Pruning can sometimes feel overwhelming but Debi Holland has some simple tips to dispel the mystery and give your plants a much-needed spring boost.
It may feel counterintuitive to make something grow by cutting it back but pruning stimulates vigorous new growth. It is an immensely satisfying gardening job that really feels like you are giving your garden a spring clean.
How it works
Here’s the science behind why we prune. Stem tips (apical buds) produce a growth-restricting hormone called auxin which is sent down the stem to stop other stems developing which would crowd out the dominant tips. When we remove these apical buds it allows the lower buds to make stems and branch out so your shrub or tree becomes bushier. So, if you have straggly shrubs a simple prune at the right time of year will reduce their size, reintroduce shape and stimulate new active growth to bulk it up.
Pruning also allows more light and air to get to the plant’s core. This maximises photosynthesis and ventilation, which is a win-win for your plant’s overall health. Make sure you do not prune shrubs that you expect to flower in early summer like Philadelphus, mock orange; because pruning now will remove their emerging flower buds.
Prune Hydrangeas
Spring is the right time to get to work on your hydrangea; they can be pruned from March to April once the risk of frost has passed. There are many different varieties of hydrangea so check what you are growing before you get chopping to ensure you don’t prune out this year’s flowers.
Mophead and lacecap hydrangeas, Hydrangea macrophylla, flower on the previous years’ growth, so if you are happy with the size of your hydrangea simply deadhead your shrub down to a pair of strong buds and these will develop into this year’s blooms.
When a shrub needs a proper haircut then I take out a couple of old stems right down at the base, this will concentrate energy into producing fresh stems. I also take out any spindly growth as these stems will not do much for the plant other than congest it.
Hydrangeas that flower on new wood; Hydrangea paniculata and Hydrangea arborescens respond best to a harder prune down to around 30-60cm from the base; this will keep your shrub’s height in check and should produce an abundance of large flowers on the new stems that form.
Leave climbing hydrangea pruning, until after they have flowered in the summer.
Pruning Penstemons
Penstemon is another perennial that has my snips twitching until the time is right to give it a good tidy up. After a winter of sorry looking stems hanging around, these can now be cut back to the base in spring; the stems have been doing an important job for months acting as a blanket against harsh temperatures. Garden snips are the ideal tool for the job as they are small, thin and sharp and can get right down into tight spaces without damaging any of the emerging new shoots.
Snipping Salvias
Many salvia die back in winter and emerge in spring but others keep their woody stems as protection against frost, but now spring is here it is time to chop back and reveal the new growth. Snip old Salvia yangii (formerly Perovskia atriplicifolia), Russian sage stems down to the ground; avoid all the lush new growth popping up.
Salvia microphylla ‘Hot Lips’, Salvia greggii such as ‘Lemon Light’ and ‘Amethyst Lips’ and the sweetly scented Salvia x jamensis ‘Nachtvlinder’ all need a slightly more reserved touch; take these shrubs back by about a third to a half of the original plant and new shoots will quickly emerge.
Dogwood
Dogwood or cornus has ignited winter with its glowing stems, casting light and colour into sometimes a more desolate scene. To keep the colour and vibrancy these vibrant shrubs need a hard prune to rejuvenate their aging, dull stems every three years or so. As the branches mature, they lose their coveted vibrant colours but this is easily restored with a hard prune.
There are two main methods to choose from; you either coppice the entire shrub down to the ground; this will mean you start at ground zero and all the dogwood stems will grow bright and fresh from the base. But my personal preference is to just take out two or three large old stems and leave the younger growth so you can still enjoy your dogwood shrub throughout the year whilst generating new colourful growth too; creating an annual cycle of rejuvenation.
Buddleja
Buddleja, otherwise known as the butterfly bush, is another shrub that thrives with a hard spring prune. This vigorous grower can quickly get out of hand and become straggly, so once frosts have passed grab your loppers and get chopping.
Buddleja plants flower on new stems, so by pruning out the old you are laying way to a season of prolific blooms. These shrubs can grow enormous so I find it best to start pruning by first chopping stems down by half to take the weight off heavy, long stems so they do not snap under the strain. That gives you a clear view of what you are doing so that you can then grab your loppers or a saw and take branches down to around 30-60cm from the base. This may seem drastic but it is exactly what your buddleja needs to rejuvenate it.
Just remember that plants ‘want’ to live and pruning really can breathe new life into them.
