Facebook Q&A Session 19th August 2014

Plants in Poor Health
- your horticultural questions answered.

View the answers to our previous sessions.

"I have an apple tree. When we first moved here it fruited. Now for the last three years it has had blossom on it but all the leaves die and nothing comes."

Sue - T&M
Horticultural Expert

"Hello Simon. It's really impossible for me to say what the problem is without further information such as how and when the leaves die back. For example, curling apple leaves are often caused by pest such as aphids. Take a closer look at your tree to see if you can spot the problem.

In the first instance, if you can find no evidence of disease or pests then I would aim to improve the growing conditions of your tree. Compacted soil can be critical to the health of a tree, reducing air, water and the availability of nutrients at the roots. You can improve the soil conditions in late autumn by aerating the ground around the root zone. Simply penetrate the soil repeatedly across the entire root zone with a garden fork, preferably to a depth of around 30cm. Remember the root zone may spread beyond the extent of the canopy. Follow this by spreading a thick mulch of organic matter such as well rotted manure across the area but avoid mounding it up around the trunk. Don't try to dig it in. Just let it break down naturally to improve soil fertility and retain moisture in the soil. This may not solve the problem directly, but will certainly improve your trees health and vigour which will make it more resistant to pest and disease problems."

"My mature, variegated Holly drops half it's leaves at this time of year. Any remedies, Sue?"

Sue - T&M
Horticultural Expert

"Hi Christine. Like most evergreens, Holly will drop its leaves when stressed in some way. Water stress would be the first thing that I would check for at this time of the year. You don't mention any other symptoms but it would certainly be worth taking a look for any indications of pest infestation or disease. However Holly is generally quite a tough and resilient species, and a mature one will often ride out any pest or disease problems without the need for intervention.

If the tree appears to be otherwise healthy then I would put this down to normal leaf drop. Even evergreens need to discard old leaves to make way for new ones. Provided that the shoots are green and healthy then you needn't worry - fresh new leaves will be produced to replace those lost. Just watch out if you are walking about barefoot!"

"Sue, I have a tree peony which I bought from your company 2 years ago. It does not seem to progress at all. It is still a small pathetic looking plant and has never flowered. I was thinking of replanting it but I would like to know what sort of compost to fill the new hole with. Best wishes Robin"

Sue - T&M
Horticultural Expert

"Hi Robin. Tree Peony's are notorious for being slow to flower. They really need to be well established before they start to produce blooms and this can take 3 years or more. It's also worth checking that they are growing in suitable conditions and making improvements where necessary. If conditions are unsuitable for the plant then it may be better to move it, but remember that this will delay establishment further still.

Here are a few tips. Tree Peonies are at their best in sunny positions and won't do well in shade. They also need shelter from cold drying winds and strong early morning sunlight. Check the soil isn't too wet as the plant will struggle and eventually rot - Tree peonies like moist soil, but it must be well drained.

If you do decide to replant it then you can mix some ordinary multipurpose compost into the soil before you dig your hole. Don't be tempted to backfill the planting hole with just compost - it needs to be mixed thoroughly with your own garden soil. It's important that the peony is planted so that the grafted union sits at least 10cm (4") below the soil surface. I know that this sounds very deep but it is necessary as shallow planting may hinder establishment and delay flowering.

Feed your peony with a high potash fertiliser during the growing season as they are heavy feeders. The potash will encourage flower production. I hope that these tips help you. Tree Peonies do require a lot of patience but they are well worth the wait!"

"I have some rose bushes in my garden that were left by the previous owner. A couple of them seem to have flowers with very floppy stems - they're not strong enough to hold up the flowers. Is this just a problem with the varieties I'm growing - but there are two different (unknown) ones with this problem, growing near each other - or are they short of minerals or trace elements, which would help them hold their heads up properly? They are growing on clay and I don't cosset them.....but my other roses seem fine with similar unkind treatment!"

Sue - T&M
Horticultural Expert

"Hi Lucy. This is quite a common problem with roses, particularly the large flowered English Rose types. It is simply because the bid puffy flower heads are too heavy for the stems, particularly in wet weather. This is their normal growth habit and tends to improve as the plant matures. You can help to prop them up by inserting a few twiggy sticks discreetly around the bush to hold the growth more upright.

Insufficient sun can also be a contributing factor to weak spindly growth. It may be worth reviewing the position of these roses and moving them in the autumn if necessary.

You can encourage stronger growth and thicker stems by pruning them back in winter by no more than a half. Don't worry about your soil type - roses growth well on clay. They are quite greedy plants however, so an application of slow release fertiliser in spring and autumn will be beneficial. I hope that helps you Lucy."

"I have an ornamental cherry tree in the front garden and its leaves have started going brown but not falling off, it is on three branches so far, is it dying? The tree is about twelve foot tall and has been in ten years. It is Autumnus or something x"

Sue - T&M
Horticultural Expert

"Hi Jane. It sounds as though your tree is definitely struggling. Without seeing it or having a little more information, it is almost impossible to say what the cause is. I would suggest that as it has been there for 10 years already and the damage is fairly localised then the cause is likely to be a disease of some sort, such as cherry leaf scorch. However it is still worth checking that there is no obvious mechanical damage to the tree, and no obvious changes to its growing conditions. If you have some pictures or can describe the symptoms in more detail then it might be possible to give a more precise diagnosis.

It's hard to offer a solution without having a proper diagnosis. I would certainly suggest that you rake up any fallen leaves and burn them to prevent the spread of any fungal spores. Trees are often more resilient than we anticipate and capable of compartmentalising wood within their branches to prevent the spread of decay and disease that may have entered the branches themselves. Don't despair just yet - it may well survive, even if it looks a bit scruffy this year!"

"Hi the leaves on my allium plants are turning brown at the tips. The allium have not flowered yet but there are buds on it so, does that mean there is still some hope? Thanks"

Sue - T&M
Horticultural Expert

"Hi Imrana. This is fairly typical of Alliums. They often start to brown off just as they come into flower. It is caused by environmental conditions and nothing to worry about. The best way to grow Alliums is to plant them in herbaceous borders among leafy perennials which will hide the browning foliage while you get to appreciate the flowers."

"Hi, I have 3 trees growing in my garden, the one on the right is going brown. Is it dying? Also what is the name of the tree on the left? I love it."

Sue - T&M
Horticultural Expert

"Hi Irminka. It's really hard to say as the photo is not particularly clear. The tree on the left could be Cornus controversa 'Variegata' but I really cannot be sure without a better image.

Regarding the conifer on the right of your picture, there are a number of possible causes of brown patches like these. The tree may well be suffering from a pest such as Cypress Aphid or scale. There are also a number of diseases that might be affecting the tree but without more information and a better picture then it is impossible to say. There is also the possibility that it is suffering from some kind of stress - drought, drying winds etc. It would be worth inspecting the tree and it's growing conditions more closely for any other symptoms that might be present.

In some instances, bare patches may eventually fill in as healthier branches continue to grow but this can take many years. Don't be tempted to cut branches back to older, bare wood as conifers cannot recover from this. I'm sorry that I can't be more specific for you, Irminka."

Sue Sanderson T&M horticulturalist

About Sue Sanderson

Plants and gardens have always been a big part of my life. I can remember helping my Dad to prick out seedlings, even before I could see over the top of the potting bench. As an adult, I trained at Writtle College where I received my degree, BSc. (Hons) Horticulture. After working in a specialist plantsman's nursery, and later, as a consulting arboriculturalist, I joined Thompson & Morgan in 2008. Initially looking after the grounds and coordinating the plant trials, I now support the web team offering horticultural advice online.

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