I planted a climbing hydrangea at the back of a raised flower bed several years ago. After a slow start is has done well, but now its roots are coming up to the surface of the soil (to seek water, presumably). I find it hard to dig holes in order to plant other things in the bed. I have chopped out the offending roots and replaced the soil a couple of times, but the same thing keeps happening. Should I give up and plant shallow-rooted annuals in the bed?
Judy Kerley, via email You mention that the hydrangea is in a “raised bed”. I smell a rat: raised on what? If, as I suspect, the bed was originally constructed by putting timber or bricks straight onto a solid, impermeable base, the potentially whopping, far-ranging roots of the hydrangea, unable to go deeply downwards to seek water, will have simply run out of space.
If this is the case, I would give up hacking about trying to get other plants established – plants that will anyway compete with the hydrangea for what little root space and water there is. The best thing you can do, I think, is to cover the bed with cobbles or bark, and if you need colour, simply stand substantial pots of plants on top of them. By keeping the pots well watered, you will be indirectly watering the hydrangea, and furthermore the cobbles or bark will help to retain moisture around its roots.
This will only be a medium-term solution, however, and I suspect the hydrangea will eventually complain and fail to thrive. But I hope your problem will catch the eye of other readers wanting to grow large climbers in pots or other confined spaces.
Wall-covering woodystemmed climbers (such as your hydrangea), need as much space underground in which to spread their roots as the amount of space you expect them to cover above it.
Annual climbers – sweet peas, ipomoea (morning glory) – and smaller clematis or any other skinny-stemmed herbaceous perennial climber, can cope with limited root space as long as they are otherwise pampered. two of my conservatory plants, a plumbago and winter- flowering jasmine. Then I also noticed small holes in their foliage. Investigation revealed small caterpillars inside the leaf rolls. What are they and how can I control them?
Marta Hayes, via email I have no idea which particular small moth or moths are responsible for the munching and leaf-rolling caterpillars. Maybe an eagle-eyed lepidopterist will feel compelled to enlighten me. Although, in fact, the precise identity of the perpetrator is not crucial to the resolution of the problem in this case.
I am presuming that you put these two plants outside for the summer (which they both appreciate) and that they probably brought in “passengers” when you returned them to their winter quarters. This is often how indoor plants become pest-ridden. The moths would have laid eggs on the undersides of leaves that would have quickly hatched in the comfortable warmth of the conservatory, with no natural predators to control them. A first generation of tiny caterpillars would have then thrived out of sight for a while before growing up to do visible damage to leaves. Having gorged themselves, they then roll up inside the leaf to pupate, then hatch out as a moth. A new generation of moths is probably doing its stuff around your conservatory now – almost certainly nocturnal, very small and probably totally nondescript.
To control caterpillars, if the problem becomes unacceptably disfiguring, indoor gardeners have to take on the slightly nasty role of unnatural predators. Pick off caterpillars by hand and destroy on a daily basis every curled-up leaf in an attempt to stop the emergence of the next generation.
The jasmine will probably flower perfectly well despite the minor infestation. The plumbago will presumably have much of its top growth cut back shortly – a routine annual maintenance job – thereby washing, in a good way (to use a slightly inappropriate metaphor that somehow sprang to mind), the babies out with the bathwater.
Winter winner: Daphne odora ‘Aureomarginata’