Learn to grow geraniums from me (part 2)

Moisture. Geranium is not resistant to water and moisture, which requires good ventilation of the cultivation medium, otherwise the proportion of rhizome is easy to be maladjusted; too much water is easy to cause root rot (Pythiumrootrot) and gray mold (Botrytis) caused by fungi (Pythium); but the cultivation medium should not be too dry. Because this will cause salt accumulation around the root system and cause cauterization, when the medium is too dry, it often turns the lower leaves of the plant into reddish to yellow.

The stems and leaves of pelargonium are pilose. When fertilizing and watering, the leaves should be avoided from being contaminated with fertilizer, or wash the leaves with clean water and dry them after fertilization.

Fertilizer. ① can be re-fertilized 7 days after planting, and the fertilizer can be applied with 800x solution of chlorophyllin or 600x solution of 15-20-20 compound fertilizer, once every 7-10 days. Fertilizers containing potassium, calcium nitrate and phosphorus should be applied during the growth of ②. Geraniums are sensitive to chlorine groups and should not exceed 10ppm, but in warm areas, the light is strong and 20-10-20 compound fertilizer may be needed to make the leaves stretch and color well.

Pick the heart. At present, F1 series varieties, such as' Elite', 'Sleeping Cat' and 'Red205'', have strong branching, and can make the plant type plump and beautiful without coring during cultivation, but 'Xiayu' (Pelargonium pelargonium) is more used in hanging basket cultivation or ground planting, because it is a trailing variety, it should be appropriately coring to promote the growth of lateral branches, so that the flowering is more luxuriant and the plant type is more beautiful.

IV. Main diseases and insect pests and their control

Grey mold.

Main symptoms: mainly harmful leaves and flowers; leaf veins primary "V" shaped disease spot, on which there are nearly round to irregular water-stained yellow-brown to dark brown round spots. The disease spot sometimes produces a gray-white mildew layer. When it occurs on the petals, it is faded and irregular, there are sparse gray mold at the beginning, the gray mold shrinks when the weather is fine or dry, and grows again when wet, and the whole flower organ becomes dark red to dark brown.

Prevention and treatment: ① should pay attention to ventilation and light in the cultivation place, and the humidity should not be too high; ② adjusts the PH value of 6.2 to 6.5 to facilitate its normal absorption of nutrients and enhance disease resistance; at the initial stage of the onset of ③, 50% hydantoin 1000 times solution or 28% Botrytis cinerea 800 times solution 1000 times solution is sprayed throughout the plant.

Brown spot.

Main symptoms: more than leaves, for round, nearly round to irregular disease spot, light brown or grayish white to reddish brown, with dark brown edge. The leaf back disease spot is slightly convex, the outer edge of the spot yellow halo is obvious, the disease spot often fuses with each other into a larger withered spot, and finally gives birth to a gray-black mildew on both sides.

Prevention and control: ① control cultivation site ventilated; balanced fertilization; plant dormancy period should control fertilizer and water should not be excessive application; the initial stage of ② disease with 75% methyl topiramate 800 times or 50% carbendazim 800 times or 25% carbendazim 1000 times solution whole plant spray.

Bacterial leaf spot.

Main symptoms: primary waterlogged round to irregular sunken spots, dark brown to dark brown, disease spots less fused, late diseased leaves wilting and curling hanging on the stem. Sometimes the disease spot forms a large necrotic horn spot on the edge of the leaf. Black plaques were produced on the stem, and the vascular bundles and pith blackened, and the plant wilted and rotted.

Prevention and treatment: ① uses drip irrigation to water and fertilize, try to avoid spray irrigation, do not splash the cultivation medium on the stems and leaves, control the medium and air humidity is not too high; ② chemical control can kill 2000 dry suspension agent 1000 times solution or 72% agricultural streptomycin 2000 times solution spray the whole plant.