Q&A - Shrubs

Q. I have an Abutilon, which is about five years old and has always flowered profusely but this year although apparently healthy in leaf there is very little bloom. Should these shrubs be pruned and if so when?

A. Abutilon don't need pruning to make them flower but the previous seasons growth can be cut back hard to keep the plant bushy. The lack of flowers may be due to lack of food or it is growing too well to bother flowering. If you have been feeding the plant a lot then stop doing so and water well, if not then feed with a liquid fertiliser such as MiracleGro or Phostrogen. You should also make sure the plant is in a warm sunny spot.

Q. Having recently purchased an Acer Palmatum Atropurpureum we have planted it into a large pot using multi purpose compost. Some of the leaves have developed yellow spots. The tree is in a sheltered spot with partial shade. Please advise how to get rid.

A. It is unusual for Japanese maples to suffer from diseases. It is most likely to be scorch, which these plants are very prone to especially when very young. Make sure the plant is well out of any wind, is kept well watered and that you keep water off the leaves especially during sunny windy weather. The spotted leaves are obviously unsightly but they are best left alone.

Q. I was given an Acer palmatum Dissectum as a present and it is starting to die back really bad. Can you please give me a few tips on how to look after the plant. Where to stand, how to feed etc.

A. Acer palmatum Dissectum can be tricky to look after particularly when young. They need to be kept out of bright sunshine and drying winds and the roots should always be slightly moist. Drainage is important too and this can be improved by digging in plenty of well-rotted manure or compost into the soil. If growing in a pot in the early years it is best to grow them in plastic pots (not black as these get too hot), as plants don't dry out so quickly in these. Later you can pot into glazed clay pots but you should avoid terracotta, as the plant would dry out too quickly. Drainage is important too so make sure you put broken pots in the bottom of the container, which should be stood on pot feet or small pieces of wood or brick etc. A good potting compost that contains loam (soil) and grit is also important.

Q. What Bamboo grows the fastest, and will be able to give me the best show of height in the first year? As I only have a small garden I was going to use Bamboo for height and as a background plant to show off the other plants that I have.

A. Bamboo is a good choice but unfortunately some of the fastest growing ones are also too invasive for a small garden as they can form quite large clumps. Most will take a couple of years to establish before they really get growing but it is worth the wait. You could try either Fargesia murieliae Simba or Fargesia nitida.

Q. Can you tell me what is the best time of year to split a bamboo? I have heard conflicting answers from two garden centres. Is it perhaps dependent on the variety of bamboo?

A. A certain amount depends on where you live and what you will do with the plants once split. It is best to split in the autumn in the south of England as the plants will be put on new roots before the winter and be ready to grow away in the spring. However commercial growers tend to split in the spring and this is certainly the safest option if you are at all unsure.

Q. I managed to split two bamboos five weeks ago. One of them seems fine but the black stemmed one doesn't look very healthy at all, although it hasn't died completely. I have been feeding it with a whole watering can of water supplemented with Phostrogen daily for a week but the leaves are still very yellow and some of the stems have no leaves at all! I've also packed the soil with lots of compost for extra feeding plus I put in slow release food pellets when it was planted. Is there anything else you can suggest, or is it just seasonal? It's right beside a large conifer so I'm wondering if the conifer is taking all the goodness from the soil, leaving nothing for my poor bamboo.

A. This often happens. You really need to wait until the spring when new leaves and shoots should appear. The plants will hopefully in the meantime be producing new roots ready for a growth flush in the spring. You should stop any further feeding and only water if the weather is dry for a period of time.

Q. I am having great difficulty in getting rid of bamboo, the previous owner of my house was a landscape gardener and planted bamboo, it has got to the point where it is overtaking everywhere it is growing under next doors fence and spreading into their garden, I have tried some weedkillers but so far they haven't worked. Every year we cut it down but it comes back thicker than ever. Have you any idea how we can get rid of it for good. We have tried digging it out but the roots are so long and tangled that we couldn't do it. Please help if you can.

A. Some bamboo are very vigorous and spread by underground rhizomes, which are difficult to contain, and yours sounds like one of these types. Weedkillers will not be effective and the only real way of getting rid of the plant or containing it is to dig it up and replant smaller pieces from the outside of the clump every few years. The plant roots are generally not very deep and a strong person should be able to dig a trench around the plant and then excavate underneath until it is loose. It should then be possible to pull the plant out and split it up to a more manageable size.

Q. Could you please tell me the best growing conditions for Camellias, i.e., soil food general conditions and best time to move them.

A. Camellias are easy to grow in any good lime-free soil that is free draining. They prefer a west or northerly aspect sheltered from winds. Woodland areas are suitable as they prefer light shade. Shelter from a wall is also good. Replanting is best in either Sept-Oct or March-April. In April give a good mulch with about 5cm (2") of well-rotted farmyard manure or compost and feed with a general fertiliser such as bonemeal, fish blood & bone.

Q. I have had a Camellia in my front garden for two years now. (This is its second summer). It gives lots of lovely glossy leaves, but not a flower in sight. It is quite near to the house so it is fairly sheltered and it gets sun in the mornings. I have been careful (I hope) not to let it dry out. The soil has some clay in it. Should I have been pruning to make it fill out? I haven't touched it yet because I wanted to let it establish itself.

A. Some plants take a year or two to flower once planted as they are busy growing and this may one of those occasions. However if you feed with a high potash feed in late summer/early autumn you will encourage the formation of flower buds for next spring. Try a combination of quick acting rose food and longer lasting bonemeal.

Q. Can you tell me how to maintain this plant during the winter months as this has grown in to a large pot specimen this year and it would be a shame to lose it.

A. Fatsia japonica is hardy in the southern half of the UK and in sheltered parts of the north, however in a pot it can suffer if the weather is cold and windy. You should place the pot in a sheltered spot out of the wind and in very cold conditions wrap the leaves in fleece. It would also be wise to wrap the pot in bubble wrap too. Whatever the weather raise the pot slightly off the ground on pot feet or small blocks of wood or similar and do water as the plant will still dry out as it is evergreen. In the autumn feed with a general-purpose fertiliser such as bonemeal, fish, blood and bone or Rooster.

Q. I have an azalea about 10 years old in a large pot, and I notice that flowers are beginning to form. There is lichen on some of the branches, is this harmful?

A. Lichen is quite normal on Azaleas particularly in wetter areas and does no harm whatsoever. If you don't like the look of it you can simply rub it off, but it adds a bit of extra colour and texture to the bark particularly in the winter.

Q. I have a two year old magnolia bush but I can't remember the exact variety. It seems to be growing relatively well but has brown spots all over it. I imagine this is a fungus problem and have used a general fungal spray but would be grateful for any further advice.

A. It does sound like a fungal leaf spot. It is generally not too damaging and a spray containing carbendazim or mancozeb is usually effective. You should also rake up and burn any leaves that fall to the ground. A good feed with a general fertiliser such as bonemeal or Growmore plus a 5-7.5cm (2-3") mulch of well-rotted manure or compost will also help.

Q. I have an established philadelphus shrub which flowers in mid to late June and has wonderful small white flowers when in bloom. I have had this shrub for many years and it has always failed to flower and annually disappoints me. I moved it a couple of years ago to a sunnier spot in the garden. I used to prune every year, and although it grew back vigorously it never flowered. This year I decided not to prune, and I now have a woody straggly shrub. Approx 5ft tall, with a canopy of growth. Will it flower this year?

A. Philadelphus are generally very reliable at flowering but the flowers are produced on old wood so by cutting it back each year you are stopping it producing flower buds. As you have left the plant alone now for a year you should get flowers this summer. Leave it unpruned for a further year except to shorten any straggly growths. In following years you can remove about one third of the old stems after flowering to keep the bush growing vigorously and compact. Do not feed the plant this year until after flowering which you should then do each spring and autumn.

Q. I bought a Pieris forest flame and planted it out a month go. The red foliage has now turned yellow and is nowhere near as attractive. Is this a problem with the plant?

A. It is only the young spring growth of Pieris Forest Flame that is red. It then goes yellow and finally a deep green so no need to worry. You will get bright red shoots again next spring and hopefully white flowers too.

Q. Can you tell me why just some of my rhododendrons are flowering and not others? Also, on some, there are only a few flowers although there is lots of new growth.

A. Some plants do not flower until they are a few years old which may be the case with your Rhododendrons. Also flower buds can get damaged in the winter by the cold and wet and some varieties are more susceptible. Some plants if they are newly planted are more concerned with growing new shoots and roots to bother producing flowers. It could be one or a combination of these with your Rhododendrons. To help the plants produce flowers for next year feed your plants with a high potash fertiliser in late summer and remove any dead flower heads as soon as they look unsightly.

Q. I planted a pot grown Weigela 'Bristol Ruby' last year in my garden and, during the autumn I cut it back to give it some shape. This year it has grown enormously producing lots of new shoots, masses of leaves but to date, only five flowers. I have been feeding it with a shrub & tree fertiliser since early summer but still no flowers. Can you please advise me what I can do to promote flower production.

A. Weigela flower on old wood so by pruning it hard last year you in effect removed all the flower buds. Leave it unpruned this year and then in subsequent years remove up to a third of the older stems or shorten them to maintain the plants shape.