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Facebook Q&A Session 3rd May 2013


Thompson & Morgan Facebook Q&A Session 3rd May 2013 - Your horticultural questions answered.

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Name: Angela Cantrell

Question: I have put my tree lilies in large tomato plant pots in the this ok? I am also unsure of how much water to give them. Also, when do I take the polythene off my seed trays - is it as soon as the seedlings start to appear...or leave till they are a little bigger? I.e. Lobelia, chillies, sweet peppers and others I can't just remember right now, thank you.

Answer: Hi Angela, your tree lilies will be fine like this for now although will eventually need potting up into bigger pots or planting out into the ground. It's best not to use a container any smaller than 30cm in height and depth as the lilies need to be planted quite deeply and due to their height will be prone to falling over in smaller pots. When planting tree lilies in the ground we recommend spacing them 15cm (6") apart but for container displays it looks much better to plant them closer together for a full display. Plant them one bulbs width apart and make sure they're not touching the sides of the container. They like a moist, well drained soil but dislike water logging - allow the top inch of the compost to dry out between watering.

With regards to your seedlings, you can take the polythene away once they have germinated. You can leave it on for longer, but as soon as the seedlings start pushing against the polythene it’s best to take it off to give them room to grow. I hope this helps Angela, good luck.

Name: Margaret Mccartney

Question: Yes how can I stop black fly attacking my cherry tree this year?

Answer: Hi Margaret, although unsightly, cherry blackfly doesn’t normally affect flowering and fruiting. For ornamental cherries you can spray the leaves with thiacloprid (Provado Ultimate Bug Killer Concentrate), acetamiprid (Scotts Bug Clear Ultra concentrate) or thiamethoxam (Westland Plant Rescue Bug Killer Ornamental Plants) in late spring when the aphids start to appear. Try and leave this until after flowering to prevent bees ingesting the insecticide. Some of the products mentioned may be suitable for use on fruiting cherries but do check the label first. Organic pesticides such as pyrethrum (Scotts Bug Clear Gun for Fruit & Veg) or deltamethrin (Bayer Provado Ultimate Fruit & Vegetable Bug Killer) are safe to use on fruiting cherry trees. These are contact pesticides so will need regular application to be effective. You can also try and reduce the amount of over-wintering eggs by using a winter tree wash such as Growing Success Winter Tree Wash - these are available at all good garden centres and are applied during the tree’s dormant period. I hope this helps Margaret, good luck with your cherry tree.

Name: Colin Swindle

Question: What’s the best type of compost/soil to use when planting a Japanese maple in a pot?

Answer: Hi Colin, as Japanese Maples are long-term container plants I would recommend using a loam-based compost such a John Innes No. 2 or No. 3, mixed with some ordinary multipurpose compost. This will make the pot very heavy but provides a much better growing environment for your Acer! Multipurpose composts break down over a number of years, becoming prone to water-logging and having little nutritional value. Acers will need feeding each spring with a slow-release fertiliser which can be applied to the compost surface. I hope this helps.

Name: Sue Taylor

Question: I think I was a little too eager to sow my annuals and they are ready to go out now. I am growing them in the conservatory and putting them outside during the day, but by the first week of June they will be huge. Does that mean they will fizzle out earlier than normal? All the usual things: geraniums, petunias, etc. and I am feeding them once a week.

Answer: Hi Sue, your plants should perform as per normal provided you keep feeding and watering them well. Unfortunately there is still a risk of frost this month so it’s best to carry on as you’ve been doing and keep your plants indoors. Make sure to dead-head your plants regularly to prevent flowers going to seed, and encourage more to be produced. Petunias, Fuchsias and many other bedding plants will benefit from being pinched out to prevent them becoming leggy - watch our How to pinch out plant tips video for further advice. I hope this helps Sue.

Name: Pauline Petros

Question: Just as Sue Taylor said - I've got beans and peas etc growing like crazy - should I risk putting them out or risk them getting pot bound?

Answer: Hi Pauline, peas and broad beans will be fine if planted out now. They will need hardening off for a week first, to acclimatise them to the cooler outdoor conditions. Although they are hardy plants, if you’re in the North of the country it might be worth giving them some added protection in the form of a cloche or layer of horticultural fleece.

Runner beans and French beans are unfortunately much more tender, so I wouldn’t advise planting them outside until all risk of frost has passed in late May or June. Ideally you should wait and sow these tender beans at the beginning of May so they are just the right size by late May to be planted out. As you’ve found they are very fast growers once they’ve germinated! Best of luck Pauline.

Name: Hannah Bufton

Question: I have a new box hedge (keep away blight!) ... mature plants at least a foot tall, Should I clip the top to let them thicken up ? or wait until they reach the desired height , please?

Answer: Hi Hannah, it’s a good idea to prune your box hedge while it’s young as it will produce more side-shoots resulting in a pleasing, dense shape. May is the ideal month to give it its first prune - simply cut back by up to one third. You can trim your box hedge throughout the summer if required although make sure you finish any pruning by late August. As the plants mature they will only need a light trim each summer to maintain their shape.

Name: Nicola Postlethwaite

Question: Are the any ways to stop red lily beetles?

Answer: Hi Nicola, the most effective control for lily beetle is to remove the eggs and larvae by hand. Check the underside of leaves as they can often be found lurking there. The small eggs are laid in clusters and are bright orange in colour. You will need to inspect your plants throughout the growing season to keep on top of the problem. However if you have lots of lilies I appreciate this could be a mammoth task! Once the lily beetles become active from April onwards, you can spray your lilies with an insecticide containing ‘thiacloprid’ (Bayer Provado Ultimate Bug Killer) or ‘acetamiprid’ (Scotts Bug Clear Ultra) - you’ll find these active ingredients listed on the label. These pesticides are systemic (enters the plant’s vascular system) so will last for a few weeks before you need to spray again. You’ll need to be vigilant in spraying, until late July/August when the beetles stop laying eggs. I find that growing lilies in large containers (45cm tall) helps and the problem is much more manageable than for those grown in the ground. Best of luck Nicola.

Name: Louise Rowley-Spendlove

Question: Given the weird weather what can we still plant veg wise?

Answer: Hi Louise, the unusual cold spell has put many of our plants behind but the temperatures certainly seem to have picked up over the last few weeks. There are plenty of vegetables that can be sown or planted now. Quick crops such as radishes, beetroot and lettuce can be sown now and throughout the summer, and carrots and peas can also be sown directly outside now. It should be safe to plant potatoes out now - if any shoots emerge they can be earthed up or protected with horticultural fleece. May is the perfect month for sowing autumn and winter cabbages, Brussels sprouts, Runner beans, French beans and courgettes and pumpkins. Take a look at our What to sow and grow in May page for more ideas. I hope this helps Louise.

Name: Clare Rushton

Question: My lawn was mostly moss, so I applied a weed and feed, then 2 weeks later scarified, aerated and applied lawn seed. 2 weeks later my lawn was brown with no germinated seed and moss still present in small areas, also areas it just looked completely bare. So I repeated the weed and feed and more grass seed - 10 days later no difference. I'm watering the lawn every night and can see the seed sat there but it is doing nothing. Just outside London so we have been having warm weather. What can I do, my lawn is just one big brown mess?

Answer: Hi Clare, the ideal environment for lawn seed to germinate in is a finely worked, consistently moist soil. Seed is normally lightly raked into the soil surface so there is some covering to aid germination. If you’re applying the ‘weed and feed’ to areas with seed in, this will be detrimental to germination. Also, if you’ve only scarified the surface of the soil and it’s still quite compacted underneath it won’t be conducive to growth. Moss in lawns often indicates poor drainage, soil compaction, excessive shade or mowing too close. The best course of action would be to skim off what is there already and dig over the area to a depth of 20-25cm (8-10") for a fresh start. If your soil is light and sandy, dig in some well-rotted manure or compost to improve the soil and help it retain moisture. Ideally you would leave the area after digging for at least a few weeks to settle the soil. Before sowing the seed, remove any weed seedlings by hand. Tread the soil several times in different directions and rake over to create a level surface. At this point it is also a good idea to rake in some general purpose granular fertiliser to feed your grass for the season. Sow the grass seed as per the instructions on the packet and lightly rake over the area so the majority of seeds are covered with soil. Keep the soil moist and germination should occur within 7-10 days. For the first cut make sure your mower blades are set high, gradually lowering them as the season progresses. Best of luck Clare, let us know how you get on.

Name: Jay Pullani

Question: None of my daffodils have flowered this year, just masses of leaves, just a few flowers last year. Do I need to split up the clumps? The clumps are not that large either.

Answer: Hi Jay, Daffodils coming up ‘blind’ (no flowers) is quite common and there can be several causes. As you’ve mentioned, it could be that your daffodil bulbs are overcrowded - daffodils naturally reproduce underground, which can lead to congestion over the years. If you think this may be the cause then lift your daffodil bulbs in the summer once the foliage has died back and re-plant them at a spacing of 5-7cm, and a depth of 10cm. Deep planting discourages bulbs from dividing. It’s a good idea to work in some organic matter and fertiliser before re-planting them, to help feed the bulbs. Lack of food can be another reason why bulbs come up blind. As the bulbs emerge in the spring try sprinkling a general purpose fertiliser around them. After flowering, feed your bulbs with a high potassium liquid fertiliser such as tomato food, every week or two until the foliage yellows. This helps them prepare for next year’s display. It’s worth keeping an eye out for narcissus bulb fly damage too. The larvae of this fly burrow into the centre of the bulb and eat the contents (which contains the flower buds), leading to death or bulb blindness.

Other things you can do to improve flowering include dead-heading the flowers once they’ve finished and letting the foliage die down naturally after flowering (don’t be tempted to tie the foliage in a knot) Dry conditions after flowering can also prevent flowers forming for next year. If you suffer from dry soil you can mulch around the bulbs in the spring with organic matter such as well rotted manure or compost, which should help retain moisture. I hope something here helps Jay and good luck with next year’s display!