Characteristics of raspberries

Red raspberries are perennial shrubs that reach 2 to 3 meters and an approximately similar width. They have woody, rounded, erect, reddish stems and overhanging branches provided with thin and straight thorns, much less resistant than blackberries. Its leaves are pinnate and have 3 to 7 serrated leaflets, fluffy on the back. Flowers 1 cm in diameter, white and grouped in inflorescences up to 10 flowers each. The fruit is an aggregate of different berries (drupetum), called raspberry, of a non-bright red colour and soft texture, that matures in summer or autumn.

They are mainly cultivated for its fruits, berries, and also to form hedges and screens for gardens or patios.

Raspberries. Irrigation and humidity.

Raspberries need high humidity to be really productive. (Between 800 and 900 liters per year) Hence, during the summers and especially if summers are dry, they should be provided with adequate irrigation. This is necessary in summer because this is the time when new shoots or stems of these plants produce flowers and fruits. Raspberries need a minimum of 350 liters of rainfall during this season.

Although they need much water, they do not like flooding because it can cause rotting of the fruits and the occurrence of many diseases. We must provide them a good drainage. They need enough ventilation to avoid moisture accumulation on the leaves and fruits, which can easily cause mildew.

Raspberries. Temperature and exposure

Although they can stand some shade, raspberries prefer sunny exposures, protected from wind and frost. They need sheltered places but at the same time, well ventilated to avoid the appearance of numerous fungal diseases.

They do not like hot summers, because hot weather lowers the fruit quality. It prefers cool winters, not too cold, even though they are frost resistant, provided that freezing does not take place too late. Spring frosts under - 0.7 º C damage the fruits and flowers.

The raspberries. Types and crops.

- According to the time of planting:

- Summer raspberries: They are those that bear the fruits during summer. Although the fruiting season is shorter, they are more productive. Among the main varieties we have, for example:

- "Latham" raspberry

- "Glen Moy" raspberry: It is one of the species that produce fruit earlier. It does not have stings and its flavor is weak.

- "Malling Orion" raspberry: It is a species that produces much fruit in midsummer.

- "Malling joy" raspberry: Very late variety. It produces raspberries with plenty of juice and flavor.

- Summer and Autumn raspberries: They are those that bear fruits since the end of the summer until it begins to freeze. Among these are:

- Raspberry "Amity": it is very consistent and its fruits are bright red.

- Raspberry "Autumn Bliss": Characterized by producing very large and very tasty raspberries.

- According to the color:

There are red varieties and varieties with yellow/golden, purples or black tones. Among the main red varieties they are: Amity, Durham, Hilton, Latham, Nova or Taylor. Yellow varieties are the Goldie or Kiwi Gold. Among the black varieties we can mention Bristol, Allen or Jewel.

- According to the characteristics:

- According to characteristics:

- Pure Varieties: Those that have not been subjected to hybridization processes , so that they retain the properties of wild plants (mainly deciduous branches and presence of thorns)

- Hybrid Varieties: These are obtained by crossing inbred varieties. With these species, we have been able to improve productivity and modify the structure of plants to make them easier to grow and collect. Among the most significant changes it is worth pointing out the disappearance or reduction of thorns and the production of more upright branches.

Many modern varieties have been obtained by hybridization between the European red raspberry (Rubus idaeus) with the American black raspberry (Rubus occidentalis) or the American red raspberry (Rubus strigosus) American species are characterized by reddish stems and for having tougher and more aromatic fruits than the European species. The latter have whiter stems and generally larger fruits. Loganberry (Rubus loganobaccus) is the result of crossing the red raspberry (Rubus idaeus) with the blackberry (Rubus fruticosus). Among the main hybrid cultivars we have:

- Loganberry (Rubus loganobaccus). Species produced in the late nineteenth century by the horticulturist James Harvey Logan. It is a tough variety that produces many fruits , but little appreciated by European consumers. It is grown mainly in the Pacific coast of the United States, where it has achieved a big market. Currently used as an intermediate to produce other hybrids.

- Blackberries: They are much more productive varieties resulting from crosses between American and other bramble varieties such as the European dewberry (Rubus caesius) . Also known by the general name of blackberries, which can sometimes lead to confusion with the real blackberry. These are classified as erect and prostrate. The first produce straight stems, without thorns; the latter are crawling and have strong thorns, shaped as hooks.

Belonging to the group called "Erect Blackberries" we have the Boysenberry, with dark and big fruit, strong and persistent flavor even after freezing or cooking; the Loganberryis another variety within the same group with the longest fruits . The Tayberry can be considered the latest variety, it has a conical shape, a considerable length and purple colour.

- Golden Raspberry: This group includes a number of hybrid varieties that deliver a superior sweetness and softer texture. This variety is grown especially in private gardens. Within this group is worth mentioning some varieties as Autumn Gold, which produces fruit from spring to autumn with a golden color and extreme sweetness.

How to plant raspberries?

There are different techniques to plant raspberries. Among them we will mention:

- By stratified seeds: The stratification consists on keeping the seeds at a temperature between 3 and 6 º C since they are collected in autumn until they are planted in spring . To do this, we will place the seeds within a seedbed with peat and we leave them outdoors when the outdoor temperature does not exceed 6 º C. With higher temperatures, they will be put into a plastic bag in the freezer.

When spring comes , they will be planted in a well protected seedbed in a mixture of peat and garden soil. Allow them to grow for winter and plant them the following winter in its final place. This planting method is very laborious and may not provide adequate production by failing to ensure the genetic wealth of the parents.

- By layering: In this case, from mid to late summer, we will take a tender branch and bury the tip of it about 6 cm into the soil. The new branch will produce roots and a new plant will grow. This can be separated after a year in spring to plant it in its proper place. This method ensures the genetic wealth of the parents.

- By shoots: It is the most common method . In this case, raspberries are planted in early winter. We plant new shoots. (Raspberry shoots are tender stems that are born during the first year ). Although the shoots of these plants can get established, we should better buy them in specialized places to ensure that they are completely healthy.

The shoots are planted directly in the ground, taking into account that the roots must be placed in the ground about 5 cm deep at a distance of about 60 cm in the same row. We will leave between 160 and 300 cm from a row and another. Subsequently, we will prune them about 60 cm above the ground or we will lower them until 6 to 10 cm from the roots. In the first case, the plants can produce fruits the first year, but his subsequent productions will be lower, so it is more convenient to cut the shoots shorter even though they do not to produce during the first year.

It is advisable to water them well throughout the summer.

Raspberries. Maintenance and harvesting

Raspberries need support so as not to bend and so they can grow well and resist the force of the winds. At the same time , these allow us to distribute the plants so that harvest can be performed more easily. The method used is that of the fence with stakes. To do this, first, we will plant stakes about 2 meters high on the ground and separated about 3 meters each other. Then. we will place at different heights parallel wires that connect the stakes. The first of these could be placed about 80 cm from the ground level, the second about 120 cm and the third at about 160 cm. Later we will tie the shoots to the wires.

Once planted, and as they get older, we need to perform some maintenance. Firstly, it is important to perform a routine cleaning of the soil, so that the field can be weed free. Plowing must be superficial and not more than a foot deep to avoid damaging the roots.

We will keep the soil always moist but not waterlogged and we will prevent birds to eat the fruits, which usually occurs in summer . To avoid this problem, it is important to place a mesh over the plants, something which is usually not necessary with the summer-autumn raspberries.

The padding or mulching is a technique well suited to conserve soil moisture. This is done by adding straw, wood chips or sawdust on the floor, covering it with a layer about 15 cm in order to diminish water evaporation. This should be done every year to achieve a higher production and a better fruit quality .

Winter pruning is carried out after danger of frost, during the month of February or March. It is important to make a pruning to clean every plant, so as to remove any material that may be in poor condition. The stems should be cut or dug up for planting elsewhere.

We will remove branches that have already yielded some fruit and the stems that are designed for production (between 6 and 12). This has to be done at different heights to produce fruit at different levels, although the minimum height should not be less than 90 or 100 cm to avoid the fruits to be to close to the ground which could them to be spoiled by excessive moisture. Buds should also be pruned if we want the plant to produce less but bigger fruits.

After fruits harvesting, it is important to prune the plants. With varieties of summer this will take place at ground level, while varieties of summer - autumn require less drastic pruning. In this case, we will leave about 20 cm from the ground.

Fruit harvesting is done when the fruits have reached their proper degree of sweetness. They must have a bright color and proper ripening. They can not be too soft.

We will know they are ready, if they do not sink easily when pressing a little on them with the thumb and index finger. At the same time, they should be separated easily from the plant with a little tug. Their consistency will allow them to be transported and sold in appropriate conditions. The fruits which are too soft are not suitable for the market and may only be used for private use, especially for jams. Given that all the fruit ripening does not occur uniformly, harvesting should be done at different days.

Raspberries. Types of soil and fertilizer.

Raspberries like a dense soil, rich in organic matter, with the capacity to retain moisture but at the same time, it must not become stagnant. Raspberries prefer soils with a pH between 5 and 6.7. They do not stand very limestone soils although they can live on sandy, granite or slaty ones . The best soil is the sandy loamy one or deep sandy, located on a hillside or slope to achieve the best drainage possible. Clayey soils found in depressions subject to periodic flooding are not suitable.

Raspberries need to have adequate levels of nitrogen, phosphorus and potassium to grow properly and produce abundant fruit. Fertilizing the soil before planting and adding fertilizer in alternate years is a necessary measure to keep the crop in good condition.

Before planting, it is convenient to prepare the soil to a depth of 50 cm. We will add a good amount of manure or compost at a rate of about 20 t / ha which will be mixed with the natural soil . Among the fertilizers that may be suitable, we will include:

- Calcium superphosphate (250-500 kg / ha)

- Potassium sulphate

- Magnesium

- Ammonium sulphate ( 325 kg / ha in areas with rainfall exceeding 325 mm / year or 650 kg / ha with lower rainfall)

Raspberries. Pests and diseases.

The main diseases that affect them are fungal diseases. These are the most common and the ones we should specially take care of . In general, a good prevention is better than the use of plant protection products. When conditions of infection are very high, we do not justify their use. Among the main general patterns of prevention, we could mention the following:

- Do not plant this crop until 3 years after planting other raspberries or blackberries; other vegetables which tend to transmit the disease (tomatoes, peppers, potatoes) or fruit trees (apricot trees or cherry trees). Likewise, avoid planting them next to wild raspberries, because these could infect and transmit some diseases. We will seek to leave a safe distance of about 200 or 300 meters.

- Use certified seed, not contaminated or clean shoots .

- Encourage the aeration of the fields to prevent mildew, proper pruning and plant copies more distantly . Avoid areas subject to waterlogging or clay soils that retain too much water.

- Remove the infected material, both on plants and on the ground.

The main diseases caused by fungi are:

 

- Gray mold is caused by a fungus (Botrytis cinerea), which takes place mainly in wet conditions. It attacks many berries, including strawberries, raspberries or bilberries, vegetables, as tomatoes or onions, and many garden plants. It is characterized by the appearance of a gray layer or web on the affected part. It is a plague that spreads quickly when conditions are favorable. ( moisture and cool weather) In the case of raspberries, gray mold attacks rotting fruit. The persistence of mycelium in the form of a compact layer on the fruits and trunks allows the fungus to withstand adverse environmental conditions.

The main treatment is the removal of infected material in order to hinder its expansion and the improvement of ventilation to remove the accumulated moisture on plants which facilitates the transmission and spread of this disease.

Plants should be planted farther apart and a proper pruning should be made to remove excess material and to allow air circulation between plants. This is particularly important when planted in greenhouses where air circulation is generally lower and humidity higher.

Appropriate fungicide application according to the conditions of the prospectus will protect healthy plants from infection.

- Stem blight is caused by another fungus (Didymella applanata) that attacks the red and purple raspberries causing leaf drop and the death of the buds. The fruits produced by infected plants are smaller and dry, with the presence of too many seeds. It can be observed that the disease has attacked plants by the presence of purple or brown spots that attack the stems born the same year during summer. As the disease progresses, the fungi spread to the leaves, causing the death of limbo, so that only the petiole stays attached to the branches. The most affected branches can be dried.

The solution, as in the previous case, involves improving ventilation, reducing moisture, burning infected material and applying the appropriate fungicide.

 

- Anthracnose (Elsinoe veneta) is another fungal disease that develops in periods of high humidity and when the plants are too close together. This fungus attacks the lower part of stems producing sunken circular spots about 3 mm thick. At first, these are dark red and then become gray with the presence of purple fringing. Especially, when it rains a lot in late spring or early summer, injuries can embrace all the stem making it hard for the sap to flow or producing an irregular ripening in fruits. The leaves are also attacked and have holes as if they had been hit by a small projectile.

If the infection is not serious is not worth applying treatments. Otherwise, we use the appropriate fungicide. Prevention goes through the use of resistant varieties, crop aeration and removal of infected material.

- Verticillium wilt: This disease, caused by the fungus Verticillium albo-atrum, attack plants from the ground. It introduces into the plant vessels thorough the inferior stems what determines the stems to turn blue and then attacks the leaves, drying them.

As there is no treatment for this disease, it is best to perform preventive actions.

In case of areas usually affected by this fungus, it will be necessary to apply a fungicide to the soil in summer or autumn. Planting must not take place until the following spring.

- Mosaic Virus: A disease transmitted by an aphid (Amphorophora ruby) and caused by many viruses. Other times it is transmitted through infected seed or by the action of some worms that come from other contaminated plants.

Sometimes there are no symptoms or they may disappear when the temperature increases, although it must be borne in mind that the virus remains latent. Sometimes it manifests as yellowish green specks on the leaves and browning at their tips. In other cases, large blisters appear on the leaves surrounded by a yellow halo. It causes the atrophy of the plant in general, the distortion of leaves, the yellowing of the veins. It also affects the fruits, diminishing its quality or aspect. It can also produce a total absence of fruits in some branches and a lower resistance to cold.

Prevention is the best method to avoid this infection. We must use healthy certified seeds and plant our crops in a ventilated and well drained place . The infected material must be removed and a suitable fungicide should be used.

Do not plant black or purple raspberries near red as the latter can carry this disease without showing symptoms. Do not plant near infected plants and control aphids or nematodes to avoid transmitting it.

 

- True Mildew is a disease caused by the fungus Sphaerotheca humuli that affects all types of raspberries. A kind of white mold can be placed on the fruits, leaves and young stems absorbing the juices from them. It produces distortion and stunting of stems, fruit rot and a yellowing or leaf drop.

Again, good ventilation and proper spacing of plants is necessary to prevent the fungus from developing. You can apply a suitable fungicide.

The main plagues that affect raspberries are:

- Crown gall disease: They are rounded formations are displayed on the branches. They are produced by the larva of an insect called Lasioptera rubi, which forms the gall to lock itself inside and resist the cold of winter.

The galls are harmful to the raspberry because they prevent the passage of the sap which lowers their production and disables the normal growth of the stems.

The treatment consists on cutting and burning the branches affected by this disease in winter.

- Bark splitting: Produced by Thomasiniana Theobaldi in the young stems. The wounds are the gateway for many diseases. The solution is to fumigate the soil in spring to kill the larvae of these insects.

Other very common pests are:

- Erinosis (Eriophyes gracilis)

- Sesia

- Brown Caterpillar

- Nematodes

More information on raspberries in the listing above.