Thompson & Morgan Facebook Q&A Session 13th May - Your horticultural questions answered.

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Name: Jo Moore

Question: I want to put a few shrubs against a north facing fence, they wont get much sun at all. I would like them to be quite quick growing and to end up about 6ft (with pruning) any suggestions please . Climbers wouldnt be suitable, its next doors fence and needs replacing. I forgot to say its a clay soil.

Answer: Hi Jo, there are a few shrubs which will fit the bill! Varieties of Chaenomeles speciosa or Chaenomeles x superba (Japanese Quince) are good choices as they will tolerate clay soil and reach an overall height of between 1.5-2.5m (this varies with each cultivar). Another good shrub to grow in clay soil and shady conditions is Pyracantha. These are often grown as wall shrubs but can also be grown as free-standing shrubs too - their heights will vary between species and cultivars.

You could also try Berberis, Leycesteria and Mahonia x media (highly scented) - all are fast-growing and tolerate the above conditions. Aralia racemosa is a more unusual but valuable shrub for its tolerance of shade and clay soils - it produces white flowers in the spring and summer, followed by dark purple berries. Some less fast-growing shrubs, but still valuable, include Aucuba, which is a fantastic dense, evergreen shrub that will thrive in shade and heavy soils; Viburnum and Sambucus racemosa.

Name: Karen Simpson

Question: What's the best/easiest way to kill off a wisteria root. We don't have the option of digging it up because most of the root system is under paving.

Answer: Hi Karen. Wisterias are very tough plants once they are established. The best thing to do is cut the trunk to ground level and spray the wound with a systemic weed-killer (such as round-up). Systemic weed-killers are carried through the plant, killing it right down to the roots. You may have to do a few repeat applications, particularly if your Wisteria is a large specimen. Also watch out for and remove any suckers that appear close by. Best of luck Karen.

Question: The leaves on my raspberry plants are turning yellow! HELP!

Answer: Hi Matthew, don’t worry this is quite a common problem when growing raspberries and normally indicates a nutrient deficiency. If the leaves are yellow all over then this may be a sign of a nitrogen deficiency. Raspberries need a rich soil to do well - if your soil is sandy or stony you need to improve it with lots of compost or well-rotted manure. The best course of action to take now is to apply a slow-release fertiliser around the base of your raspberry canes and mulch around them with well-rotted manure or compost (take care not to mound the compost up against the canes).

Alternatively if your raspberry leaves are yellow with green veins this may indicate an iron or manganese deficiency. Raspberries prefer a neutral or slightly acid soil; they cannot absorb manganese or iron very well in alkaline soils. To remedy this try applying sequestered iron around the base of your raspberry canes. I hope this helps Matthew, let us know you get on.

Name: Sarah Griffiths

Question: Is Sue still doing the Q&A sessions? If so I have two queries I would be grateful to have her advice on. The first one is, what is this plant? started growing in the corner of my border but have no idea if its a plant or just a weed. Thanks.And for my second query, are these firs dead (I have 3 in varying sizes)? I didn't get to cover them before the snow hit although did after but think they may have already been destroyed. No sign of the green shoots unfolding.

Answer: Hi Sarah. We’re not quite sure what this plant is either! If you didn’t plant this yourself it was probably dropped as a seed by birds or the wind. It may be fun to leave it and see what happens, after all weeds are only plants that are in the wrong place! We would be interested to see a photo when it does flower and this might help us to identify it for you.

With regards to your ferns it doesn’t look too promising - you would normally expect the new green fronds to be showing development by now. It is worth waiting a few more weeks just in case your fern is making a slow recovery. Unfortunately it only takes one exposure to harsh weather for the damage to take place - I would definitely have a cover on standby this year in case of sudden freezes. For really secure protection pack the top half of the trunk with straw or shredded paper before wrapping it in fleece - this will insulate the crown which is the most vulnerable part of the plant.

Name: Pamela Howat

Question: Can anyone identify this shrub for me please? I thought it was a cotoneaster but I don't think it is. Readily roots by layering.

Answer: Hi Pamela. This shrub has got us scratching our heads too. I agree with you that it is probably not a Cotoneaster, although I suspect that it is from the same family - Rosaceae. Perhaps if it flowers or fruits later in the year that would help us to pin it down. Do let us know if you find out what it is.

Name: Lynne Geddes

Question: Every year my small cherry blossom tree looks like it's going to burst with lovely blooms, but instead the branch just seems to wither and die. I have had only 2 branches this year with blossom. I pruned it last year and I did get new branches with lovely green foliage. It just seems that spring time is a complete disaster. Do you think it's maybe diseased?

Answer: Hi Lynne, it sounds like you may have Blossom Wilt or Brown Rot on your cherry tree. This causes the flowers and fruit to wither and die. Leaves may also shrivel and there may be die-back of the shoots. The pruning you carried out last year was a good idea as this improves air circulation around the branches. If you haven’t already, prune out any infected branches/blossoms and put the clippings in with normal household waste (don’t compost or recycle them). I would also spray your cherry tree with a systemic fungicide such as Westland Plant Rescue Fungus Control (containing Difenoconazole). Start applying it as the flowers open next year, following the instructions on the label. Good luck Lynne, I hope you have better flowers and fruit next year!

Name: Lucy Garden

Question: New question for Sue, please - one of my Viburnum Opulus plants has had its newest leaves turned into lace by some sort of caterpillar - is it the dreaded Viburnum Beetle and will it decimate all my other Viburnum varieties? I plan to pick off the affected leaves and see if my hens can deal with the creepy crawlies.

Answer: Hi Lucy. I’m afraid that it does rather sound like your plant has been attacked by Viburnum Beetle. They are particularly fond of Viburnum opulus and the damage that you describe is quite characteristic of this pest. The eggs hatch in May, and the cream/ yellow larvae (with black markings) feed on the leaves for about a month before dropping to the soil. They pupate in the soil, and when the adults emerge in mid to late summer, they return to the plant to continue feeding on the leaves and lay more eggs at the shoot tips. Because both the larvae and the adults feed on the leaves of Viburnum they are capable of doing quite a lot of damage. You can pick off the infected leaves as you suggested, however if your plant is severely affected then I would suggest that you spray your plant now with a contact insecticide containing the chemical thiacloprid.

Name: Sarah Griffiths

Question: Hi, question for Sue, something is attacking my strawberry plants in the greenhouse, the leaves are intact but some of the small fruit has been munched on. Any ideas what preventative measures I can use? Thanks so much.

Answer: It sounds very much like slug damage Sarah. Pop down to your greenhouse one night and see whether you can spot them. Pick them off the plants and kill them, use beer traps, or apply a sharp scratchy mulch such as gravel to deter them. If you are not keen on creeping about by torch light then put down some slug pellets. For an organic approach try using nematodes.

Name: Kevin Joseph

Question: Question for sue, you probably can remember me about my camelia well i pruned it about 2 weeks ago and has new leaves which is good, however two of the leafs have small brown spots on them.

Answer: Hi Kevin. It’s good to hear that you pruned your Camellia. I’m sure that this will improve its shape as the new growth develops. Regarding the spotting on your leaves it looks like they have developed a fungal disease. 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. It is worth knowing that Camellia leaf spots often colonise other small spots on the leaves that have been initially caused by overwatering or nutrient imbalances. So in many cases, this can be prevented by ensuring that your plant is growing in optimum conditions. If the problem persists then you may need to consider spraying with a fungicide.

Name: Chrissianne Carpenter

Question: I bought some honey berry bushes from you about two years ago - they just flowered this spring, at last, but only on one bush. The other two bushes are bare. Would they be males? If that is so then should I not have received two females? Or if the two are another variety, can I expect fruit from them another year? Thanks!

Answer: Hi Chrissianne. The variety of Honeyberry that we now sell (Lonicera caerulea var. kamtschatica) is self fertile but planting them in close proximity to one another will certainly improve pollination. However, about two years ago we were supplying two different varieties in each pack which included a male and two females. In order for pollination to occur the females and the males would need to be in flower simultaneously in order for pollen to be transferred between the flowers on each plant. Your honeyberry plants are still quite young plants and it does take a few years for them to reach maturity and flower. It’s a good sign that one of them has flowered, as it suggests that they are now reaching maturity so the others should catch up soon.

Name: Joseph Marshall

Question: I'm trying to garner a list of annuals, beyond what I currently grow [Pansies, Petunias, Dwarf French Marigolds, and Portulaca, all from flats; Cosmos, Morning Glories, and Sunflowers from direct sown seed] that will meet the following conditions:Containerable plants, very full sun, direct sewn seed, capable of standing heat and water stress, long blooming period [particularly in the mid-July to mid September lull], trailers and climbers welcome, and minimal deadheading needed. I admire T&M's color variety and species range and would love to purchase seed from you, but I need some help sorting out from your very full American catalog.

Answer: Hi Joseph. Have you tried Eschscholzia (Californian Poppies)? These colourful little plants fit your requirements perfectly and will grow almost anywhere from a direct sowing. I would certainly recommend them. If you don’t mind sowing indoors and transplanting later them you may like to try this Osteospermum (Dimorphotheca) for a sunny display. They look wonderful in containers and absolutely love the sun. You might also like Delosperma which we sell as plants or seeds. Hope that gives you some ideas Joseph.

Name: Pamela Howat

Question: A question that I hope Sue can answer (can you get that I'm just managing to get the weeds under control and can start thinking about planting?). I've a couple of hydrangeas (sp) one existing in the garden and one a cutting from my aunt. How can I get them to thicken out from the base? The more established one seems to be doing better this year and starting to sprout more from the roots but the cutting, whilst healthy looking is just a single stem. Any suggestions or is it just a waiting game? Also (sorry) I'd a lovely white lilac which was very overgrown for the garden and I opted to cut it back. However my dad got a bit overenthusiastic and cut it right back to the base. It is a lovely size and shape now but we've been about 4 years since it was butchered and still no flowers. Could it still be sulking and could it suckering nature be putting energy into that rather than flowering. Again any help would be fab.

Answer: Hi Pamela. To encourage your Hydrangea cutting to branch out, simply cut the stem just above the top-most bud. This will encourage the plant to put energy into developing side-shoots lower down.

With regards to your lilac, they do respond well to hard pruning but as you’ve found out, flowering can be delayed (normally for about 3 years). If your lilac has been grafted on to a rootstock the re-growth could in fact be from the rootstock (your dad may well have taken out the white grafted lilac completely), in which case the flowers will probably be pink/purple. In either case, the re-growth should be thinned out. If there are lots of congested stems, thin them out by cutting a number of them right down to the base. Don’t be tempted to prune any growth on the remaining stems as lilacs flower on old wood. Hopefully you should soon be rewarded with flowers!

Name: Sarah Hacker

Question: Can you grow sweetcorn in pots (one pot per plant)? My garden is maxed out but I could put pots in amongst my strawberries. That way they wouldn't compete for water/nutrients and won't compete for light for a while. Thanks.

Answer: Hi Sarah unfortunately sweet corn plants aren’t a good choice to place in-between other crops. They often reach heights of 5 feet or more, which would block out the light to your strawberry plants. They also need to be planted in blocks (12 is a good number), not rows, to help with pollination and formation of the cobs. Lastly you would need to grow the sweet corn in a fairly large container (at least 45cm deep and wide) to allow for stability and a decent crop. They really are better off given their own patch of ground on the vegetable plot! I hope this helps Sarah.

Name: Lucy Garden

Question: Another question for Sue, if I may - I'm growing Romanesco cauliflower this year and have planted them out into my new raised bed. I put fleece over them to protect them from pigeons, cabbage whites, cats and my hens, and it's worked well so far - the little seedlings are growing well. But can I safely leave the fleece in place or will it damage the plants if I leave it on indefinitely?

Answer: Hi Lucy, it sounds like your cauliflowers need good protection this year! I think it is worth considering using fine netting instead of fleece to cover your crops for the rest of the summer. The main reason for this is that temperatures would become too warm for your cauliflowers on hot days. Brassicas prefer cooler growing conditions. Also, fleece does block out a small percentage of light and it’s always worth giving your plants the maximum amount of light possible. I hope this helps.