Q. I have a hedge of pyracantha on the northeast corner of my property. It is 16 years old. It grows underneath three large pine trees. It does not get much sun. The soil, if you can call it that, is mostly just rocks. The plant is thinning and getting bare in the center. The top is still fairly green. The amount of berries in the winter has been decreasing. I dug around the roots as much as I could and amended the soil with Paydirt. I added about a cup of sulpher and some bone meal to the amended soil. I plan to add fertilizer in a couple of weeks. What more would you suggest? By the way, there is very little yellow on the leaves.
A. Pyracantha is in the Rose family and so it likes soils that are similar to fruit trees in the Rose family. This includes apples, pears, peaches, apricots and the like. It is also susceptible to some of the same problems as fruit trees in that family. It isn’t terribly fond of desert landscapes and rock mulch.
|Dwarf pyracantha in winter hedge sheared|
Without seeing it I am guessing it is a combination of light as you mentioned, lack of soil improvement, perhaps irrigation, maybe improper pruning and borer problems. Pyracantha needs a lot of sun but it is thin-barked so it sunburns easily if it’s canopy is open. Sunburn leads to borer problems. It is not a desert plant so it likes improved soils and wood mulches. It would like surface mulches made of wood that can decompose. Rock mulch will mineralize the soil over time and it does not like this.
|Pyracantha fruit in winter. Pyracantha or Firethorn is in the Rose family.|
Pruning is a little tricky but should result in shading any exposed trunk or major branches. From your description it sounds like it has been a hedge pruned; pruned with a hedge shears not pruners. It hedges nicely but I don't recommend this unless you plant it as a hedge. As far as borers, you would see the trunk or major limbs with bark coming off and some darkened areas because of sunburn. Borers can be active for a couple of years and cause no obvious visual damage. There is an insecticide you can apply to the soil that gives the plant season-long control of borers if it is a problem.
|Pyracantha in bloom in the spring|
So what to do? Check the irrigation and make sure it's getting enough water or increase the amount it gets. I would not increase how often but the amount it receives each time. Pull rocks away from the plant and put down 3 to 4 inches of compost and wood mulch. When pruning, be very careful you don’t open the canopy up too much which might allow sun burning the trunk and limbs. Fertilize once a year in the spring with a fertilizer formulated for flowering woody plants. You can substitute a rose fertilizer which will work. Apply a soil insecticide as soon as you start to see new growth. I hope this helps.
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