I have a Chilean Fire tree (Embothrium) that I planted about four years ago. It has grown rapidly to about seven feet tall. It has not yet bloomed. At what size or age does this tree bloom? Does it require some encouragement, like root pruning, to get it to bloom?
I have not fertilized it because I have read in at least two sources that these plants should not be fertilized.
There are many reasons a plant may fail to flower, immaturity being one of them. You are correct to avoid over-fertilization, as that is often a cause of lack of flowers. Another cause is unusually cold weather.
I found an article by Roy Lancaster on Embothrium coccineum in Gardens Illustrated, May 2005. He mentions that if the tree is planted in a somewhat shady site, it will not flower as prolifically. Acid soil which is moist but well-drained, and a sunny but sheltered spot are ideal.
There is a discussion of the problem of Embothrium’s failure to flower on the NPR Talking Plants blog (no longer online) in 2007 (formerly hosted by Portland gardener Ketzel Levine). It appears that this is not an uncommon problem. Here is an excerpt, from a gardener responding to Levine’s complaint about the lack of flowers:
“Many have found Embothrium to be a slow bloomer. It is a polymorphous plant in many ways: some are evergreen, some deciduous, some are trees, some are shrubs. Some bloom in a 1-gallon container, others need to put on some size first.
“The danger of phosphorus toxicity rules out some of the usual bloom-stimulation therapies using fertilizer. Provided that it’s getting enough sun exposure, I’d say just sit tight and give it a few more years. If you’ve been watering it on a consistent basis all summer, hold back and let it dry out for a few weeks between good soakings.
“If you get really desperate and are contemplating its removal, you might first take a propane torch and try burning the leaves and twigs off when autumn comes (don’t scorch the bark on major limbs). I know that sounds a bit absurd, but some plants respond to environmental adversity by blooming, and the fire trick has been known to work on some other proteaceous flora. From the plant’s point of view, why expend the energy of going into a reproductive cycle when everything’s fine and there’s no threat to survival? Give ’em something to worry about.”
If you feel daring or desperate, I suppose you could try the blowtorch approach, or you could make sure to provide the ideal conditions, and wait patiently. Levine, like you, thought of root-pruning her Embothrium to induce flowering. You could try to contact her and ask if she tried it or the fire method, and if either worked.