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Sue's Facebook Question and Answer Session -13th August 2010

Name: Lucy Garden
Question: A question for Sue for next time - crocosmia Lucifer grows really well for me, as does the wild montbretia - it's a weed- but the fancier members of the family don't seem to thrive. Are there any robust varieties? I've tried Solfatare and Emily Mackenzie but they seem to peter out. George Davison was just about OK. But I want something as tough as Lucifer. I've got heavy clay soil. Any suggestions?

Answer: There is a big difference between Crocosmia varieties when it comes to robustness. As you have already found out, C. Lucifer and C. masoniarum are really tough. I have to agree with you that C. Emily McKenzie can be a bit difficult. My plant failed too and I grow on light, well drained soil (too hot and dry for her!). I believe that C. Star of the East is more tolerant of clay conditions. It is a wide flowered, yellow variety that makes quite a good display. C. Gerbe d'Or is another yellow variety which tends to be pretty tough. You might also like to try C. Firebird.

If you are a great fan of Crocosmia then it may be worth experimenting with some varieties again, but this time improve your soil by adding lots of well rotted manure and some grit to improve fertility and drainage. I would also provide a thick mulch of chipped bark to protect them over winter (and retain moisture in the soil during summer).


Name: Helen Miller
Question: I have impatiens planted in a 6ft high wall container, planted vertically, and they have been doing well until recently when some of the plants now have leaves that are going yellow and have black spots on them. I gather this could be due to either too much or too little water - not much help when trying to rectify the problem. But can I spray them with anything to stop this spreading, I have been picking off the affected leaves, but as I have about 60 plants it takes ages! Thanks.

Answer: It sounds as though they are suffering from a strain of fungal leaf spot. There are many different fungi that can cause this problem, which tends to occur during warm, wet weather, or where plants are watered from above the foliage. Plants that are fed with high nitrogen feeds and grown tightly together (thereby reducing ventilation) are also particularly susceptible.

The warm, wet conditions that we have had in recent weeks will have created ideal conditions for the spread of black spot fungal spores. Remove and destroy any affected foliage that you can and spray the new growth with a fungicide that is suitable for use on ornamental plants to try to restrict the spread of the problem.


Name: Dinah Marshall
Question: Please. What has happened to my beetroots. I have got four white ones what has gone wrong anyone know.

Answer: There must have been some stray seeds of a white variety in your seed packet. Beetroot comes in many shapes and colours –we even sell a bicoloured one called 'Chioggia Pink'! It will be perfectly edible, and at least you won't get purple stains anywhere!


Name: Sheila Frost
Question: Can you help please? Part of my (established) gold and green variegated Euonymus hedge has suddenly died in the middle. The leaves on the infected part have withered up and dropped off, and when I look closely I can see what looks to be like tiny 1-2mm long white lines covering the stems (this has also spread to the leaves of the neighbouring parts of the hedge which are still healthy - at the moment). The lines don't move so I don't think it's an insect infestation. Is this some sort of fungal infection and if so what should I use to treat it? It looks really unsightly having a dead chunk in the middle of my nice hedge! PS. The white lines are only on the tops of the leaves.

Answer: Its sounds as though your euonymus may be infested with Euonymus scale. This particularly affects evergreen species of Euonymus. These little insects clamp down upon the leaves, sucking sap from the plant and causing a pale mottling to the leaves which eventually turn yellow and drop off. Such infestations weaken the plant, causing severe die back.

The male scales are white, elongated oval-shaped, and measure about 1- 2mm in length. They generally appear on the undersides of the leaves, but it is not unusual to see them on the top of the foliage. If you take a closer look at the stems you may also notice larger, brownish oyster-shell coloured scales. These are the females. When scale insects first hatch they are quite mobile and crawl around the plant sucking sap until their hard scaly shells form, when they become firmly fixed to one spot. Males, females and juveniles may be present at the same time and they are particularly prevalent from May to August.

The best way to control this is to target the young mobile insects using a systemic insecticide such as Provado Ultimate Bug Killer Concentrate or Scotts Bug Clear Ultra. A systemic insecticide is absorbed through the foliage and kills the scales as they feed. I would also cut any dead stems back to healthy growth to encourage the plant to rejuvenate. Hope that helps Sheila.


Name: Kay Mckenna
Question: Should I prune my blueberry, if so, when and how?

Answer: Hi Kay, blueberries fruit on stems produced in the previous year and should not need to be pruned in their first 3 years except for the removal of dead, damaged or diseased stems. After 3 years, begin to prune out the oldest stems at their base between late autumn and early spring in order to encourage healthy new growth the following season.


Name: Jess McCloskey
Question: Add honeyberry to that question, please. My honey berry bush is so long and far-reaching it has got to be pruned, surely, otherwise I'm going to have to move out before it takes over my life completely.

Answer: Hi Jess, these shrubs certainly do like to spread out! Their pruning requirements are similar to that of blueberries in that they flower and fruit on wood that is a year or more old. Cut back about a quarter of the oldest shoots to the base after you've finished harvesting the fruits. If you feel you need to cut back more to make space, try to leave some shoots unpruned so you have a crop next year. Repeat this annually to promote replacement growth.


Name: Emma Bowden
Question: I have a small plot at the bottom of my garden, what winter veg would you recommend? Am trying Garlic and have second cropping potatoes in bags but don't want the winter weather to wash all the goodness out of the soil.

Answer: Hi Emma, many Brassicas make ideal winter vegetables but will need sowing straight away to give them a chance to grow before the frosts. Try hardy cabbages such as 'Tundra'-plants 'Tundra'-seedsor 'January King'. Similarly Kale also makes an excellent winter vegetable and can be quite attractive, such as 'Black Tuscany. On the theme of attractive vegetables, purple sprouting broccoli makes an unusual addition to the winter vegetable garden. Hardy lettuce 'All the Year Round' is a great crop for sowing now for winter salads. You could also try onion sets for autumn planting such as 'Hi Keeper'.


Name: Andy Clayton
Question: What winter crops should I consider for grow bags in my mini-greenhouses?

Answer: Hi Andy, all the winter-hardy vegetables mentioned above for Emma's vegetable garden would be suitable for growing in grow bags, although it's worth bearing in mind that sprouting broccoli can grow 60-90cm tall so would probably fare better in a deeper container. You could also try spinach in your greenhouse, such as ‘Scenic'. New varieties of carrots such as 'Nantes Frubund' are ideal for sowing under cover in the autumn or winter for early crops.


Name: Stasya Ng
Question: How and when do I prune my rosemary bush?

Answer: Hi Stasya, it's best to prune rosemary in mid to late spring. If you prune it now you could run the risk of any new growth dying back with early frosts. Rosemary is like lavender in that it does not re-grow well from old wood. It's best to only give the shrub a light trim and remove any shoots you feel have become out of control.


Name: Sarah Gregory
Question: Question for Sue : Hi, I have a north facing fence at the top of my garden that gets no direct sunlight. Can you recommend any plants for this space? Everything I've found so far has specified part-shade. Thanks

Answer: Hi Sarah, there are a number of climbers that originate from woodland areas that will be happy growing in part shade or fully shady conditions. You could try Hydrangea petiolaris which produces large heads of small white flowers in the summer. For foliage cover you could grow Parthenocissus henryana (Virginia Creeper) which has lovely bright red autumn colour. Sweet smelling honeysuckle is a fantastic plant to grow in the shade, particularly if you choose the evergreen Lonicera japonica ‘Halliana' (Japanese Honeysuckle) as you will also have winter foliage. Pyracantha will do well in a sunless position and will provide both summer flowers and colourful autumn berries although bear in mind it does have thorns. A slightly more unusual climber is Berberidopsis corallina which has lovely red flowers in the summer and early autumn.


Name: Ann Cleverley
Question: I grow lillies in pots. This year they have been very disappointing. Brown spots on leaves - some like blisters. Buds rotting and, of those that open, some of the petals are brown. Can I repot or should I throw away? Should I use ericaceous compost?

Answer: Given the recent heavy rain across the UK in recent weeks I would expect that this was the cause of the rotting flower buds and brown petals. What a shame! The brown spots may be fungal leaf blight or lily disease. This type of fungus spreads freely in wet, humid conditions. The best way of preventing it is to grow lilies in sunny, well ventilated positions where the foliage will dry out quickly following rainfall. Also, take care to water directly into the pot and not from overhead.

Cut off and burn any severely infected leaves and let them die back this year as normal. Destroy any remaining plant debris in autumn. The spores overwinter in the soils surface so I would repot them once they have died back to ensure that they are in fresh, clean soil for next year. You shouldn't need to use ericaceous compost as most lilies are quite happy in a neutral soil.


Name: Ann Norfolk
Question: Can you advise me what to do with my Monarda the flowers are beautiful but the leaves and stems have a white powdery mildew. At the moment i have stripped the plant of all leaves, thank you Ann.

Answer: Powdery Mildew is quite prevalent at this time of year and affects a wide range of plants. It is often associated with humid conditions and the plant becoming dry at the roots. It can be controlled by spraying with a fungicide. There are lots available, just check the manufacturers label to make sure you choose one that is suitable for clearing powdery mildew on ornamentals.

Prune out and burn any infected plant material to reduce the spread of spores, and try to prevent the plants becoming dry at the roots by ensuring that they are adequately watered. You could also apply a mulch in spring to help conserve moisture in the soil throughout next summer.


Name: Jeanie Taylor
Question: This is a question for Sue; I have an oak sapling that I saved for a community garden (I didn't grow it) and have kept it on our patio (facing southeast) for the past 6 weeks or so. It grew some fresh leaves and then started looking a bit sad; it's got mildew I guess. As it's final destination is not yet sure I need to... keep it in a pot for the time being but need to know if it will recover and how best should to look after it now? If you have any advice for me I would be very pleased.

I also have a walnut sapling kept in a shady place in the garden (I thought it was an ash and was in the throws of pulling it up when I realised there was a walnut attached to it!). This I potted up into a multi purpose compost but a root is starting to show through and I would like to know how to look after it now. Hope you can help.

Answer: Hi Jeanie. With regard to the powdery mildew on your Oak I refer you to Ann Norfolk's question. My advice would be the same. Except that I would not prune your tree as this will promote lateral shoots to form and would ruin the shape of your young oak. It will probably defoliate when it is ready to so just make sure you collect up the infected leaves as they drop. I would also repot it in a deep container using soil based compost such as John Innes No.3, and make sure that it is kept moist at the roots. Container grown plants are particularly susceptible to powdery mildew because they are reliant on us for their water source. Try not to position it in full sun all day long. A semi shaded site will slow water loss and reduce plant stress. Look after it, and it should be fine next year.

Repot the Walnut at the same time. Use the same John Innes No. 3 compost and a deep pot. Ideally you should start thinking about where you eventually want to plant it as large trees like this do not do very well in containers in the long term and would much rather be planted in the ground.


Name: Stephen Muddell
Question: Hi Sue, this is the first season for my family apple tree purchased from T&M and its really struggled! As soon as the flowers came out and leaves began to open, it had a severe attack of aphid - I tried rubbing them off as I didn't want to... spray when flowers were open, but ended up having to spray because it looked more and more sick! The apples are still very small despite feeding the tree, and it now has woolly aphid plus more normal aphid! How should I treat it over the next 6 months or so? Shall I remove all the fruit to help it concentrate on building up strength for next year? How do I get rid of the woolly aphid? And what should I do next season if the same sequence of problems occurs? Sorry this is so long-winded!

Answer: You did the right thing by trying to squash the aphids earlier in the year but I appreciate that it can be difficult to control in heavy infestations.

I would suggest that this year you use a systemic insecticide such as Bayer Provado Ultimate Bug Killer Ready to Use to reduce the aphid population. Systemic insecticides that will be absorbed throughout the plant to kill the feeding aphids. However, if you decide to use the apples, you will need to be very careful to read the manufacturers recommendations for the use of this product and the interval before harvesting crops. Personally I would be inclined to remove them this year anyway to give the tree a chance to establish.

In winter use an oil winter wash such as Growing Success Winter Tree Wash to remove overwintering aphid eggs. This winter treatment is likely to be most effective at reducing the problem for next year but you will need to be vigilant in spring for a recurrence of the aphid which will need spraying. If the problem recurs next spring you could try using an organic spray such as Bayer Organic Pest Control. This has quite a short persistence and works on contact so you will need to be thorough and may have to spray several times throughout the season. However, this spray can be used right up to a day before harvesting which is a great benefit.


Name: Lynn Sutherland
Question: Hi how do i go about collecting seeds from my sweet peas? many thanks for any replies

Answer: Hi Lynn, wait until the seed pods have turned brown and cut them carefully from the plant when they are ready. Spread them in paper-lined containers in a warm place to dry thoroughly. Then you can either twist or squeeze the pods to split them open and extract the seeds. It's best to do this over a container and take care, as the seeds can sometimes fly from the pods (the plant's natural way of dispersing the seed). Store your seeds in a paper envelope and keep them cool and dry until next year.


Name: Natalya Boyd
Question: Hi Sue, I got some "Irresistible" strawberries from T&M and am very disappointed with them as they fell prey to some fungus rendering scarce fruit inedible. I got some pics and might attach them for you. T&M was very late sending them off to me (they took almost two months!) so I think that was the reason for the plants being so weak. On the other hand strawberry "Cupid" had done very well.

Answer: Hi Natalya. I'm afraid that there are a lot of different fungus species that can affect strawberries and without more information it is hard to diagnose the exact problem. However many fungal problems can be reduced by practising the following cultivation tips. Water the plants from beneath the foliage rather than over the top, as this may cause the plant to rot and also improves conditions for the spread of fungal spores. Don't crowd the plants too closely together – the better the ventilation, the less the risk of fungal infection. Remove and destroy any infected plant material as soon as you spot it. After harvesting your crop, remove any mulch from around the plant and cut back the foliage to reduce the build up of pests and diseases. Hope these tips will help you.