All non-conifer deciduous trees are technically flowering plants, but for most the flower is inconspicuous. Many of us desire to have that pop of color that a flowering bonsai imparts in the spring. We are looking for is the combination of good bonsai characteristics and reliable, showy flowers.
There are a few generalities that we need to recognize about flowering bonsai. First, flowers do not reduce. You should choose species with flowers that are relatively in scale to bonsai, or decide that when the tree is in flower you just don’t care about the scale. That’s the approach the azalea people take! Second, many people prune back their bonsai hard in late winter or early spring. That can remove most or all of the flower buds that have developed, leading to a disappointment in spring. These trees should be hard pruned after flower production, at least in the years when your trying to maximize the show. Many people use fertilizers with a higher % of phosphorous (lower nitrogen) during flower bud development (2nd half of the year). Others don’t make that adjustment and still seem to get enough flowers to make themselves happy.
So which species should you pick? Surprisingly, you tend to see very few types of flowering bonsai, assuming you group azalea varieties together, and Prunus species together. This is due to the fact that you’re looking for a combination of characteristics, not just good flowers.
The trees used most often are:
Azalea – Flowers often not in scale for bonsai, but nobody cares. Out of flower they make nice looking bonsai. There are many, MANY, cultivars, and the people really into azaleas adjust specifics of care for each. If you’re heading down this road consult the experts.
Bougainvillea – love heat and full sun. There are many color varieties, and they’re easy to propagate from roots, cuttings and air layers. They are vines, though, and are difficult to style in traditional bonsai designs.
Crab Apple (Malus) – Profuse, small flowers and ultimately small fruit make crabs a great choice for flowering bonsai. If you propagate by air layer or cuttings (semi-hardwood) from a tree already flowering they will continue to flower. They are difficult or impossible to propagate by hardwood cuttings. Seedlings can take a long time to mature enough to produce flowers. They make great bonsai but you have to deal with a relative lack of ramification, and a tendency for trunks to make cylinders with little or no taper.
Flowering Quince (Chaenomeles) – Several varieties with colors from white to red. They are easy to propagate from cuttings, but it’s hard to get a thick trunk. They are often not impressive when out of flower, but the flower display is worth it.
Hawthorn (Crataegus) – Excellent bonsai subjects with the flowers as a bonus! There are more than 200 species to choose from with many varieties. Similar look to crabapple flowers and fruit, but hawthorn will develop better taper and ramification. They can be propagated from cuttings or air layered to get a flowering tree quickly. Seedlings take 15 to 20 years to mature enough to flower.
Prunus – There are more than 400 species of Prunus, all with nice flowers, many of these with dozens of varieties. Some, for example almonds, peaches, some cherries, don’t make good bonsai for other reasons. Probably the species most often used in bonsai are mume (flowering apircot), tomentosa (Nanking cherry), campanulata (Taiwan cherry), serrulata (Japanese cherry), and subhirtella (winter flowering cherry). They are susceptible to insect and fungal pests as well as spring freezes.
Pyracantha – aggressive grower, considered an invasive species in some parts of California. They are easy to propagate from cuttings, and they air layer very quickly. They put on a great show of small flowers and fruit in scale for bonsai. They often have flowers and mature fruit at the same time. Drawbacks are that they don’t heal over large scars, they have wicked thorns, and are susceptible to fireblight.
Wisteria – an impressive vine with impressive flowers. Flowers hang in large racemes, not in scale for bonsai but again, nobody really cares. Leaves are compound and not ideal for bonsai, but this is all about the flowers. The two most common species are W. sinensis
(Chinese wisteria) and W. floribunda (Japanese wisteria). Many color varieties are available. Seeds and other parts of the plant are poisonous so watch your pets.