Read an Excerpt

Strawberries

Strawberries — such small plants, such beautiful fruit, such wonderful flavor. At a time when these luscious fruits are being produced for export in regions far from where they are being consumed, the quality of the strawberries one finds at the grocery store may not be as good as it once was. Strawberries grown in places like California and Florida, which have longer growing seasons than other regions, are bred for firmness, size, and color, rather than flavor. The good news is that you can easily grow strawberries in your own private paradise, however small, and the flavor will be wonderful. The strawberry can be thought of as the tomato of the berry world: you can certainly buy them in the grocery store, but the difference between that variety and the ones you grow in your own backyard is like night and day. In addition, the plants make a wonderful groundcover in the garden, and they are highly productive. Many cultivars are also quite disease resistant.

Historical background and other interesting facts

Strawberries are an ancient crop. The first written reference to the strawberry is from ancient Rome, but the berries were likely collected from the wild for medicinal purposes and as a source of food long before recorded history.

The question of why these fruits are called "strawberries" is widely debated. The name may be based on the fact that the seeds are the color of straw, or that in medieval England the berries were often strung on pieces of straw and sold. An alternative explanation is that the natural growth habit of the plant results in fruits "strawn" (strewn) on the ground. The name most certainly does not stem from the current practice of applying straw as a mulch for winter protection.

The history of the modern cultivated strawberry is an interesting one. The cultivated plant, Fragaria ×ananassa, is a hybrid between F. virginiana, the meadow strawberry, and F. chiloensis, the Chilean strawberry. The Chilean strawberry first made its way to European gardens in the early eighteenth century. In 1712 a French spy named Amédée François Frézier was sent by King Louis XIV to survey and map the coasts of Chile and Peru to obtain information about the Spanish fortifications there in anticipation of war. Monsieur Frézier was not just a spy, however — he was also an amateur horticulturist. As such, he was extremely impressed with the large, tasty strawberry fruit that grew wild on the Chilean coast, and he dug up several of the most vigorous plants he found and transported them back to France. (Quarantine restrictions had not been invented at this point in history.) Only five plants survived the rigorous journey across the ocean, and one plant was given to the Jardin des Plantes in Paris. The plants were eventually distributed around Europe, and the Chilean strawberry, F. chiloensis, became commonly cultivated throughout the continent. Because F. chiloensis is dioecious (fruiting plants have only female flowers), other species that bear male or perfect (bisexual) flowers were interplanted to ensure pollination and fruiting. The pollinator used was often the North American native F. virginiana. The hybridization of these two species, probably in several locations, led to the development of today's commercial strawberry, F. ×ananassa. The hybrid was clearly superior to all the other strawberry species available in Europe at the time. Since then, breeding efforts have improved fruit quality, productivity, pest resistance, winter hardiness, and various ornamental qualities. This work is ongoing, and many strawberries produced today are superior in productivity and pest resistance to any previously produced in history.

Beyond its relatively short western European history, the strawberry has been cultivated extensively in Chile for many centuries. Long before the European discovery of the New World, probably as far back as 2000 years ago or more, the Chilean strawberry was most likely domesticated by the indigenous Mapuches. The Mapuches were hunter-gatherers, but they learned about agriculture from the Picunches, who in turn had been influenced by Incan invaders. These native peoples consumed both wild and domesticated strawberries, which were eaten fresh or dried or made into a fermented juice known as lahuene. The domesticated fruits were probably the larger, white form of strawberry, which has been found at three locations in southern Chile. The red-fruited forms were certainly consumed as well, but since they were abundant in the wild, it was not necessary to cultivate them. One legend has it that red strawberries were planted by the indigenous peoples as traps for the Spanish soldiers. The Indians would place the plants in small, open spots in the forest, and when the soldiers dropped their weapons to pick the tempting morsels, they were sprung upon and attacked by the natives.

The Chilean strawberry was transported to other South American locales as well. The largest land area of cultivated strawberries was at Huachi-Grande, near Ambato, Ecuador, where an estimated 1200 to 1700 acres (500–700 hectares) were used to grow strawberries from at least the late 1700s until 1970. In the early 1900s it was written that the fruit was three times the size of the European strawberry and was produced throughout the year. The fruit was not only large but tough. In 1921 a North American pomologist, Wilson Popenoe, wrote:

It is the custom in Ecuador to throw the fruits into boxes: they are then carried six or seven miles on mule-back to the city of Ambato, where they are sorted by hand, for shipment by train to Quito or Guayaquil. There is probably no other strawberry in the world which could tolerate this sort of handling.

The traditional plantings of the Chilean strawberry began to disappear in the 1950s, when they were mixed with Northern Hemisphere cultivars of Fragaria ×ananassa. They were eventually completely replaced by California cultivars, including 'Chandler' and 'Pajaro'. Several expeditions to Chile by North American researchers have sought to collect and preserve some of these remarkable Chilean strawberries. (Among the researchers are J. F. Hancock from Michigan State University, J. S. Cameron from Washington State University, and C. Finn from the U.S. Department of Agriculture in Corvallis, Oregon.) These collections have been conducted in collaboration with the governments of both countries, and it is hoped that the plants will yield valuable traits to breeding programs throughout the world.

Today, strawberries are produced in every state in the United States and in nearly every country in the world, most notably Italy, Poland, Russia, and Japan. This wide distribution suggests that the strawberry plant is widely adapted, and as a genus, this is true. However, many individual genotypes or cultivars of strawberries are narrowly adapted to local conditions, and so selecting cultivars that are proven to perform well in your specific region is particularly important.

Biology of the plant: knowing it and using it to your advantage

The strawberry plant is in many ways unique among fruit plants. It is a herbaceous perennial composed of leaves, a crown (a compressed, modified stem), and a root system. The root system is composed of two types of roots: those that are semipermanent, lasting for more than a season, and those that are transient in nature, lasting only days or weeks. In light sandy soils the roots may extend as deep as 12 inches (30 cm), with half of the root mass in the lower 6 inches (15 cm). In heavier soils, such as clay loams, 90 percent of the roots maybe located in the top 6 inches (15 cm) of soil. This shallow root system is, in part, responsible for the plant's sensitivity to deficient or excessive water in the soil. Another aspect of the strawberry root system that has practical importance to the grower is that new roots arise from the base of the developing leaves. Since leaves (and along with them, roots) are formed successively higher on the crown as the plant ages, the strawberry tends to grow "out of the ground." For this reason, mounding soil around the bases of the plants at renovation time, particularly as the bed ages, is good practice. It supports the base of the plant and gives the newly forming roots a place to call home.

Each leaf of the strawberry plant is composed of three leaflets, each oval in shape and with serrated edges. Leaves can exhibit considerable differences in size, from alpine strawberries, the leaflets of which are often less than 1 inch (2.5 cm) long, to some common short-day cultivars, which may have leaflets up to 2 inches (5 cm) long. The runners, or stolons, arise from buds in the leaf axils and are the strawberry plant's device for asexual propagation. Runners form during the long days of summer, and they generally require a day length of more than 12 hours for formation. The matted-row system of culture, which is the method of strawberry cultivation recommended in this book, takes advantage of the plant's runnering capacity as a means of establishing many plants from a few.

The flower cluster (inflorescence) of the strawberry plant arises from the terminal buds. Bud formation occurs deep in the plant tissue and is invisible to even the most observant onlooker. The inflorescence formed from this single bud contains a number of flowers, which will result in a number of fruit, with about 30 days between flower opening and fruit ripening. The terminal flower opens first and is referred to as the king flower. The king flower also has the highest number of cells in it. Why is this important? Because it will yield the largest fruit, appropriately called the king fruit. Unfortunately, since it opens first, the king flower is also more likely to be damaged by late frosts. The remaining flowers on the inflorescence open sequentially down the stem, from the terminus to the base of the inflorescence. In other words, the second flowers to open are those located just below the terminal flower, and they will open slightly later (usually a day or two) and have slightly smaller fruit. This arrangement means that the fruit is smaller as the season progresses. It is also a good reason to avoid frost, if you can.

More than one inflorescence may be borne on a single plant if branch crowns (small compressed branches on the thicker main crown) have developed, since each branch crown can also terminate in a flower cluster. After several years, however, if too many branch crowns develop on an individual plant, intraplant competition for resources can result in reduced berry size as berry number increases. For this reason, 3- to 4-year-old plants are not as desirable in a planting bed as younger plants, which have fewer crowns.

The strawberry fruit is an aggregate fruit, composed of achenes (a type of seed) that are fused together on a tissue (the receptacle) at the end of the flowering axis. The majority of the consumable portion of the fruit, therefore, is receptacle tissue. Fruit size, which ranges from º inch (0.5 cm) to 2 inches (5 cm), is dependent on a number of factors, including the fruit's location on the inflorescence, the density of the crowns on the individual plant, and the particular cultivar (certain cultivars are simply larger or have less variation in size within a given cluster), as well as environmental factors such as water availability and plant density.

The fruit will also vary somewhat in shape, primarily as a result of genetics. Some cultivars produce fruit with a more spherical shape, whereas others bear long and thin fruit. Certain cultivars tend to form a long "neck" — a disappointing trait. In such plants, the area of the fruit just under the cap (calyx) becomes distended and develops a thin skin, making that area weak and prone to skin rupture or insect attack. Color can vary among strawberry cultivars from fairly light oranges to very dark reds or near purples.

Strawberry types

The different strawberry types are defined primarily by their time of flower bud initiation, and hence fruiting. The two main types of strawberries are short-day (also referred to as June-bearing) strawberries, which initiate flower buds when the days are short, and day-neutral strawberries, which will form flower buds regardless of day length. This difference in time of flower bud initiation translates to differences in time of fruiting.

Strawberry types can also be distinguished by the different species from which they were bred. Most cultivated strawberries are hybrids of two or more species, although the alpine strawberry is a separate species (Fragaria vesca). It is little grown but is included here because of its potential as a garden plant and as a delightful addition to the plate.

Short-day or June-bearing strawberries. The short-day strawberry is by far the most widely grown type of strawberry. Also known as the June-bearing strawberry, it bears its fruit during that month in most regions of the Northern Hemisphere. This type forms flower buds during the short days of autumn (late September through early November), becomes dormant in the winter, and then flowers and fruits when the weather turns warm again in the spring. Some bud formation may continue through the short, warm days in spring as well. The plant must have a full, well-established leaf canopy because the leaves provide the energy for flower bud initiation. Note that the day-length response relates only to when flower buds are formed and has nothing to do with when the plant actually blooms.

Temperature also plays a role in flower bud formation. Temperatures below 60°F (16°C) are ideal for bud formation; generally, if night temperatures exceed 70°F (21°C), bud initiation is inhibited. The ability of the plant to substitute cool temperatures for short days accounts for the plant's production in areas of higher elevations. In this case, short-day strawberry plants may form flower buds whenever stimulated by cool temperatures, so they may behave more like day-neutral plants than short-day plants.

Day-neutral strawberries. Day-neutral strawberry plants, which yield fruit almost continuously from spring through fall, are becoming increasingly important commercially and are useful for home producers too. They initiate flower buds regardless of day length, thus producing some fruit throughout the summer and a sizable fall crop that is a great bonus for backyard growers. The plants will flower and produce fruit and runners simultaneously, with runner plants often flowering prior to rooting.

Day-neutral cultivars begin fruiting at roughly the same time as the short-day sttawberries, usually between mid-May and mid-June. At this time, plants produce a medium-sized crop of medium-sized fruit. The crop borne by day-neutrals in the spring is not as large, and individual berries a