Answer: Your double purple is a French lilac and it has the same growing requirements as the species - they bloom best when they receive a pronounced winter chill; they like slightly alkaline, well draining soil and full sunshine. It should bloom prolifically, just as your common lilac does. Since lilacs bloom on new shoots which develop the previous year, you might try lightly pruning your French lilac now to encourage new growth. Over the summer it will develop flower buds for next spring's display. As long as it receives a winter chill, it should bloom for you. Best wishes with your landscape!
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