Archives For strawberries

Strawberries

Mike Kwiatek —  May 26, 2014 — Leave a comment

When I was 8 years old, I traveled with my family to Przysietnica, Poland, to spend the summer with relatives. My grandparents’ farm was the home base for my adventures with cousins and siblings. We spent hours in the breezy northern hills, picking the sweetest strawberries I ever had. They grew wild and tasted like candy. We often brought some back to share with the family, but there is nothing quite like a strawberry fresh off the plant.

PHOTO: Blooming strawberry plant in the garden.

First described by the ancient Romans, strawberries were first cultivated in gardens in the 1300s.

The Cultivated Strawberry

The garden strawberry is the strawberry we most often think of when we think of strawberries. This is the strawberry from the clear plastic boxes you find at the grocery store. This strawberry is Fragaria × ananassa, which has only been around for about 260 years, and has undergone a lot of breeding in that time.

Fragaria × ananassa is actually a cross of the Chilean and Virginia (or wild) strawberry, which arrived in Europe in 1712 and 1624, respectively. The hybrid plant was discovered in the 1750s and recorded in 1759 by Philip Miller, a famous English horticulturist. He referred to it as the “pine strawberry” for its taste, which was similar to pineapple.

If you’re taken aback by this assessment of flavor, you’re not alone—the modern garden strawberry has undergone a great deal of breeding, which improved firmness but did little for its taste. Some of the modern breeding programs are working to fix this problem.

Fragaria × ananassa is not the only cultivated strawberry on the market. There are more than 20 species of strawberries worldwide, with only a small portion of those being grown in gardens for eating. Some of the popular species include the musk strawberry (F. moschata), the alpine strawberry (F. vesca), the Chilean strawberry (F. chiloensis), the Virginia strawberry (F. virginiana), Fragaria nipponica, and Fragaria viridis. Most of these strawberries originate in Europe (Fragaria nipponica is Japanese in origin); the Chilean and Virginia strawberries are the only cultivated New World species. While there are many edible strawberries, these tend to be the most popular.

PHOTO: Rows of strawberry plants mulched with (what else?) straw.

Strawberries planted in rows and left to their own devices will spread wildly within a few years.

Biology

Do you know how the strawberry got its name? The popular theory is that strawberries are so named because they are cultivated on straw. The truth is, strawberries were named before straw was ever cultivated. Have you ever seen strawberries growing? They spread by stolons, or above-ground roots. These stolons reach out, find a good moist spot away from the parent, and put out roots, producing a new clone of the mother plant. In this way, a single cultivar of strawberry can reproduce itself dozens of times and still be identical or nearly identical to the mother plant. The stolons that give rise to new strawberries are called “runners.” This habit of growing is what gave it its name; strawberries tend to be strewn (spread) about.

It’s generally accepted that strawberries will either produce runners or flowers. Though sometimes producing both simultaneously, the energy is usually dedicated to one task over the other. This is why there are three main types of garden strawberries: ever-bearing, day-neutral, and June-bearing. Strawberries tend to be June-bearing by nature, which means you’ll harvest your fruit in late spring to early summer. Though you sometimes end up with a second crop in fall, the June-bearing strawberry will produce runners for the rest of the year. Ever-bearing strawberries prefer to put their energy toward making fruit, so you’ll end up with few runners and strawberries several times per season. Day-neutral will produce strawberries continually throughout the year, and create the fewest runners.

The white tissue under the pistils is what swells into a red juicy strawberry

The white tissue under the pistils swells into the sweet edible “fruit”

“Fruit”

Did you know that a strawberry isn’t a fruit? It’s an “aggregate of achenes on a swollen receptacle.” Achenes are those little specks on the surface of the strawberry; these are the true fruit of the strawberry. The achenes break apart much the way that sunflower seeds do. An aggregate refers to a cluster or grouping, and the receptacle is the part of a flower that bears the sexual organs.

Seems complicated? Try this: cut a strawberry flower in half and look inside.

The female parts of the flower (pistils) are near the top center of the flower with the male parts (stamens) forming a ring around the outside. When the flowers are pollinated, the area under each pistil swells and turns red. When the whole flower is pollinated, you end up with a perfectly red strawberry.

VIDEO: Time lapse of strawberry fruiting process.

Time lapse of a strawberry, flower-to-fruit, by Tomas ‘Frooxius’ Mariancik.

Humans have known about strawberries for hundreds of years, but strawberries only became commercially common within the past century, thanks to refrigerated trucks and breeding programs that gave strawberries their firmness. Ever since, they have been one of the top ten favorite “fruits” in the United States.

©2014 Chicago Botanic Garden and my.chicagobotanic.org

Historically, fruit trees, shrubs, and berries were grown at home out of necessity. Colonialists were entirely dependent on what they could produce themselves, and in time, a fruitful garden became a common symbol of independence from foreign imports—highlighting a new American pride in agriculture.

The farm-to-table movement of today epitomizes the fruit-growing traditions of the past by “growing as close to the plate as possible.” Sweet, juicy fruit can be easily grown in gardens of all sizes: on small urban lots, in containers on terraces, or in large suburban gardens. Harvesting homegrown fruit continues to be a gardener’s most satisfying pleasure, and with a bit of advance planning, choosing suitable varieties to plant this spring is possible. Here are a few ideas to get you started creating, and/or caring for, your edible landscape.

PHOTO: A hanging basket growing a mix of strawberry cultivars and lettuces.

Day neutral strawberries are grown in our vertical wall and hanging baskets in the Regenstein Fruit &  Vegetable Garden.

Plan to plant strawberries

No grocery store strawberry ever tastes as good as one grown in your own yard. An easy starter crop, strawberries are self-fertile, so you can start small if you like—plant just one variety or only one plant—and still reap a reward. Choose strawberry varieties carefully, however—they vary greatly in flavor, disease-resistance, tolerance of different climates, and harvest time.

Good choices for Illinois gardens are larger June-bearing strawberries such as ‘Earliglow’ and ‘Allstar’. Day-neutral or everbearing strawberries were developed to produce flowers and fruit continuously throughout summer and fall, ignoring the seasonal effects of day length on fruit production. Of the many day-neutral and everbearing varieties to choose from, ‘Tristar’ is a reliable berry for our zone. At the Garden, we grow everbearing strawberries ‘Mara de Bois’ and ‘Seascape’ in hanging baskets and vertical plantings, because they are among the first to fruit in the spring, but also produce a June crop followed by a final fall crop.

Planting several varieties together in your garden extends your harvest time, ensuring there are plenty of strawberries for eating out of hand and enough fresh berries left over to make strawberry jam.  

Choose healthy plants for a healthy harvest

Start with quality, virus-free, and disease-resistant plants. Mail order nurseries and garden centers have bundles of bare-root plants available. Lesser quality plants are prone to fruit rot, mold, and fungal diseases like Verticillium wilt.

PHOTO: Glass cloche cover strawberry plants in a garden plot in early spring.

Strawberry flowers are susceptible to frost. Here, a transparent plant cover called a cloche (from the French word for bell) is used to protect plants if frost is expected.

Select a planting location in full sun; avoid low-lying spots or crop beds that have grown tomatoes, potatoes, or cane fruit in prior years. These crops can harbor soil pathogens like Verticillium and Phytophthora which can affect new plantings. While strawberries prefer to grow in soil with a bit of acidity, a pH of 6.2 is ideal; the varieties mentioned above perform well in Chicago.

Aim for early spring planting, as soon as the soil can be worked, and its temperature is above 40 degrees Fahrenheit. Mid-April to mid-May is ideal. Space plants 12 inches apart, leaving 3 feet between rows. Fifty plants produce enough fresh home-grown fruit for four people all summer long.

Plant with midpoint of crown at soil level. Roots should be planted straight down. Strawberries are shallow-rooted, and mother plants spread by runners—which can be removed if desired, to develop stronger plants and to promote bigger fruit.

Water your plants well, particularly when they are fruiting. Mulching with straw helps keep fruit clean and dry, and up off the soil.

Spring tasks: Prune Raspberries

Red, yellow, black, or purple raspberries are easy to grow in hedgerows as natural barriers along lot lines or on post-and-wire trellises. Cane fruit is best managed with proper spring pruning, which prevents a tangled mess and makes your late-summer harvest far easier. Regular pruning keeps brambles in line while allowing air flow through the plant—lessening the risk of fungal diseases like Botrytis and rust, and increasing both yield and berry quality. Both types of raspberries—summer-bearing and everbearing (or fall raspberry)—benefit from a good March pruning.

PHOTO: Different kinds of berries in baskets, lined up in a grid.

A bountiful berry harvest on its way to our Farmers’ Market? A bountiful home harvest is also possible with vigilant pruning.

Summer-bearing raspberries produce a single crop in the summer on canes which have overwintered. It is important to confine them to a 1- to 2-foot-wide hedgerow to encourage air flow and sunlight. Begin your pruning by removing dead, diseased, or damaged canes first. Then, head back (prune) the spindly top 6 inches of cane tips. Removing the thinnest wood which produces the smallest berries forces the growth into the more vigorous lower part of the plant.  Finally, remove less vigorous canes—in an established plant, those canes with less than a pencil’s diameter thickness—leaving 6 inches between canes (enough room to easily pass your hand between canes).

Fall-bearing red and yellow raspberries can produce fruit on both the current season canes (called primocanes) and second-season growth (floricanes). Thus, they can be pruned to bear one or two crops with a method called, “double cropping.” (We demonstrated both methods last year on our brambles in the Regenstein Fruit &  Vegetable Garden.)

  1. To produce one heavy fall crop, cut all autumn raspberry canes back to ground level in the spring. Canes should be cut as close to the ground as possible to encourage new buds to break just below the surface. All new canes will grow from this radical pruning and produce a single crop of berries.
  2. A second method of pruning produces a small crop on the previous year’s growth and later, a second crop on the current season’s canes. When a double crop is desired, remove dead, diseased, or damaged canes in March, leaving the vigorous canes to fruit. Tip-prune those back by one-third of the total length of the cane, or to trellis height. The new shoots or primacies will produce the second larger crop. After the second fruiting, the canes will die and should be removed.

Pruning for blackberries is similar to raspberries. They are also pruned in March by heading back the “leaders”—the main canes—by one-third (or about 36 inches). This tip-pruning helps to stimulate the growth of lateral branches, which is where blackberry sets fruit. The lateral branches should be pruned back to 12 inches, or where the branches’ thickness is about the diameter of a pencil. 

Want to learn more about cultivating berries? Join us for Growing Fruit Trees and Berries, May 29 to July 10, or check out other fruit cultivation classes at the Garden this spring.

©2014 Chicago Botanic Garden and my.chicagobotanic.org