Thorny problems: how can I grow herbs outside the kitchen? Compost for herbs in the trough should be a mixture of soil-based John Innes No 3 with about 30 per cent multipurpose compost, which lightens it up a bit. The shrubby Mediterranean herbs that need perfect drainage in addition to sun would appreciate added grit. Compost in the containers should be topped up and generally revitalised every couple of years. Raining acorns This year our two tall oaks have produced an absolutely massive crop of acorns. I spent an hour yesterday (enjoyably in the sun) picking acorns from a large flower bed and the adjacent lawn. Am I going to spend next year digging out young oak trees? Also, if either of these trees were to come down in high wind, they would both reach our house. Should we have their crowns reduced? Jane Hampton, via email First, the danger, as you see it. Although healthy trees, especially oaks, don't have a tendency to topple, I suffer from the same insecurity and also excessive shade in my garden and, like you this year, a carpet of acorns. I therefore had the crown of my tree considerably reduced. You need to check there are no restrictions on them (for example, Tree Preservation Orders) and get the job done by a reputable tree surgeon. To find one go to the Arboricultural Association website (trees.org.uk). Pruned this winter, the tree will of course look rather strange next year, producing masses of twiggy growth that will alarmingly develop mildew in late summer. It will settle down subsequently. And the acorns? Inevitably you will encounter sprouted acorns around your garden next year, but if you pounce on them quickly they come out relatively easily. To minimise the problem, when the acorns and the weather are dry enough I use a blower (a delightful battery one) or a witches broom to roll them off the borders on to the grass. I then (noisily) mow them up with leaves and add to my leaf heaps. Nearly all are too damaged by the mower blades to germinate. There are cumbersome garden vac/shredders that will do the same job, of course. Help for nerines I have five bulbs of Nerine sarniensis bought in flower many years ago. Although they have consistently produced leaves, they have not flowered since. I now have them in a pot, but am not sure when to water them to encourage growth and when to allow them to lie dormant. Please advise - they are gorgeous and deserve to flourish. Clive Moorhead, via email I have never grown these particularly lovely spidery pink November "lilies." They are reputedly even more fussy than the more often seen Nerine bowdenii, which can flourish outdoors in Britain against a warm, south-facing wall. I phoned people in the know at Cotswold Garden Flowers (cgf.net) who confirmed that it would be risky to grow them in the ground in mainland Britain (as opposed, for example, to the slightly warmer Channel Islands from which they come). It is the combination of wet and cold that knobbles them. So you have done the right thing to put your bulbs in a pot, which should now be kept frost-free (but not centrally heated) for the winter and watered occasionally while in leaf. The bulbs should have their noses well above the level of the compost, which should be John Innes No 3 with a little added grit and laced with a slow release fertiliser. The leaves, now looking green and vigorous, will yellow and fade in the New Year, at which point the bulbs become dormant and should be kept quite dry: given just enough water to make sure the bulbs stay plump, but not enough to rot them. If they are put outside in a sunny spot, how you treat them depends on what kind of summer we have, but you will need to keep an eye on them and if necessary, during hot, dry weather, give them a good soak. Flower stems should show up in early autumn. After having had a bit of a rough ride, yours may take a year to adapt to life in their pots, but it is worth persevering. They will benefit from being repotted in fresh compost every couple of years. Book ahead... I should like to thank all those readers who wrote in with their suggestions of plants for late summer colour in the garden after I mentioned some of the stars in my own borders. A list of these would make perfect fodder, I feel, for the next volume (I can't believe I have just written those rather grand words) of Thorny Problems, for which I am compiling the "worst" of your more recent tales of woe. I can't believe, either, that it is three years since I went through the same process for volume one, which sold so well. If I get myself into gear, which of course I must, More Thorny Problems should hit the bookshops next April. Please, keep your problems flowing in. Any choice little nuggets about which I can try to be helpful in the next few weeks may even get included. Thud: muddy gauntlet, just thrown down. And finally... an audience You are cordially invited to the Telegraph offices on November 28 to join me, Helen "no question is too daft" Yemm, for an informal "live" Thorny Problems session. In addition to having your gardening conundrums answered, you will have the chance to take a tour of the Telegraph offices, and enjoy a glass of wine and a mince pie. It should be a lively horticultural warm-up to Christmas. Tickets cost £65. For more information, and to book, visit Garden Shop or call 0844 873 0789.