The raspberry plant belongs to the berry fruit family. It is found in the wild in the undergrowth of alpine and pre-alpine areas. In recent years, its great value has been rediscovered, and cultivation has intensified, not only in Northern Italy but also spreading rapidly throughout the country. Regions with a strong vocation for raspberry cultivation include Piedmont and Trentino. Additionally, Tuscany, Emilia Romagna, Sicily, and Campania also hold certain importance in cultivation. This plant is robust and easy to grow, even for the inexperienced. However, understanding it well and knowing its needs is essential.
In this article, we aim to provide a complete guide to raspberry cultivation.
Identification and botanical characteristics of raspberries
The raspberry plant belongs to the botanical family Rosaceae, genus Rubus. There are several species, but the one of interest to us is Rubus idaeus, known as the European raspberry. It’s a plant that appears as a typical bushy shrub with a very shallow root system (comprising rhizomatous main roots) and fasciculated secondary roots. The bush consists of numerous shoots that have a biennial lifespan. These shoots continuously renew and expand. Those that are one year old are called “suckers”, while those that are two years old are fruiting canes. Suckers have a light green color and are covered with small thorns. Upon full maturity, they can reach a length of over 2 meters. They can be “radical”, if generated from buds along the roots, or “from the crown” if they arise from the base of the plant.
Leaves, flowers, and fruits of the raspberry plant
The leaves of the raspberry plant are oval-shaped, dark green, and develop in groups of 3-5. They have serrated margins and are deciduous, meaning the plant loses its foliage during the winter.
The flowers are white and gathered in small racemose inflorescences. This species has entomophilous pollination, carried out by bees and other pollinating insects. The raspberry is a honey plant from which excellent monofloral honey can be obtained if it covers large surfaces. However, the pollen is very light, and therefore, pollination can also occur anemophilously, meaning it can happen with the help of the wind. The fruit is a sorosis consisting of a cluster of small drupelets, very similar to the blackberry. The raspberry’s shape can vary from round to slightly oval, more or less elongated. The color ranges from pale pink to ruby, to dark red, almost purple.
Uniannual or biannual raspberries
The raspberry plant is classified into two groups based on its type and fruiting period: uniannual and biennial (bifera). Uniannual raspberries have a production cycle that spans two years. In the first year, there is vegetative growth of the suckers, which are completely lignified by the end of autumn. During the second year, starting from spring, the suckers become fruiting canes that produce lateral branches. These bear fruit during the summer. In autumn/winter, the fruiting canes dry up and are replaced by new suckers. Bifera raspberries also have a two-year production cycle, but the difference is that the suckers can bear fruit twice. The first time occurs in the apical part at the end of the growth season, in autumn. And a second time in the area below the vegetative apex, in the summer of the following year. In this case, the plant produces fruit twice a year.
There are many varieties of raspberry plants, both uniannual and biennial. Most are crosses resulting from selection processes, allowing the choice of cultivars best suited to our cultivation environment. Always seek advice from your trusted nursery regarding the best variety for your area.
Let’s look at the main types.
Among the uniannual varieties, we note:
- Malling promise
- Malling exploit
- Glen ample
- Niniane rubaca
- Cascade delight
For biennial varieties, we have:
- Himbo top
- Autumn bliss
Wild raspberries usually grow in the undergrowth, in medium mountain areas. They require a humid, cool environment rich in organic matter. Therefore, they are highly robust plants. Cultivated varieties are generally more delicate but still possess excellent resistance and adaptability. Uniannual varieties grow well up to 1500 m in altitude, while it’s recommended not to exceed 1000 m for biennial varieties. More than cold, the raspberry plant fears high temperatures and excessive sun exposure. Hence, it’s advisable to choose a partially shaded spot in your orchard. The area should also be sheltered from winds, which can cause damage. Young fruits are delicate, and wind, through the rubbing of canes, can easily spoil them.
Raspberry plants prefer slightly acidic, fresh, and well-draining soils. They avoid clayey and compact soil types that are too calcareous and don’t drain well, causing root asphyxiation. Before planting, it’s always advisable to conduct a soil pH analysis.
The planting period varies depending on the nursery material available. Both bare-root suckers and small potted plants with soil are sold. Planting bare-root suckers should be done during the dormant period, i.e., autumn-winter, making it the best choice for this type of plant. Potted plants with soil, on the other hand, should be planted in spring, once the risk of late frosts has passed. For further technical details, we recommend reading this article on how to plant a fruit tree.
Planting layout and training system, uniannual varieties
The setup and management of a raspberry plantation vary depending on the chosen variety. For uniannual varieties that fruit every two years, an interesting system is the cordon system with alternate production. With this system, part of the plantation is dedicated to the current year’s production, while another part is for renewing the suckers. To explain it better, the cordon system involves preparing supports. These are made with 2.50 m iron or wooden poles placed in the same row, two meters apart. Between the poles, longitudinally, pass iron wire at different heights to anchor the plants through tying. Tying allows for supporting the suckers, preventing heavy vegetation or wind from bending the canes, breaking them, or tangling them. The plants (or bare-root suckers) are placed 40 cm apart in the row. Between two rows, the distance to maintain is 2 m. The cordon training system with alternate-year production involves separating the suckers for renewal from the fruiting canes. Part of the plantation is solely dedicated to production, while the other part is for renewal, reversing roles the following year. This way, production is ensured every year, even if only on half the field, but the management is much simpler. The traditional training of uniannual varieties involves having both renewal suckers and fruiting canes in the same row. This creates competition between renewal and production, causing significant issues with pruning. With the system of training with alternate-year production, vegetative growth improves, plant production per plant increases, and, most importantly, plantation management is simplified.
For biennial varieties, the cordon training system is also the most suitable. We’ll see what this entails for pruning operations.
Irrigation and fertilization
In raspberry cultivation, much attention must be paid to irrigation. Usually, irrigation interventions are limited, almost negligible, as raspberries grow in hilly and mountainous areas. Unfortunately, increasing drought, with long periods without rainfall, forces enthusiasts to equip themselves with a drip irrigation system. Therefore, immediate watering after planting the seedlings in spring, during the vegetative growth resumption, during flowering, and especially during fruit enlargement in mid-summer, is crucial. After harvesting, especially in autumn, irrigations should gradually decrease, favoring wood maturation and the development of the root system and new suckers. Fertilization is advisable at least once a year, applying organic matter at the base of the plants. Mature manure, worm humus (which you can purchase here), and home compost are recommended.
Pruning of uniannual raspberry varieties
Generally, pruning uniannual varieties of raspberry plants is relatively simple. It involves removing the canes that have produced in the year. In cordon training with alternate-year production, productive canes are removed in autumn when they are completely dry. The suckers grown for renewal need thinning, leaving 12-15 per linear meter. They are then topped at about 1.80 m in height. Therefore, the following year, there will again be a productive row (the topped suckers) and a renewal row (the fruiting canes removed, from which new suckers will grow). In traditional cordon training, however, this operation is carried out in the same row. In practice, simply eliminate the productive canes immediately after harvesting. The difficulty lies in the limited spaces and the competition created between the productive cane to be removed and the renewal sucker, which needs to be allowed to grow.
Pruning of biennial raspberry varieties
For biennial raspberry plants to obtain two harvests, pruning interventions are carried out differently. After the autumn harvest of the first year, the apical part of the productive canes is removed. This way, there will be a second production in the middle part of the same canes in the summer of the following year.
In organic agriculture and mountainous environments, excellent results have been recorded using the technique of permanent mulching. It’s advisable to combine inter-row mulching with natural mulching, placed at the base of the plant in spring, during the vegetative regrowth. Mulching allows for saving on irrigation interventions while keeping raspberry plants clean, as they suffer from the excessive presence of weeds at the base.
Raspberry Pests and Biological Defense
The raspberry plant may suffer attacks from some typical orchard pests. Among these, the most common are: aphids in spring, red spider mites in summer, bugs between late summer and autumn. For biological defense against these pests, we recommend reading the related in-depth articles.