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A hedge in a trough, raspberry pruning and how to grow a winter iris

olive trees underplanted with rosemary hedge
Large planters accommodate olive trees underplanted with rosemary Credit: Marianne Majerus Garden Images

TROUGHS OF DESPAIR?

The subject of garden boundaries rears its head over the top of the trellis again. Rachel Evans, in her attempts to form an attractive defining barrier between her and next door’s block-paved drive, has come up against an oh-so-common problem – namely, how to achieve an attractive, at least partially evergreen, thicket in containers (four of them in a row, each 3ft/1m long and barely deeper than most window-boxes), and each with its own metre-high backing trellis.

The rather exposed site gets afternoon sun. The current mix of clumps of thrift, small clematises and scrambling variegated euonymus does not work, and she asks for ideas. The following may help, bearing in mind that this will always be a difficult, high maintenance project.

  1. Limiting the planting to two to three evergreen species will look smarter.
  2. Each container of the size above should house a maximum of two shrubs or climbers, to allow sufficient root space for proper growth.
  3. Evergreen climber Trachelospermum jasminoides (on Rachel’s “wanted” list) when grown in containers is relatively slow-growing and manageable, but may not enjoy the site. Easier still would be exposure-tolerant evergreens (e.g. Griselinia littoralis, Olearia macrodonta, Brachyglottis ‘Sunshine’) that can be controlled/shaped by early summer pruning, their taller shoots tied to the trellis to provide coverage.
  4. Compost should be loam-based (John Innes No 2 or 3), topped up with organic matter yearly.
  5. After planting, a covering of porous weed-smothering membrane, topped with a layer of coarse gravel or cobbles (which can be removed and replaced when the compost is refreshed each spring) will help to retain moisture.
  6. For “colour”, if required, potted annuals could stand neatly on the stony mulch, thus providing no competition for the roots of the hedge, which would also benefit from any drainage of liquid fertiliser watered on to the annuals.

RELUCTANT RASPBERRIES

I bought 10 ‘Tulameen’ raspberry canes in autumn 2016. They produced a few canes (that didn’t fruit) the following season that I cut down early last year. Production of new canes was prolific last summer, but I still got no fruit. What now? I live in the Norfolk fens on alkaline clay soil, but have had no trouble with raspberries in the past.

Mrs Raina Corridon – via email

Raspberries Credit: Picasa

I am not surprised that they did not fruit in their first year after planting, but you are right to have expected better the following year.

Although raspberries favour slightly acid soil, you say you have succeeded with them before so I can only surmise that the ferocious hot, dry weather last summer has got a lot to do with the lack of fruit, effects made worse by rock-hard clay soil.

Canes of autumn-fruiting raspberries such as this are generally lopped down to a few inches from the ground around now (as you did last year), but you could try a different tack this year: cut only half of the canes down to the ground, the rest to about half their current height.

Those that are half-pruned should produce early fruit, and the rest will behave as you expect and produce their “normal” late crop. After pruning, you could feed the row with a fistful per yard of sulphate of potash and blanket the ground with a really thick organic moisture-retaining mulch.

IRISES IN FEBRUARY

I recently admired a lovely, solitary blue iris in a vase at a friend’s house. She inherited the plant (huge and ugly-looking, despite the beauty of its flowers) along with the house and claims she “does nothing to it” to make it flower, which it does on and off for weeks. I am tempted to accept her offer of a piece 
of it. Have you any advice?

Bea Barford – via email

Iris unguicularis

Many a donated piece of the winter-flowering Mediterranean Iris unguicularis has come to grief because it was dug up immediately following its winter floral performance. By all means take up this offer but go back to your friend in the autumn, when a transplanted piece is far more likely to prosper.

Other advice is to find a suitable site for it in your own garden, the dry and impoverished alkaline soil at the bottom of a sunny wall suiting it best. When you plant it, give it no fertiliser, no organic matter, just a little water to settle it in. Thereafter, simply keep snails at bay by scattering a few wildlife-friendly pellets every autumn, and in spring, after flowering, snip out the tattiest brown leaves with scissors to ensure the roots get a good baking during the summer.

If you get all this right, your plant will expand and should flower increasingly well.

 

Do you have a question for Helen Yemm? Email your gardening queries to [email protected] - and add your own tips to the Comments section below. 

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