Thompson & Morgan Facebook Q&A Session 29th June 2012 - Your horticultural questions answered.

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Name: Kevin Joseph

Question: I have a 10 plus year camellia that always gets problems with the leafs it gets small brown spots on them I’ve been spraying with rose ultra 4 which I thought was helping for awhile then tonight I’ve been out and had a look and seen the problem starting to come back on the fresh leafs which was clear a few days ago. I’ve attached a picture to help you.

Answer: Hi Kevin. That’s disappointing as I know you are keen to get your Camellia in tip top condition - but leaf spotting seems to be a persistent problem with your plant. From your photograph I would say that this is probably a leaf spot called Phyllosticta camelliae which tends to colonise other small spots on the leaves that have been initially caused by overwatering or nutrient imbalances. It isn’t particularly damaging to your Camellia but it can look unsightly. However, it is a good indicator that there is a problem with the plant’s growing conditions.

A lack of nutrients can be easily rectified by starting a regular feeding regime. You can use a general purpose liquid feed. The plant is quite mature now, and the soil is likely to have been exhausted of nutrients so it’s also worth mulching around the base of the plant with some well rotted manure or compost in the autumn to help improve soil fertility and structure.

As it is only a few leaves then you can probably just pick them off and destroy them. Clear up any infected plant debris from the base of the plant too. I hope that helps Kevin.

Name: Linda Theaker

Question: I am growing courgettes this year. The leaves are very yellow, I have given them Tomorite. Is there any way of preventing this yellowing?

Answer: Courgette leaves do tend to show signs of nutrient deficiency in a rather dramatic way, and surprisingly quickly too! You are doing the right thing by feeding them. They are probably flowering and starting to produce courgettes now so continue feeding once a fortnight, as this will also increase your crop. Also try to keep them well watered to prevent stressing the plants. Courgettes need a lot of water so regular watering is essential. Best of luck with them, Linda.

Name: Lydie Taylor

Question: Came home from a holiday to discover these, I thought they were bulbs coming up before I left, now a good 4ft high, and appears to be potato? I haven't planted potatoes! Been in flower a week, so are they ready to harvest and are they edible?! I think once someone told me to be careful with strange potato plants so asking first!

Answer: Yes it does look like you have got a potato plant there! Potatoes will often grow from tubers left in the ground from the previous year. Leave them to flower and let the foliage turn yellow and begin to die back. Then you can dig the plant up and see how many potatoes you have. The main problem with potatoes that grow from old tubers is the risk of them harbouring plant viruses and diseases that could spread to this year’s crops. But they are certainly not dangerous to human health. Enjoy your free crop, Lydie.

Name: Sarah Griffiths

Question: The bottom leaves on my tomato plants have started to turn yellow - any ideas ? Thanks.

Answer: Hi Sarah. Tomato leaves can turn yellow for lots of reasons. If your plants are putting on good growth now then it may simply be the case that the lower leaves are being shaded out by foliage higher up on the plant. This is nothing to worry about and perfectly normal. However I would guess that they probably also need some fertiliser. Start feeding them once a fortnight with a soluble tomato feed and make sure that you water regularly to ensure that the soil is kept evenly moist - never let them get too dry or sit soaking wet for long periods. Best of luck, Sarah.

Name: Christina Goozee

Question: What has happened to my Rosemary? Another one ready for the compost.

Answer: Well, Christina - it certainly looks dead to me! Without more information it’s hard to say what has caused its demise. However I would not be surprised if it started to suffer over the cold winter that we had which was followed by some very wet weather - Rosemary is not particularly keen on the cold or wet, and this would certainly upset it.

In your photo, it’s looks as though it was being grown as a standard. Standard plants are always more vulnerable in winter as the cold can damage the main stem and cause die back of the whole plant. If you can give me a little more information about it then I may be able to figure out whether something else went wrong.

Name: Andrew Rogers

Question: Hi, my greenhouse tomatoes have a virus which has caused the lower leaves to turn yellow. I have stopped feeding them and sprayed them with a solution of Epsom salts. How often should I treat them and when can I resume feeding. Also should I remove the affected leaves. Thank you

Answer: Hi Andrew. I’m a little confused as to why you are using Epsom Salts to treat a tomato virus. This is usually used to treat magnesium deficiency as Epsom Salts are Magnesium Sulphate. However a magnesium deficiency would certainly show the same symptoms of yellowing leaves, particularly lower down on the plant.

There are lots of other reasons why the lower leaves can turn yellow, but more often than not it is simply a nutrient deficiency, or sometimes the lower leaves are shaded out by bushy foliage higher up on the plant. Overwatering and underwatering can also turn the leaves yellow - try to water regularly to keep the compost moist but not soaking wet.

Rather than spraying, can I suggest that you try feeding them at the roots with a liquid solution of Epsom Salts - spraying the foliage can cause scorching particularly during bright sunny weather. I would only give them one or two treatments like this and then get them back onto a proper tomato feed once a fortnight.

If it is just a few leaves that are affected then you could remove them - the plants may well shed these leaves naturally anyway. If there are any particular symptoms that make you think this is definitely a virus then let me know - a picture would be useful too. Keep your eye out for stunted, curled or bronzed leaves as these are all symptomatic of tomato viruses. I hope that helps Andrew.

Name: Tracie Watson

Question: Hi there I live in Sunderland so not best weather I'm just wondering if I can use plastic greenhouses as cold frame over winter x

Answer: Hi Tracie. Having lived in Sunderland many years ago, I remember the weather well. Cold frames are usually used to protect hardy young plants from the winter weather, particularly those that are susceptible to rotting in cold, wet conditions such as alpines. With this in mind, a plastic greenhouse would do an equally good job. However I would be concerned that it might take flight in windy Sunderland - a cold frame would certainly be sturdier.

If you were planning on overwintering half hardy or tender plants then I would recommend that you invest in a heated greenhouse as neither a cold frame or a plastic greenhouse will be capable of providing the protection that these plants would need. Hope that answers your question.

Name: Sarah Griffiths

Question:My lilies are being smothered with this - any ideas what it is please? I do have the dreaded lily beetle so wondered if this is the larvae?

Answer: Hi Sarah. Yes that’s definitely lily beetle and the larvae do more damage than the adult beetles. Remove and crush any larvae or adults that you see. Check for the underside of leaves as they can often be found lurking there. You will need to inspect your plants throughout the growing season to keep on top of the problem. If you have a severe infestation then you may need to use an insecticide such as Bayer Provado Ultimate Bug Killer or Scotts Bug Clear Ultra. Good luck Sarah.

Name: Jonathan Pollard

Question: I have a question for your Friday expert. There are three copper birch outside my front door which are fairly old and create a bush about 7 feet high. I'd like to reduce them to about 5 feet then remove the branches from about the bottom two thirds of the "trunk". I hope to create a pleached tree effect. Are the plants likely to survive and is there any time of the year that is better to do it.

Answer: Hi Jonathan. I am assuming that we are talking about copper beeches, and that ‘birch’ was just a typo. For this type of pruning Beech trees are best dealt with in winter around February time while still dormant. They generally respond well to pruning.

I would recommend that you tackle it over two years as you will be reducing their size significantly. Reduce its height in the first year and then let it recover, before removing the lower branches the following February. On both occasions you should mulch around the base of the plants after pruning with well rotted manure or compost, and keep them well fed and watered over the following season to encourage new growth. Good luck, Jonathan. We’d love to see a picture of the finished hedge.