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 some discussion of the lack of flowers on Embothrium on Portland gardener and NPR commentator Ketzel Levine's site, suggesting that this is not an uncommon problem.
Here is an excerpt, from a gardener responding to Levine's complaint about no 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 might write her and ask if she tried it or the fire method, and if either worked.
Season
All Season
Date 2008-06-04
Link to this record only (permalink)
The people at the nursery may be thinking of Embothrium's reputation for resenting transplanting. According to Graham Stuart Thomas's book, Ornamental Shrubs, Climbers, and Bamboos (Timber Press, 1992), Embothrium coccineum seldom thrives when transplanted. However, I think he is talking about the difficulty of transplanting a mature tree, not a small seedling. Simon Toomer's Trees for the Small Garden (Timber Press, 2005) confirms this: "It has a reputation for being difficult to transplant when large and so container-grown plants of moderate size should be used."
Local gardening expert Ciscoe Morris has said of Embothrium: "Only buy it if it's a small seedling. They hate pots and if they are pot-bound for very long, won't survive transplanting. Plant Embothrium in a sunny location in acid very well-drained soil. Never fertilize these trees as phosphorus is known to kill them."
Since you have several starts, why not try transplanting at least one or two of them to an ideal spot in your garden. Try to get as much root system as you can when digging them up, and if more than one start comes up, don't try to cut them apart if it means you will lose any roots. Now is probably a good time to attempt this, and there is not too much risk in trying.
Season
All Season
Date 2008-10-31
Link to this record only (permalink)
