Facebook Questions and Answers for the 27th April 2012

Hello Facebook fans, thanks for your questions this week, here are Carly's replies:

Gillian Roberts

Is it true that planting marigolds near tomato plants will help keep white fly at bay? Thank you.

Hi Gillian, marigolds and tomatoes are a well known planting combination for combating whitefly. Many gardeners claim it works a treat but there are others who have found it makes no difference. Unfortunately I'm not aware of any published studies which prove this either way. I tried it myself last year and didn't suffer any whitefly in the greenhouse but then I may not have suffered any way! (I will be trying without marigolds this year) It's always worth a try if you are suffering from whitefly - you have nothing to lose and you'll also enjoy colourful flowers all summer which are beneficial to predatory insects. For a more guaranteed cure try using biological controls (natural whitefly predators) which are available online or alternatively use chemical sprays. I hope this helps, let us know how you get on!

Claire Worrell

Would love to receive a suggestion for my garden - I have a border which sees sun for a few hours in the morning before it becomes shaded for the remainder of the day. Am looking for something to fill approx 1ft square that my two cocker spaniels wont easily trample over but already have hydrangeas and hibiscus. Any help greatly appreciated.

Hi Claire, plants which thrive in full shade (2 hours of sunlight or less per day) are often plants of woodland origin. For an area that's 1ft square you would be best to grow perennials, such as hardy geraniums, which produce flowers from early summer through to autumn. You could also try taller ferns such as Polystichum munitum (sword fern), Dryopteris filix-mas (male fern) or Matteuccia struthiopteris (ostrich fern). Other perennials that will do well in shady positions include Alchemilla mollis along with Epimedium, Millium effusum 'Aureum', Brunnera, Pulmonaria and Tiarella cordifolia (Foam Flower). These perennials are all quite low-growing plants so may not discourage dogs from stepping on them.

You could try Hosta - the big leaves would provide a lovely contrast to your hibiscus and hydrangeas and may be less tempting for your dogs to climb over! Other taller plants that will do well in shade are Dicentra, Astilbe, Astrantia and Thalictrum. You could also try Lunaria annua (Honesty) which is a tall but colourful spring biennial. Although you may find euphorbia and foxgloves recommended for shade, take care as they are poisonous to both pets and humans. I hope this gives you some ideas Claire, good luck.

Elaine Alison Fowke

How do you keep the slug and snail population down?

Hi Elaine, there are several things you can do to keep the slug and snail population down. The most effective method is through slug pellets, used sparingly around the areas where they cause damage. The organic pellets (containing ferric phosphate rather than metaldehyde) are just as good as the chemical ones and are safe to use around children, pets and wildlife. You can also try picking the slugs off the leaves and stems at dusk when they are at their most active. Although this can seem laborious it is very effective. There is an organic product called Nemaslug which you water into the soil. It contains nematodes (tiny parasitic creatures) which infect any slugs in the soil and kill them. It remains effective for about 6 weeks and is perfectly safe to use on food crops too (it is not harmful to humans, pets or wildlife).

Beer traps are also effective at drawing the slugs in and drowning them. Just cut the bottom off a lemonade bottle and sink it into the ground so the top is level with the soil surface, and then simply fill the trap with beer. Other similar traps can be made by placing empty grapefruit skins or melon skins upside down on the soil. Slugs love to gorge on the sweet, aromatic flesh of fruit and the darkness and moisture suits them well. All you have to do is check the skins each morning and destroy the slugs hiding in there! For a long-term solution try to encourage more birds into your garden, they are excellent at removing slugs!

Margaret Madgen Chinn

I have masses of white morning glory coming up in the garden. I've already dug out miles of roots. How can I eradicate this pest, and still remain eco-friendly?

Hi Margaret, it sounds like you have bindweed which is a rhizomatous perennial. The rhizomes spread deeply and in all directions. They can reproduce from just a small fragment of stem or rhizome which makes them difficult to get rid of. It's a good idea to try and fork out as much of the roots as you can before collecting them and disposing of them in household waste (don't compost the pieces) or via burning. You can also persistently hoe the new shoots to weaken the plants. It may take several years of digging and hoeing to eradicate it completely. If the plants appear to be creeping in under a neighbouring fence then you could try erecting a solid physical barrier 45cm (18") deep along the fence boundary. This should prevent rhizomes spreading into your garden and help you get the problem under control.

If you want a faster method then the only alternative is to use weed killers that contains glyphosate, which is carried through the plant to its roots, causing death. This is a non-selective chemical and will kill your garden plants so make sure you cover the plants you want to keep before spraying! To get the best results spray the plants when they are flowering as their leaf surface area will be larger. Also spray in the evening rather than during the day. I hope this helps Margaret, best of luck.