Thompson & Morgan
Facebook Q&A Session 17th April 2014

Thompson & Morgan Facebook Q&A Session 17th April 2014
- Your horticultural questions answered.

Our horticultural expert Sue Sanderson runs a fortnightly question and answer session - so if there is something that has been eluding you in your garden, post your question on our facebook page and she will get back to you during her next Q&A session.

View the answers to our previous sessions.

  • Nicola Postlethwaite
  • Hi, we have had to remove some hedges and hawthorns from our garden to make way for a greenhouse. What if any is the best product for killing/ breaking down the stumps without poisoning the soil?

  • Sue - T&M Horticultural Expert
    Sue Sanderson - T & M Horticulturalist
  • Grubbing out the roots would be ideal if at all possible to prevent any suckering. Otherwise your best option really is to kill the stumps with a systemic glyphosate based herbicide such as ‘Roundup tree stump and root weed killer’. Glyphosate becomes in active once it comes in contact with the soil and is readily broken down by microbes, so this should not have a lasting effect on the soil.

    Glyphosate will need to be applied to fresh cuts so you may need to recut the stumps before you apply the weed killer. You can apply this with a brush and it will begin to destroy the plant from the inside. Target the outer ring of the stump, just beneath the bark as this is where the live wood will take up the herbicide. You may need to apply glyphosate several times but eventually it should do the trick. Persistence and regular application is the key here! After application, cover the stumps with plastic sheeting to prevent rain washing the chemical away and avoid harm to people and animals. Alternatively, if you have had to recut the stumps, keep the disc of wood removed from the top of the stump and this can be nailed back in place after the glyphosate has been applied to the fresh cut. This makes for a neater finish. Enjoy your new greenhouse, Nicola.

  • Imrana Rashid
  • Hi the leaves on my allium plants are turning brown at the tips. The allium have not flowered yet but there are buds on it so, does that mean there is still some hope? Thanks

  • Sue - T&M Horticultural Expert
    Sue Sanderson - T & M Horticulturalist
  • Hi Imrana. This is fairly typical of Alliums. They often start to brown off just as they come into flower. It is caused by environmental conditions and nothing to worry about. The best way to grow Alliums is to plant them in herbaceous borders among leafy perennials which will hide the browning foliage while you get to appreciate the flowers.

  • Nathan Apperley
  • What's the best way to prune Pyracantha, to keep it within its boundaries, and keeping as many flowers and future berries as possible? Thanks!

  • Sue - T&M Horticultural Expert
    Sue Sanderson - T & M Horticulturalist
  • Hi Nathan, now is the time to prune your Pyracantha but it will mean that you will lose some of the flowers and berries – there is really no way to avoid this. Bear in mind that it flowers and fruits on two year old wood so the more of this that you can retain, the better.

    If the plant is a free standing specimen then simply remove any wayward branches completely to reduce its size. If you are growing a wall trained Pyracantha, start by cutting back outward growing shoots and then shorten the remaining shoots to fit the space available. Make sure that you use clean, sharp secateurs to reduce the risk of Fireblight.

  • Jean Wearmouth
  • Should you take the runners off raspberry plants and if transplanted do they stay true to parent plant?

  • Sue - T&M Horticultural Expert
    Sue Sanderson - T & M Horticulturalist
  • Hello Jean. Yes it’s a good idea to remove Raspberry suckers to keep the plants with their allotted space. If you would like to use them elsewhere in the garden, or share them with a neighbour, then they can certainly be potted up and they will be true to the parent plant. When you remove the suckers try to dig down a little and get some roots. These can then be potted up at the same depth that they were growing in the ground. It’s really that simple!

  • Jemma Gilmour
  • I'd like to pot something up, perhaps a perennial, that we can leave at my mother in laws grave, but we only get to visit the church yard a few times a year; could you recommend something nice but hardy that can deal with a little neglect? Thank you.

  • Sue - T&M Horticultural Expert
    Sue Sanderson - T & M Horticulturalist
  • Hello Jemma. That’s a lovely idea. It might be worth checking with the church warden as there will almost certainly be a protocol for decorating graves. Often it is actually possible to plant directly in the ground by the headstone, and this would be preferable as even the toughest plant will still need watering if it is grown in a container.

    I would suggest trying low maintenance perennials with a compact growth habit such as Primrose vulgaris, Polyanthus ‘Most scented Mix’ or Dianthus ‘Gran’s Favourite’. These could be under planted with spring bulbs such as Narcissus ‘Tete-a-Tete’ and Russian Snowdrops. All of these are fairly resilient and should cope with a bit of neglect. I hope this gives you a few ideas.

  • Jane Wells
  • My dad grows giant kelsae onions every year but this year all of his seedlings have collapsed and died ,do you know what would cause this .There is nothing in the compost and he has done them the same as always sowing them on boxing day x Thankyou

  • Sue - T&M Horticultural Expert
    Sue Sanderson - T & M Horticulturalist
  • That’s such a shame, Jane. The cause is almost certainly a fungal disease - either a strain of Pythium or Phytophthora. Both are water moulds that flourish in wet compost and need water to spread from plant to plant. They penetrate the plant cells and cause plant collapse which looks like wilting. This often prompts gardeners to water the plants, thereby exacerbating the problem.

    These fungal diseases can easily be introduced via the compost, rainwater, unwashed seed trays etc. The best way to avoid the problem is to be meticulous about garden hygiene - use fresh compost, thoroughly clean seed trays, and water with tap water instead of rainwater. If you have compost left at the end of the summer then spread it on your garden as mulch. Don’t be tempted to save it for next spring!

    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. It sounds as though your Dad is an experienced gardener so he may well have encountered this problem before, as most gardeners do from time to time. Despite our best efforts to avoid the dreaded ‘damping off’ diseases, sometimes it’s just bad luck. Please send him my best wishes and better luck next year.

  • Fahima Khalil
  • Hi a question for next week Q&A please. Poppies are one of my favourite flowers I ordered blue, pink plum, red (seeds) and coral reef (seeds) from T &M. The majority died except 2 out of 24 plum ones survived despite T &M kindly sent replacement blue ones, but they did not survive. Please help What might have I done wrong or how to keep the 2 survived ones. Thank you all indeed.

  • Sue - T&M Horticultural Expert
    Sue Sanderson - T & M Horticulturalist
  • Hello Fahima. That’s a great pity. I’m sorry to hear that you have lost them all. It’s hard to say what the cause is without seeing the plants, but I can make a couple of suggestions and see whether something rings a bell with you.

    Poppies really do prefer a well drained compost, and are quite susceptible to root damage if over watered. Is it possible that this might have occurred? Ideally the compost should be kept consistently damp, but never wet. Over watering can cause the plant to rot and facilitate fungal diseases such as Pythium and Phytophthora. Tell tale signs of overwatering include wilting of the leaves and stems, and the bottom of the stem rotting off. Take a look at my response to Jane’s question above for suggestions on how to prevent this.

    My other thought is that perhaps the plants were affected by a significant change in temperature. If you are growing them on a windowsill for example then it may be advisable to move them when you draw your curtains as windows can become very cold at night. They can be returned to the window sill in the morning. Make sure that seedlings are kept away from draughts and radiators too as these can be equally damaging.

    Young plants and seedlings are very vulnerable to changing environmental conditions and so it is important to try to keep soil moisture, temperature etc as constant as possible. I do hope that your remaining plants survive. Please don’t let this put you off – we all have gardening disasters from time to time!

  • Ahabwe Edwina
  • What flowers can be grown for commercial cut flowers in Uganda EastAfrica apart from roses, something that can produce flowers as constantly as the roses? Thank you

  • Sue - T&M Horticultural Expert
    Sue Sanderson - T & M Horticulturalist
  • Roses are certainly the main flower crop in East Africa but other flowers are produced there too. Carnations, Alstroemeria, Gypsophila and Chrysanthemum for example.