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Facebook Q&A Session 12th July 2013


Thompson & Morgan Facebook Q&A Session 12th July 2013 - Your horticultural questions answered.

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Name: Joy Gardner

Question: I have been inactive for several months and my garden has received minimal attention. During this period a garden adjacent to mine, & managed by the local authority, has produced masses of ivy that has now grown over & under the dividing fence and become a dreadful nuisance for me. I have approached the local authority concerned and request that they control the ivy but they replied that they could only use a strimmer as it is illegal to use any chemical deterrents. Can you advise how I might control this nuisance that has invaded all my garden including the lawn? I'm at my wits end!

Answer: Hi Joy, it is unfortunate when this happens and all you can do is to try and keep control of the plant growth on your side of the fence. Strong chemical herbicides such as Glyphosate or Vitax SBK Brushwood Killer aren’t always effective on ivy due to its glossy moisture-resistant leaves. Ivy is very resilient - if you decided to spray the ivy on your side of the fence, the plant would have many healthy new shoots on the council’s side in which to recover from. Ideally the entire plant would need spraying multiple times. You could try erecting a physical barrier at the base of your fence to prevent the ivy shoots creeping across the soil surface into your garden. This could be made of paving slabs turned on their side, wood, metal or relatively thick plastic. I would dig the barrier down to at least 15cm (6") to make absolutely sure it is effective. Any ivy coming through the sides or over the top of your fence will need regular pruning to prevent it taking root in your garden. I hope this helps Joy.

Name: Sarah Griffiths

Question: My tomato plants are nearly 5ft tall and have hardly produced any flowers/tomatoes, have trimmed them down to ensure growth on main stalks, am watering and feeding, any advice? Can hardly move in my greenhouse due to the jungle they are creating!

Answer: Hi Sarah, it’s normal in the UK for tomato plants to start producing flowers and fruit from July onwards. I find August and September the best months for flower and fruit production. Your tomato plants also look very lush and green which could be a sign that they are being slightly over-fertilised, or your fertiliser contains high levels of nitrates. Well-fed plants are more likely to put energy into leaf and stem growth at the expense of flowering. You could try easing off the fertiliser, making sure that when you do fertilise, you use one with a low nitrogen content such as Chempak Soluble Tomato Food. This tomato food also contains calcium and magnesium to help fruits set and prevent blossom end rot. The lower leaves of tomato plants may naturally turn yellow and eventually fall so don’t worry if this happens - it shouldn’t be detrimental to cropping. It’s also worth making sure your greenhouse is well ventilated on hot days as very high temperatures can cause the flowers to abort. Indoor plants also benefit from being shaken, to dislodge the pollen in the flowers for good fruit set. I hope this helps Sarah, best of luck with your tomatoes, I’m sure you’ll be seeing bumper crops later this summer.

Name: Clare Rushton

Question: Hi Sue, I have a small 3ft high magnolia grandiflora growing in a large pot, that I bought this spring. It gets watered daily in this heat but all its leaves are turning yellow and half have now fallen off. What is wrong with it?

Answer: Hi Clare, it looks like your Magnolia is naturally shedding its leaves to make way for new growth. Evergreen trees and shrubs tend to shed their leaves in the warmer months of the year. Magnolia grandiflora leaves are long-lasting but they will drop after several years, resulting in a big leaf fall in early summer. Although it doesn’t look particularly healthy, your tree should be fine - just make sure the soil is kept evenly moist and feed your Magnolia every few weeks throughout the summer months with a balanced fertiliser. I hope this helps Clare, best of luck.

Name: Sarah Jackson

Question: I've got a fig tree growing in a huge pot on the south facing patio. About a month ago, there appeared to be 3 or 4 figs forming, but now they've disappeared. It's about 6 or 7 years old and has never produced any fruit. Any advice?

Answer: Hi Sarah, if the figs are simply dropping from the plant then this could be a result of drought or another stress on the plant. If they have disappeared entirely then I would look to squirrels being the culprit! Squirrels are renowned for nibbling or removing unripe figs from trees. The best way to prevent this on smaller trees is to create a cage out of strong plastic netting or chicken wire while the plant is bearing fruit. The reason your fig may have been shy to produce fruit until now could be due to winter weather. Although figs are hardy, the fruit-bearing shoot tips can be damaged by winter conditions so it’s worth wrapping them in straw, hessian sacking or horticultural fleece for the winter. Also, figs are vigorous growers and benefit from re-potting every few years. If you’ve already reached your maximum size pot then try tipping the fig out of its container and prune off about 20% of the root ball. Re-fill the pot with a layer of fresh, loam-based compost such as John Innes No.3 before planting your fig back in its pot. Figs will benefit from regular feeding with a high-potash fertiliser throughout the summer months.

Question: Also, my white onions are really struggling. They started to grow, although were slower off the mark than the red onions, but they seemed to have stopped at about 6-8 inches, with only 2 or 3 leaves which have yellowed at the tips. The neighbouring red onions, on the whole, are doing OK. I operate a 4 year rotation, so onions haven't grown in this section of the veg patch since 2009. Potatoes grew in this spot last year. Any advice?

Answer: There could be a few reasons why your onions are not thriving. There could be a lack of nutrients in the soil. Onions need a very fertile soil - particularly in spring and early summer when they’re putting on lots of crucial leaf growth. Alternatively your onions could have onion downy mildew, which causes the leaves to turn yellow from the tip downwards. In moist conditions a white, and later purplish, mould develops on any dead tissue. If you do identify this as the problem then the general advice is to avoid planting the area with onions for 5 years. Mildew is most prevalent when we have mild, humid, late spring and early summer weather. If the foliage is wilting this could be a sign of onion white rot or onion fly damage. Onion white rots shows as a fluffy white mould around the roots. Onion fly feed on the internal tissue of the stems.

Question: Sorry, lots of questions today. I have a plum tree - can't remember if it is a Czar or a Merryweather, but it is on pixie rooting stock. It was just a twig when I moved in 10 years ago. It only produced fruit (3 plums!) after 7 years and a very stern verbal warning(!), and the following year it had about 10 fruit. This year, there is NO fruit whatsoever. But there is plenty of vegetative growth. The neighbouring plum trees have always had a good to excellent crop, and grew a lot faster. I am seriously considering grubbing it up - do you have any advice?

Answer: Plums are notoriously slow to fruit but I would expect crops to be reasonable after 7 years. Both ‘Czar’ and '‘Merryweather' are self-fertile so it shouldn’t be a pollination problem, although crops are generally better when other varieties are grown nearby. Common problems with plums not fruiting include the flowers being killed by spring frosts, a lack of pollinating insects due to weather or a lack of moisture in the soil, both in spring and summer when next year’s fruit buds are initiating. However as the neighbouring plum trees are thriving this is a bit of a puzzle! Unless your plum tree is sited in an area which would give it different soil conditions or a different micro-climate to the other trees it may be the plant itself. If you wanted to give your plum tree another chance you could try scattering a slow-release balanced fertiliser around the base of the tree next spring along with a mulch of well-rotted manure or compost (although take care not to mound mulch against the trunk). It may also be worth taking a close look at the leaves and stems for any signs of disease such as unusual colourings or bumps, or oozing sap. I hope this helps Sarah, good luck with your fruit and vegetables this year.

Name: Eve Bradley

Question: I am considering purchasing a Bluebell creeper, I am going to redo my front garden which faces north west and gets the sun in the afternoon but I note that the plant isn't entirely hardy would this situation suit it ?

Answer: Hi Eve, Bluebell Creeper (Sollya heterophylla) originates from Australia and needs a very warm environment to thrive. It may survive temperatures to near freezing but is best kept at a minimum temperature of 5°C over winter. I would recommend growing it in a patio container which can be moved outdoors for the summer and brought in for winter. Although Bluebell Creeper will grow in sun or partial shade, outdoors I would recommend growing it in full sun to provide it with as much heat as possible in our unpredictable summers. For some alternative climbing plant suggestions take a look at our article on Climbing Plants for Walls and Fences. The plants in the 'east and north-facing walls' table will probably grow best on a north-west facing wall. I hope this helps Eve, good luck.

Name: Adam Jacobs

Question: Help! I really hope someone can tell me what I'm doing wrong with my cucurbits. I have lost all my cucumbers (Marketmore), about half my courgettes (Defender), probably all my butternut squash (Harrier), and most of my pumpkins (Jack of all Trades). Only my melons (Eldorado) are doing well. They all started off looking healthy enough, but then the leaves started to turn brown. They've all started off in the greenhouse, but I move the cucumbers and courgettes out of the greenhouse when they started to turn brown (thinking maybe they were too hot?) to no avail. What could be wrong? Too much heat? Not enough water? Too much water?

Answer: Hi Adam, oh dear they don’t look too happy, I’m sorry to hear you lost so many plants. Cucurbits thrive in the heat so I think it’s unlikely that this is what has caused their death. Having said that, young plants are more susceptible to temperature changes, so it may be worth ventilating your greenhouse in future. Cucurbits are prone to foot and root rots which cause rotting at the base of the stem and plant death. It could also be verticillium wilt which is a fungus causing wilting and death of the plant - it can reside in the soil for many years. In both cases the plants and compost should be disposed of in household waste to minimise spread.

To help prevent this happening in future try not to bury the stems of the plants when planting out into their final positions - keep them at the same level as they were originally planted. Using sterilised compost and mains water to water your plants will also reduce the risk of this happening. Keep the soil just moist, allowing the compost to dry out between watering. When planting into their final positions, planting on a slight mound helps keep the area at the base of the plant well drained. I hope this helps Adam, good luck for next time.