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Hedges & hedging plants

Help solve your gardening problem. Here are the answers to some commonly asked gardening questions about hedges and hedging plants with hints, tips and advice.

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I have a large copper beech hedge (about 30m/100ft long) that is infested with whitefly. What is the best and most economical treatment to try to control them?

The most economical way would be to leave the whitefly to get on with things! Although not the best solution the damage is unlikely to be significant (as long as the hedge is healthy – keep it well watered and fed if necessary; seaweed-based tonics, such as Maxicrop, are an excellent tonic for plants under stress).

The next cheapest is to blast the infestations with water from a hose, high-pressure sprayer or even a pressure washer; make sure the latter is used carefully to prevent damage.

Probably the most effective treatment would be to spray the hedge with Provado Ultimate Bug Killer or Scotts Miracle-Gro BugClear Ultra, but this may be beyond your budget.

What is the best way of cutting my conifer hedge?

Always ensure all conifer hedges are cut back by the end of September. Otherwise frost getting into the pruning cuts can cause the hedge to brown during the winter.

Cut the hedge so that the final shape is a broad-topped A; this ensures light reaches the foliage at the base of the plants and so stops it turning brown.

Never cut into old wood, always cutting back branches that are green and covered with foliage.

Even new hedges should have their sideshoots cut back to help bush them out; again never cut back into brown wood. Don't cut out the top until the plants are 15cm (6in) above the final required height, then cut off the top 30cm (1ft).

I'd like to make a screen from Photinia fraseri 'Red Robin', but can't afford to buy lots of plants. Is there a cheaper alternative?

Photinia fraseri 'Red Robin' is a beautiful large shrub which produces red young foliage. Although it isn't often used for hedging, it can be used to make a delightful screen.

Early to mid-summer is the perfect time to take semi-ripe cuttings to produce a lot of plants cheaply. Make the cuttings about 12.5-15cm (5-6in) long and take them just below a node (where the leaf joins the stem). Pinch out the soft growing tip, remove the leaves from the bottom half, cut the remaining leaves in half widthways, and remove a shallow piece of bark about 2.5cm (1in) long at the base of the cutting. Dip the base in hormone rooting powder and insert in pots of gritty cuttings compost or in gritty soil in a cold frame.

Water them in and cover the pot with polythene, or replace the lid of the cold frame. Place the pot in a warm, shady site and shade the cold frame from strong sunlight.

When the cuttings have rooted they can be potted up individually and then planted out when they have developed a good root system.

My privet hedge has started to die at one end. The leaves first turn yellow then fall off. Progress is about 1.8m (6ft) per year. What can I do?

It could simply be that the plants are short of water. Privet is a very thirsty and hungry plant, and needs regular watering in dry periods otherwise it becomes stressed.

However, there could be a more serious problem. The symptoms you describe are very characteristic of honey fungus - a fungal disease which kills woody plants - especially those that are otherwise under stress.

Sadly, the only option is to grub up the plants and burn them. To check whether it is honey fungus you should look in the soil for the black 'boot laces' or rhizomorphs with which the disease spreads. A white fungal sheath also appears below the bark of affected plants.

If it is honey fungus and you wish to replace the hedge, then try using beech, box, laurel, hawthorn or yew which show some degree of resistance. The soil should be kept clear for a year and any rhizomorphs removed before replanting.

We have just moved into a new house. Our next door neighbour has planted a conifer hedge between our gardens. It is about 4.5m (15ft) high, and I suspect still growing, although it does appear that the hedge has been trimmed recently.

Apart from the problem of the hedge keeping out the afternoon sun - the roots seem to have travelled right across our lawn - making it impossible to even contemplate trying to put down a greenhouse or put in place a couple of flower beds.

1. What would be the effect on the trees if we were to cut the roots back to the boundary? We have checked on the legal position and we can do as we wish on our own property. What I hope is that a severe root pruning might slow down the trees growth. Will it? And what will be the effect on our lawn as the roots die? The house is protected by an extension that has much deeper than usual foundations.

2. Supposing we could trim the roots back so that we could create some flower beds (which would get some sun in the morning only) what kind of plants could we plant under the trees? The soil is a typical London clay.

As you say, you are within your legal rights to prune back any growth - above and below ground - which comes over your boundary line. However, if you prune too close back you may damage/kill the conifers - which you aren't allowed to do. I would say you would have to come out around 18in from the base of the plants and do your root pruning along that line.

It's unlikely that the roots have travelled too far as conifer roots don't generally, so I doubt cutting them back will have any affect on the lawn.

The roots will grow back, so I would suggest placing a vertical barrier in the soil to prevent the roots coming back over. There are a couple of types available from suppliers:
RootBlock from Easy Gardener (available in garden centres)
Root Guard from Terram

Don't forget that the Government has passed legislation to control the height of hedges, so your neighbours may have to control the overall height of the hedge.

Suitable plants to grow in this area include:

Sambucus nigra
Viburnum tinus
Iris foetidissima
Symphytum grandiflorum
Waldsteinia ternata
Euonymus fortunei
Philadelphus coronarius 'Aureus'
Viburnum davidii

Many bulbs including daffodils, snowdrops, crocus, bluebells. And lilies L. martagon, L. auratum and L. tigrinum.

But don't forget, the dry soil will be more the deciding factor than the shade, so dig in plenty of well-rotted compost or manure and keep the plants well watered for the first year and subsequent dry summers.


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