Strawberry Science

• The strawberry is a member of the Rosaceae (Rose) family. The genus of strawberry plants is Fragaria, and there are over twenty species. Additionally, there are numerous hybrid strawberries and many varieties of cultivars. Fragaria, derives from the Latin word for strawberry, “fraga” which ” itself is a derivative of “fragum,” which means “fragrant” and accurately characterises the olfactory sensation of freshly picked strawberries.
• It is known as a soft fruit along with raspberries and is not a true berry like blueberries, cranberries, currents and gooseberries which grow on bushes.
• It is a herb plant that doesn’t have significant amounts of woody tissue above the ground but is still vascular. The lack of woody tissue causes the plant to be relatively short as the stems do not thicken to support tall growth. The strawberry is sometimes called a ‘false fruit’ as it consists of tissue derived from the flower receptacle and the true fruits are the one seeded achenes that are embedded in the surface of the fleshy structure. It is unique as it is the only fruit with seeds on the outside rather than the inside.
• Strawberry species have varying numbers of chromosomes which accounts for a great genetic diversity. All strawberry plants share seven common types of chromosomes and   species differ in the number of pairs of these chromosomes. Most species are diploid, meaning they have two sets of chromosomes, one set of chromosomes is normally inherited from each parent, meaning they have two sets of the seven chromosomes (14 total). Others are tetraploid (4 pairs, 28 total), hexaploid (6 pairs, 42 total), octaploid (8 pairs, 56 total), or decaploid (10 pairs, 70 total).  This phenomenon is called Polyploidy and is common in plants and can be summarized as when multiple pairs of chromosomes are present in the genetic component of an organism.  Generally, the strawberry plant species with higher chromosome counts are more robust, grow larger as plants, and produce bigger strawberries though there are exceptions. The strawberry is a robust plant and occurs naturally in many climates apart from Africa, New Zealand and Australia which do not have any indigenous species.
• Fragaria vesca is a species of strawberry plant that is native throughout the northern hemisphere and goes by many different names. The varying names for Fragaria vesca include: the woodland strawberry, wood strawberry, wild strawberry, European strawberry, fraises des bois, and alpine strawberry (more specifically, the alpine strawberry plant is generally understood to be of the cultivated, everbearing type).
• Genetically, an ancestor to the Fragaria vesca species (which is diploid) likely formed a hybrid strawberry plant with an ancestor to the Fragaria iinumae (which is also diploid) to eventually produce the octoploid strawberry plants.
• The cultivated strawberry Fragaria × ananassa is probably the most important species of Fragaria. As a species, the cultivated strawberry is very young; it originated as an interspecific cross between the octoploids F. chiloensis and F. virginiana in a French garden sometime between 1714 and 1766.
• The maternal F. chiloensis was brought to Europe from Chile in 1714 by a French spy, Captain Frézier. As time passed, strawberry seedlings with unusually large fruit and red flesh began to appear in European gardens.
• In 1766, botanist Duchesne determined these seedlings to be hybrids of F. chiloensis and F. virginiana, and the new species was named as F. × ananassa.
• Fragaria vesca strawberries have been consumed by humans for many centuries. Archaeological evidence suggests human consumption of strawberries as far back as the stone age though the  first cultivated varieties  were grown in ancient Persia. The fruit from these Persian-cultivated strawberry plants was referred to as Toot Farangi. The seeds of this strawberry plant travelled both east and west along the silk road and were being widely cultivated from Europe to the Far East.
• The first recorded documented botanical illustration of a strawberry plant is believed to be from 1454.
• There is some disagreement as to how the strawberry plant got its name. It is generally accepted that the English word “strawberry” comes from the Old English “streawberige” or the Anglo-Saxon “streoberie” (sometimes also spelled “stroeberrie”). It was not spelled in the current manner until about 1538. It is likely that the straw that was traditionally used as mulch and to keep the weeds out and berries clean gave rise to the name. Another school of thought is that the straw-like appearance of the strawberry plant runners led to its current English name.
• The productive engine of a strawberry plant is contained within the crown. The crown produces both runners also known as stolons and flowering fruit stalks which are the daughter plant that eventually yield strawberries. The runners are usually between 8 and 18 inches long, depending on the strawberry variety. These extensions serve to spread a strawberry plant’s range and find areas more favourable to growth, whether through higher soil quality or increased exposure to sunlight. The runner plants have a distinct advantage over seedlings as they start out larger and have a more fully formed support system providing the energy needed for development.
• The daughter plants are maintained by the runners until their root bud encounters soil and then establishes an independent root system. The runner will then become dry, shrivel, and eventually separate completely leaving a new and independent strawberry plant clone.
• After producing fruit, the plant devotes its energy into producing runners. Long days trigger the production of a hormone called gibberellin that causes stems to grow longer.
• Scientists have discovered that the strawberry plant must finish producing its runners before temperatures drop to about 10 degrees Celsius as cooler weather causes the plant to become dormant. The dormant strawberry plants must survive on stored energy through the winter until next spring as they are perennial.
• Throughout their life, strawberry plants provide many times their own weight in harvested strawberries. They are one of the most productive plants when what is produced from the weight of the parent plant is considered. Strawberries begin to ripen four to five weeks after the first flowers open and continue to ripen for about three weeks.
• Strawberries aren’t just wonderful to eat but just seven per day provides a person with the recommended daily amount of vitamin C !

For primary aged children and school groups, you can take part in our experiment to extract DNA from strawberries.

Strawberry DNA Experiment

Article by Samia Qureshi, Science Learning Officer