Q: I have an overgrown thuja with heathers growing underneath, which have become leggy. These are situated in a raised bed surrounding my patio, and provide a screen to the raised patio. What shall I plant instead and at what time of the year? UC, Co Limerick
A: I’m not sure whether you want to replace your thuja hedge and heathers because you think they’re past the point of salvation, or because you’ve grown tired of them and fancy a change. If it’s the former, then it’s worth cutting this coniferous hedge back hard in stages to see if it can be successfully reshaped and resized, starting with the top of it at the beginning of September, followed by one side next spring and then the other side next September. But I’d suggest scrapping the heathers as they sound too far gone.
If you want to replace your thuja hedge with something different, then the big challenge you face is removing the existing hedge along with as much of its dense root system as you can safely excavate from the ground without damaging both your raised bed and your patio. Although thujas aren’t generally very deep-rooting, you’ll need to proceed carefully and slowly.
Suitable hardy evergreen alternative hedging species that will give you year-round shelter and privacy, and also tolerate regular clipping to keep them neat include Portuguese laurel (Prunus lusitanica) and yew (Taxus baccata). When grown well and properly pruned to encourage a dense, bushy network of branches, handsome deciduous hedges such as hornbeam (Carpinus betula) and beech (Fagus sylvatica) can also offer great shelter all year round, and are well worth considering. Both keep their dead leaves over winter, which offers further protection.
If you do decide to replace your hedge, make sure to revitalise the tired, spent soil before replanting by working in plenty of home-made garden compost or some well-rotted manure fertiliser. I’d also suggest that you avoid underplanting it as any new hedge will quickly outcompete nearby plants in its need for nutrients, water and light.
[ The dangers, and health benefits, of gardeningOpens in new window ]
The optimum time of year for planting a hedge depends upon the species that you choose, the type of plant (container-grown, root-ball or bare root) as well as the weather and soil conditions. As a general rule, deciduous species are best planted in mid-autumn to late winter during the bare-root season (but hold off if the ground is badly waterlogged or frozen) while evergreen hedges are best planted in early autumn.
