Growing a wisteria in your garden can be one of the most impressive plants to welcome you home. In summer wisteria have jaw-dropping pendulous (raceme) lilac flowers that hang down like purple pendants in mid-summer. These climbing giants can add a green vertical gardening layer to your homes. Whether it is around a door to soften an entrance, grown as a standard for a container garden or providing a draped walkway of purple flowers in summer there really is a wisteria for all sized gardens.
Let’s take a look at wisterias and how to prune them for flowers year after year!
- What is a wisteria?
- Do wisteria need pruning?
- How to prune wisteria in winter
- Summer wisteria pruning
- Why is’t my wisteria flowering?
- How long does it take a wisteria to flower
- How big do wisterias grow?
- What conditions do wisteria need?
- Why don’t we prune straight back to 3 in summer?
What is a wisteria?
Wisteria is a deciduous (drops its leaves in winter) woody climbing plant native to China, Japan and the USA. They are fast-growing plants that have amazing displays of lilac and purple flowers in summer.
There are ten species of wisteria. The three most commonly grown in gardens are:
- Wisteria floribunda (Japanese wisteria)
- Wisteria sinensis (Chinese wisteria)
- Wisteria brachybotrys (silky wisteria).
The wisteria is actually part of the pea family the Fabaceae and has compound leaves. Compound leaves are individual leaflets on a stalk that can help you spot both wisteria and other pea family plants. You’ll even recognise the wisteria flowers as looking very similar to the Sweet Pea.
Wisterias have huge symbolism around the world, in particular Japan. Given the fact they live so long – around 100 years, wisteria are often seen as a symbol of everlasting wisdom. Wisteria also symbolises longevity and endurance given they are tough as old boots!
Why prune wisteria?
Pruning wisteria is essential to ensure a healthy plant and flowering year after year. Without pruning your wisteria will grow rapidly putting out lots of leafy green growth in all directions. They also can send out runners from the base of the plant in their search to colonise the garden. These runners can take precious energy away from flowering so needs to be managed.
Wisterias in the wild send out runners and put on lots of foliage to ensure they have the best chances of survival and whilst your wisteria will still flower if you do this it may take 12-25 years.
By pruning your wisteria you are helping to shape it to the structure or property you’re growing it up. Pruning helps divert energy away from areas of the plant to other areas. With wisteria pruning, we are aiming to restrict the green leafy whip growth and focus the energy back to flowering spurs.
You need to prune wisteria twice a year. Once in summer after it has flowered (late July) and then again in Winter (February).
Pruning wisteria twice a year helps to:
- Control the growth andf shape of your wisteria (formative pruning)
- Focus energy to flowering parts of the plant
- Ensure your wisteria doesn’t waste energy with green leafy whips instead iof flowers (maintenance pruning)
How to prune wisteria in winter
Winter is the prime time to prune wisteria ready for flowers in summer. It’s this process that enables you to focus the plant’s energy on creating flowering spurs rather than sending out all of its energy into green whippy wisteria growth. It’s this long growth that zaps the energy from wisterias taking it away from flowering and into taking over whatever structure they ate planted next to.
So let’s look at the beginner gardening steps to prune a wisteria easily.
Step 1: Use the right pruning tools
When pruning wisteria in winter you’re going to be met with lignified/woody branches and stems. It’s important that you use a pair of sharp, clean secateurs that are capable of cutting sometimes pencil-sized stems from the wisteria. Don’t be tempted to use scissors or a knife. The cleaner the wisteria cut the better the climber will heal. Which helps flowering over recovery of the wisteria.
If you have to use brute force to get the secateurs or snips to cut you need bigger secateurs. Don’t force them as you will damage your secateurs, wrists and your wisteria. Also, make sure you keep your secateurs sharp too which will make the job far easier!
Step 2: Locate side shoots and count 3 buds
Locate the side shoots of your wisteria. These are shoots that come off from the main thick stems of your wisteria. You then want to count 3 buds from the base of that stem.
You can spot buds as little red or dark purple lumps that have broken through the woody shoots. You can feel them with your fingers as little bulges. These are the buds that are going to grow into both foliage and potential wisteria flowers this year.
Step 3: Cut back laterals / side shoots to 3 buds
Now that you have identified the buds it’s time to count! You want to make a cut just above the 3rd bud. This is counting from where the lateral joins the stem and counting outwards. (Don’t count from the very end backwards as some online guides show you!)
Step 4: Ensure your pruning cuts are clean
When making any pruning cut above a bud or lateral you want to make the cut on a diagonal 3mm above the bud. See below for an example of a poor pruning cut and then a good pruning cut.
The first bad example has left too much stem above the cut. This will die back leaving a black brittle stump. Which is not good for plant health. The second image shows the amount of ‘spare’ stem you should leave. This will heal nicely and provide a clean healthy pruning cut.
Step5 : Take your time and work around the wisteria
Take your time cutting back all laterals to 3 buds across the wisteria. If you come across laterals that are in the way or are growing out too much cut them right back to their ‘parent’ stem to stop them from growing.
You can also remove any ‘runners’ that spring up from the very base. You can recognise these as they are bright green long and flexible. These will zap the energy from the rest of the plant so best to remove them.
Step 6: Recycle your cuttings
Once you have finished pruning your wisteria back to 3 buds and removing any runners or vigorous shoots from the base you are left with a number of woody prunings. Don’t just bin them though, they make excellent kindling for log burners or can be chopped up and added as a carbon layer for your compost bin. You could even use them in bug hotels too for solitary bees and other insects to make a home with them!
How to prune wisteria in summer
Summer pruning of wisteria follows the same guidelines but takes back the growth to 6 buds – not 3. This is because we want to prevent too much green whippy growth after flowering. If we don’t prune the wisteria will put all its efforts into foliage again and may get out of hand.
By cutting back to 6 buds after flowering – usually late July or August in the UK – we can help keep the wisteria neat and tidy. If we don’t do this it can mean lots of tying in over the winter to then prune these longer stems back out again. What a faff!
So use the pruning guide above in summer to cut back to 6 wisteria buds in summer.
Then in winter (around February), we shorten the wisteria further by pruning to 3 buds.
Why isn’t my wisteria flowering?
I hear from so many followers that their wisterias never flower. With proper pruning, all established wisterias that are in the place should flower. Patience is a virtue of all successful gardeners.
The most common issues with wisterias that don’t flower are:
- Wisterias that are not pruned correctly
- Wisterias that are overfed and therefore put their efforts into more leafy growth
- Poor location in a shady spot – wisterias need full sun
- Young wisterias that are only a few years old won’t flower until at least 7 years old
How long does a wisteria take to flower?
Wisterias are not plants that liked to be rushed. They can take up to 7 years once planted before they flower. This is because they only flower, once they have established a suitable root system and have enough structure above ground to then, think about reproducing via flowers. Don’t forget, any plant that produces flowers is therefore aiming to reproduce using some form of seed from that flower.
Although wisterias can take 7 years to flower they really are worth the wait. Especially given the rustic charm of their woody twisted branch network and then lilac summer racemes of hanging flowers.
How big do wisterias grow?
A mature adult wisteria can reach around 10m (33ft) in tree form or spread up to 20m (66ft) against a wall, pergola or archway. They require regular pruning and cutting back each year to promote flowering in summer and also control their scrambling growth!
Whilst you can grow wisteria in a container they will need regular feed and eventually outgrow their pot. It’s best if you have a small garden or need a wisteria in a limited space to choose a standard wisteria. This is a wisteria that has been grown and pruned to have one main stem. When growing wisteria as a standard its ultimate growth can be reduced due to the limited branch network.
What conditions do wisteria need to thrive?
Wisteria like bright sunny south facing positions in the garden. Whilst wisteria will grow in partial shade this is likely to be at the loss of flowers each summer. They will survive in pretty much all soil types but don’t like waterlogged or boggy soil conditions. If you have heavy clay soil it may be best to help open up the soil structure with some peat-free compost worked into the soil and a heavy mulch once the wisteria is planted.
Wisterias can cope with exposure but windburn may make the leaves unsightly and cause the flowers to drop off prematurely if in a very windy site. Usually, you will see them grown up walls and pergolas in warmer positions where the wall or structure can help retain heat during the summer months.
Why don’t we prune back to 3 in summer?
You may be asking why we don’t just skip straight to the winter prune in summer after the wisteria has flowered. The reason we don’t prune wisteria straight back to 3 in summer is 3 fold:
- It would cause you to lose valuable foliage for the remainder of the year
- It can cause your wisteria to look scalped & uneven
- The wisteria needs foliage to help create food and recover from flowering
Wisteria can add a real wow factor to your garden in summer and provide a soft green canopy to climb up walls or pergolas. For wisterias to perform consistently pruning them twice a year is a must. Now that you know how to prune your wisteria you will be set for success.
Hopefully, this guide will have given you the confidence to enjoy pruning and understand why cutting back your wisteria increases the chances of those gorgeous flowers!
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