Introduction

Strawberries are a high-value fruit crop, with a great degree of versatility. Depending on whether the variety grown is June-bearing or Day-neutral, harvest times and production systems can vary; this offers producers flexibility in cultural management and marketing.

In this fact sheet, renovation of June-bearing strawberries will be covered in detail. This practice is essential to maintaining healthy, productive plantings.

June Bearing versus Day Neutral

There are two types of strawberries: June-bearers and Day-neutrals. Each has its own unique physiological and growth characteristics which influence the types of management practices. The key differences to note between these two groups are harvest windows, the development of flower buds, and growth pattern.

Harvest Windows

June-bearing strawberries, as the names suggests, produce their crop in June, with one late-season variety producing into early July. June-bearing strawberries will produce a single, substantial crop per year. There is some flexibility to extend the picking season with the range of early-, mid-, and late-season varieties available.

Day-neutral, or Everbearing, varieties will produce two to three crops per year – one in June, one in mid to late summer, and one in the fall. These crops will be much smaller than those produced by the June-bearing group. However, Day-neutrals provide a much longer harvest season and may work well for some markets.

Flower Bud Initiation

June-bearing strawberries are short-day plants. Short-day plants receive photo-signals from the environment to initiate flower bud formation, when days begin to get shorter. For June-bearing strawberries, this is generally when nights (dark-periods) are longer than 14 hours, and temperatures are below 59°F. This means flower buds are initiated the year before the crop is to be harvested.

Day-neutrals are not photo-sensitive in the same way. Their flower buds are initiated at various times throughout the year, when temperatures are between 40-85°F. For the first crop, flower buds are initiated the year before, in the late summer to fall. For subsequent summer/fall crops, flower buds are initiated earlier in that same summer.

Growth Habit

The final distinction between June-bearing and Day-neutral strawberries is their growth habit, specifically, their tendency to produce runners and daughter plants. June-bearing strawberries runner easily, and spread in the production area via runners or stolons (horizontal, above-ground stems). From these stolons, new crowns develop which root into the soil (Figure 1). This tendency to runner allows plants to fully colonize the planting area, creating an interconnected mat of new plants that can be leveraged for years to come (Figure 2). This spread of plants is one reason that renovation is required. Day-neutral strawberries historically have only produced runners sporadically, depending on the variety. However, many modern varieties runner profusely.

Renovation and Benefits

Renovation refers to a process of rejuvenating a strawberry planting area, preparing it for the subsequent season. Since strawberries are grown in a semi-perennial nature (three to five years), it is important to keep them clean and productive to maximize yield, quality, and revenue (Figure 3).

The process of renovation involves mowing over the tops of strawberry plants, removing daughter plants that have rooted outside of the planting area, and narrowing the row, thinning plants, adding soil to the crowns of plants, fertilizing, and applying herbicides. The process for this will be discussed below in the How-to Renovate section. First, the benefits of these activities will be discussed.

Mowing

Mowing off the tops of the plants serves multiple purposes. First, old diseased leaves are removed, which reduces any overwintering inoculum that could serve to infect plants next year. This process also introduces light and airflow down into the planting area. Increased light penetration to the crown of the plant helps to stimulate the initiation of flower buds, increasing potential yields. Increased airflow can help reduce pest-related issues.

Narrowing Rows

Due to the growth habit of June-bearing strawberries, many runners and daughter plants will likely have grown outside of the planting row, and into the drive rows. These plants should be removed to maintain neat, orderly, and distinct production areas, leaving plants within the planting row. This ensures all other production activities, such as fertilization and pest management, are targeted and effective. This will also increase the ease of access for farm labor, or pick-your-own customers.

Adding Soil to Plant Crowns

Tillage equipment is an effective means of weed control between planting rows. If tines are set at an angle, there is a dual purpose of adding soil to the crowns of strawberry plants. This new soil encourages plants to send out new roots, increasing the overall vigor of plants, and may provide increased protection from winter temperatures.

Fertilization

For June-bearing strawberries, renovation is one of the most important times fertilize. With so much disturbance, and the removal of a large amount of plant mass, it is essential to provide plants with nutrients so they can begin to redevelop canopies, and send out new roots and runners.

Weed Control

Renovation is also a great time to manage weeds. In addition to tillage, pre-emergent herbicides may be applied during this window. It is important to irrigate or water-in these materials, so they make their way down into the soil.

How to Renovate

Timing

Renovation should take place as soon as harvest is completed, which is late June to early July. Do not wait for the very late variety, Malwina, to complete harvest before renovating your other June-bearing varieties. Renovate Malwina separately.

1. Mow off the tops of your strawberry plants about two inches above the crown (Figure 4). It is extremely important NOT to hit the plant crowns to avoid killing the plant.
2. Narrow the width of the planting rows. Single rows can be reduced to as little six inches, as daughter plants will fill in to the desired 12-14”. During this process, adding soil to the crown of plants is recommended to encourage root growth and for winter protection (Figure 5). Thin plants if needed.
3. Begin weed management. Survey for weed pressure and decide if a broad spectrum or broadleaf herbicide application is warranted. Cultivate and apply any appropriate burndown materials. Utilize hand cultivation in small or organic operations. Materials such as 2,4-D only affect actively growing plants and should not affect strawberries which are not actively growing at the end of their season.
4. Apply pre-emergent herbicides and water in.
5. Fertilize. Broadcast applications of nitrogen can vary depending on soil type but will range between 25-60 lbs/acre (see table below). An NPK fertilizer can be used if phosphorus or potassium is needed. This decision should be informed by foliar tests. (See table below).
6. Irrigate the planting.
7. Collect tissue samples. Tissue sampling should be done after renovation, and the plant has begun to grow again. The sample should consist of the first fully expanded leaves. There are no leaves to sample after the plants are mowed off. Fertilization is based on many factors such as crop load, drought, heavy rains and the tissue results from last year. However, if tissue and soil samples indicate non-nitrogen elements are low, those materials should be applied the same year – unrelated to renovation. The process of renovation is demanding of nitrogen. Last year’s tissue results should be taken into account when deciding the amount to apply. The table above is for general maintenance applications and should not be used alone.

Nitrogen (N) Recommendations for June-bearing Strawberries

Method/Timing

Other Considerations

Irrigation

Irrigation is essential for the productivity of all strawberries. At least one inch of water per week is required, from either rainfall or irrigation. This ensures adequate vegetative growth and promotes the development of large, high-quality berries. Irrigation during renovation provides the added benefit of assisting applied fertilizers and herbicides to move down into the soil.

Tissue Samples

All fertilizer applications should be informed by tissue testing. Annual tissue testing should be performed.

Weed Control

Weed control during the renovation process will vary by operation. Some operations with lower weed pressure, or with concerns over potential harm to strawberry plants may not wish to apply burndown materials.

Resources

University of Massachusetts Amherst. (n.d.). New England small fruit management guide. https://www.umass.edu/agriculture-food-environment/fruit/ne-small-fruit-management-guide

University of Minnesota Extension. (n.d.). Strawberry end-of-season renovation. https://extension.umn.edu/strawberry-farming/strawberry-end-season-renovation

University of New Hampshire Extension. (n.d.). Northeast and Midwest strawberry production guide. https://extension.unh.edu/resource/strawberry-production-guide-northeast-midwest-eastern-canada-2nd-edition