Citrus

This section describes the citrus growth cycle and its stages through a practical and dynamic approach. In addition, you will also find a guide detailing the main nutrient deficiencies that can affect your crop and how to identify each of them.

What happens at each stage of citrus development?

  • REPRODUCTIVE (R1): Sprouting just starting, with scarcely visible V2 floral buds, generally partially covered by the leaves of this sprouting.
  • FLOWERING (R2): Floral buds easily visible, still completely covered by the sepals (green leaf-like structures).
  • FLOWERING (R3): Elongation of petals; the sepals reach half the corolla (white buds).
  • FLOWERING (R4): Corolla still with the calyx forming just the bottom bit of the floral bud.
  • FLOWERING (R5): Corolla at its maximum size. Buds will imminently open.
  • FLOWERING (R6): The marked occurrence at this stage is anthesis, when the buds gradually open into flowers, until practically 100% of the buds are open (full flowering). The final phase of this stage corresponds to the beginning of noticeable fallen and/or dry petals.
  • FLOWERING (R7): Final phase of flowering, when about two thirds of the petals have already fallen and/or dried and the ovary under development and growth transfers from anthesis to the beginning of fruiting. This is, therefore, a stage in which the transition between flowering and fruiting becomes more evident.
  • FLOWERING (F1): Fruit growth has started. All petals have fallen and/or dried and the young fruits are 3 to 5 mm in diameter.
  • FRUIT GROWTH (F2): Fruit still in initial development phase with, diameters measuring between 5 to 10 mm. At this stage physiological fruit drop is at its maximum.
  • FRUIT GROWTH (F3): Fruit at one quarter (1/4) of its full size: 15 to 20 mm in diameter. Physiological dropping of the fruit in its final stage. At the beginning of this stage (fruit at approximately 15 mm in diameter) the increase in fruit size predominantly occurs by cell multiplication in the white tissue (mesocarp) of the fruit.
  • FRUIT GROWTH (F4): Fruit at half (1/2) its final size: 30 to 40 mm in diameter. Soon after phase F3, increase in fruit size is predominantly by cellular expansion, where the loculi and juice vesicles are growing, compressing and stretching the peel.
  • FRUIT GROWTH (F5): Fruit at three quarters (3/4) of it’s final size: 50 to 60 mm in diameter.
  • FRUIT GROWTH (F6): Fruit at final size, almost entirely defined, with a reduced rate of growth: 65 to 80 mm in diameter. In this phase, the fruit peel is light green with some yellowish tones, starting the phase of maturation (colour break).
  • FRUIT GROWTH (F7): Fruit at the intermediary maturation phase, with green-yellowish peel.
  • FRUIT GROWTH (F8): End of maturation, when the fruit has all its peel yellowish orange colour and internal characteristics which are adequate for consumption.

 

Nutrient Deficiency

MICRONUTRIENTS

  • Zinc: New leaves are small, in the shape of a spear and may have intervein chlororis, as well as short internodes. Reduced blooming occurs and small fruits yield little juice.
  • Boron: New leaves are small and malformed with undulations at the petioles and outward projecting veins. Reduced sized fruits are deformed and have a thick and irregular peel. Seeds are small, dark and malformed.
  • Manganese: New leaves of normal size bearing intervein chlorosis, but more pale and less affected than by the lack of zinc. Small fruits and reduced production.
  • Iron: New leaves bear the typical chlorosis of thin reticula (folds of the membrane). The veins remain green, but with interveinal  chlorosis.
  • Copper: Large new leaves on stems growing excessively as if there were an excess of N. In some varieties death of new stems may occur.
  • Molybdenum: Old leaves bear yellowish spots; flowers and small fruits fall off.

MACRONUTRIENTS

  • Nitrogen: Old leaves bearing a homogeneous yellowing occur. Vegetation is poor with small leaves and small fruits have a thin peel.
  • Potassium: Symptoms of potassium deficiency are more visible on the fruits which are smaller and have a smooth and thin peel. Leaves and fruit may fall off prematurely.
  • Calcium: Young leaves show a yellowing from the borders to the centre, as well as the death of new stems. Poor shoot and petiole development occurs as a result of low resistance to drought causing leaf, ower, and fruit drop.
  • Phosphorus: Old leaves have a copper tint; leaves and flower buds fall off. The peel of the fruits have a rough, thick and spongy feel and fruits have a hollow centre.
  • Magnesium: Old leaves may bear a yellowing from the tip to the leafstalk in the form of an inverted “V”.
  • Sulfur: New small leaves have a homogeneous yellowing.