It’s time to give those roses a long hard stare with loppers in hand. Here is a quick guide to make sure you make the right cut.
Words Hayden Foulds
The good news is that if you do get rose pruning wrong, roses are very forgiving. The worst they will do is sulk for a while – it’s very difficult to kill a rose by pruning it. So, with that said, it is coming up to that time of the year to get pruning. In most parts of New Zealand, rose pruning is done in July through to mid August. Up north, people usually start a bit earlier and down south a bit later.
Get the blooms
Though it is not absolutely essential to prune your rose, it is highly recommended. Roses have been around for a reported 35 million years – people considerably less, so they can survive without it. But to get optimal results, the most satisfaction and the best blooms, you need to get pruning.
When you prune roses, you are removing unproductive growth in order to encourage new growth. You also need to open up the centre of the bush to let more light and air circulation into the centre of the plant. This helps to minimise disease problems.
Pruning also controls the shape of your rose plants and, for climbers and pillars, helps to train them.
Don’t be tempted
From March, your roses will start looking a bit worse for wear and you may be tempted to prune them to tidy them. Resist. If you prune early, the plants will come into new growth that will be knocked back by the cold weather later in winter – pruning early doesn’t result in earlier flowering either. The exception is if you need to remove any large canes. This is best done during May to prevent infection by silver leaf. The spores are not around during this time so it helps to prevent infection.
Rose thorns have a remarkable habit of finding bare skin, so make sure to cover up as much skin as possible. A good pair of gloves will protect your hands and allow you to handle even the thorniest material. Next, make sure you have a good, and comfortable, pair of secateurs. Keep them sharp by using an oil stone or a hand-held sharpener.
For larger stems, a pruning saw and a pair of loppers will come in handy – don’t strain your secateurs trying to remove a large branch. I find a pruning saw is good because it can get into tight places that loppers cannot.
To prevent double handling, make sure you have something to put your prunings in as you go.
The bud union (also known as the basal union or crown) is the area where the new shoots (called basal shoots) are produced from. These are the lifeblood of the plant and form the basis of future seasons of growth and flowering. When removing complete stems at the base, make sure it is cut off cleanly at the union, rather than leaving an ugly stub that will die back.
It is also beneficial to give the bud union a light scratch with a wire brush after pruning. This area often gets a build up of flaky bark, moss and lichen that often inhibits the production of new shoots. Just be careful when giving it a brush that you don’t accidentally damage any shoots already growing underneath. Clear away any soil or mulch covering the union.
These steps cover the pruning of bush roses and shrub roses – including English roses and miniature/patio varieties. Bear in mind, though, that the latter are naturally smaller so you need to work on a reduced scale.
Of all types of roses, climbers often cause people the most problems when pruning. Many people make the mistake of cutting the long stems back each year, just like a bush rose, and then wonder why the plant isn’t climbing. Don’t keep cutting them back!
Instead, you should retain these stems and train them according to how you want to grow your climber. If it’s against a wall or fence, then train and tie the stems into a fan shape with the younger shoots at the top and the older ones horizontal.
The stems are quite flexible so there is little chance of them breaking, but take care all the same. Then cut back any side shoots to two or three buds.
For those who grow climbers up pillars and post, you still retain the long canes and wrap them around the supporting structure. Cut back any side growth as before but also try and stagger the height of the canes so there are flowers all the way up.
Old-fashioned & species roses
Very little pruning is required with these roses. Just remove any dead and diseased stems and then trim to shape the bush. Many such varieties resent hard pruning. Varieties should be pruned after flowering has finished by removing as much old growth as possible. Members of your local branch of Heritage Roses New Zealand (heritageroses.org.nz) will be able to advise you on pruning such roses.
Standard roses – including bush & mini standards
Standard forms of roses should be pruned harder as they are further from the ground. Light pruning only results in a taller plant that is more prone to wind damage and the flowers are further from your view. Older wood may need to be retained for longer as standards generally produce less new shoots than those grown the usual way.
Check the stakes and ties, making sure the ties are not cutting into the trunk. For weeping roses – those that have long trailing stems reaching towards the ground – you need to remove the dead wood and then thin out any spindly wood.
Those new season roses in the garden centres have not been pruned, just trimmed for ease of handling. They require very little pruning in the first year. Just remove any dead or damaged wood and cut the branches back to the first good bud.
A sloping cut is the best. As a guide, start around 5mm above the bud. The bottom of the sloped cut should be level with the bud. Make sure this cut is clean with no ragged edges that will encourage dieback.
Ideally, cut to an outward-facing bud. (However, it is better to cut to a strong bud first rather than one facing outwards.) The bud will grow in the direction it is facing.
Let the cut wounds heal naturally. Pruning pastes can interfere with this process and also seal in any disease that lands on the cut surface prior to application.
Clean it up
It is highly recommended that you apply at least one, preferably two, of the winter clean-up sprays – even if you don’t like to spray. Common diseases such as rust and black spot will appear much later in the growing season if a clean-up spray is used.
n application of lime sulphur can be followed up with liquid copper and spraying oil, as long as it’s at least 14 days later. The time frame is important as these sprays are otherwise incompatible. Take care when using lime sulphur near paintwork as it will stain.
Try and get at least one spray on before pruning and another once the plant is pruned. It is also a good idea to spray the ground around the plant as diseases will overwinter here and reinfect the plant in spring.
Just give the area around your roses a good clean up and remove any weeds. Remove any fallen foliage still on the ground and then lightly fork over to aerate the soil. An old pair of kitchen tongs are great for picking up fallen leaves where you can’t get your hands to easily.
Compost or well-rotted animal manure can then be added. Mulch the ground in September and October, once the ground has warmed up. Mulching keeps the roots cool, retains moisture and keeps the weeds down.
If you have a tall rose growing in the garden and think giving it a hard prune will thwart its growth, think again. In most cases, the rose will just grow back to the same height, if not more, over the following season. If it’s too tall for the site, either shift it or remove it altogether.
Hedge trimmers & chainsaws
While you can prune using hedge trimmers and chainsaws, there are some disadvantages. Trials conducted overseas have found that roses produce more flowers when pruned this way, but the flower quality isn’t as good. It also leads to a build up of twiggy and dead growth in the centre after a few years, which will need removing. Chainsaws and hedge trimmers generally produce rougher cuts, which causes more stem dieback.
While trimmers and chainsaws are probably not worth the hassle, it may be worth a go if you have a lot of ground cover roses (like the Flower Carpet series) that are often pruned this way in street plantings.
Roses are heavy feeding plants, but overfeeding can cause problems. Instead, feed them little and often. Apply all fertiliser to moist soil and dig in lightly after applying.
Stop fertilising roses after March. April is a good time to check your pH, which should be around 6 to 6.5, particularly if you feel your roses look hungry despite your best efforts. Raise the pH by applying lime (dolomite is particularly good as it contains magnesium) and lower it with sulphate of ammonia.
After pruning, apply some blood and bone or a similar slow-release fertiliser. Start applying a general rose fertiliser in September once the soil has started to warm up and the roses are shooting into growth.
Most rose societies and also a number of garden centres hold pruning demonstrations each winter. These are a good opportunity to get those burning questions answered and to also have a go yourself. Pruning demonstrations organised by rose societies are listed on the New Zealand Rose Society website (www.nzroses.org.nz) and its Facebook group: Roses Aotearoa.