Top 100 gardening questions answered

By Andy McIndoe

Top ten plant issues us get from 10 to 100 by posting queries on the blog!

I’ve been answering gardening questions and giving gardening advice for many years, on the radio, in garden centres, on garden tours and through magazines and newspapers. It’s amazing how often the same questions arise. It just shows that regardless of our gardening experience we all face the same challenges. I thought I would share my top 100 gardening questions with you; and of course my answers. Do feel free to add your questions at the end of this post and I’ll either add them to the list or tell you if they are coming up over the next few weeks. Here are the first ten of my top 100 gardening questions and answers.


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Q 1. Many of my daffodils failed to produce flowers last spring. Most have been in the garden for many years. Should I feed them and are they likely to bloom again next spring?

A. After afew years daffodil bulbs can become overcrowded, restricting their ability to grow and develop; this reduces or puts a stop to flower production. You could lift, divide, replant and feed, but it is probably more sensible to lift and dispose of the old bulbs and plant new ones. Daffodils and narcissi are an inexpensive commodity so you certainly get value for money if they last a few years.

Flower production can also be disappointing if the foliage has been cut down too early, or if it dies back quickly due to drought. The foliage needs last long enough to feed the bulbs ready for next year’s flowers.

Q2. I love lavenders and keep planting them in my garden but they rarely survive. Usually they thrive in the first summer and then deteriorate over winter; any suggestions?

A. Some lavenders are excellent long-term plants, and others are not quite as hardy as they might be. The best ones to choose for general planting are selections of Lavandula angustifolia with narrow silver-green leaves. ‘Hidcote’ and ‘Imperial Gem’, although they have been around for many years, are still the most reliable dark blue lavenders. If you are on heavy damp soil add plenty of grit and mulch the soil surface with coarse grit.

As soon as the flowers start to fade in late summer trim the plants back to just below the bottom of the flower stalk.

Q3. I planted a wisteria several years ago. It is in a sunny spot on the house wall and has grown vigorously but refuses to produce many flowers. How can I encourage a better display?

A. Wisterias fail to flower well for a number of reasons. Grafted plants which are propagated from selected free flowering cultivars are the most reliable. Seed raised plants are variable when it comes to flower production. However pruning has a big influence. You should prune twice a year, summer and winter. In summer shorten back the long new shoots to I5cm, 6inches. The resulting long, thin shoots are then pruned back in mid-winter to 2-3 buds.

Wisteria sinensis 2

Q4. What’s the difference between climbing and rambler roses?

A.Climbing roses are generally less vigorous and have larger flowers, more like hybrid tea, floribunda or shrub roses. Ramblers are usually stronger growing, larger plants that produce clusters of smaller flowers. Most climbing roses repeat flower, most ramblers bloom only once in early summer, however there are exceptions in both cases. Many climbers are climbing forms of bush roses, or just shrubs that are tall enough to train as a short climber.

Q5. What is the best safe method of controlling slugs and snails?

A. There are countless recommendations for controlling slugs and snails; probably the most despised but persistent garden pests. You can of course use nature friendly slug pellets; these are the ones without metaldehyde which should be avoided. To protect individual plants the pellets based on wool waste make an effective barrier. Some recommend beer which attracts the pests and they drown in it. Others say that wheat bran from the health food store is really effective;the pests basically overeat and it kills them. I have more snails than slugs and I find slate tiles in shaded positions, and stacks of old flowerpots are brilliant at attracting the snails. I the collect them and take them up the lane to a hedgerow where I hope the birds find them. I suspect they make their way back, but I feel better about it!  See also how to protect hostas from slugs and snails


Q6. I grew tulips in pots last year. When they had finished flowering they died down naturally and I have kept them in the pots over the summer. Should I repot them or feed them, and will they flower again next spring?

A. I never recommend that you grow tulips in pots for more than one year; normally they are very disappointing in the second year. It would be better to start with new bulbs. If your tulips are hardy single varieties: Darwin, triumph or single late they may well produce some flowers and can establish well if you transfer them to the open ground.

Q7. I was given a lovely Phalaenopsis; it bloomed beautifully and produced side branches with more flower buds. Recently these have been dropping off the plant without opening. What has caused this?

A. Bud drop is nearly always caused by either overwatering or temperature variation. If your plant has been on a windowsill where it gets warm in the day, and then is cold at night when the curtains are drawn, it may drop its buds, especially if the compost is too wet. Either leave the curtains open at night, or move the plant onto a table near a window and keep it there all the time.

Usually the label warns against direct sunlight. This is usually only harmful in scorching weather in summer; you must make sure that your plant has enough light, otherwise it will not flower. The best way to water is to immerse the pot in a bowl of room temperature water once a week until it stops bubbling. Then drain thoroughly before replacing in a pot cover. If the compost is too dry both flowers and leaves tend to wilt; if too wet the roots suffer and the buds drop. See more about caring for orchids here


Q8. I have a black sooty deposit all over the leaves of my camellia. I’ve tried spraying with a fungicide but I can’t get rid of it. What is it and what’s the solution?

A. This is sooty mould and it’s common on camellias and other evergreens with thick, leathery leaves. It is caused by an insect pest, brown scale, on the underside of the leaf. These creatures usually lie along the midrib so are well concealed. They secrete sticky honeydew that sticks to the leaf; the black sooty mould is a secondary infection on the secretion. It’s tricky to get rid of outdoors without a systemic insecticide. Once you clear the pest the sooty mould will be gradually washed away by rainfall. Insecticidal soap is available in the US and this is effective if you wash the foliage with it. In the UK some use a mild solution of soapflakes; I am not permitted to recommend this!

Q9. I had some agapanthus roots given to me a couple of years ago. They are planted in the garden and are growing happily and producing plenty of lush green foliage. How long will it be before they flower?

A. Agapanthus are natives of South Africa. They like a sunny position and free draining soil but they do need enough moisture in summer to thrive and flower successfully. Some are shier to flower than others. Leave them undisturbed and apply a high potash general fertiliser in early spring. Water generously during any dry spells in the summer. If they fail to flower in the next two seasons transfer them to a pot on a sunny patio, the root restriction imposed by the pot works wonders. If you are in a colder area it is easy to move the pot to a sheltered position during the winter.

Those in colder areas will have more success with the cultivars bred for their growing conditions such as Agapanthus ‘Headbourne Hybrids’

Agapanthus 'Headbourne Hybrids'

Q: I have a number of Hellebores in the garden. Should I cut off the leaves in winter or leave them alone until the new shoots appear next spring.

A: It is really only Helleborus x hybridus (varieties of Helleborus orientalis) that you remove the leaves from before the plants flower. Personally I leave the leaves in place until late winter, when the buds start to poke through the soil surface. Then I cut back the leaves to ground level and mulch the plants with multi-purpose compost. This gives a nice clean, dark background to show off the flowers. I would remove the leaves earlier if the start to show any signs of spotting on the leaves. This fungal disease can spread to the flowers; removing the leaves prevents this.

Helleborus x hybridus double

Don’t forget to post your questions below – I’ll attempt to answer them for you in future posts. Happy Gardening

Andy McIndoe

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