Thompson & Morgan Facebook Q&A Session 27th January - Your horticultural questions answered.

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Name: Darran Bird

Question: Can sue please advise me on my wisteria, I have a tree formed 10 year old specimen in a huge 3ft pot, last year it didn't flower, I'm worried it won't this year either - any advise much appreciated. It did flower in previous years.

Answer: Hi Darran. There are several reasons why wisterias can fail to flower. Summer drought is often a cause, and containerised plants are particularly susceptible. Make sure that you keep your wisteria well watered from July to September as this is when the flower buds for the following spring begin to develop. I have a wisteria myself (although not in a container) and I was astonished at how well it bloomed after I started to give it supplementary water during the summer months. I would also recommend an occasional high potash feed which will encourage flower bud development too.

The other main cause of poor flowering is incorrect pruning. In winter you should cut back the sideshoots to within two or three buds from where they join the main branches. These will form flowering spurs that will bear this year’s flowers. You can get on and do this now. In summer, tie in the main branches to their supports. Two months after flowering, cut back the sideshoots to about 6 buds from the main branches. With proper pruning and extra water your wisteria should begin to flower again.

Name: Gill Le Fevre

Question: Question for Sue: I have a fruit bed with summer and autumn fruiting raspberries. Last year I didn't stay on top of maintenance so I haven't cut down the right canes at the right time. What's the best way to tell the difference when I'm tidying up?

Answer: Hi Gill. The easiest way to tell them apart is to wait until they fruit. The main distinguishing features of Autumn fruiting varieties is that they will fruit over a long period from August to October, or even into November. They will produce fruit all the way up the cane and not just at the tops. But, of course you won’t see this until they start to fruit!

I appreciate that you want to crack on and get your garden tidied now, so try taking a good look at the general growth habit - you may notice a difference. Autumn fruiting raspberries tend to be more self supporting than summer fruiting varieties with shorter, stiffer, more upright growth. In contrast, summer fruiting varieties have more lax, sprawling growth. If you have trained some of your raspberries onto a post and wire framework in the past, then these are likely to be the summer fruiting ones.

If all else fails, you can prune all of your raspberry canes back to 7cm (3") above ground level in February. This does, of course, mean that you will miss out on this years crop from your summer fruiting canes, but the autumn ones should certainly fruit this year. Once you have worked out which is which, be sure to make a note for next year. Best of luck Gill.

Name: Gill Le Fevre

Question: I have many more grass clippings for my compost than other waste - is there a way to make them rot down better or should I throw away the surplus?

Answer: This is a really common problem. Grass clippings are very high in nitrogen and have a high water content which can cause the compost to become slimy and smelly (usually and strong ammonia smell). You can overcome this problem by adding it to your heap in thin layers, interspersed with layers of torn up cardboard or screwed up pages of damp newspaper. This adds more carbon and air pockets to the heap which will improve the compost dramatically.

You can use grass clippings as mulch around your borders and vegetable plot to help keep the soil moist during the summer months, but this can look a little unsightly and should only be used in moderation. They can also be added to bean trenches in autumn to feed your beans the following year. If you collect autumn leaves for leaf mould then you can also add some grass clippings to your leaf mould bin/ bags in the summer, to speed up decomposition. Just make sure that you mix it in thoroughly.

Alternatively you can look into a mulch attachment for your mower which would chop the clippings into much finer pieces that can be left on the lawn to decompose. The main rule when using this technique is that you should not cut more than a third of the length of the blades of grass at a time. If all else fails, most councils will have a recycling facility for green waste. Hope that gives you some ideas Gill.

Name: Gill Le Fevre

Question: My vegetable garden has slightly raised beds separated from gravel paths by boards - if I used weed-killer on the paths would it seep into the beds and damage/kill the plants?

Answer: It depends entirely on what type of weedkiller you are using. If it is a residual weedkiller then it will persist in the soil for weeks or even months and may damage any surrounding plants within close proximity. You will find that many path and patio weedkillers are residual in order to provide long term weed control.

Instead, choose a non residual contact or systemic herbicide. (It will tell you this information on the product label.) Contact herbicides act by scorching the top growth of plants and are ideal for killing annuals. A systemic herbicide is more suitable for deep rooted perennial weeds. When it is applied to the foliage of the plant, the active ingredients are moved through the plant to the roots, which will then die off. Whether you use a contact or systemic herbicide, I would recommend that you apply it on a still day so that the chemical does not drift on the breeze and damage your plants. A simple method of protecting you plants is to ask a friend to hold a board in front of your plants while you are spraying. This will shield them from coming into contact with the chemical.

Name: Anna Mason

Question: I have just successfully germinated some Antirrhinum and Begonia Seeds - so tiny I had to ensure I didn’t sneeze. Can you recommend the best mixture for pricking out? I was intending to put into small individual cells and then move up to larger pots when they are established as I often find that not all survive so I waste compost.Maybe some fool proof tips please as this is often the point at which I lose half my seedlings.

Answer: Hi Anna. It’s good to hear your begonias and Antirrhinums are coming along - small seeds can be quite tricky!! Before you prick them out, you should check one or two individual seedlings first to see how much root they have - don’t be in a hurry to prick them out until their roots are well developed. Depending on the species, this may not be until another 2 months after germination. Plants grown from very fine seed often need a little more patience than larger seeded species. Your patience will be rewarded, because you are likely to have a higher survival rate if the plants have better root systems!

Always choose a good quality, free draining compost. I would recommend John Innes No. 1 potting compost. You can add some perlite to improve drainage if you like, but this isn’t essential. Given that your Begonias will still be quite small, you may find it preferable to prick them out into rows in a deep seed tray rather than individual pots. This will save you a lot of compost and save space in the greenhouse too. You can transplant them again later on into individual 7cm (3") pots when they have put on more growth and are a little more robust.

When dealing with seedlings it is always important to be meticulous about hygiene - use fresh compost, thoroughly clean seed trays, and water with tap water instead of rainwater. Careful watering is absolutely essential. It is always better to water sparingly and keep the compost just moist. Small seedlings are particularly susceptible to damping off in wet compost, so always let the compost dry out slightly between watering. Take care to keep them away from cold chills too. With patience and careful watering, I’m sure that you will have a better success rate. Let us know how you get on, Anna.

Name: Jackie Mason

Question: Hi Sue, I have sedums which get very 'leggy'. I was told that early in the season I should cut down the new growth - the next stems would then be more sturdy? Is this right?

Answer: Hi Jackie. That is correct. You can cut back the old stems and foliage of your sedums to just above ground level and they will produce plenty of fresh new growth this summer.

Name: Wendy Moss

Question: Hi T&M.; I have a big indoor 'money plant' which had this year become very sticky on the leaves, almost like sap. I cannot see any pests. Any thoughts?

Answer: Hi Wendy. It’s hard to say what the problem is without seeing the problem first hand. However, the most likely cause is one of the common houseplant pests such as mealybug, aphid or scale. These insects all feed on the sap of the plant and secrete honeydew which makes the foliage sticky. Unfortunately houseplants are particularly prone to this type of infestation as the warm conditions indoors provide ideal breeding conditions all year round.

Take a really close look at the stems, particularly around the leaf axils, and check the undersides of the leaves - these pests can often be minute and a magnifying glass can be a really useful tool when looking for them. On smaller plants it is often possible to diminish these pests by wiping the foliage and stems with an insecticidal soap or a weak solution of washing up liquid. I you discover scale insects then these can often be scraped off of stems and foliage with your fingernail. However on larger plants it may be more practical to spray with an appropriate insecticide.

Name: Lesley Gilbert

Question: Please can you advise as to how easy/difficult it is to grow Cavolo Nero vegetable on an allotment in the South East.

Answer: Hi Lesley. Cavolo Nero is a type of Kale, and like most Brassicas is really very hardy. The flavour actually improves once the leaves have been frosted. You should have no trouble growing it in the South East, and it is perfect for allotments as it is very resistant to pests and diseases and requires little aftercare. It is best grown in a sunny, open position on soil that as enriched with plenty of manure in the previous year. Good luck with your crop, Lesley.