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Photinia Red Robin is one of those plants that you don’t have to worry that you’ll over prune. I usually recommend that you regularly prune photinia to keep it to the shape and height that you want. And also to stop the unpleasantly scented white flowers from blooming or to prune back a photinia that has been badly infected with black spot disease as discussed here.
Why prune photinia Red Robin?
This shrub grows very actively, often increasing 30cm (1ft) or more in height in a single growing season. This is matched by a growth in width. Without pruning, photinia can become straggly and leggy. Within eight to ten years, the bush can reach 5m wide and high. In addition, pruning ensures that good air flow circulates through the bush which I have found reduced the chances of getting black spot and mildew. Photinia responds well to fairly aggressive cutting by growing healthier and faster, and producing more of the stunning red shoots. I personally have a very long photinia red robin hedge and it does amazingly well and is pruned once or twice a year.
When to prune photinia Red Robin?
The best time to prune photinia Red Robin is between March and mid-July. However, give new plants a chance to grow and settle in for a few years before you start cutting them. The only time I would say prune young plants is if you buy them and there long and leggy, cutting them back about half will encourage them to bush out and make better plants.
Pruning encourages new shoots to grow and they’re quite delicate at first. Pruning after July means that you may damage these shoots as you cut bits off the shrub. And pruning in autumn leaves the plant susceptible to any early frosts that may occur and I think could increase the chances of getting leaf spot, something you want to avoid. However, you can prune after flowering occurs (usually in early July) if you really don’t like the smell of the flowers.
How to prune photinia Red Robin?
As i’ve said, give young plants a few years before you approach them with the pruning shears unless there leggy.
As always, sterilise your pruning shears or clippers first. This is especially important if you discover something on the leaves and stems that could be a disease or a pest.
Remove long scanty branches and any that are out of place. Consider how crowded the inside of the photinia is. Then take out some branches to restore good air circulation as this will help prevent diseases. These are hardy plants and it’s difficult to overprune them so don’t worry too much.
If your photinia Red Robin is really out of control, I would recommend pruning it back to around 60cm (2ft) above the ground. Do this in May at the start of the growing season when the plant is at its strongest. This encourages new growth during the summer.
What if something doesn’t look quite right?
When you’re paying this much attention to your photinia shrub you may notice that something’s a bit off. Maybe some of the leaves have spots on them or the stems appear a bit soft. My article Photinia Pests and Diseases goes into details about what causes the ill-health of photinia plants and gives solutions to the problems.