Sunday 18 August 2019

Gardening with Diarmuid Gavin - multiply your shrubs

Follow my easy guide to taking hardwood cuttings this week to produce a free garden bounty next year

A sharp pair of secateurs is necessary for taking cuttings.
A sharp pair of secateurs is necessary for taking cuttings.

Diarmuid Gavin

I spent the month of December 1986 in a freezing shed. I was a Botanic Gardens student on my final work placement in St Anne's Park, in Dublin's Raheny.

The park had a very large nursery area where plants were propagated and grown on to supply much of Dublin city's green spaces with colourful bedding and woody shrubs. And so, each weekday morning that month I cycled across the city to join the hardy St Anne's gardeners in a very large corrugated shed, where the job of the season was to take and prepare hardwood cuttings.

As Christmas music played on the radio, trolleys filled with newly clipped cuttings from the park shrubberies and stock beds were wheeled in. My job was to cut them down to size, dip the ends in rooting powder and carefully place them in trays of gritty compost. I found the experience of preparing new plants which would help to green a city exhilarating.

Since shrubs were first brought to these islands, often from the Americas, we have used them as the solid backbone of our gardens in hedging or mixed borders. Many of them are very easy to propagate, so if you're planning a large plantation over the next year, consider growing your own from hardwood cuttings.

It's an easy but sometimes slow method of propagation and we are entering the perfect time for it. Deciduous plants that are dormant in the winter - shrub roses, dogwood (cornus), willow, poplar, flowering currants (ribes), spiraea, abelia, deutzia, kerria, philadelphus and viburnums - are perfect candidates.

Also suitable are fruits such as gooseberries and currants, and climbers such as honeysuckle, parthenocissus and vines. Hardwood cuttings from evergreen plants such as holly (ilex), privet, cotoneaster and skimmia can also be taken at this time of year.

You need a sharp pair of secateurs, rooting hormone powder, containers and compost. The compost should be a free-draining mixture, such as a cuttings compost. Make sure you sterilise your propagation tools fully before starting because it takes some time for the roots to develop and the cuts will be susceptible to fungal infection.

With your secateurs, or a sharp knife, take the cutting from an upright growing stem. Choose the healthiest, most vigorous-looking specimen available as this is the exact genetic material you are producing from. The best cuttings will be made from stock that was hard pruned last year, as these will be fresh and vigorous.

Long branches can be divided into a number of cuttings and should be no thinner than a pencil. Each cutting should have at least two leaf nodes and should be roughly 4-6 inches. The top cut should be sloping just above a bud, the bottom cut straight and just below a bud.

Once you have separated the cutting from its parent, it is in danger of drying out, so get it potted up as soon as possible. If this isn't possible, put it in a plastic bag somewhere cold.

Dip the lower end in some rooting hormone powder which will encourage roots to shoot (and often contain a fungicide to help prevent rotting) and now plant in your container. You want about two-thirds of the shoot buried beneath the soil, as roots will grow from these underground buds, and then about one-third above soil which will develop leaves in the spring.

If you are planting several cuttings, space 4-6 inches apart. Gently water in using a hose or can with a rose attachment so you do not dislodge the cutting.

It's possible to insert prepared cuttings in a trench in the ground. Otherwise, leave in a cold frame or unheated greenhouse or somewhere with a bit of shelter and make sure they don't dry out. For months nothing will appear to happen, then a callus will slowly form over the cut and, in spring, the roots will emerge.

It will take a year before they're ready so if you did this last year, you should have some healthy specimens that can be transplanted to their final situation.

It's cold outside, so make yourself a cup of coffee and get out into the potting shed and keep growing. The Christmas tunes are optional!

This week in the garden: 

Continue your general clean up, gathering leaves for the compost heap or to make leaf mulch. 

Borderline hardy plants that you are leaving in the ground, such as melianthus and some agapanthus (pictured), should have a heavy layer of compost around their base to protect them from frost. 

Secure all garden furniture in case of winter winds. 

Bring the lawnmower for a service - stores get very busy next spring when we all try to do this at the same time.        

Do a big clean up in your greenhouse - trays, equipment, benches, floors and glass will all benefit from cleaning and  sterilisation to zap overwintering bugs. 

Remove stakes from herbaceous borders that have died back.

Irish Independent

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