How to plant geraniums? Learn to grow them with me (Part 2)

Water. Geraniums are not tolerant of waterlogged conditions and require a growing medium with good aeration, otherwise the root-to-shoot ratio easily becomes imbalanced; too much water makes them prone to root rot caused by the fungus (Pythium) and gray mold (Botrytis); but the growing medium should not be too dry either. Because this causes salts to accumulate around the root zone and leads to burning, and when the medium is too dry, the lower leaves of the plant often turn reddish to yellow.

Geranium stems and leaves are covered with fine hairs, so when fertilizing and watering, avoid getting fertilizer solution on the leaves, or after fertilizing, rinse the leaf surface with clean water and let it dry.

Fertilizer. (1) Fertilize again 7 days after planting out; you can apply a 800x dilution of "Yelüjing" solution or a 600x dilution of a 15-20-20 compound fertilizer, once every 7 to 10 days. (2) During growth, fertilizers containing mainly potassium, calcium nitrate and phosphorus should be applied. Geraniums are very sensitive to chloride, so the application of such fertilizers should not exceed 10 ppm, but in warm regions with stronger light, a 20-10-20 compound fertilizer may be needed to make the leaves spread out and color well.

Pinching. The current F1 series varieties, such as 'Elite', 'Womao', 'Red205' and others, have quite strong branching, so even without pinching during cultivation the plant shape can be full and beautiful, but 'Xiayu' (ivy geranium) is more often used in hanging basket cultivation or field planting, and since it is a trailing variety, it should be pinched moderately to promote side branch growth, making the flowering more abundant and the plant shape more beautiful.

4. Main pests and diseases and their control

Gray mold.

Main symptoms: It mainly damages leaves and flowers; on the veins, "V"-shaped lesions first appear, on which nearly round to irregular water-soaked yellowish-brown to dark brown concentric-ringed spots then appear. The lesions sometimes produce a grayish-white mold layer. When they occur on the petals, they appear as faded spots, irregular, initially with sparse gray mold; in sunny or dry weather the gray mold shrinks, and when humid it grows again, and the entire flower becomes dark red to blackish brown.

Control: (1) Pay attention to ventilation and light transmission at the cultivation site, and control humidity so it is not too high; (2) Adjust the pH to 6.2-6.5 to facilitate normal nutrient uptake and enhance disease resistance; (3) In the early stage of disease, spray the whole plant with a 1000x dilution of 50% iprodione solution or a 800-1000x dilution of 28% Huimeike solution.

Brown spot disease.

Main symptoms: It mostly occurs on leaves, as round, nearly round to irregular lesions, light brown or grayish-white to reddish-brown, with dark brown edges. The lesions on the underside of the leaf are slightly raised, and the yellow halo at the outer edge of the spots is obvious; the lesions often merge with each other into larger dead spots, and finally grayish-black mold-like growth appears on both sides.

Control: (1) Control ventilation and light transmission at the cultivation site; balance fertilization; during the plant's dormant period, control fertilizer and water and do not apply excessive amounts; (2) In the early stage of disease, spray the whole plant with a 800-1000x dilution of 75% thiophanate-methyl or a 800x dilution of 50% carbendazim or a 1000x dilution of 25% benomyl solution.

Bacterial leaf spot.

Main symptoms: Leaves first develop water-soaked round to irregular sunken spots, dark brown to blackish brown; the lesions rarely merge, and in the later stage the diseased leaves wilt, curl and hang down on the stem. Sometimes the lesions form large necrotic angular spots at the leaf margin. Black patches appear on the stem, and at the same time the vascular bundles and pith turn black, and the plant wilts and rots.

Control: (1) Use drip irrigation to water and fertilize, try to avoid sprinkler irrigation, do not let the growing medium splash onto the stems and leaves, and control the medium and air humidity so they are not too high; (2) For chemical control, spray the whole plant with a 1000x dilution of 53.8% Keshade 2000 dry suspension or a 2000x dilution of 72% agricultural streptomycin solution.