Zone 8, full sun, clay soil. Why has my 6 year old tree not bloomed yet? One next to it is fantastic and blooms without fail
Non-blooming plants can be perplexing. Your Robinia pseudoacacia “Purple Robe” is planted in what should be its preferred conditions – it likes full sun and grows well in clay soils. There are many reasons why trees fail to bloom, amongst them winter injury, insufficient sunlight, and cultural practices such as fertilization with nitrogen which promotes leaf growth over flowering and heavy pruning which may remove bud-bearing branches. Tree immaturity is another reason. Is the adjacent tree is the same age? It is possible that your six-year old tree has not reached physiological maturity. Most experts advocate patience in the absence of any discernible pest, disease or other conditions that might affect the ability of a plant to flower.
You don’t say where you are gardening, but if you are in a Zone 8, we are assuming you are on the west coast in BC. If so, it may be helpful for you to contact your local Master Gardeners Association of British Columbia, because often local master gardeners have had similar experiences with their plants due to local conditions.