Bolivian begonia "Copacabana Yellow" F1

RECOMMENDATIONS FOR GROWING.
Growing Bolivian begonia is practically no different from growing tuberosa begonia (Begonia tuberhybrida).
But there are also additional recommendations:

Pre-sowing stage.
* High-quality sowing substrate (pH 5.5–5.8) with the addition of complex mineral fertilizer N:P:K (14-16-18) per m3.
* Begonia sprouts are very delicate and unstable to adverse factors, therefore, for prevention, we recommend using Trichoderma fungus and "Previcur" (propamocarb+fosetil).
* The presence of larvae of sciarids (Bradysia paupera, Bradysia aprica) in the substrate also sharply reduces the survival rate of sprouts. In such cases, we recommend the prophylactic use of the parasitic nematode Steinernema feltiae.

Stage 1.
High air humidity approaching 100% and temperature +21+23°C are the main preconditions for a good result. Do not fill up the granules!
Duration of the stage: 7-10 days before the appearance of the radicle (root of the sprout).
Observed signs: by the end of stage 1, the granule is destroyed, from which the radicle grows and roots begin to form.
Moisture of the substrate: the degree of moisture - 5 (saturated).
Humidity: 100%, even a short-term decrease in the relative humidity of the air can damage the germinating seeds, so it is advisable to cover the sowing containers with foil to maintain high air humidity.
Substrate EC: 0.5–0.75.
Germination requires good light with an intensity of 200-1000 lux.

Stage 2.
At this stage, it is important to provide optimal conditions for the growth of the root system (mainly high humidity).
Observable signs: by the end of stage 2, the seeds germinate completely (the root system is already developed, the hypocotyl is formed, the cotyledons are fully developed).
Substrate Moisture: The degree of moisture varies between 4 (wet) and 3 (wet). Excessive impregnation of the substrate with water at this stage already prevents the roots from germinating into the depth of the substrate, since there is already insufficient air there. The sprouts are still small, so watering should be very careful, because the primary roots that fix the plant in the substrate can be washed out, which can significantly distort the entire further vegetation of the plant...
Humidity: constant relative humidity of about 95%
Substrate temperature: +21+23 °C
Substrate EC: 0.5-1.0 (begonias are sensitive to high EC at this stage).
Light conditions: after the plants germinate, start supplementary lighting (the most inexpensive and effective way is LED systems).
Bolivian begonia is a long daylight plant. With a short light day, growth is delayed, and the plant forms underdeveloped mini-tubers, so the length of the day is increased to 14–16 hours due to artificial light. The high quality of bred seedlings at this stage is achieved at illumination of 4500–7000 lux.

Stage 3.
The correct mode of watering and fertilizing at this stage provides the power of the root system, which allows the aerial part of the plant to develop intensively (it is very desirable to use a root formation stimulator, such as Kornevin or Heteroauxin).
Observable signs: By the end of stage 3, roots should be growing through the substrate in the cell of the cassette, and the first true leaves should also have developed.
Substrate Moisture: The degree of moisture varies between 4 (wet) and 2 (moderately moist). The alternation of the indicated degrees of humidity provides an abundance of air throughout the entire volume of the substrate in the cell of the cassette and allows the roots to germinate to the very bottom.
Substrate temperature: +18+20 °C.
Top dressing with fertilizers: if necessary - 2 times a week with mineral fertilizer, 50 ppm N:P:K (19-6-20).
Substrate EC: 1.0–1.5.
Light conditions: same as for germination stage 2.

Stage 4.
At this stage, it is necessary to pay increased attention to the state of plant health and, if necessary, apply fungicides. Thickened plantings can be affected by gray rot under unfavorable growing conditions.
Observable signs: By the end of stage 4, the roots have completely grown through the substrate of the cassette cell. Shoots have 2-3 true leaves.
Substrate Moisture: The moisture content of the substrate ranges from 4 (wet) to 2 (moderately wet). Watering should be plentiful in order to moisten the entire volume of the cassette cell. Too frequent, but insufficient watering is not recommended.
Top dressing with fertilizers: as needed (approximately - twice   a week 100 ppm (19-6-20))
Substrate EC: 1.0–1.5
Light conditions: same as for germination stage 2 (when the light intensity approaches 25,000 lux, it is advisable to shade the plants).
Temperatures below +14 °C result in stunting of the plant and a delay in the formation of full-fledged tubers.
Growth regulators: Not required under normal circumstances. If necessary (overgrowing of seedlings), you can resort to spraying with drugs like "Athlete". The maximum number of sprays is two.

Further cultivation.
Temperature: after transplanting to a permanent place, it should be at least + 18 + 20 ° C at night (as the plant gets used to new conditions, the temperature can be + 16 + 18 ° C).
Moisture of the substrate: the degree of moisture varies between 4–2.
Humidity: 40-70%. The use of horizontal fans has a beneficial effect on plant health.
Fertilizing: as needed.
Changing the ratio of N:P:K in favor of K (potassium) has a positive effect on plant health and compactness. The use of fertilizers with a high nitrogen content can cause damage to the roots (especially at low temperatures).

Note regarding the moisture content of the substrate:
5 (saturated) - water in the substrate is visible visually
4 (wet) - the substrate is moist to the touch, but not saturated
3 (wet) - the substrate is dark, but does not shine.
2 (moderately moist) - the substrate changes color from black to medium brown or light gray.

* This cultivation description is only an indicative guide and may be adjusted by the grower on an individual basis.

Eng.: Bolivian Begonia.