Raspberry is a perennial shrubby deciduous flowering plant. As such, raspberries contain vegetative and fructifying organs. Vegetative organs serve to maintain the life of the individual and are differentiated into root, stem, leaf. Fructifying organs or reproductive organs enable the survival of the species. These include flowers, seeds and fruits.
The root is the basic vegetative organ of raspberries. It has radial symmetry, is perennial and well developed. The role of raspberry roots is multiple. It absorbs water and dissolved minerals from the soil, establishes the plant in the soil, serves as an organ for storing organic matter and for vegetative propagation - root cuttings of red raspberry.
The tree is the basic vegetative organ of the raspberry and has a radial structure. The leaves are spirally arranged on the raspberry tree and there are buds in the axils of the leaves. The tree together with the leaves builds a shoot, which consists of two parts. Above the ground in the air there is an aerophilic, photophilous shoot that lives for less than two years and an underground geophilic shoot that is perennial and rich in reserve nutrients. In the second half of the summer, a larger number of buds are formed on the underground shoots and on the young veins, from which new young shoots are formed. These shoots grow during the fall and winter until the soil freezes. The following spring, the shoots begin to emerge, depending on the growth achieved in the previous year. Adventitious roots develop on the underground part of the shoots. Shoots that do not emerge to the surface by the middle of the vegetation die.
Knowledge of the manner of formation and growth of raspberry shoots underground is of great importance for determining the appropriate system of soil maintenance in native orchards and orchards for seedling production.
The above-ground shoot lives less than two years, it reaches full height at the end of the first year. Young annual shoots bear large odd-feathered leaves with 3 or 5 leaves. In the axils of the leaves of annual shoots usually develop one or two and rarely three buds that are arranged one above the other serially. If there are two buds, the upper buds are better developed and from them the fruiting branches develop in the following years. The lower buds remain undeveloped and rosettes develop from them. In case of injury of the upper bud, late frost, then a native branch can develop from the lower bud. Annual shoots of raspberries reach a length of several tens of centimeters to over three meters. The length of the shoot depends on the variety, the physiological condition of the plant, soil fertility, meteorological conditions and care. The one-year-old shoot matures from the base to the top.
Two-year-old raspberry shoots do not form a cambial ring, do not thicken secondarily and do not form rings. During the second year, from the lateral buds of the aboveground shoot, fruiting twigs can develop, which bear flowers and fruits. The largest number and the largest fruits of raspberries are formed on the fruiting branches on the middle third of the shoot, and when on the fruiting branches of the lower part of the top third of the shoots. Therefore, the pruning of raspberries should be adjusted so as to preserve the largest number of fruiting branches.
The top buds on the one-year-old shoot of some raspberry cultivars develop into fruiting twigs and bear fruit at the end of the first vegetation period, September-October, including Lord George, large two-rowed, September. According to the purpose, there are two types of shoots for replacement and for propagation.
In addition to the roots and stems, the leaf is the basic vegetative organ of raspberries. In the raspberry leaf, the synthesis of organic matter is performed - photosynthesis, decomposition of organic matter - respiration and evaporation of water vapor, transpiration. The leaves are formed from leaf buds, which differentiate into leaf base, leaf stalk and leaves. The raspberry leaf is compound oddly feathered and consists of 3 or 5 ovate leaves. The leaves are spirally arranged on a raspberry tree. The oddly feathered structure of the leaves and their spiral arrangement allow the raspberries to make full use of the available amounts of light for the photosynthesis process.
The formation of flower buds of raspberries begins in September or October. First, the terminal flower is formed in the inflorescence, its development is the fastest. Other flowers are formed towards the base in the form of an irregular spiral, and their development is slower. The raspberry flower is bisexual hermaphroditic.
It consists of a cup, a crown, anthers and pistils. A cup of raspberry consists of five green cup leaves, the crown has five white or pink crown leaves. There are many anthers and they build a ring around the pistils. Raspberry flowers are gathered in inflorescences, flowering usually lasts 20-25 days.
The collective fruit of the raspberry consists of a large number of stone fruits collected around the dried flower bed. The raspberry fruit is made up of 20-160 individual stones. Each stone is formed from one fertile leaf - carpel. The fruit is usually red, yellow or black. Elongated or spherical in shape. If fertilization is weaker, some stones do not develop, so the fruit may be irregularly shaped. Varieties whose fruits are shed should not be grown. The weight of the fruit of the noble raspberry is 1.7-8.4 g, and sometimes up to 12 g.
By developing the seed germ of raspberry, seed is formed after fertilization. It contains the membrane, the seed and the germ. When raspberry seeds come to favorable conditions, they germinate.
Stages In The Raspberry Annual Cycle
There are two ages in the life of a raspberry:
the period of active life or vegetation the
period of winter rest
Vegetation lasts from the moment when the first raspberry buds develop, until the leaves fall off in autumn. The rest of the time is winter vacation. During the annual cycle, raspberries go through the following phenophases:
Beginning of Growth and Leafing
During April and the first half of May, new shoots begin to emerge on the surface of the earth. Their growth is most intense from mid-May to late June. Two-year-old raspberry shoots begin to leaf in early April, and the beginning and duration of leafing depends on the variety, temperature and other environmental factors. From the bud in the axil of the leaves of biennial shoots, fruiting twigs are formed.
In our raspberry areas, raspberries begin to bloom in the second decade of May, and flowering lasts 20-30 days, depending on the variety and meteorological conditions. The difference in flowering between early and late varieties is 6-10 days.
Pollination And Fertilization
Raspberry is an entomophilous plant, and the most important insect pollinator is the honey bee. Most raspberry varieties have a hermaphroditic flower, which consists of a cup, a crown, anthers and pistils. Successful pollination is a condition for fertilization. The fruit of the raspberry is a collective stone, built of 20-160 individual stones. In order for the collective fruit of raspberries to develop normally, it is necessary to pollinate in all or almost all pests.
Education And Fetal Development
From the fertilized egg cell-zygote, a germ-embryo is formed, and the wall of the ovary develops into the fetal membrane-pericarp. It is composed of three layers of outer-exocarp, middle-mesocarp and inner-endocarp. From a practical point of view, the highest yields and the best quality of raspberry fruit are achieved if the soil moisture is preserved by surface treatment or irrigation, or if there is abundant rainfall for twenty days after full flowering, or 12-14 days before harvest.
Flower Bud Education
Flower buds are formed in autumn in the year preceding flowering. In red raspberries, flower buds are gradually differentiated from the top of the shoot to the base, while this tendency is less pronounced in black and purple raspberries. Differentiation of buds begins in the first half of September and in black varieties during October.
Winter vacation in our conditions begins in November, when the leaves fall off. Winter vacation is very important for raspberries, without it it is impossible to form native branches on a two-year-old tree.
Taken from the Agronomy website, Predrag Nastić , B.Sc.
Text used: “Manual for raspberry production”