Move the runners out of the aisle at any time in summer but before the runners begin to set roots. Arrange the runners so they stretch about 12 inches out from the main plant but so they remain within the row.
Pinch off the excess runners where they emerge from the main plant once the runners are 2 to 3 inches long and visible. Grasp the runner stem between your thumb and forefinger and pinch until the runner is severed.
Check the runners you left to root every two to three weeks throughout summer. Lift the new developing plant gently and check for resistance, which indicates the runner plant has rooted completely.
Sever the runner from the main plant once the new runner plant is rooted. Pinch or cut the sucker stem where it joins to the original plant.