Facebook Questions and Answers for the 4th July 2014

Click here to see our previous Q&A sessions.

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

Ray Baird

Your comment on using vinegar to make soil more acid would be helpful and would this be worthwhile depending on water pH. Thanks.

Hi Ray, you can use vinegar as a soil acidifier but it would need applying at every watering to lower the soil pH, as it quickly dissipates in the soil. You would end up using quite a lot of vinegar! Ideally you would buy a pH tester kit so you could work out how much vinegar is needed to make your water acidic - a pH of 4.5 or 5 would be ideal. It is much easier to use sulphur, which soil organisms break down slowly into sulphuric acid. Sulphur dust is fairly fast-acting and will start to have an effect after a period of weeks, whereas sulphur chips will take longer. Digging in the sulphur is much more effective than applying to the soil surface, so try to carry out this work before planting. I hope this helps Ray, best of luck.

Anthony Wareham

Hi I was given two of these - any help in what they are please? Many thanks.

Hi Anthony, my initial thoughts were that this was a houseleek, Sempervivum tectorum. However the thick fleshy, glaucous leaves may suggest this is an Echeveria, perhaps Echeveria elegans. The biggest clue will be when it flowers. Houseleeks produce quite showy pinkish flowers in summer, on thick fleshy stems. Echeveria produces rather more elegant stems of smaller red or yellow flowers. Echeveria are not hardy plants so will need a bright, frost-free position over winter. I hope this helps.

Olive Mac Farlane Fulton

Hi I have a Medinilla magnifica which I've had for the last 6 years it flowers at least 7 months of the year. Question is how do I get it to propagate please?

Hi Olive, this is quite an unusual but stunning plant. You can take softwood cuttings in spring (fresh new growth) or semi-ripe cuttings now. Fill suitably-sized pots loosely with a mixture of 50% compost and 50% perlite (available at all good garden centres) for good drainage. Collect non-flowering shoots around 10-15cm (4-6") long and trim just below a leaf joint (this is where all the hormones are concentrated for new growth). If you don't have any non-flowering shoots at the moment it's probably best to wait until spring, for fresh new growth. Remove any leaves on the lower third of the shoot and cut the remaining leaves in half to reduce water loss.

Dip the base of the cutting into hormone rooting powder to encourage rooting and protect from rotting. Insert the cuttings around the edge of the pots, spacing them so the leaves aren't touching. Water well and allow the pots to drain before placing inside a clear plastic bag to increase humidity around the plant material. Keep the pots somewhere warm and bright but out of direct sunlight if possible. A heating mat placed underneath the pots would be an advantage, to encourage rooting. Make sure the compost remains moist. After 6-10 weeks you should start to see roots appearing out of the drainage holes, at which point your Medinilla cuttings can be potted on. I hope this helps Olive, we've love to hear how you get on.

Kate Rose

Any idea why my golden Philadelphus didn't flower this year? I did prune it last year, can't remember when exactly but it would have been after flowering. It has had lots of growth and foliage this year. Also, I have 3 young clematis sieboldii, I was wondering about planting them around an obelisk, is this a good idea and do you have any ideas for a companion plant to go in the middle? Thank you.

Hello Kate. Philadelphus flowers on the previous year's wood and requires annual pruning to make the most of the blooms. It's best to prune immediately after flowering to ensure that sufficient new growth can be made during the remainder of the season to ensure flowers in the following year. It is possible that you pruned it just a little later in the season and the subsequent growth was not sufficiently mature to flower this year. It certainly won't do any harm. In fact, Golden Philadelphus is sometimes pruned more than once during the summer to enhance the foliage (albeit at the expense of the flowers). Enjoy the foliage this year and prune at the normal time - normal flowering should be resumed next year.

Kim Bridger

I have an Olive standard in a container. It has produced some long random shoots. Can these be trimmed while green to keep its shape?

Hello Anna, Yes by all means go ahead and trim them. Olive trees are best pruned from late spring to early summer because they need time and warmth to heal the pruning wounds. For this reason you should never prune them in the winter months. Now is the perfect opportunity to remove old unproductive branches and misplaced growth to encourage new shoots. I hope this helps.