Canes are one of the easier types of begonias to grow and will grow in all the different types of pots available. Plastic pots are the most commonly used type of pots for canes. They grow well as either hanging baskets or as potted plants. They also do well grown in the ground. Like nearly all begonias, canes require a well drained potting mix and resent soggy feet.
When repotting, canes should be placed as low in the new pot as possible. This may require removing extra mix from the bottom of the rootball to be able to have them sit lower. The reason for potting lower is to bury more stem buds which will encourage more basal growth and also cause more roots to form on the buried parts.
Unless grown indoors, where pruning can be done any time of year, most canes should be pruned in the spring. Unless you’re purposely trying to grow a tall specimen plant, most varieties should be pruned fairly hard to encourage new basal shoots. Canes not pruned have the tendency to become bare stemmed on their lower parts. Superba types should be pruned back fairly hard in Spring, then allowed to grow freely the rest of the year. The other types should be cut back the same but the smaller leaved varieties benefit from routinely pinching the tips to force side branching and fullness.
Canes routinely send up strong sturdy stems from the roots. This growth appears almost like some sucker type growth but this is the normal growth of the plant. On superbas, these can be left alone. For growing in baskets, or for the other types of canes, these stronger shoots should be pruned back as they appear, down to the lowest outward facing bud. This will force the plant to put out weaker side branching. This will fill in the plant and make it conform to the rest of the plant’s growth.
Watering and Fertilizing
Canes don’t like to be overwatered. Mature plants however are among the most tolerant of overwatering than any of the begonia types. A well draining mix is preferred. Extremely warm areas of the country made need a more water retentive mix though. Canes should be watered after the mix surface has become dry. Canes benefit from quarter strength fertilizer given weekly through out their active growing season. Over watered canes will drop lower leaves. Avoid getting water on the leaves of canes when they are in direct sun or the weather is overly hot to avoid causing leaves to burn. Under ordinary conditions getting water on the leaves doesn’t bother most canes. Any varieties that are prone to brown tips will be less prone to this problem if you avoid getting their leaves wet when watering. An example is B. albo picta which is very prone to brown tips.
Light and Heat
Cane begonias do best when given good light all year. Most benefit from full early morning or late afternoon sun. Filtered sun all day is preferred. There are very few canes that will perform well in complete shade. Most won’t bloom in low light. Canes in hot climates may burn if given late afternoon direct sun. Most canes do well in 50% shade provided by shade cloth in coastal areas of California. Begonias in Texas or other hot climates may require more shade than other areas.
In frost free areas most canes will over winter outdoors with no protection. Many canes suffer from leaf drop during colder weather. This is normal unless caused by disease, overwatering, or pests. Some of the more tender canes such as B.’maculata’ and it’s hybrids, mallets, small stemmed and miniature canes, and especially mildew prone varieties may require winter protection. This can be provided by a temporary greenhouse or by bringing indoors if you don’t have a greenhouse to move them to. Even an unheated clear plastic shelter will usually be enough to carry them through.
Canes are prone to sudden leaf drop during sudden extreme temperature changes. Not sure of the cause, may be a genetic feature designed to protect the plant from extremes. It is normal but you should be aware of this problem when moving plants. It is common for plants taken to shows to drop leaves and all their flowers afterwards. They quickly recover when put back in their normal growing conditions however.
Pests and Diseases
The most common insect pests for canes are mealy bugs and aphids. Keeping dried stipules removed from your plants will remove most of the hiding places for mealy bugs. Yearly pruning, as suggested above, will take away any pests so you’ll start out fresh each year. Canes can also be prone to Prichard’s mealy bugs, which are a type of mealy bug that lives in the soil and attacks the roots. This pest should be suspected in any plants that decline for no apparent reason. The root death caused by these mealy bugs mimics overwatering type symptoms. An insecticide specifically for root pests is required to get rid of them.
Aphids are most commonly seen on canes in the winter and spring on the under side of new leaves. Routine inspection under the leaves will help catch and infestation before it gets out of hand. Any plant that puts out new leaves that are distorted or mottled should be suspect for aphids and inspected. Nearly every insecticide kills them. They can also just be washed off with a strong spray of water but they usually return using that method.
Many canes are prone to powdery mildew. Superbas are the least prone and mallets are the most prone. Varieties found to be mildew prone have to be sprayed routinely to prevent reoccurrence and to control. Sometimes moving them to a different location will help them be less prone. Air circulation has very little influence on the amount of mildew.
Canes can also be prone to bortrytis especially during cool damp weather. This can cause stem and leaf drop. Seeing leaves that seem to rot from the petiole is usually bortrytis. On worse cases, a gray fuzzy mold appears on the rotted portions. Keeping bad leaves picked up and removed will help with prevention. There are also some fungicidal sprays that can help control the problem.
Nearly all canes can only be reproduced by stem cuttings except for the species which of course can be started from seed. Only a handful can be started from leaf cuttings and all of these are hybrids between canes and other types such as some of the mallets.
Special Uses and Tips
Cane begonias are very flexible and there are varieties for nearly every specific purpose. They also respond very well to training. If planted in the ground and allowed to grow in a semi wild state, most will be tall large plants. Many of the superbas and some of the others can attain eight or ten feet tall easily if allowed to. With the exception of a couple of the more vigorous superbas though, nearly all begonias can be kept to a small manageable size. There are very few that can’t be confined to an eight or ten inch pot and kept to two feet tall or less tall for many years. Most canes can also be grown as nice full hanging baskets with proper pinching and pruning. Some of the superbas would require large baskets however. Canes can also be easily trained as standards or grown on trellises.
Credits / references:
Brad Thompson | Brad’s Begonia World