Growing The Tuberous Begonia

In the East, tuberous rooted begonias are grown successfully in many locations, some perfect, others makeshift. In Massachusetts, potted begonias with saucer-size blossoms of strong, pure color, brighten the shade of a brick terrace under a wide-spreading maple.

Equal splendor has been achieved at Ogunquit, Maine, where these begonias are grown in window boxes of summer cottages overlooking the cool sea.

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In a New Jersey garden, tuberous begonias are grown in open ground in the filtered shade of old apple trees. Light, softened by leaves of the high-pruned trees, is of just the right intensity. The gentle sway of branches is a natural fan warding off heat from the exotic beauties below.

Such a location, however, is by no means perfect. Apple trees produce their own September beauty and the competition sometimes gets rough. Once in a while, a heavy red apple fells a 6- or 8-inch blossom by a direct hit from above. But, the spot happened to be the only shade I had.

Five Octobers ago, in planning a rectangular place for roses on a slope by the house, it seemed that two apple trees, hanging over the edge of one of the 35-foot beds, had to be cut down if the roses were to get enough sun.

As the slope was being leveled, I remembered spring. Clouds of fragrant pink blossoms against an azure sky. Showers of petals when the bees had had their fill. Song and flash of blue birds as they chased each other through branches in May.

The remembering resulted in 60 less rose bushes – and apple trees and 100 begonias instead. It was a wise decision and seems especially so in August when begonias are most glorious and roses at their lowest ebb.

Tuberous begonias are succulent, tender perennials from rainy tropical forests where they grow in cool places in the rich organic litter of the forest floor, or in porous pockets on the sides of cloud-drenched mountains.

Wild in Puerto Rico

Last February, I saw begonias growing wild in the shade of a great tree fern in the rain-soaked forest of El Yunque, Puerto Rico, 3,000 feet above the Caribbean, where they get first rain then sun all-day.

It’s said that these shade-loving plants, through crossbreeding, have been changed more from their wild form than any other flower. Be that as it may, it is well to keep their ancestral homes in mind. For success in every growing season, try to satisfy their native needs.

No matter how civilized, begonias still require high humidity, constant moisture with good drainage, light well-drained soil rich in humus, coolness without frost and dappled shade or light without sun.

The ground under our apple trees would not have satisfied these conditions unaided. In leveling the slope, unusually good open ground was gained. It was necessary to fill this to a depth of 2 feet on the side where the trees grew.

A well was built around the tree trunks and the ground over their roots filled with stones of all sizes, to a depth of one foot. Then, the stones were covered with sub-soil, compost and manure and finished with a layer of topsoil mixed with leafmold.

Besides supplying good drainage, the moisture collecting under layers of stone in hot weather, cools the soil and mitigates the heat of a New Jersey July.

Deliberate planting of stones to cool the soil is a technique I have found useful even in growing wild flowers native farther north. Whether or not the stones are a great factor in cooling the ground may be debatable.

A layer of ashes, deep down, may be as good. Any old shade, however, won’t do. And the ground under it must be right, soft and free.

Aside from apples and stones, my procedure for growing begonias is standard. First in importance is good stock. Choice tubers, which produce the largest flowers, are 2 inches or more in diameter.

They cost, at the best sources, about 40 cents each this year. They are cheaper by the dozen if colors and types are mixed.

I buy them mixed and plant them hit or miss. I used to try to keep cerise away from orange but finally gave up.

In rationalizing my failure, I came to believe that the great green leaves blend as well as frame the colors. Then, too, when types and colors are mixed, the effect is more interesting and dramatic.

For a long time I believed that nothing could touch Belgian begonias. This may have been due to the fact that I first saw and fell in love with them years ago in Brussels.

After a visit to the West Coast in 1999, I changed my mind. A tour of nurseries in California and Oregon was enough to convince me that the best stock is grown there.

At one nursery, on the approach to Mt. Hood in Oregon, blossoms in hanging baskets were 12 inches across. These should appeal to the gentleman who prefers dahlias red and the size of dinner plates.

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New tubers arrive for planting in late March or April. I have no greenhouse so I lay them right side up in flats partly filled with damp peat moss and place them in a sunny window of barns where the temperatures are around 60 degrees. This starts roots at the rounded bottoms and little pink buds around the collars of last year’s stems.

When they are well sprouted, in four or five weeks, they’re ready to be transferred to 3-inch pots filled with a mixture of equal parts sand, soil and leafmold. The tubers are covered only 1/2 inch deep in the pot and the potting soil is kept moist.

When May brings warm days, the pots of young plants beginning to leaf are put outside during the day. Here they enjoy the cool spring sun and become hardened to outdoor life.

It’s not safe to leave them out all night until all danger of frost is over. In my garden, the planting time seldom comes before June 1.

Then, plants with good sized leaves and flower buds are arranged, under the apple trees, a foot apart with tips of foliage facing the front of the bed. One by one, they’re gently transferred from pots to holes dug with a trowel.

Before each plant is set, a heaping teaspoonful of fishmeal is buried in the hole and covered with a layer of soil.

Fishmeal is the preferred fertilizer on the West Coast and is, indeed, excellent but here in the country, unless it’s buried, every cat for miles around, and perhaps a raccoon or two, will paw the ground for the dead fish they hope to uncover.

When we buried it, our feline guests became fewer. Fishmeal and bone-meal mixed is equally effective.

Previous to planting, the bed is prepared. The winter cover of strawy manure is removed, a layer of compost or leafmold is spaded in and the ground is made tidy.

After planting, the bed is covered with a mulch of buckwheat hulls to equalize the moisture, keep shallow roots cool, save weeding and prevent mud from splashing on the flowers when it rains.

After begonias are in the ground and mulched, they should not be disturbed again except for staking and a dose of liquid fertilizer on August 1. Liquid feed water or a cup of 5-10-10 dissolved in two gallons of water will do.

My begonia plants are watered with the roses in the adjoining beds by a hose with a gadget on the end which can be shoved underneath plants to spread the water and soak a 6-foot area at a time.

Treated thus, plants will grow 2 feet high and produce luxuriant flowers of various sizes, depending on the type of begonias. The fimbriata or carnation type may be 3 inches in diameter; the camellia, rose and picotee, 8 inches.

When heavy blooms appear, plants need staking. I use a green stick, cut from a bush or tree, with a pointed end. I push this down as far as possible so that it’s inconspicuous.

Instead of wire and string which cut into stems, soft green rags, cut in inch wide strips, are used to tie stems.

Flowers bloom until blackened by the first frost. Then, it’s time to lift the tubers. They are laid on the barn floor for a few days to dry off and then packed away in dry peat moss.

They should be stored in a cool, dry place (35 to 40 degrees is ideal) until spring.

If tubers are cared for over the winter and given unchecked growing conditions in summer, they’ll last for several years. If the stock seems to run out and blooms to get smaller, it means you have something yet to learn about growing tuberous begonias.

A few may rot over the winter, true, and a few may fail to start in spring, or a borer may get in a stem and destroy a plant or two.

These you’ll want to replace: The development of new varieties is so rapid that it’s impossible to resist buying new ones, anyway. You’ll want to do this just to see what’s going on and to keep your garden in style.

The secret for growing tuberous rooted begonias in the East in open ground seems to revolve around the word “good” and a few firm “don’ts.”

You must have good stock, soil, drainage, moisture, shade and mulch. Then let them alone!

Don’t spray or worry about disease. If possible, plant begonias in the coolest part of your garden. If you provide these conditions, you can sit back and marvel.

by H Hull

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