Q: The soil in my flower beds is very poor, and is clogged with roots of ivy and invasive climbers and brambles from the home’s previous owners. However, I don’t want to dig up the entire beds as I now have plenty of plants I like growing in the space. If I dig in grit and compost to improve the soil will I damage the roots of my newer plants? Or is the only solution to take up all the plants and start again with better soil?
A: The tricky thing here is that you’re grappling with two quite separate problems, one of which is the challenging issue of stubborn shrubby and perennial weeds while the second is the poor quality of the soil itself. Adding lots of home-made garden compost, well-rotted manure, leaf mould or any of the great commercial Irish products available (see mulch.ie; envirogrind.ie; geeup.ie) as a generous mulch to the surface of the soil will help a lot with the latter by adding organic matter, boosting earthworm and beneficial soil microbial activity, improving soil structure and bolstering soil health while simultaneously helping to replenish lost nutrients.
This in turn will also make it easier to dig out any troublesome weeds. You don’t have to dig in these kinds of organic mulches as the worms and soil microbes will do a good job of gradually integrating them into the ground for you. And if your soil is sticky and inclines to winter-wet, then yes, adding some horticultural grit (not to be confused with builder’s sand) will also help to make it more porous and free-draining.
But (and it’s a big but), brilliant as these soil amendments are, they won’t solve your weed problem as the weeds you’ve mentioned are woody or perennial species with deep, persistent root systems. Instead, you’ll have to cut these right back to the ground and then dig out as much of their roots as possible using a sharp secateurs and a garden fork and spade. This is going to be a slow, tedious job, especially as you’ll need to avoid accidentally damaging the root systems of the plants you want to keep. You’ll almost certainly have to go at it several times over the course of the coming year, keeping a watchful eye out for any new growth that emerges from any remaining root fragments still buried below ground.
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The alternative, as you say, is to lift all of the plants you want to keep, dig/fork the beds over thoroughly to remove any weeds and their persistent root systems, add some well-rotted organic matter and good-quality top soil if required, replant (only after making sure that you’ve also thoroughly removed any weedy root systems possibly hiding in the root-balls of the plants you’re keeping), and then finish off with a weed-suppressing organic mulch.
Which is the better course of action? An awful lot depends on the size of the flower beds and the size and type of plants that you want to keep. Large, mature shrubs with big, deep root systems, for example, are notoriously difficult to lift and replant successfully, especially if you’re doing it by hand. My advice is to leave these in situ and work around them. But most perennials, herbs and ornamental grasses can be temporarily lifted at this time of year and stored on a sheet of strong black plastic, making it much easier to properly dig out any weeds’ root systems before replanting. Adding plenty of hardy, vigorous ground-cover plants will also help prevent weeds from recolonising your flowerbeds.
Another approach (if your garden has access) is to consider hiring a local landscaper with a small mini-digger to do the job for you? This might sound extravagant, but if it’s a large area then a mini-digger will make the arduous, time-consuming chore of lifting plants, digging out shrubby/woody weeds, spreading mulches and/or top soil and then replanting the area so much easier.
