Have you finished raising your strawberry seedlings?

As the weather grows warmer and greenhouse temperatures rise, strawberry production south of the Huai River is drawing to a close, with some growers already beginning to clear their fields. In northern greenhouses, too, the harvest is steadily winding down. Strawberry farmers are either preparing to start or have already begun raising new seedlings—indeed, in Anhui, mother plants were collected as early as November 2017 to kick off the propagation process. With the season nearing its end, have you got your strawberry seedlings ready?

I. Source of Seedlings and Saplings

Currently, the sources of seedlings are mainly divided into two categories: purchasing mature seedlings from the market and propagating seedlings independently.

1. Mature seedlings

Mature seedlings are typically purchased from nursery farms or obtained from local, well‑known sources. Acquiring established seedlings ensures their purity and robustness while saving considerable time and labor that would otherwise be required for propagation.

Finished seedlings mainly include plug‑tray seedlings and conventional seedlings. Plug‑tray seedlings, since they do not come into contact with soil, are less likely to harbor soilborne diseases; however, because plug‑tray production typically takes place in greenhouses, the unique greenhouse environment can make these seedlings more susceptible to powdery mildew. Therefore, after transplanting into the greenhouse, effective measures to prevent and control powdery mildew should be implemented. Conventional seedlings, on the other hand, are often chosen by many growers due to their lower cost. As most of these seedlings are raised outdoors in standard planting soils, they may carry soilborne pathogens and, owing to rainfall, are particularly prone to anthracnose. When purchasing such seedlings, it is advisable to select those produced using sound breeding techniques, under proper management, and grown on the same plot for no more than two consecutive years in open‑field conditions.

2. Propagation of seedlings by self-reproduction

Self-propagated seedlings are those bred on‑site; at present, most growers cultivate strawberries using this method, which eliminates the high costs of purchasing commercial seedlings and ensures greater confidence in the quality of the plants.

II. Key Factors for Successful Seedling and Sapling Propagation

Seedling propagation is a large-scale, labor-intensive process that requires significant manpower. The quality of the seedlings directly affects strawberry growers’ income, making the production of high‑quality seedlings essential. Key factors in producing superior seedlings include selecting and preparing the planting site, choosing and transplanting mother plants, and properly managing those mother plants—addressing these critical steps to ensure the cultivation of top‑grade seedlings.

1. Land

Growers who propagate seedlings themselves typically opt for open-field nursery production, while seedling companies prefer greenhouse cultivation. Open-field nurseries generally yield inferior results compared to greenhouse-grown seedlings; however, greenhouse production entails higher costs, more stringent management, and the need for a comprehensive management plan. At present, open-field nursery production remains the more common approach.

1.1 Site Selection

Open‑field seedling production requires careful site selection. The land should be situated on higher, well‑drained ground with ample water access and good drainage. Prior crops must be rigorously evaluated: the site should not have hosted strawberry seedlings for at least ten years, and the same plot should not be used for strawberry propagation for three consecutive years. Additionally, solanaceous and cucurbit crops should not have been grown there within the past three years to prevent soil‑borne pathogens from being carried by the seedlings. For greenhouse seedling production, soil must be replaced each season; greenhouses should undergo thorough disinfection before planting or be promptly renovated, with replacement frequency determined by available resources.

1.2 Land Preparation and Bed Formation

The methods for land preparation and bed formation vary across different regions, but they all adhere to certain principles: during the seedling‑raising period, excess moisture must be drained promptly to prevent localized “mini‑sauna” conditions that can arise when sudden summer downpours give way to clear weather; and tall vegetation should be kept away from the perimeter. South of the Huai River, raised beds with deep furrows are essential to ensure rapid drainage, while the bed surfaces must be leveled to maintain soil and water retention and to facilitate nutrient supply. In northern areas, a dedicated drainage system is not required, but the land must still be kept level. For base fertilizer, select a balanced, all‑natural potassium sulfate–humic acid compound fertilizer (40 kg per mu), supplemented with approximately five bags of “one top, three organic” fertilizer (5 bags per mu), and apply it to the field after rotary tillage.

2. Selection of Mother Plants

The selection of mother plants plays a crucial role in the nursery‑raising process; the quality of this selection directly determines the incidence of pests and diseases in the propagated seedlings. Therefore, when choosing seedlings, the following considerations should be taken into account.

2.1 Timing for Selecting Mother Plants and Seedlings

The timing for selecting mother plants is determined by local winter temperatures. In northern regions, mother plants are typically reserved before orchard sanitation; however, this early‑season reserve often harbors a high load of pathogens, compromising the health of the resulting seedlings. To mitigate this, it is advisable to set aside a portion of mother plants during the previous crop cycle, or to designate a specific field during strawberry cultivation as a runner‑production plot, collecting runner growth points that have not come into contact with greenhouse soil as mother plants. In southern areas, the selection of strawberry mother plants tends to be more concentrated: most growers use the runner growth points generated during the growing season as mother plants. Key timing windows include around September, around November, and in May of the following year.

2.2 Key Points for Transplanting Seedlings

9. The mother plants selected in November and December should first undergo centralized cultivation and propagation. As a perennial crop, strawberries exhibit strong frost resistance but relatively poor heat tolerance. To ensure the production of robust, healthy seedlings, appropriate frost‑protection measures must be implemented. During the early transplanting stage, adequate moisture management is essential to prevent low survival rates caused by excessive water or excessively high temperatures. In the centralized nursery, apply a small amount of sulfur‑based humic acid compound fertilizer (15‑15‑15) as a base fertilizer, taking local conditions into account. To lay a solid foundation for vigorous mother plants, transplant them into the nursery field in May. When selecting cultivated seedlings as mother plants around May, be sure to transplant them with soil intact.

2.3 Transplanting to the nursery field

To cultivate healthy mother seedlings, it is essential to select the optimal timing and transplant them promptly into the nursery field. After transplanting, irrigate immediately to prevent low survival rates caused by dry weather. Prior to planting, you may dip the roots in a rooting solution to promote root development and help control soil-borne diseases. Once in the field, provide meticulous management. When the mother seedlings begin producing stolons, apply a microbial fertilizer—such as “Yi Ba Zha”—at a rate of 10–15 kg per mu, adjusting according to plant condition. In southern regions, complete this topdressing no later than August 10; in northern regions, no later than August 20. Thereafter, use a fertilizer high in phosphorus and potassium but moderate in nitrogen (avoid nitrate‑nitrogen). Following fertilization, ensure adequate watering or apply fertilizer just before rainfall. If the mother seedlings become overly vigorous, employ growth‑regulating agents to curb excessive vegetative growth, preventing premature elongation that could hinder flower bud differentiation. However, during the mid‑ to late‑stage nursery period, exercise caution when applying growth inhibitors to avoid delayed recovery at transplanting or stunted growth after moving into the production greenhouse.

3. Field Management of Mother Plants

3.1 Disease Control and Prevention

During their growth and development, seedlings in different environments face varying disease pressures; accordingly, the diseases that require control also differ. As mentioned earlier, open-field seedlings should be primarily protected against anthracnose, while greenhouse-grown seedlings require focused management of powdery mildew.

Anthracnose, a devastating disease of strawberries, requires focused management. It thrives in warm, humid conditions; therefore, adequate field drainage is essential—particularly after sudden clear weather following summer downpours—to promptly prevent waterlogging. Timely application of fungicides is also crucial, with protective agents taking priority and curative treatments used as supplementary measures. In southern regions, spray applications should be scheduled approximately every 10 days until mid-to-late June; in northern areas, around every 15 days until early July. Once the rainy season begins, the frequency of spraying should be appropriately increased. Targeted coverage should focus on stems, leaves, and stolons close to the soil surface, as these parts are more susceptible to infection than those elevated above ground.

Powdery mildew is a disease that thrives in high temperatures and dry conditions. In greenhouses, ensure adequate ventilation to prevent overheating and excessive humidity, which can trigger widespread outbreaks. To manage powdery mildew, apply a protective fungicide every 7 to 10 days in the greenhouse.

3.2 Management of Stolons

During the management of stolons, in addition to effective pest and disease control, it is essential to promptly stimulate stolon formation. The number and vigor of stolons directly determine the strength and health of the propagated seedlings. Based on the condition of the seedlings, apply gibberellic acid in a timely manner to promote stolon development (around mid-June). Once the stolons reach a certain length—determined by the width of the prepared planting beds—manually secure them to encourage the development of root systems at the growth points, thereby fostering robust seedlings.

3.3 Differentiation of Flower Buds

Strawberry flower bud differentiation occurs relatively early, so special attention must be paid to water and fertilizer management to prevent delays in market availability or a failure to achieve a concentrated harvest due to conditions in the nursery bed.

The temperature required for strawberry flower bud differentiation is above 17°C, and a short-day photoperiod of 8 hours is sufficient. In southern regions, this period begins after August 10 and continues until transplanting; in northern regions, it starts about 8 to 10 days earlier or later. During this time, careful management of water and fertilization is essential, and chemical treatments should be applied with caution to avoid hindering bud differentiation. Flower bud differentiation for the second crop begins immediately after seedlings have established and continues until the first flush of flowers has fully opened. Whether buds have differentiated can be determined by examining the leaves: typically, strawberry seedlings with fully differentiated buds will exhibit leaf auricles on their older leaves.

Throughout the seedling‑bed management period, timely cultivation and weeding are essential. Based on the condition of the seedlings, promptly remove any senescent leaves to prevent disease outbreaks caused by poor ventilation, and maintain a leaf count of around 5–6 leaves. This year’s weather has been rather unusual; in southern regions, cutworms have already inflicted widespread damage on strawberry mother plants, so preventive measures should be taken in advance when raising seedlings in northern areas.

4. Principles of Successful Seedling Production

The success of seedling cultivation depends on many factors. First and foremost, it hinges on visible characteristics. Through research, the author has learned of the “three‑cigarette rule”: a robust strawberry seedling should have roots and an above‑ground height each roughly equal to the length of a cigarette, while the stem base should be about as thick as a cigarette. Seedlings meeting these criteria exhibit several advantages after transplanting: rapid establishment, timely nutrient uptake, easy management, and reduced susceptibility to soilborne diseases.