We have a huge old boxwood hedge, planted 40 odd years ago along the top edge of a stone wall. One end of it died this year and we carefully removed the dead branches. We cannot dig out the old roots and stems – they are too hard and thick. But there is very little room to plant a new boxwood. The hedge looks awful at this dead end, but the rest of the hedge looks healthy and glorious and we would truly miss it as one of the main features of our garden. Any advice about removing the old stems or planting a new box? Soil is sandy, well drained, and full sun. Thank you very much for your help in deciding what to do: our research turned up nothing helpful.
Do you know what might have caused the demise of a portion of your old hedge? It could well be that the boxwood died a normal death, some experts mention that boxwoods live around 20-30 years, although others note that boxwoods can live 40 years or more. My concern is that the hedge might have been attacked by a relatively recent and very unwelcome pest invader that has been attacking boxwoods – see Box Tree Moth: A Toronto Master Gardeners Garden Guide. I’d suggest that you inspect your boxwood carefully – if this is the culprit, the remaining (healthy) hedge is at risk. There are also other factors that can damage boxwoods – e.g., stress from drought, pests like the boxwood leaf miner, root/crown rot, winter injury, salt damage. See Michigan State University’s Browning of boxwood: Is it boxwood blight?, which discusses several of these factors. It’s important for you to be aware that whatever happened at the “dead end” of the hedge won’t be repeated or is not affecting the healthy hedge.
If it turns out that your hedge has not been under attack, you can plant a new boxwood (ideally of the same variety as the remaining healthy hedge) in the now bare spot. As you mention that the “dead end” looks awful, the available space must be at least a few feet long, so you may need two or more plants. The new boxwood(s) will need good, well-draining soil and room to grow in order to thrive, and should not have to compete with dead roots/stems. It is understandable that your old hedge has developed tough, gnarly roots over the years, making them difficult to remove – but it is important to do so. Landscape Ontario has a terrific list of landscaping companies, or perhaps someone at your local nursery could help you source a company that would remove the thick roots/stems. It’s important that the healthy roots/stems of the adjacent hedge that could be intertwined with the dead material remain intact as much as possible.
The spacing between plants depends on the eventual size of the new hedge. If you need more than one plant, avoid planting them too close to one another, and to the remaining healthy hedge. Air circulation is important to promote good plant health and avoid fungal and other diseases, and you should not crowd their shallow root systems. Before planting the new plant(s), trim the adjacent edge of the healthy hedge of any dead/dying branches.
All the best with your lovely hedge!