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Facebook Q&A Session 6th September 2013


Thompson & Morgan Facebook Q&A Session 6th September 2013 - Your horticultural questions answered.

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Name: Vivien Henderson

Question: Please can you tell me why my crystal apple cucumbers have no fruit only blind flowers? There are plenty of bees around to pollinate them. Vivien

Answer: Hi Vivien, as you say 'Crystal Apple' is an outdoor variety of cucumber which requires pollination. It’s worth checking the flowers to see which type are being produced. Cucurbits have a habit of producing flushes of male flowers and no female flowers, particularly when they’re first planted out. The female flowers will have a tiny baby cucumber beneath, at their base (probably round in this case) while males just have a plain stem. If your cucumbers are growing in a greenhouse, bees may have trouble finding the flowers, even with the windows open. Plants growing in the open are much more likely to be pollinated. It’s also worth checking the general health of your cucumber plants, they like a sunny and warm position in the garden and are quite greedy feeders so will need regular feeding with a high potassium fertiliser. You can try hand-pollinating your flowers - simply use the tip of a fine, soft paintbrush and dab it gently into a male flower before transferring the pollen to the centre of a female flower. Give the flowers a good dab to make sure enough pollen has been deposited on the stigmas. I hope this helps Vivien, do let us know if there is no further improvement.

Name: Jenny Tennet

Question: Acer planted in a pot. Growing well but sprouting high branches. Want it to grow more as a bushy shrub. How and when do I prune to encourage lower growth?

Answer: Hi Jenny, the best time to prune Japanese Maples is when they are dormant, from November to January, as they are prone to ‘bleeding’ if pruned at any other time of year. Simply identify the long branches you wish to remove and prune them out where they meet a side branch. This should encourage the tree to branch lower down and create a more shrub-like habit. I would also suggest giving it a good mulch of well-rotted organic matter in spring to feed it up after heavy pruning, to encourage new growth. Take care not to mound mulch up around the stem though. I hope this helps, best of luck.

Name: Jackie Nicholls

Question: My clematis leaves are going brown should I cut this back for the winter and when? Thank you.

Answer: Hi Jackie, some browning of the lower leaves of Clematis plants can happen when the plants have been stressed. We have had a hot, dry summer and Clematis plants don’t like dry soil, or open positions, preferring the soil to be deep, moist and shaded at the base. If environmental factors are the cause then it’s best to leave your clematis plant alone, pruning at the normal time, which is early spring for most summer-flowering Clematis, or straight after flowering for the winter and spring-flowering varieties. Take a look at our ‘How to Prune Clematis’ guide for more details. If the browning is occurring all over the plant it’s worth checking that your Clematis isn’t suffering from the fungal infection Clematis Wilt. Symptoms include wilting leaves and blackened leaf stems, which also wilt too. If stems show a black discolouration when cut open this is also a sign of the fungus. The remedy is to cut back all affected stems to healthy non-stained tissue, cutting back to ground level if necessary. The plant will regenerate from the base. Any infected plant material should be disposed of in household waste rather than composted. I hope this helps Jackie, best of luck.

Name: Paris Brookfield

Question: I have a hydrangea in my garden that hasn't flowered at all this year. We have had it for over 10 years and it stopped flowering a few years back but flowered last year. Please could you give me some advice as to what I am doing wrong, I have occasionally given it some food to see if that would help. The leaves are very green and other than it is not flowering but the plant looks healthy. We also have a Hibiscus that also hasn't flowered for a few years. Any advice would be appreciated.

Answer: Hi Paris, it’s worth looking at the environment your Hydrangea is growing in. Hydrangeas like a moist soil and a position in full sun or partial shade. Heavy shading will result in fewer flowers. Hibiscus plants need warmth and at least 6 hours of full sun to flower well. Is there perhaps a tree which has grown and is now casting shade? Incorrect pruning can also prevent flowering. If you have a mophead or lacecap Hydrangea (Hydrangea macrophylla) they don’t require pruning, but are often pruned lightly each spring for better flowering. Branches are pruned back by up to 30cm (12") to a pair of healthy fat buds, as these will produce flowering shoots. Pruning these types back to the base can prevent flowering for a few years as they only flower on mature wood. However, Hydrangea paniculata and Hydrangea arborescens can be cut back to a low framework of 25-60cm each spring, as they will flower on the current year’s growth. Hibiscus plants do produce flowers on the current season’s growth but mature plants will struggle if pruned too vigorously.

The flowering wood on mophead Hydrangeas can also be damaged by hard frosts - if badly damaged the plants will sprout from the base in spring and the old branches will suffer some dieback. A late spring frost can also damage the emerging flower buds, killing them before they have a chance to develop, although plants look otherwise healthy. It’s best to leave the spent flower heads on the plant over winter. It looks a little messy but the old flower heads help to provide a little protection against the stem tips being frosted. As your Hydrangea is mature you could try cutting a few of the oldest stems back to the base to help encourage vigorous new growth. I hope this gives you some ideas Paris, best of luck with your shrubs next year.

Name: Donald Chell

Question: I have a 7ft Christmas tree in my garden which I want to dig up and put in a large container. What would be the best way to go about it, and what would be the danger of losing it? Many thanks Don Chell

Answer: Hi Donald, Christmas trees are unfortunately not suited to container cultivation and can be very short-lived if grown this way. Most Christmas trees want to reach eventual heights of 20 metres or more and don’t like to have their large root systems constricted. If you have a Fraser Fir or Korean fir they are much smaller and will cope better with container cultivation. If you would still like to go ahead with this, do it in October when temperatures are cooler, to help the tree recover. Part-fill your container with a soil-based compost such as John Innes No.2 or 3. (better for long-term planting as multi-purpose composts break down quickly). To dig the tree up, give the trunk a wide berth and aim to lift a potential root ball diameter of about a third of the tree’s height. Dig a trench around the tree and gradually work around the root ball with a fork, easing soil away from the roots a little at a time. Finally, undercut the tree with a spade. Any large roots that cannot be lifted can be cleanly cut with a knife or saw. Re-plant quickly into the container, filling any air gaps with more compost and gently firming in. Water well. Make sure the tree is well watered during hot or dry weather. I hope this helps, best of luck.