Rooty prob­lem

The Daily Telegraph - Gardening - - Front Page -

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’

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