Vigorous, young strawberry plants produce the best berries. As strawberry cropping slows, plants produce long horizontal stems (runners). Along each runner a small plantlet begins to form and tiny white roots will appear at the base – see photos below. Vigorous runners can produce two or three plantlets along each runner. If you remove mulch from the area under each new plantlet and anchor plantlets to the soil surface by placing a stone on the runner on the parent side of each plantlet, you can produce many new plants for your strawberry patch. Anchoring plantlets in this way allows the crown of the plantlet to sit on the soil surface. (Strawberry crowns will rot if buried.) If your strawberry bed contains plenty of organic matter, all you need to do is give the bed a drink of seaweed extract tea to stimulate root growth and build disease resistance, and keep the soil damp. Otherwise, add a handful of mature compost to the soil surface under each plantlet. Each parent plant will provide nourishment to the new plants until they develop enough roots to grow independently.
When plantlets are well established in autumn, the runners connecting them to the parent plant can be cut, and the new plants can be left where they are or transplanted to a new spot.
Tip: While strawberries are still cropping, place a marker beside the plants that produce the best berries and only use the runners from these plants to improve the quality of produce in your strawberry patch.