I’ve been answering gardeners’ questions for quite a number of years on BBC Radio Solent. Gardeners’ Questions Hour is now part of ‘The Goodlife’ with Georgina Windsor
Over the years I’ve learnt so much from Solent gardeners. There’s no better way to broaden your gardening knowledge than to listen to other gardeners’ challenges and attempt to advise them. Some questions come up time and time again, however there are always new challenges and different answers. That’s the wonderful thing about gardening; there is never just one right or wrong way to do anything, and rules are often made to be broken. Here are a few more of my top 100 gardening questions and my answers. Do add your opinions and questions on the end of the blog.
Q 1. I have a number of dahlias in the garden that have been lovely through summer and autumn. Should I lift them and store them over winter? If so, how do I go about it; the foliage looks as if has now been hit by frost.
A. Traditionally dahlias are lifted in the autumn when the first frost has knocked down the foliage. They are not frost hardy, so you need to dig them up, cut off the fleshy stems leaving a few centimetres above the tuber and then turn them upside down and put them in a cool dry place. When they have dried off dust with sulphur powder (acts as a fungicide) and store them in dry sand or compost until next spring. A frost free garage is the ideal place.
However in milder areas gardeners increasingly leave dahlias in the ground over winter. You can help to protect them by heaping chipped bark or any other mulch over the planting position. Just watch out for slugs and other pests when the new shoots emerge in spring.
Q 2. I have two lovely roses in pots that were fantastic in early summer but have gradually looked more tired as the year progressed. They have had some blackspot and produced only a few flowers in the autumn. What do I do now? When should I cut them back, and would it be a good idea to repot them?
A. Most roses grow well in pots in loam-based compost, but you do still need to feed them twice a year with rose fertiliser. I suspect your roses have just run low on nutrients in the second part of the season. This makes them more susceptible to disease. In autumn just tidy the plants and remove any diseased foliage. Prune in mid to late winter. If these are shrub or English roses prune lightly, cutting back by no more than one third. I have Rosa ‘Grace’ in a pot an that’s how I treat it.
You do not need to repot, however you should scrape away the surface of the compost in late winter or early spring. Add a handful of rose fertiliser and top up with fresh loam-based compost. This boosts the nutrient content and gets rid of any fungal spores lingering on the compost surface. Remember to feed again midsummer and keep the plants well-watered.
Q3 . I have an old privet hedge in the garden which appears to be dying in patches. Areas are thin and weak and have failed to produce new growth. Could this be due to honey fungus; I can’t find any trace of the toadstools or black boot laces in the ground. If I remove it what should I replace it with?
A. Privet, Ligustrum ovalifolium, is often associated with honey fungus so whenever a hedge shows signs of dying it is often attributed to honey fungus. However the more likely cause is just old age and starvation. Remember all those shrubs are in competition in a hedge and eventually the ground beneath becomes very poor an starved. This means the weaker plants succumb and die.
Firstly I would try rejuvenating the hedge by feeding with a slow release fertiliser and mulching with well-rotted manure or garden compost. Cutting back weak areas of the hedge will also help. If this does not work consider replacing sections of the hedge. Osmanthus x burkwoodii is a good alternative which would sit well alongside the privet. This osmanthus has good dark green foliage and fragrant white flowers in spring. If clipped lightly from an early age it will produce dense, bushy growth.
Q 4. I was given some lovely apples a few years ago and I planted some of the pips. I got one young apple tree from them which I’ve grown on and has now produced fruit. Although the apples are good they don’t seem to be anything like the apples I got the pip from. Is that due to my soil or the way that I’m growing it?
A. The difference is down to seedling variation. Offspring raised from seed vary and do not necessarily have the same characteristics as the parent plant, in fact they can be very different. Named varieties, or cultivars cab only be propagated vegetatively; in other words by cuttings, grafting, budding or micro-propagation. This ensures that the offspring are identical to the individual. In other words ever Apple ‘Cox’s Orange Pippin is derived from a single plant that was selected and given that name.
The other factor that will influence the growth habit and possibly the fruiting is that your plant is a seedling growing on its own roots. Apples and other top fruit are usually budded onto a rootstock which imparts certain uniform characteristics to the plants.
Q5. I’ve had a really good crop of tomatoes in my greenhouse this year, but they were late. As a result I have a lot of unripe green tomatoes. It’s now too cold in the greenhouse and the plants are on their way out. I’ve picked the green tomatoes and brought them indoors. Will they ripen?
A.Some of the more mature green fruit will ripen after picking. What you need is a cardboard box with a lid or an empty draw. Line it with newspaper and spread out the fruit – ideally preventing the individual fruits from touching. Close the lid or the draw.
Ripening fruit gives off ethylene which accelerates the ripening process. Containing the ethylene in this way increases the concentration of the ripening gas and hastens the process. You will get much better results with this method than you will spreading the tomatoes out along a sunny windowsill; this usually causes them to lose water and shrivel.
Q6. I have fig tree in the garden which has grown vigorously and is now getting too big for its position. When is the best time to prune it? Also there are lots of small fruits on the branches this autumn. Will these continue to grow and develop into fruit next year?
A.The harder you prune a fig, the more vigorously it will grow. You may be able to restrict its growth by root pruning: cutting a circle around the plant about 90cm, 3ft from the main stem using a spade to the depth of the head of the spade. If you need to remove branches then take these out altogether to the base. Then, if possible, bend over branches and anchor them rather than cutting back. This encourages side shoots which produce more fruit. Weighing the branches by tying them on to heavy stones looks best and works effectively.
If a fig has small fruits in autumn, and you are in an area that gets frost, it is better to remove all embryo fruits that are bigger than a pinhead in early spring. Those that have been there over winter will be damaged and will fail to develop but their presence can hinder the development of new fruits which will grow through the year to maturity.
Q7. I planted a plum tree in my new garden two years ago. It produced quite a few plums this year which weighed down the branches. I now need to prune it to cut back some of the long shoots that it has produced. Do I do this when the leaves have fallen in winter?
A. No. Plums should only be pruned when they are in full leaf. Pruning in winter often results in disease spreading through the tree and can cause die-back and even death. The best time to prune is mid to late summer. Shorten back the long growth that has been produced earlier that year. If you need to remove larger branches or ones that are fruiting do this as soon as you have harvested the fruit.
Q8. We have just taken on a garden with very heavy clay soil. It is sticky and difficult to dig and drains badly when it rains. What’s the best way to improve it? I’m not expecting miracles; I just want to be able to garden!
A.In defence of your clay soil it is worth remembering that it is very fertile. Clay soils are made up of small mineral particles which are good at hanging on to water and nutrients. They are also solid enough to support plants which do not make a good rootball; roses for example.
Autumn and winter is a good time to tackle soil improvement, particularly if you are in a part of the world that gets frost. If ground is unplanted then rough digging and letting the frost get to work helps to break up the heavy slabs of soil. This is more effective if you rough dig and spread coarse grit and well-rotted manure, or good garden compost over the ground. Grit and organic matter is very effective and you cannot overdo the organic matter on this type of soil.
The other thing that makes a difference is liming the ground and this is particularly beneficial on vegetable plots. Most vegetables grow better in alkaline conditions, but the real benefit is how lime makes the clay particles stick together to make larger particles. This promotes a more open soil structure.
Q9. How do you go about pruning climbing and rambler roses? What’s the right time of the year to do it and are they pruned in different ways?
A. Climbing roses are pruned more lightly than ramblers to encourage side shoots that produce flowers; main pruning is usually done in winter. Ramblers can be pruned as soon as the flowers fade, cutting out some of the stems that have flowered to allow new shoots to develop that will flower the following season.
If possible the stems of climbing roses should be bent over and trained horizontally to encourage side shoots to grow, these produce the flowers and summer and winter pruned accordingly. Vigorous rambler roses that grow through trees, over buildings and pergolas are rarely pruned; they are just left to grow.
Q10. How can I keep my cordyline through the winter? I seem to replace the ones I grow in pots every year due to frost and snow damage. I’ve tried covering them with polythene but they still die.
A.It is nearly always the growing tips of cordylines that succumb to frost damage in winter. Covering them in polythene is not a good idea because it traps moisture which then freezes and causes more damage. The best protection is horticultural fleece. With a cordyline the best way to treat it is to gather the leaves together before severe weather and tie them loosely together with one of the plant’s leaves or an old nylon stocking or a strip of fleece. Then slip a heavyweight fleece plant protection sleeve over the plant until the weather warms up. If you cannot get hold of the sleeves, loosely wrap two or three layers of fleece around the tied up plant and secure as you have the leaves.
Please do add any of your questions on the bottom of the blog and I’ll get to them next time.
Listen to ‘The Goodlife’ on line at http://www.bbc.co.uk/programmes/p002tzfg