2 ½” inches diameter and up) generally produce more flowers.
Small tubers (¾” to 1″ inch sizes) often make the same grade of blossoms but not as many.
Spend a little more and buy tubers with at least 1 ½” inch diameters.
Try Hybrid Seedlings
Another good way to start a collection of tuberous begonias is to buy seedling plants.
These are available from commercial growers about the middle of May.
They travel well by air and cost less than tubers.
To help you be more successful in starting the tubers, Pat Antonelli offers this tip:
Make sure that a sprout appears before you plant the tuber.
Earlier sprouting can be induced if you move them to a warm, dark place.
Just put them in shallow boxes—no damp soil or medium is required.
Starting Begonia Tubers
In the years, commercial growers of tuberous begonias have made two important changes from their former methods for starting the dormant tubers each spring.
They’ve discovered that the old-fashioned starting mix was subject to over-watering because peat moss holds too much water. This, in turn, led to rot.
These growers substitute a coarse mix that will not pack and become soggy.
Unscreened leaf mold, redwood soil mix, or fir bark is preferred now.
Another old system is being discarded too.
Growers formerly planted the tubers so that the top was completely out of the rooting medium and exposed to the air.
They’ve learned that it’s better to completely bury the tuber, covering it with ½” inch of the rooting medium.
A much larger root system results because roots form on all sides of the tuber.
Previously, they formed only on the base and partway up the sides.
Keep These Tips In Mind
With these new concepts about tuberous begonia growing in mind, here is an outline for success with these summer beauties:
Planting Tubers
When the pink sprouts begin to show (usually from February to April), it’s time to start the tubers in flats filled with a coarse material such as leaf mold or fir bark.
Follow these steps:
- Fill the plastic or wooden flat (or a shallow box) with the starting medium.
- Space tubers about 3″ inches apart.
- Carefully add enough potting mix to cover them to a half-inch depth.
- After planting, water the medium well.
- During the rooting period, keep the medium evenly moist, but don’t let it get soggy wet, or you may rot the tubers.
- Keep the flat in a spot where it will get good light but no direct rays of sunlight, except perhaps in the early morning or late afternoon. Warm temperatures (65 to 75° degrees Fahrenheit) speed growth.
- When the tops have grown to 2″ or 3″ inches, shift the plants to pots.
- Tuberous begonias may be put outdoors as soon as the weather is warm and settled.
Choosing A Planting Site
The ideal site for tuberous begonias outdoors is a place in partial shade.
Protection from the hot afternoon sun is a necessity. But don’t mistake planting them in dense, dark shade.
Lack of light causes weak, spindly plants and encourages powdery mildew.
In warm areas, give tuberous begonias plenty of water every day during periods of drouth.
Another caution, wherever you are:
Do not plant them against a hot south-facing wall.
Some hobby gardeners are using overhead mist systems like those seen above vegetables in supermarkets to grow prize-winning tuberous begonias.
Operating costs amount to only pennies per month.
Watering tuberous begonias is tricky since the idea is to keep plants moist but not so veiled that the roots get soggy.
Watering in the morning is considered best. Over-watering encourages mildew and bud-drop and often makes a single-out of a double-flowered begonia.
These plants have shallow roots which suffer when allowed to be dry or water-soaked for more than a few hours.
Fertilizing Tuberous Begonias
Feed tuberous begonias regularly. Organic liquid fish emulsion is highly recommended.
Use two tablespoons per gallon of water every 3 weeks, or one tablespoon per gallon every week.
Tuberous begonias are bothered by few insects and diseases.
Regular dusting with a fungicide will help keep mildew away.
Tuberous begonias started in April should bear flowers from July to October.
When planted in beds or containers, these add beauty to the garden, and they are excellent for floral arrangements.