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Plantland Home & Garden

Prince George, BC, Canada

Gardening Tips

What you Need to Know When You Don't Have a Green Thumb

Tuberous Begonias

Growing Orchids

February is a good time of year to start thinking about Tuberous Begonias. These beautiful shade loving plants add wonderful colour to flowerbeds and containers and are well worth the extra effort to grow them. They are grown from a tuber, which is started indoors in February, so that by May when all threat of frost has passed they are ready to bloom outdoors. Tubers are available now in the garden centre as well as the indoor soil, peat pots, labels and trays to start them in.
When purchasing tubers, look for large, firm tubers that have no signs of damage or disease. When it is time to plant them use a light, airy, well-drained indoor potting soil. You can plant them in any type of container that the tuber fits in but we like to use 4-inch peat pots as this makes transplanting easier, later in the season. (The nice thing about using peat pots, is that there is no stress on the tubers root system, as the entire pot is placed into the soil, when it is time to transplant.) To plant the tuber, first fill the pot with moistened soil to within 3-5 cm from the top rim. Next get the tuber and place it on top of the soil, hollow side up as this is the top end, and gently press it into the soil so that it is barely covered (1 cm) with soil. After it has been planted, water the soil surrounding the tuber, being careful not to get water inside the tuber as this can cause it to rot. Put the peat pot on a tray or inside a larger container to make it easier to handle and place a plastic dome or clear plastic lid over it to create a greenhouse effect. Place the planted tuber on a window ledge or under a grow light, where the temperature is 17-20 Celsius. It can take anywhere from 5-30 days before you start to see new growth appear. As soon as there is signs of growth, remove the plastic dome, and place the tuber in a well-lit location. Tuberous begonias are shade loving plants so avoid direct, hot midday sun. Keep the soil moist but not soggy and fertilize with 10-52-10 to promote healthy young growth. Plants should be placed in a cooler area so that they become strong and stocky. After they have grown two full leaves, switch to an all-purpose fertilizer such as 20-20-20. This is also the time they can be transplanted into a larger container.

Tuberous begonias are not frost tolerant and a slight frost will harm them, so make sure that when you are ready to plant them outdoors there is no threat of frost. Plant them in a shaded area where they will receive early morning and late afternoon sun. Too much shade will create spindly plants, but full afternoon sun, can cause the foliage to burn. Be careful when watering, as you don’t want to get water on the foliage of the plant, which can lead to mildew. Water the soil, and not the foliage, and water in the morning so that by nightfall when temperatures dip the plant is not wet. For flower production, starting in April fertilize plants weekly, with a flowering plant fertilizer such as 12-36-12 and continue to do so over the summer months. Keep plants healthy by removing all finished flowers, and any damaged or diseased foliage.

If cared for properly, you will be able to enjoy beautiful tuberous begonia flowers throughout the summer months until the first fall killing frost. To lengthen the growing season, place plants in a protected area when there is a threat of frost. Eventually the season does come to an end, and once the frost has blackened the foliage it is time to dig out the tuber. Tuberous begonia tubers can be dug up and stored indoors and re-planted again in February for next season, making them an economical flowering plant. To store tubers, place them in a cool, frost-free location for the first 10-14 days after they have been dug up, and then cut back the foliage to 12-15 cm from the tuber and remove any excess soil. The remaining foliage will eventually dry up and fall off, which is when the tuber is sprinkled with bulb dust and then placed in a container filled with either vermiculite or dry sand and then stored in a dry dark, cool (6-10 Celsius) location until February, when it is time to re-plant them again.