A bare run of my south-facing brick wall is now a full green, berry-heavy panel, and one Mohave firethorn did all of it in a few seasons. I planted a single whip at the base of that wall with nothing else around it. The first year its new shoots stretched out past two feet, and I tied them flat along the brick as they came. That speed is the short answer on firethorn growth rate. Yes, firethorn is fast growing. The second year side branches broke out and fanned up toward the gutter line. By the third autumn the whole espalier was packed with orange berries from end to end.
This is one of the reasons you might plant a fast growing pyracantha in the first place. You get a real screen or a covered wall in two or three years instead of waiting most of a decade. New canes shoot up long and whippy, and they keep coming through spring and summer. If you have a fence to hide or a corner to fill, this shrub does it on your timeline, not the slow one most plants force on you.
The speed is not random. Three things drive it, and you control all three when you choose the spot. Get them right and your plant runs. Get them wrong and it sulks in the shade with thin, stretched growth and few berries.
Good light and open room matter most, so give your firethorn the sunniest wall or border you have. Soil fertility is the third lever, and it surprises people. Plant firethorn in very rich ground and it pushes out soft, leafy growth even faster. You might think more speed is always better here. It is not. Soft new growth raises fire blight risk, and a plant racing into leaf tends to set fewer berries. You can grow your shrub too fast for its own good, and then you spend the next year cutting out blackened, blighted shoots.
The published numbers back up the firethorn growth rate I saw on my own wall. Clemson reports that the shrub "grows very fast." It can add more than 2 feet (0.6 m) a year, in their words. That matches the long shoots I tied in during my first season. NC State rates its growth rate as rapid too. So you are not looking at one lucky plant on my brick. This is how firethorn behaves across the board once it has sun and space to work with.
Put that vigor to work for you. Firethorn fills a gap faster than almost any thorny shrub you could pick for a security hedge or a covered fence. Space your young plants about two to three feet apart and they knit together within a couple of seasons. You end up with a dense, spiny barrier that nothing wants to climb through. The same pyracantha growth speed that covers your wall, though, will swallow a path or a window if you turn your back on it.
So plan to prune from day one. Cut your firethorn back once or twice a year, after it flowers and again in late summer, to hold the shape you want. Pruning also steers the berries onto older wood where they show best. Skip the heavy feeding and the rich soil amendments while you are at it. Plain, decent ground gives you strong canes, good berry set, and far less disease than a plant you have pushed into rampant, soft growth. Use the speed to your advantage, then keep your shears handy and your plant will reward you for years.
Read the full article: Firethorn Shrub Care, Berries and Cultivars
