Growing Strawberries

If you're thinking about growing strawberries, know that it can be a fun and rewarding experience! The first berries to ripen are the ones that are suitable for picking throughout the summer until late fall.

Growth Cycle

The growth of common varieties is greatly affected by temperature and the length of the daylight period. During summer, runner production occurs in new plants. In the fall, when the days are short and cool, the plant stops producing runners and forms flower buds within the crown. When spring comes and plants start to grow, the days are too long for any new flowers to bloom. The flower clusters emerge over a period of three weeks, beginning in late May and early June. The berries will be ripe 4-5 weeks after the first flowers have bloomed and will continue to ripen for another 3 weeks. Toward the end of the harvest period, plants produce runners that create new plants.

Everbearing and day-neutral varieties are not as affected by changes in temperature and day length as normal varieties. The berries form flower buds in the fall and develop into berries the next summer. The plants form flowers during the summer that turn into berries by late summer and fall.

How to Select & Plant Strawberries

Strawberry Plant Varieties

The key to successfully taking care of Strawberry plants is choosing the right cultivar for your area and needs. Strawberries can be grown outside in any location that falls within USDA Hardiness Zones 3 through 10. When choosing a Strawberry variety, pick one that is appropriate for your Zone.

Strawberry plants are classified into three primary groups based on their fruit production habits:

• June-Bearing Strawberry plants are the most common. These plants produce one large harvest of berries—usually in June—making them perfect for the gardener who likes to make jam or cook with large quantities of berries. The plants multiply by sending out “runners,” so Strawberry patches need to be thinned and mowed each summer immediately after harvest to prevent overcrowding.
• Everbearing Strawberry plants generally produce two harvests each year—one in June, and another in early fall. While these plants send out runners, they should be pinched off and removed in order to encourage the main plant to grow larger and produce more fruit.
• Day-Neutral Strawberry plants are unique in that they rely on the temperature, rather than length of the day, to produce fruit. When temperatures are 40-80°, these plants may continue to flower and produce fruit, making them ideal for summer-long harvests in cooler regions. But in areas where the average summer temperature exceeds 80°, Day-Neutral Strawberries will follow fruiting patterns similar to Everbearing plants, with harvest periods in the spring and fall. And, just like Everbearing plants, Day-Neutral Strawberry plants should have their runners removed, as they can inhibit the main plant from growing and fruiting.

In order to decide which type of Strawberry plant is best for you, think about how you plan to use your berries.

Planning Your Strawberry Patch

Strawberry plants can be grown in different ways to suit a variety of conditions. If you have a lot of space in your garden, you can grow strawberries in the ground or in raised beds. If you have limited space, you can grow them in containers on your deck or patio. Although strawberries can grow indoors in cooler climates, they will not produce fresh berries in the winter. Growing methods for Strawberries include:

• In-Ground or Raised Beds – Strawberry plants can be placed in the ground in early spring when the soil has thawed. Select a location with well-draining soil that receives at least 6 hours of sunlight each day, though 8 hours or more is preferred.

You should not plant strawberries in the same place as potatoes, tomatoes, eggplants, or peppers. If you have plants that have wilted, it may be because the Verticillium fungus is present in the soil. This fungus can be harmful to your plants.

A pH level of 6.5 to 6.8 is considered ideal for soil. Test the pH level of your soil and make changes as needed before planting. You can help fuel plant growth by working compost into the soil, or by filling raised beds with a high-quality organic mix.

Different types of strawberry plants should be planted 12 to 24 inches apart. Runner-producing varieties of plants require more space to spread, while Alpine varieties which produce few or no runners can be placed closer together.

June-bearing strawberries should be planted 12-24 inches apart, with 4 feet between rows. Spread runners evenly and plant in a matted row system.

To grow Everbearing and Day-Neutral Strawberries, raise the rows 8” tall, 24” wide, and as long as necessary for your space. On each hill, plant two rows of plants, staggering them and leaving 12 inches between each plant. Place hills about 4’ apart. Make sure to keep an eye on your growth after planting and get rid of any runners as soon as possible so that all the energy can go to the main plants.

Put a layer of mulch around the plants that is 2 inches deep. This will help the moisture stay in the ground and protect the berries from dirt and pests.

• Containers – when using traditional cylindrical containers, calculate the planting surface area and plant no more than 3 Strawberry plants per square foot. When using a multi-pocket Strawberry jar, plant 1 plant in each pocket and no more than 3 plants in the top of the container.

The best potting soil for growing produce is an organic mixture that drains well. Applying a thin layer of mulch will help retain moisture, cool the soil, and protect berries from dirt and bugs.

If the plant produces runners, you can either trim and remove them, or replant them in their own containers.

In cold-winter climates, it is best to move the containers inside to a garage or cellar in the fall and keep them at 30–45ºF. Water the plants just enough to keep them from drying out every week. Set the containers outside in the spring.

• Hanging Baskets – Strawberries can be easily grown in hanging baskets. Follow the planting and care instructions for growing in containers.
• Indoors – regardless of whether you grow them indoors or out, Strawberry plants require at least 6 hours of sunlight each day. Place your potted plants in a location where they receive enough sunlight, or supplement them with an LED grow light. 

Once the plants flower, you will need to hand pollinate them to produce fruit. To collect pollen from a flower, dip a paintbrush or cotton swab in pollen from the outer edge of the flower's center, and then transfer it to the innermost edge.

If the plant produces any runners, cut them back and replant or discard them.

Planting

Time

Start planting in the spring as soon as the ground can be worked. This helps plants to get a head start and begin generating new growth. If a plant forms runners early on, it will produce more berries than a plant that forms runners later on. Fall planting is not recommended. Commercial plants are generally not available in the fall.

Plants

Choose plants that are healthy and have many white or creamy roots. Obtain plants from the Ontario Strawberry Plant Propagation Program. The plants have been grown following guidelines to control for viruses and other pests. The Agricultural Information Contact Centre can provide you with a list of strawberry plant propagators in Ontario. You can reach them at 1-877-424-1300.

Storing Plants

Get plants as close to planting time as possible. Plants are usually sold in plastic bags without soil. If you are going to store plants for a short amount of time, keep them in closed packages in the fridge until it is time to plant them. Although the roots may appear to be dry, it is best not to water them while they are in storage as this can cause them to rot.

Plant Distances

Strawberries are usually grown in the “matted-row” system. Place plants 60 cm (24 in.) apart in rows that are between 90-120 cm (3-4 ft.) apart. Plant runners should be allowed to fill out the rows to create new plants.

The “hill” system is useful for runnering varieties that aren't good at running, such as many of the ever-bearers. Space plants 10 inches apart in the row, and remove all runners. The system works best when two to three rows are spaced 25 cm apart with a walking space of 75 cm left in between the group of rows and the next.

Setting Plants

To plant the flowers, use a spade, shovel, or trowel. Make sure the hole you dig is large enough for the roots to fit straight down, but with some space to spread out. The top of the crown should be level with the surface of the soil. If the crowns of the plants are set too high, the roots and crowns may both dry out. If crowns are buried, they smother and rot. Use the soil to fill the hole around the roots and press it firmly in place.

It's important to keep plants moist while planting them. Without protection, the delicate fine roots of plants will dry out and die in a matter of minutes on a sunny, windy day. If the roots of your plants are dried out, you can dip them in water right before planting. But don't leave them sitting in water. Leaving plastic bags of plants in the sun can cause the temperature to get very hot inside the bags. After planting, water the plants.

Care of Young Plants

Blossom Removal

Pick off any flowers that show up a few weeks after you've planted the plant. The plant will grow better and produce more runner plants when the blossoms are removed.

Hoeing

Weeding and aerating the soil around your plants is important to keeping them healthy. This helps runner plants to grow well and to root quickly. Only hoe shallowly around plants to avoid damaging their roots. The space between rows can be used to grow plants with manual cultivators or rototillers.

Watering

Water during dry periods. Water the soil until it is moist to a depth of 15 cm (6 in.), then allow it to dry out until it is only lightly damp.

Mulches

Placing sawdust or other mulching materials around plants in the row can help suppress weeds, improve moisture retention, and keep fruit clean. This is particularly useful for hill-system plantings. Do not put mulch on the top of the plant's crown.

Black plastic film or plastic-coated paper can be used as mulch, especially in the hill system. This is because the black color will absorb more heat from the sun, which will help keep the soil warm and help the plants grow. You shouldn't use clear plastic because weeds will grow under it. Put the plastic on before planting. Tuck the edges of the plastic down around the planter to hold it in place, then cut slits in the plastic that are just big enough to fit your plants through. To allow new runner plants to root in the mulched area, you must make slits in the plastic. It is difficult to add fertilizers to the soil after a plastic film is in place. Roots may have difficulty getting water. Cutting holes in the plastic may be necessary to allow rain or irrigation water to enter the soil. Leaving a small soaker hose under the plastic will allow you to water the plants.

Spacing Runner Plants

Space plants in matted rows about 15 cm (6 in.) apart in the row. You can hold a runner plant in place by placing a small amount of soil behind it. If plants are not given enough space, they will not produce a large quantity of fruit. Plants that are crowded together may not be pollinated as well as those that have more space, and they are also more likely to experience disease.

Keep the rows at a convenient width for picking. Wider plant rows are usually more difficult to manage than narrower ones. If space is limited, wider beds can be allowed. Once you have the plant stand you want, remove any excess runners regularly.

Fertilizers

After you plant, you generally won't need to fertilize again until late summer. If you see that your plants are pale and lack energy, it might help to apply ammonium nitrate to the soil around them in late June or early July. Use the same application fee as for an August or September application.

It is often helpful to apply ammonium nitrate at a rate of 15 grams per meter of row in late August or early September. Apply the mixture to the leaves when they are dry, then brush it off. If this fertilizer isn't brushed off quickly, it will burn leaves. You can also wash it off with water.

Winter Protection

Why Needed

Low winter temperatures injure roots, crowns, and flower buds. The freezing and thawing of soil can also cause damage to plants by lifting them up and breaking their roots. Ontario's climate is suitable for growing strawberries year-round, as long as the plants are protected from the winter weather.

Material

In the late fall, cover your plants with wheat, oat, or rye straw. Make sure your straw is free of weed and grain seeds. One bale will cover about 9 m2 (100 ft2). Although hay is often used as a mulch, it is not ideal because it contains too many grass and weed seeds. Leaves, grass clippings, and other materials are not suitable for mulching strawberry plants because they can prevent air and light from reaching the plants and cause them to suffocate.

When to Apply

Apply the straw after there have been several light touches of frost but before the temperature goes much below 7 degrees Celsius. Temperatures below -7oC can cause injury. After mid-November, straw is usually applied in Southern Ontario. If straw is applied too soon, before plants are dormant, it can cause the rotting of leaves and crowns.

When to Remove

Remove the straw in the spring as soon as there are signs of new leaf growth, which is usually in late April. The new leaves of the plant will be a pale yellow color, which indicates that the plant is growing. Some straw can be left on the plants and they will grow through it. The rest of the mulch can be placed between the rows to help smother weeds and keep berries clean. The material can also be used to protect plants from frost damage during the blooming period.