A wild Hawthorn/Crataegus monogyna flowering in the UK during May
As a native species, the sight of wild Hawthorn trees covered in white blossom is common throughout the UK during May each year. Hawthorn are also a popular hedging species and it is not unusual to see miles of white flowers flanking the British roads for 3-4 weeks.
However, as bonsai, Hawthorn are notoriously reluctant to produce a single flower!
An old wild Hawthorn branch, laden with flowers
This article focuses on the subject of encouraging Hawthorn bonsai to flower, however, the basic principles can be applied to flowering bonsai of all species.
Hawthorn/Crataegus monogyna bonsai in flower. Height 42"/102cm
Maturity and Reproduction
All trees are genetically predisposed to be dominant over surrounding trees and plants in an effort to reproduce. The most successful specimen (of any one species) are those that are able to outgrow their neighbours in an effort to gather as much light, water and soil-space as possible.
Once they have grown to their fullest extent (as high and as wide as they are able, given their local environment and circumstances, (whether that be 100 metres or just 1 metre tall) they then begin to try and reproduce themselves by flowering and spreading their seed.
Hawthorn bonsai berries in September, each bearing seed that potentially can reproduce the parent tree
These two different phases, of gaining maximum height and then of seed-production, are known as immature and mature growth.
In the immature phase of growth, a tree will put out predominantly (or exclusively) vegetative growth in order that they can 'outcompete' its neighbours by growing as tall and wide as possible, commonly known in most tree species as apical dominance. This is a pre-disposition and it does not matter whether the tree in question is growing wild or in a bonsai pot.
Conversely, during the mature phase of growth, the tree reduces the amount of energy put into growing new vegetative shoots and begins to try and reproduce by flowering.
This mature or flowering stage of growth is triggered when the tree can no longer spread upwards or sideways, and continues the process of dominance by trying to reproduce itself.
These same events occur with a bonsai; a bonsai will continue to grow vegetatively in an effort to grow taller and wider until such time that it is unable to grow any bigger and begins to enter a mature, flowering phase. Ergo, in order to encourage a bonsai to flower, first it must be encouraged into maturity.