Japanese knotweed

Japanese knotweed should be watered deeply and regularly, ideally every 2-3 days, during the growing season, from spring through fall. Water should be applied gradually and soaked thoroughly into the soil. Avoid wetting the leaves, as too much water can cause fungal disease to develop. When the temperatures begin to cool, reduce watering and stop completely once temperatures reach below 10°C/50°F. If winter temperatures become too cold, provide some water occasionally to help the plant get through it. If the soil becomes dry during a drought, provide deeper watering but less often to help the plant conserve water.

Japanese knotweed (Fallopia japonica var. compacta) is a tough, vigorous plant, and it should receive at least 6 hours of sunlight a day. Sunlight helps it to grow and thrive during the warmer months. During the summer months, Japanese knotweed should receive the most sunlight, with a few hours of partial shade in the afternoon. In the winter months, however, it requires less sunlight and is best protected from the harsh winter sun. It should form part of a partially shaded area, with protection from the winter winds.

Japanese knotweed (Fallopia japonica var. compacta) should be pruned late in the year, from October to November when the plant’s sap reserves have been depleted. This will minimize the vigor of re-growth and the spread of rhizomes. Prune all stems back to soil level. Cut all shoots to the ground level or remove any suckers. Smaller stems may be hand-pulled, while larger stems should be cut off so they can be disposed of more easily. Subsequent pruning sessions will be necessary throughout the year to keep the plant under control.