Strawberries (Fragaria) belong to the Rosaceae family and therefore belong to the same plant family as apples, cherries, quinces and many other fruits. Decorative shrubs such as the finger shrub (Potentilla), the firethorn (Pyracantha) and the spar shrub (Spiraea) are also included. Typical for the plant family are the relatively simple flowers with five petals. The natural range of strawberries extends across America, Europe and Asia. The ancestors of our cultivated strawberry come from America: In the middle of the 18th century the North American scarlet strawberry (Fragaria virginiana) and the Chilean strawberry (Fragaria chiloensis) came to Europe. At this time, the so-called pineapple strawberry (Fragaria x ananassa) arose from a cross between the two species – a hybrid that is considered the archetype of today’s garden strawberries. A variety of native forest strawberries (Fragaria vesca) are the monthly strawberries (Fragaria vesca var. semperflorens), which bloom from May to October and bear fruit continuously. For this reason they are now called strawberries that carry or remount. Of the approximately 1,000 strawberry varieties worldwide, around 100 are cultivated in Germany, predominantly the once-bearing garden strawberries.
Appearance and growth
Strawberries are perennial plants that are classified as perennials because of their way of life. The flowers and fruits form on long herbaceous stems near the ground. The three to five-fold, rich green leaves stand in a rosette. After a cold stimulus, umbels with small white flowers emerge, which, depending on the variety, are clearly to barely visible in the foliage. Since the fruit of the strawberry is a pomegranate fruit and the actual seeds appear as small yellow nuts on the outside of the fruit, the fruits of the strawberries belong to the so-called pomegranate fruits.
Location and soil
Strawberry plants thrive best in full sunny locations. The more sun the plants get, the sweeter the fruits become. The site should be a little sheltered from the wind, but not completely windless, so that the leaves dry off as quickly as possible after rainfall and leaf diseases cannot gain a foothold so easily. The soil should be loose and not too heavy, deep and rich in humus, and the pH value should ideally be between 5.5 and 6.5, i.e. in the slightly acidic to acidic range. Root diseases develop more easily on compacted soils, so it is important to loosen them up with deciduous compost or sand before planting and prepare them for the sun-hungry soft fruit with green manure. Do not use conventional compost from the garden for strawberries. The right soil preparation is the basis for a good harvest: dig the soil deep with a digging fork and then work in four to five litres of humus or compost leaves and about 30 grams of horn meal flat with a cultivator per square metre. Two weeks after the bed preparation, the soil has settled so far that you only have to rake the bed smooth. Then you can plant the strawberries.
Crop rotation and mixed cultivation
Strawberries provide the greatest yield in the second and third year after planting. The yields and the quality of the fruit then decline continuously. You should therefore change the bed and plant new young plants or your own offspring. Like most rose plants, strawberries are very sensitive to reproduction – this means that you should plant new strawberries in a bed in which strawberries have stood at the earliest after four years in order to prevent soil fatigue and soil pests such as nematodes. Vegetables with a short cultivation period, such as kohlrabi, salads and radishes, are ideal as pre-fruits. Garlic has also proven its worth as a mixed crop plant for strawberries. Bulbs protect strawberry plants from fungal diseases. For example, lupins or incarnate clover can be used as green manure.
Two months before planting you should improve the soil with deciduous compost and – if available – rotten cow manure. As a rule, there will be young strawberry plants on the market from July onwards. The best planting time for garden strawberries begins in the middle of the month and ends in August – then they already give a good yield in the first standing year. Multiple-bearing varieties can be planted in the soil from August to September, while monthly and climbing strawberries are best planted in spring.
The distance between the rows should be at least 60 centimetres, so that you can harvest the fruit easily. In the row, 25 to 30 centimetres planting distance are sufficient. The plants should be planted so deep that the heart of the plants remains above the surface of the earth. With bare-rooted young plants, make sure that the roots get into the soil vertically and well spread out. They shouldn’t be kinked.
Especially during the growth phase and in dry weather, the plants need a lot of water. It is also important to regularly remove weeds from the soil when caring for strawberries. This can be done in the planting year by careful chopping – after that you should do without mechanical soil cultivation and mulch the bed with dried lawn cuttings instead. This prevents weeds from growing. By spreading straw between the plants from the beginning of May, you protect the sensitive strawberries from moisture and grey mould infestation. In addition, the fruits lying on the ground remain clean and weeds continue to be suppressed.
After harvesting, the straw should be cleared away again. Now cut off the leaves and remove all the children you do not need for propagation. The old foliage is usually infected with fungal diseases and must therefore be carefully removed from the bed. The same applies to weeds that have grown through. Loosen the soil compacted by the harvest between the rows with a sowing tooth. Then spread organic berry fertilizer around each plant and mulch it with leaf compost. You can pour the cut plants in so far that only the tips of the cut petioles are visible. Strawberries are always fertilized after harvesting, because from then until autumn the new flower buds are planted for the coming season, for which the plants need a lot of nutrients.
Once and twice strawberry varieties in the field do not need any special protection during wintering – unless it is extremely cold. However, strawberries that are kept as tub plants must be provided with winter protection in good time and moved to a protected place, for example to a roofed house wall. In permafrost, you bring them into the house to be safe.
Cultivation in pots
Strawberry varieties, which produce fruit until October, can be cultivated very well in planters. The small and aromatic fruits of these remonting varieties hang in the air instead of lying on the ground.
If you want to put raspberry or pineapple strawberries in a pot, a bucket with a diameter and depth of about 20 centimetres is sufficient. Of the smaller Pineberrys, about three plants fit into such a pot. As a precaution, potted strawberries should spend the winter in a cool, dark place in the first year, frost-free and not forget to water. Slightly larger pots, tubs and balcony boxes with water drainage holes are well suited for planting. For the varieties you should use robust, ever-bearing strawberries such as ‘Camara’, ‘Cupido’ or ‘Siskeep’. Put potting soil with organic fertilizer in the plant tubs and place the planted containers in a fully sunny location. In autumn you should prune the plants back so that they will bear fruit for another two years.
Harvesting and recycling
Garden strawberries are usually ready for picking in June. During the harvest, the plants can be harvested two to three times a week. If varieties with different ripening times are grown next to each other in the bed, the season for fresh strawberries can be slightly extended. Remonting strawberries are ripe for harvesting several times a year, but not as productive as garden strawberries.
Since strawberries are very sensitive and can only be stored for a short time, they should be eaten or processed as freshly as possible – for example to make strawberry jam or sauce. The fruits can also be frozen, although they are somewhat muddy after thawing. The freezing process has proved to be particularly effective for later processing the fruit into jam. This tastes even more aromatic than jam made from fresh strawberries.
The varieties bred for yield cultivation are very different from the strawberry varieties for the home garden. They are mainly grown on firm flesh so that they can be easily transported. In terms of taste, however, they do not come close to the house garden varieties. The most common strawberries are the once-bearing garden strawberries. Of these, there is also the largest variety on offer. Early to medium early varieties are for example: ‘Polka’: high yield, relatively robust ‘Senga Sengana’: rich bearing, strong growth ‘Ostara’: remonting variety, medium sized, heart-shaped fruits ‘Jubilae’: good taste, robust ‘Elvira’: high yields, early ripening Mid to late ripening varieties are ‘Thuriga’, ‘Salsa’ and ‘Symphony’.
Typical garden varieties form very soft, but highly aromatic fruits. They are usually somewhat more small-fruited than the yield varieties and should be processed quickly, as they cannot be stored for long. These include ‘Hummi Praline’ (dark red, fragrant fruits, very sweet and aromatic) or ‘Hummi Silva’ (large and very juicy, aromatic strawberries). . Attention: These varieties are not self-fertile and should therefore be combined with other strawberry plants, as strawberries with multiple foliage are less common in the garden. They bear their first fruits in June/July and, after a resting period in late summer/autumn, replenish. While the first harvest is often plentiful, the late fruits usually appear only sporadically. The strawberries are usually smaller, but more aromatic than the fruits of the once-bearing varieties. You can only harvest larger fruits if you thinn out the first fruit hanging in May to such an extent that only five to six strawberries remain per fruit shoot. Well-known varieties are ‘Ostara’, ‘Selva’, ‘Sweetheart’ or ‘Rapella’, which produces large sweet-sour fruits.
Monthly strawberries, derived from the forest strawberry, are very robust and produce tasty small fruits from June to October. The most common variety is ‘Rügen’, but only the fully ripe fruits develop their aroma. Disadvantage: They can only be propagated by seeds and their yields will decrease quickly after the first two years. Special cultivars are for example the meadow strawberry (Fragaria x vescana), the raspberry and the pineapple strawberry. The meadow strawberry is a cross between the garden strawberry and the forest strawberry and produces small, aromatic fruits. Their runners grow together to form a dense meadow. It is planted in May with three to six plants per square metre. The raspberry-strawberry is not, as the name suggests, a cross between raspberry and strawberry, but a protected new breed of strawberry. The appearance and taste of Fragaria x ananassa, however, look like a mixture of the two red berries. The fruits are firm and not quite as big as those of the classic strawberry. The seeds are sunk deep into the fruit, forming the characteristic small pits. They are a little darker than the usual strawberry with a shade of violet. The name “Framberry” is a combination of “Framboos” (Dutch for raspberry) and “Strawberry”. Recommended varieties are for example ‘Framberry’ or ‘Purple Fresh’. The flowering period of raspberry-strawberries lasts from May to June.
The pineapple strawberry traded under the brand name “Pineberry” is also a cultivar of the garden strawberry. Known varieties are ‘White Dream’ or ‘Anabella’. The pineapple strawberry has a light pineapple aroma in addition to its strawberry flavour. But the most striking thing about it is its appearance, because the berry is not red, but white with red seeds. In fact, white strawberries were already known in South America in the 18th century, but have not yet been commercially bred. The Pineberry is now, thanks to another cross, the robust variety of a very old strawberry form. The berries are green at first, then turn whitish and ripe when the nuts turn red. Since there is currently only one breeder, the pineapple strawberry can be considered a real rarity. With growth heights of about 20 centimetres and fruits only two centimetres in size, the plants remain considerably smaller than ordinary cultivated strawberries and are also somewhat more sensitive to pressure. Flowering time is from March to June. The first fruits can then be harvested between May and early July.
Both raspberry and pineapple strawberries are hardy and bear perennial fruit. If the plants become too old, however, the crop yield is significantly reduced, so strawberry plants should generally be replaced after about three years. The two can be increased by lowering. Since the two are crosses, however, it is possible that the original form will occasionally prevail. Our tip: Combine different varieties of self-fertile garden strawberries as well. On the one hand, you can extend the harvest time by combining early and late breeding, on the other hand, the yields are higher if a second pollinator variety is planted.
Strawberries multiply via runners, which in turn multiply by new leaf rosettes and new runners. If you do not intervene, a dense carpet of plants will develop over time. Most strawberry varieties have hermaphroditic flowers and, as already mentioned, can fertilise themselves. For purely female varieties, such as the old and very aromatic ‘Mieze Schindler’, it is necessary to plant a nearby fertiliser variety.
Garden strawberries in particular, which form runners, can easily be propagated by cuttings: The runners can be removed and potted or placed directly in the ground. You should take care to propagate only healthy mother plants. The selection is important: During the harvest, mark the plants with the richest labels and grow only of these daughter plants in small pots filled with soil. After rooting, you can separate the cuttings from the mother plant. Note, however, that strawberries grown from children degenerate more and more over time. After each self-produced generation, it is therefore advisable to freshen up the stock with purchased young plants.
Monthly strawberries do not form runners and are therefore propagated by sowing. From February to March, spread the seeds thinly in seed boxes or seed trays filled with growing soil. Sieve the seeds only lightly with soil and moisten them. A bright place with about 17 to 20 degrees Celsius is ideal for germination. Keep the pots moderately moist. As soon as the seedlings have set five leaves, the plants can be pricked into individual pots and kept evenly moist. After about ten weeks, the young plants are fertilized and then planted at a distance of about 25 centimeters from the beginning of May. In the first year the harvest will still be small, but from next year the strawberries will bear plenty of fruit.
The seeds of the monthly strawberries can also be obtained by crushing the fully ripe fruits and mixing them with water. After a few hours the suspended particles have settled with the seeds and are poured off. After they have dried for a few days, you can easily remove the seeds from the fruit residues with your fingers.
Due to the problem of replication already mentioned, it is important to change the location of the strawberry bed every three to four years. If this is not observed and the weather is damp for a longer period of time, various diseases can occur: The most feared disease is grey mould (Botrytis cinerea). It is caused by a fungus that survives in leaves in humid conditions. The pathogen that causes the red spot disease and the very similar black spot disease are also fungi. Furthermore, the red root rot can occur, which makes the main roots look pale and smooth. Curled, brownish heart leaves indicate strawberry mites. As a preventive measure, you should observe the care measures such as removing the old leaves and cuttings in summer, keeping a sunny and airy location and cultivating varieties that are less susceptible to disease such as ‘Pegasus’. Tausenfüßer like to nibble at the plants, especially in dry weather. If you discover bent stems and dried blossoms, the strawberry blossom weevil is probably in for a treat.