Facebook Questions and Answers for the 28th September 2012

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

Christina Goozee

My conservatory seems to have been taken over by webs & small white spiders which are resiliant to pest sprays or even bio candles. It has devastated my Trichterwinde(?) and now my peach tree brought in for additional care.

Hi Christina, your plants do look very poorly! The culprit is red spider mite, a very tiny creature which sucks sap from the plant and severely weakens it - and in extreme infestations causes death. The white spiders you describe are most likely the skin casts of the mites - the mites themselves are yellow-green, turning red during the autumn. 'Trichterwinde' seems to be the German name for morning glory (Ipomoea) which is what the trailing plant in your photo most looks like. Most Ipomoea species are annuals or short-lived perennials so it's probably not worth trying to save this plant. Your peach tree however should survive if given the right care.

I would be tempted to clear the conservatory completely, disposing of any dead plants in your normal household waste. Sweep up all debris - spider mite can hibernate in the smallest pieces of plant material. Also wipe over all surfaces with soapy water or a mild disinfectant. Spray your plants with an insecticide before bringing them back in - try using a different spray to the one you've already used as spider mites can build up resistance over time. Sprays containing thiamethoxam or abamectin are effective against red spider mite - this should be mentioned as an active ingredient on the back of the bottle. Unfortunately there are no chemical sprays suitable for use on edible plants such as your peach, but you could search for those based on plant oils - they're normally labelled as 'organic' and will say if they're suitable for use on edible crops. Spray underneath the leaves as this is where they hide! To deter them from breeding try misting your plants regularly and keep the conservatory as cool as possible. Spider mites thrive in hot and dry conditions so increasing the humidity and keeping the temperatures cool will decrease their activity. Keep spraying your plants with an insecticide until the infestation appears to have gone, following the instructions on the label. If you use several different types of spray you have more chance of getting rid of them for good.

Peach trees are hardy so you could over-winter yours outside if necessary, provided you erect a shelter over it to keep the rain off (to prevent peach leaf curl). Make sure you clear the dead leaves from around the base of your peach tree to reduce the chance of over-wintering mites. I hope this helps Christina, keep an eye out for the mites on the underside of the leaves next year so you can treat them early on if necessary. Best of luck.

Liz Lowry

If I gather the seed pods from my Sweet Peas can I sow them next year and will they come true or become just 'wild'?

Hi Liz, yes you should be able to grow sweet peas from the seeds you gather. Do this as soon as the pods have browned as they are liable to burst suddenly, sending the seeds everywhere! Seeds are unlikely to come true - you may get a few the same colours as the parents but I would expect the rest to be mixed. It's a bit of a gamble - I grow mine from collected seed each year and always get some nice surprises! Depending on the parentage of your original sweet peas you may see a number of colours and flower sizes coming through - the wild form of sweet pea (Lathyrus odoratus) is shorter than normal and has fairly small but striking burgundy and violet flowers. I hope this helps, good luck for next year.

Maria Weaving-Gómez

Hello. I just purchased 3 clematis montana off the internet. They are about 4 inches tall including the soil plug. I assume I should repot them and let them grow a bit more before planting out. Will they be okay out there in the cold being so young? Thank you. :)

Hi Maria, yes as the plants are so small it would be best to pot them up and keep them in a cold frame, cold greenhouse, or against the house wall which will offer them some protection through the winter, yet still give them the cold period they need. In extreme weather give the young plants some protection by covering them with horticultural fleece. By spring they should have put on good root growth and can be planted out into their final positions! I hope this helps.