When deciding to plant willow you should consider the cultivar of willow that matches the size and nature of the proposed living structure. The main considerations are the vigor of the plant, the physical strength ant the aesthetic qualities. Most willows are flexible enough to be weaved with the exception of Salix fragilis. Cultivars of Salix alba are especially suitable as their brightly colored stems look spectacular in winter.
If you decide to create a willow structure you should consider doing this in winter when planting are dormant. Willow can be used as normal hardwood cuttings or as long rods. As cuttings, use current year’s growth of about 38 cm long and set them 30 cm deep, allowing them to grow on site. As long rods they can be woven together immediately and they will establish as successfully as cuttings as long as the ground is well prepared and the rods are freshly cut and kept well watered. An easier option is to use multi-stemmed plants developed from nursery-grown stock and hard-prune them to encourage the growth of two more stems.
Before planting the willow wall plan its shape and height and work out how many rods of what length you will need. The screen can follow a straight or a curved baseline just bear in mind that willow need bright light to thrive. Mark out the outline before planting. Plant the rods at least 15 cm apart and more widely for tall screens, also using more vigorous cultivars for the last option.
After planting a row of evenly spaced rods weave them together by angling them at 45 degrees from the vertical and alternatively criss-crossing over and under each rod to create a diamond pattern. Tie firmly the crossing points with tarred wire. This will force the stems together as they expand forming pressure grafts to hold the structure. The twine will biodegrade in about two years but the grafts may form more quickly than this so check the tied crossing points regularly and if the stems have united remove the tie. At the top of the screen join the last row of crossing points with rubber plant ties to allow the rods to move slightly in the wind and prevent their tops breaking.
If you have planted long rods from the beginning you should consider removing the sideshoots as they appear to encourage extension growth and the formation of the pressure grafts. Once the stems have united allow the sideshoots to develop and use them to fill in the structure as required. Weave them over and under the main stems. New top shoots can be used to continue the structure upwards if needed but it will not follow the original rods exactly. Once the structure is established and had reach the desired dimensions, trim back or weave in new shoots regularly.
Another weaving technique which is used to form arches and tunnels is to bend and twist the stems around each other. The twisted stems need to be tied to hold them together. To provide extra stability consider to plant large rods deeper than 30 cm. Do not worry as this will not affect their ability to root successfully.