Success with Wisteria

A good-looking wisteria vine is an awesome site in any garden. The resulting waterfall of cascading colour encourages every gardener to at least have-a-go at growing one. Here we show you how to get the best from your chosen wisteria plant, from purchasing to pruning these amazing early-season climbers.  The pendulous flowers of wisteria may be white, pink, lilac-blue or purplish-blue. Related to the pea family, wisterias are hardy, vigorous twining vines for gardens or house walls which receive a lot of summer sunshine.

The two most commonly grown varieties are Wisteria sinensis from China and Wisteria floribunda from Japan. Wisteria tend to be at their best around late-April to mid-May.

Before you purchase Wisteria

A good general rule I use for all types of climber, is to NEVER purchase a plant which shows NO SIGN of having produced buds. There are non-flowering ‘runts’ in the plant world and they cost you the customer just as much as a flowering plant – so take a minute and be sure your plant is capable of flowering by checking to see if it has flowered before or is capable of flowering. The sight of flower buds is all the proof you need to be certain.

Pictured above: A distinctly deep-coloured form with larger flowers. This plant was just five years in the ground when this picture was taken. Wisteria ‘Murasaki Kapitan’.

Wisteria Site Requirements

Their vigour demands a location that will provide as much bright sunlight as possible in deep soil for their extensive roots. They will adapt to most soils, but prefer those which are slightly acidic, that can retain their nutrients and which do not drown their roots every winter.

Most plants arrive in a six-inch pot and I would recommend providing a hole 2 x 2 x 2ft to give those roots the best start. Don’t leave the sides looking like a steel box if you have a heavy soil, use a fork to crumble them and make it easier for those soft young root tips to pierce the surrounding soil wall and continue further. Then empty a large bag of fresh, moist (not wet), crumbly (aids aeration and drainage) compost in the hole. It’s the easiest method and your new plant, which will almost certainly have ‘rotating roots’ won’t believe it’s good fortune. ‘Tease away’ the roots from the existing root ball to encourage the roots to explore. Don’t be afraid to be a little ‘brutal’ about this, because if you do leave the main root stems alone they will continue to grow in a circle. This will ultimately be bad for your plant and its flowering because such roots will exhaust all the soil nutrient from around the base of your plant and not go searching further afield for the nutrient and water that any healthy, fast-growing climbing vine craves for.

Wisteria Support

Climbers always take me three times as long to plant than any other new addition to my garden and they should also take you a similar amount. It’s all due to untangling the top growth and then tying them to their support. Do not skimp this, get it right first time and it will save both you and your plant a lot of heart ache. Once established wisterias are very heavy and well able to snap thin wires and force weak supports right out of the wall. If you are proposing a timber frame, ensure it is pressure treated and substantial.

2×2 timber is OK, for a while, but what do you think will happen after ten years and that once super-looking frame is looking rather sad? How are you going to strengthen it without damaging your precious wisteria plant that’s entwined all around it? Far better to begin with have a substantial frame, with good strong galvanised wire – even though it may look oversized initially.

Close-up of Wisteria ‘Murasaki Kapitan’

Establishing the main Wisteria framework

The easiest method is to train the main stem vertically and encourage branches to left and right, so they run along your lateral wire supports. When nature produces a branch where no wire exists, cut it off. Or, lead the new off shoot to join the lateral support just above it and not attempt to turn it back on itself in order to reach any lateral support beneath it.

The Key: – Stressing the fundamentals

Wisterias are very vigorous and if permitted, will waste terrific energy to achieve their natural growth in all directions. You have to harness that energy and redirect it into greater flower production.

I believe most wisteria are not pruned often enough. To me, there is no point bemoaning poor flower production during April/May, then watching the plant waste energy during the summer producing great long stems over eight/ten feet in length which will have to be cut later anyway. A far better solution is to prevent all that wasted growing effort by pruning more frequently. During the summer months I will often prune a wisteria every 12/14 days or so to prevent energy being expended upon unnecessary stems. When I make those summer cuts I will prune the stem so there are just 5 or 6 buds remaining. Later, during my mild winter I will cut back those shortened stems to just three buds. But if your winters regularly go below -10C I would retain those 5 or 6 buds until the worst is over – just in case you lose 3 buds to the cold.

In my experience cultivating wisteria this way will not only accelerate the spread of your plant along its intended routes but will also produce a thick mass of buds in springtime. Pictured above on the west-facing wall at Winsford Walled Garden is a five year-old Wisteria alba.

Moving your wisteria?

The short answer is best not to, because with their extensive root system wisterias do not transplant well if they have been planted for more than two years following purchase. If you must, then excavate as big a root ball as you can lift. If you have prepared the hole as recommended above this shouldn’t be too difficult, but if possible it would be better to plant another wisteria in your new location.

Pictured left: Wisteria alba remains one of the best white forms.

Poor flowering Wisteria?

One of the gardeners’ greatest frustrations is having a wisteria, or indeed any other exotic flowering climber, which fails to perform as intended. There are several possible reasons for a wisteria failing to bloom, check each one out and see which applies to your situation.

1. Immature plant. Some wisterias do take longer to reach flowering maturity. They produce plenty of buds but a young plant will simply not have the resources to draw upon necessary to produce flowers. (This makes regular summer pruning as described above all the more important).
2. If a plant does not receive sufficiently bright sunlight for long enough it will not flower or flower poorly.
3. Excessive nitrogen in a fertiliser will be evidenced by excessive stem and leaf growth, use one with a greater proportion of potash to encourage flower growth.
4. Flower buds can be killed off by harsh winters. Adjust the number of buds retained during your seasonal summer pruning to compensate for your local conditions.
5. Avoid any heavy pruning during the winter and spring. You will notice from reading my advice that the heaviest pruning is done when the plant is most active and at it’s strongest in order it has time to properly seal its wounds. If pruning is done too late when the plant is ‘winding down’ for the winter it will not repair itself in time and will be left open to possible infection.

The following wisteria are grown at Winsford Walled Garden:

W. floribunda ‘Black Dragon’

W. floribunda alba

W. floribunda ‘Reindeer’

W. brachybotrys ‘Murasaki-Kapitan’

W. floribunda macrobotrys