Facebook Questions and Answers for the 12th August 2011

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

Laura Fraser:

Needs pet safe ways to get rid of slugs.

Hi Laura, organic methods of slug control include 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. You could also use 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!

Liz Hall

Planted a tub of nasturtiums in my neighbour's front garden a few weeks ago using fresh compost mixed with some originally in the tub. Last 4 days loads of leaves were destroyed by 'flea beetles'. I removed the damaged leaves and sprayed the nasturtiums with some old derris powder which I found in my shed from a few years back. I've since been 'reading up' on flea beetles, and pesticides, and find derris is now withdrawn in UK on health grounds as it has been linked to causing Parkinson's Disease. Is this correct? (I have used derris powder occasionally for over 40yrs.) The beetles have now mostly gone, and rain has now washed the derris off onto gravel beds. I understand flea beetle eggs were probably laid earlier in the old soil so, when I remove the nasturtiums at the end of summer, should I water the soil in the tub with a weak Jeyes Fluid solution to sterilise it, and kill any remaining beetle eggs, before planting bulbs, or will a winter frost be sufficient? If derris powder is now illegal what should I treat any future flea beetles with please? Also, if derris is now banned, am I legally bound to dispose of that which remains in my shed, if yes, then how, and where?

Hi Liz, you're absolutely right - Derris powder was withdrawn in 2009 although I couldn't confirm the links with Parkinsons disease (this was rumoured at the time). As with any pesticide, they can be dangerous if breathed in or swallowed. You should really dispose of your remaining Derris powder - follow this link and click on the relevant area of the map to find out how to dispose of pesticides safely in your area.

Flea beetles over-winter as adults in leaf litter so it worth clearing the area of debris in the autumn/winter. Jeyes fluid shouldn't be necessary as flea beetles only lay their eggs in the spring and summer so there will not be any over-wintering eggs or larvae in the soil. The best course of action is to spray the flea beetles as soon as you see damage in the spring. The earlier you catch them the better control you will have over the population! Sprays for flea beetle are available in all good garden centres and will normally state which pests they are effective against. Use a pesticide which contains deltamethrin, lambda cyhalothrin or pyrethrum - this should be stated somewhere on the label. I hope this helps Liz, let us know how you get on.

Sharon Shaz Chandler

Please tell me how to improve my lawn? I have a dog but i don't think he's the reason it bald in patches! It just need some help and ive tried loads of dressings and after cut stuff....all to no avail! Thanks

Hi Sharon, there are a number of reasons why a lawn may be patchy. I think you are right about your dog as only female urine burns patches into lawns. It could be due to aspect, compacted soil or lawn grubs such as chafers and leatherjackets. If your soil is compacted then top-dressings may be unsuccessful as the seeds cannot root easily. The best course of action is to give your lawn some TLC by aerating it and scarifying it this September or October. Make sure the weather is moist before treating your lawn as dry weather could make the problem worse. Scarifying is carried out to remove 'thatch' which is a build up of decaying blades of grass and other materials on the soil surface. Too much thatch prevents water from reaching the soil beneath and the lawn loses vigour. To remedy this simply rake the lawn over vigorously with a spring-tined rake. Make sure you press hard so the rake breaks the soil surface and clear up any debris your rake picks up. To aerate your lawn and reduce possible compaction, push a garden fork deeply into your lawn at regular intervals. If you angle the fork back slightly after inserting it, this will raise the turf and loosen the soil, allowing air in. Make sure you don't walk on the lawn for a few weeks after treatment as this will undo all your hard work. You can apply fertiliser and a lawn top-dressing (available at all good garden centres) afterwards to help boost growth. You can try re-seeding patches a few weeks after treatment or wait until the spring.

If you don't see any improvement next year there may be another underlying cause. Lawns do tend to struggle if they are shaded - dry shade in particular can quickly make a lawn become very sparse. If your lawn is shaded by a tree or building it's best to use a special grass seed mix or turf suited to shadier conditions. Brown patches can also appear due to chafer grubs and leatherjackets feeding on the roots of the grass. Whilst renovating your lawn look out for maggots in the soil - birds feeding on your lawn is also a sign that there may be grubs underneath. The grubs can be treated by watering in a nematode which will infect and kill them (this is harmless to humans, pets and other wildlife).

If your lawn is in very bad condition, it may be worth completely replacing it with seed or turf. This would give you the opportunity to thoroughly dig the soil and incorporate organic matter such as compost or well-rotted manure before laying the turf or seed. Organic matter would help improve the soil structure, improve drainage and provide some nutrients for the grass. I hope this helps Sharon, best of luck.

Sharon Shaz Chandler

I bought a mimosa from you earlier on in the year and its outdoors as it was classed as "hardy" We have extreme winters here -14 a couple of nights! Im wondering if this mimosa will be ok in the garden over the winter........thanks again Carly

Hi Sharon, your Mimosa (Acacia dealbata) probably wouldn't survive temperatures of -14, even more so because it is young. It can be overwintered outdoors in mild Southern areas of the country but should still be offered some protection in the form of fleece and mulch throughout the winter months. Ideally it should be planted in full sun against a South-facing wall as the wall retains heat and offers some wind protection too. If you are unable to provide these conditions it would be best to bring your Mimosa in to bright and frost-free conditions over the winter. As the tree matures it does gain more resistance to the effects of frost but if your winters are frequently extreme it may be best to keep your Mimosa as a container plant so you can bring it under cover each year.

Jane Rhoda Marsh

My husband has planted potatoes in the same pots as some Lupin plants, I have heard that Lupins are poisonous will this affect the potatoes? or will they be edible? Thanks

Hi Jane, your potatoes will be fine to eat. Only the seeds of Lupin plants are harmful if eaten as the poisonous substance (an alkaloid) is concentrated here (even then the alkaloids are only mildly toxic). Lupins can be of benefit to some crops as they host bacteria on their roots which fix nitrogen into the soil. This is great if you're growing lettuces and cabbage as these crops need a lot of nitrogen!

Maria Hayward

Bought some perennial trailing pansies this year, have done really well but seem to be coming to the end of flowering, do I need to cut back ready for next year, please help?

Hi Maria, it's a good idea to give your pansies a light trim to remove all the spent flowers and seed capsules. There shouldn't be any need to cut back your pansies unless they are looking leggy or the plants are badly shaped, in which case feel free to cut them back to a more bushy shape. It's a good idea to keep feeding your pansies for the rest of the summer to help them build up energy for next year. I hope this helps Maria.