Pruning Euonymus and croton, and troubleshooting non-blooming irises

DEAR JESSICA: I have a few Euonymus japonicus on my property that are shaped as tight bushes. Two are getting quite large and need to be cut way back. When is the time to give them a hard pruning, and when is the time to just prune to keep its shape?

— Ricki Sokol, North Bellmore

DEAR RICKI: For hard, rejuvenative pruning, your Euonymus bushes should be cut back in late winter/early spring, before new growth begins. But if you just want to clean up their shape or reduce their size, you should do that in late spring or early summer. Just don’t prune after Aug. 1, because pruning stimulates new growth, and that wouldn’t allow sufficient time for the new growth to mature before frost hits, likely damaging it.

DEAR JESSICA: I have a croton that is about 20 years old and about 6 feet tall. It is getting kind of large for our small home. Is it possible to prune it back, and if so, when and how should it be done?

— Christina Fumasoli, New Hyde Park

DEAR CHRISTINA: First of all — congratulations on keeping your plant alive for 20 years. It’s not every day one comes across a 6-foot-tall indoor croton. It can, in fact, be pruned, but the job likely will require loppers because of the plant’s size.

Sterilize blades with a solution of one part chlorine bleach and one part water both before beginning and between each cut to prevent introducing disease. (This is plant surgery, after all.)

Your photo doesn’t seem to depict any dead or diseased branches, but if there are any, remove them first, cutting back to the main stem or to a healthy, living stem.

To reduce the size of the plant, cut each branch back to the desired length, making your cuts lower down on each branch, just above a leaf. Plan your cuts before making them to ensure you maintain a pleasant shape.

Good luck!

DEAR JESSICA: I planted all different irises, but year after year, I am getting plenty of green shoots but not many flowers.

— Lynne Denis, East Moriches

DEAR LYNNE: After confirming with you that your irises are the German bearded species, I can advise you that there are several factors that can diminish their blooming. The first is crowding; German irises should be divided every three years or so. Other causes can be too little sun, too little water or too much nitrogen, which could be the case if they are planted in or near a lawn that is regularly fertilized.

If you haven’t divided them in more than three years, do so after the (albeit diminished) blooming period this year. Simply dig them up and cut the root section in half, thirds or quarters, depending on their size. Just ensure there are leaves attached to the top of each root section. Then replant elsewhere, taking care to maintain the same depth. Planting too deeply also can result in diminished blooming.