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

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Name: Sam Risdale

Question: whats a good fairly fast growing tall plant that I could put in a pot to screen a wall? south facing wall gets a lot of sun!

Answer: Hi Sam, the best choice of plants for this purpose are climbing plants and grasses. Annual plants include Petunia ‘Skytunia’, which can be trained to climb up and over a support and will quickly cover any surface with long-lasting colour. You could also try growing Geranium ‘Skyrocket’, which can reach 1.8m in height when trained on to a support.

Perennial plants include the climbing snail vine, which is a very fast grower in a sunny position. It will need winter protection though as it doesn’t tolerate frost. You could also grow clematis in pots - they are fairly fast growing. For something a little less tall but very attractive you could try Pennisetum setaceum ‘Fireworks’ .

If you have a large container you could try growing bamboo which is great for screening, although it will take a few years to attain a good height. For something more unusual you could grow beans on wigwams in pots. Both runner beans and French beans can be sown now and will quickly reach heights of two metres this summer; at the same time providing you with a fresh crop. I hope this gives you some ideas Sam, good luck!

Name: Anna French

Question: Hi, I bought some Lost Label roses about 2 weeks ago, only 2 of the six seem to be 'alive' and growing shoots the others seem to be dead :( I am not happy at all. Just wondering if the 2 that are growing will need some of the green shoots cutting back when they grow really long, I don't expect they will be producing any flowers this year, or will they? All advice is welcomed xx

Answer: Hi Anna, sorry to hear about your roses. You may well get a few flowers this year but probably not a prolific display. It’s best to leave the new growth and prune your roses in February next year, when growth starts again. When pruning your roses, cut out any diseased or dead shoots first. Cut the remaining strong shoots to about 15cm from the base, making the cut just above a bud. If there are any weaker shoots they can be pruned back more severely, leaving just a few buds remaining (normally about 5-10cm from the base). It’s also a good idea to feed your roses annually in the spring by scattering a slow-release fertiliser around the base of the plant and mulching with a 5cm layer of compost or well-rotted manure. This will ensure healthy foliage and flowers. I hope this helps Anna.

Name: Brian Cockburn

Question: Could you please tell me what is the best time of the year to divide my Polyanthus ?

Answer: Hi Brian, you can divide your Polyanthus any time between now and the autumn, provided they have finished flowering. Place the divisions in pots or a nursery bed in preparation for planting out in the autumn. Make sure you keep the compost moist, particularly during hot weather. You may find it easier to divide your Polyanthus in the autumn when the hot weather has passed. This way you won’t need to be so vigilant about watering, yet temperatures are still warm enough for the divisions to establish roots. Polyanthus are a lovely plant for dividing as they root very well! Best of luck Brian.

Name: Sarah Hacker

Question: Can you divide hardy geraniums now? They've got a bit out of hand.

Answer: Hi Sarah, it is a bit late to be dividing Geraniums as they won’t establish well in hot and dry conditions. If you can provide a constantly moist soil in a lightly shaded position you could divide them now but you would probably be better to wait until the autumn, when temperatures cool and there is more moisture. After your Geraniums have finished flowering you can keep them tidy by cutting the foliage back almost to ground level. This encourages fresh foliage and often a second flush of flowers later in the summer.

Name: Nicola Partridge

Question: What is the best method of taking clematis cuttings? Any tips?

Answer: Hi Nicola, now is a good time to take Clematis cuttings before the new stems become too woody and hard. Use clean tools and equipment to reduce the chance of disease on your cuttings. Make sure you choose non-flowering shoots to take cuttings from, and prune them off just above a bud. You can prune off a long shoot which can be cut into several pieces later on. Cuttings will eventually need to be 6-15cm long. It’s a good idea to place your cuttings in a plastic bag until you’re ready to use them as this retains moisture in the cutting material.

Start by preparing a pot or tray. Fill it with a mixture of 50% compost and 50% perlite (available in all good garden centres) for good drainage. When you trim your material to size, make a cut directly above a pair of leaves and another cut below, about mid-way between two leaf joints. Remember to aim for a cutting that is 6-15cm in length. Dip the bottom of your cuttings in rooting hormone powder and tap them to shake off the excess. If your clematis leaves are large it’s best to cut the leaves in half to reduce the amount of water loss. Insert your cuttings into the compost so the leaf joint is resting just above the soil. Cover them with a clear plastic bag or place in a propagator in a warm, bright place (keep them out of direct sunlight). Rooting normally takes place after 6-8 weeks but can take longer! Once you start to see lots of white roots appearing through the drainage holes it is safe to gently tip out the cuttings and pot them on. Don’t worry if a few cuttings don’t make it - this is quite normal, just remove any that have browned completely. Good luck Nicola, let us know how you get on.

Name: Anna Mason

Question: I want to make a gravel garden in a large clay pot what is the best mix?

Answer: Hi Anna. Gravel garden and alpine soils mixes need to be very free draining. I would suggest that you use equal parts of garden soil, peat, and sharp sand or grit. The peat or (peat free compost if you prefer to go peat free) provides organic matter that will help to retain sufficient moisture for the plants to grow. The sharp sand or grit will ensure that any excess moisture drains away. This is particularly important during the winter to prevent the soil sitting wet and causing the plants to rot. You could also add a top dressing of grit which will help to prevent soil moisture being lost through evaporation and also makes your plants look very smart! Best of luck with your gravel garden Anna.

Name: Sue Boniface

Question: I have a balcony which I cannot use as my neighbour objects to losing her privacy. I thought I would put some containers out there with some plants in to "hide behind". What size pot and plants (I can only think of bamboo) would be best, assume use John Innes no 3.

Answer: Hi Sue. What a shame that you can’t use your balcony! You could try bamboo but they may take a while to get to a size that you could hide behind! You are right in thinking that John Innes No.3 would be best. If this makes the container to heavy for the balcony then you can always use perlite to bulk up the compost without adding weight. You might want to consider some quick growing climbers trained onto trellis or obelisks. This would create some privacy for both yourself and your neighbour quite quickly. Try some of the large flowered clematis for summer colour or Jasmine  for its beautiful fragrance. If your balcony door is glazed I would recommend deciduous climbers as evergreens will block out valuable light in winter. I hope this gives you some ideas Sue.

Name: Judi McCafferty

Question: I have some lovely hellebores which have just gone over. Do I tie them up and stake them, or can I cut them back please?

Answer: Hi Judi. Hellebores are evergreen so it is best not to cut back all of the foliage simultaneously until it becomes really scrappy (usually in winter before they begin to flower). However you can certainly remove a few of the oldest leaves now without weakening the plant, and the faded flowers can also be cut back now if you don’t want to collect any seed.

Name: Karen Simpson

Question: I recently inherited a monarda from neighbours when they moved and unfortunately some strong winds over the last couple of days have damaged it quite badly, breaking many of the woody stems at soil level. Can I save them by using rooting hormone and potting them or are they lost for good?

Answer: What a shame Karen. But don’t worry; Monarda is perennial, so even if you have lost those stems for this year, it will still produce new growth for next year (though it might be worth staking the stems if windy weather threatens again). Monarda is best propagated from basal cuttings in spring if you are hoping to increase the plants about your garden. Although it is getting a little late in the year now, I would always recommend giving it a go - they may just surprise you!

Name: Jay Brogden

Question: I have a 5 year old pear tree and its covered in pear tree blister mite.. I am not sure what to sort this.. The tree is full of fruit and is doing well apart from this problem.

Answer: Hi Jay. Pearleaf Blister Mite can be a tricky problem as there are no chemicals available to gardeners for its control. The adults overwinter in the leaf buds and lay their eggs here in spring. The leaf blisters are caused by mites feeding on the developing leaves and these blisters are later colonised by mites until just before leaf fall in autumn, when they return to the buds to spend the winter months.The only real control option that you have is to interrupt that life cycle by picking off any infected leaves as soon as they are seen. Make sure that you destroy them to prevent infection recurring.

Name: Lorna Jane Morley-Medd

Question: Hi I've got a 10 year old bay tree in a large pot, and it has sudden;y developed a fungus on the stem and the leaves are all turning pale brown with spots on. Is there anything I can do to save it please? Thanks (can send pictures if needed).

Answer: Hi Lorna. The little white blobs that look like mould are actually scale insects. These little insects suck sap from the plant and causing a pale mottling to the leaves which eventually turn yellow and drop off. Such infestations can weaken the plant, and may even cause severe die back.

When scale insects first hatch they are quite mobile and crawl around the plant sucking sap until their hard scaly shells form, when they become firmly fixed to one spot. Males, females and juveniles may be present at the same time and they are particularly prevalent from May to August.The best way to control this is to target the young mobile insects using a systemic insecticide such as Provado Ultimate Bug Killer Concentrate or Scotts Bug Clear Ultra. A systemic insecticide is absorbed through the foliage and kills the scales as they feed. I would also cut any dead stems back to healthy growth to encourage the plant to rejuvenate. Hope that helps Lorna.