Lesson 5 - Canes, vines and berries
The last group of fruits we will study are the berries and related fruits. It includes those growing on vines, such as grapes, passionfruit and kiwifruit; those growing on shrubs, such as currents, feijoas, gooseberries, cranberries and blueberries; those that fruit on ‘canes’, such as raspberries, blackberries and youngberries; and herbaceous perennials like strawberries.
One of the most delicious berry fruits for the home gardener in the raspberry (Rubus idaeus). Like other deciduous cane berries, such as youngberries and blackberries, raspberries produce fruit on long thorny stems or ‘canes’ as they are commonly known. In the case of raspberries there are two different groups of cultivars. The first of these are the autumn-bearing raspberries that produce fruit on what are called ‘primocanes’ – first-year canes that grow up from the base during spring and summer, before flowering and fruiting in autumn, such as the ‘Autumn Bliss’ and ‘Heritage’ cultivars. The second group are the summer-bearing or dual-cropping raspberries, such as ‘Chilliwack’ or ‘Golden Raspberry’. These produce biennial (two-year old) canes or ‘floricanes’ that only have vegetative growth in their first year, but produce flower and fruit in their second year, sometimes twice, beginning with a heavy crop in summer and a lighter crop in late autumn. Winter pruning is important for raspberries but is a little different for the two groups. For autumn-bearers, all canes are cut to the ground over winter. While for summer-bearing raspberries, the spent floricanes are removed, these will have died back anyway after fruiting, but the new one-year old canes are retained.
Raspberries prefer open, sunny locations with well-drained but slightly acid soils and as a temperate plant, they need some winter chilling to break dormancy. This is between 900-1700 chill hours (below 7°C), with summer-fruiting cultivars, such as ‘Chilliwack’, needing the most. In warmer or even subtropical climates, where chilling hours are much less, sone of the autumn-fruiting forms, such as ‘Heritage’ can often be successfully grown. Raspberries originate from the cooler climates of Europe and northern Asia. This, coupled with the fact that they are shallow-rooted plants, means that they are not very drought-tolerant and benefit from mulching and irrigation over summer to reduce moisture stress. This is particularly true for autumn-bearing forms which grow over the warmest and driest months of the year before they finally set fruit.
Raspberries are best grown in rows with a strong post and wire trellis that supports the vigorous canes, making them easy to manage and harvest. This particularly important for summer-bearing types where individual floricanes can be as much as two metres in length. The trellis needs to be 1.2 to 1.5 metres in height with two to three tightly strung horizontal wires, supported by posts along its length, and 400-500 mm apart. For autumn-bearing raspberries, the primocanes can be tied together during late spring and fixed to the trellis. For summer-bearers, winter pruning and training involves removing the old floricanes, followed by tying and bundling together the new primocanes, discarding the any small or underdeveloped canes which are unlikely to fruit. The bundles of canes can then be tied directly to the horizontal wires, making sure there is an equal spread of canes along the trellis. The trellis also makes the plants easy to net from birds, a major problem during harvest. It’s also possible to grow raspberries in containers where space is limited, although cultivar selection is important. Autumn-bearing raspberries are best as some are more compact and can be grown against a wall or fence to support them as they develop. More details can be found on our webpage on raspberry growing
One of the easiest to grow berries is the strawberry (Fragaria × ananassa). First grown in France in the 1750’s, strawberries are a hybrid and were created by crossing the Virginian Strawberry (Fragaria virginiana) from North America with the Beach Strawberry (Fragaria chiloensis) from Chile. The resultant plant is the parent of all modern strawberry cultivars, of which there are now more than 100. Botanically, a strawberry is not actually a berry, but rather an ‘aggregate fruit’. The fleshy and sweet part of the ‘fruit’ is an enlarged receptacle that develops after the flower is fertilised. As it grows and swells it becomes dotted with the real fruits that develop from the flower – one-seeded ‘achenes’, the ‘seeds’ that coat the exterior of the strawberry. Strawberries need to be picked when they are ripe as they won’t ripen any further after harvest. As strawberries begin to fruit, they also send out stolons or runners with new plantlets (shoots roots) at each node, spreading the plant even further. These can be used as new planting materials for subsequent seasons or years, depending on the cultivar.
Strawberries are a perennial herb, forming a basal ‘crown’ that grows for many years. And while the plant may continue to grow, it becomes less productive with age. The crowns start to be crowded with leaves, in turn producing less flowers, with individual increasingly affected by virus. Replacing the plants with fresh, virus-free plant material (runners) from a reputable source ensures that you will continue to have productive plants. It’s a good idea to renovate a bed of strawberries each year – during winter if you are in a cold climate, or early autumn in warmer areas. The plants can be lifted, divided and replanted, with the best new plants and runners kept, and the older woody crowns discarded.
The strawberry flower is produced on a short pedicel (stem) from the crown of the plant in groups of three, gradually turning from a greenish white to a deep red colour when ripen. Two climatic factors – day length (photoperiod) and temperature – strongly influence fruiting and have led to different cultivars for a range of climates. Some are ‘short-day’ strawberries, needing <14 hours daylight and cooler temperatures (~10-25°C) to initiate fruit; while most spring-summer grown strawberries tend to be ‘everbearing’ or ‘day-neutral’ forms – less sensitive to daylength and able to produce multiple crops over the season. Flower initiation is reduced in strawberries when temperatures >30°C, which can make them difficult to grow in very warm locations. Check the diggers page on growing strawberries for detailed cultivar information.
When planting or renovating a bed, place the runners ~20 cm apart in sunny locations with fertile soils. The more fertile the conditions the more productive the crop, so don’t be afraid to provide some organic fertiliser when preparing the bed and over the growing season, the plants will respond in kind! Strawberries do best in well-drained soils, so some form of elevated or raised bed will improve growth and fruit production. Mulching is also recommended for strawberries – to reduce weed competition, increase soil moisture and to provide a clean bed for the fruit to set. Irrigation will also be needed over summer in most locations and at about the same time protect your plants through netting. This needs to start just after flowering to ensure the ripening, red berries are not consumed by birds, beware – they can demolish your crop in just a few hours! Strawberries are also an excellent container plant and one of the most productive. There is more on container growing coming up in Module 6.