Ask Mr. Smarty Plants

Since this is a non-native of North America, we do not have the Philadelphus coronarius (mock orange) in our native plant database. Our emphasis at the Lady Bird Johnson Wildflower Center is the planting, propagation and protection of plants native to North America and, indeed, to the area in which they are growing. However, we are always interested in plants, and will try to find some answers to your question about this native of southern Europe.

This site from North Carolina State University on mock orange was about the best at presenting the facts on care and appropriate conditions for this plant. The USDA Plants Profile shows it growing all the way from Georgia in the South up into far northeast Canada, including New Hampshire, so you must be in the right zone for it. One interesting fact we picked up in our research is that non-blooming mock orange can be the result of too little sun or too much fertilizer. The flowering of any plant will be affected by the application of too much fertilizer, especially high nitrogen fertilizers. At bloom time (late Spring to early Summer) you might try a shot of high phosphorus plant food. High nitrogen encourages lush leaf growth, but not blooms. Mock orange apparently does best in rich soil, well-draining, that is slightly acidic to neutral. To encourage bloom, it should be pruned right after blooming, and oldest branches should be pruned right down to ground at the same time. But, if it hasn't bloomed at all, that makes it a little difficult to know when to prune.

If you feel your plant is getting enough sun, not too much fertilizer, and the roots are in well-draining soil, we would suggest you take it out and replace it with something else that better fills that space. We haven't seen it grow in Texas (way too much sun and heat, probably), but we understand it's not a particularly handsome shrub when it's not blooming, that not all mock oranges have any or much fragrance, and it doesn't bloom very long. Why waste your time, resources, and energy on that?