Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu
Plasticulture strawberry growers may decide to produce their own plants for September planting due to the cost and availability of strawberry plug plants. This requires rooting strawberry tips from desired varieties. Tips are the daughter plants produced by mother strawberry plants on runners and are how strawberries produce new plants.
Tips are commonly ordered from Canadian growers or regional greenhouse growers, or growers can produce their own tips. It is important to note that some strawberry varieties are still protected by plant patents and cannot be propagated except by license from the breeder or patent holder.
Plug plants can be produced in a greenhouse, tunnel, or cold frame. Obtain mother plants from a reliable nursery and plant in to produce runner tips for propagation. Growers should not take tips from carry over plantings because of the possibility of spreading diseases such as viruses or anthracnose. Mother plants can be planted in the field, grow bags, large pots, gutters or hanging baskets. Runner production is enhanced by warm temperatures and long days. Greenhouses can be managed to provide ideal day time temperatures (above 75˚ F) and long photoperiods (about 16 hours). With supplemental heat and light, runner production can produce tips for spring or fall planting. In the field, runner tip production is limited to June – August normally for fall planting.
Use a growing system to produce tips that do not allow runner tips to come in direct contact with soil. This is easy to do in the greenhouse with suspended growing systems. In the field, a combination of straw mulch between rows and plastic mulch within the row will prevent runner tips from contacting the soil. We have a producer in Delaware starting to grow tips in gutters in a lighted converted poultry house.
In the greenhouse, the first runner tips can be harvested in about 8 to 10 weeks as runners are produced by the mother plant. As mother plants get bigger, more runners are produced. The number of runner tips produced will vary by variety: some are strong runner formers, others are sparser. Runner growth is encouraged by nitrogen fertilization, especially with day neutral varieties. Flowers should also be removed regularly to encourage runners and tips.
Runner tips should be harvested when root initials are present on the runner tip and have at least two trifoliate leaves. Runners should be removed such that the trifoliate leaves are not damaged and approximately ½ inch of the runner is left to be used for an anchor when planting. Runner tips should be planted immediately after harvest into 50-cell plug trays. Tips should be planted such that the root pegs and anchor are just below the soil surface, with the leaves and the crown remaining above the soil surface. The soil should then be pressed lightly around the runner tips to hold the plant in place. After the runner tips have been planted, leaves need to remain moist until the plant can establish a new root system. This is done by misting the plants periodically for 7 to 12 days. Shaded greenhouses or frames provide the best environment. After the misting is finished and plants have rooted, plants should be hardened off in the greenhouse for 1 to 2 weeks before going to the field. Plugs finish in about 4-5 weeks.
Some plasticulture varieties that can be propagated without a license from the patent holder include Seascape, Camarosa, Sweet Charlie, Camino Real, and Flavorfest. Most others will require a license and fees paid. See this post from Cornell will additional information https://blogs.cornell.edu/berries/2022/01/18/patent-status-of-select-strawberry-varieties/
Runners and tips.
Runner tips with root initials, 2 trifoliate leaves, and anchor.
50 cell tray with runner tips rooting. The smaller tips without the two trifoliate leaves did not root.