Key Production and Cultivation Techniques for Geraniums

1. Timing Schedule

For the zonal geranium series, if grown under suitable conditions in northern regions, the time from potting up rooted cuttings to flowering is:

Pot diameter (cm) Weeks

　　107―8

　　139―10

　　1511

　　1714

Under warm southern conditions, the growing period can be shortened by 1-2 weeks.

Climbing series: if growing rooted cuttings, pinch 2-3 weeks after potting up:

Pot diameter (cm) Weeks

　　1011―12

　　1313―14

　　1515

　　1718

Under warm southern conditions, the time can be shortened by 1-2 weeks.

2. Production for 4 Weeks After Potting Up

(1) After arrival: Open the packaging and plant immediately. If potting up cannot be done promptly, place the rooted cuttings on the bench. If the rooted cuttings are not in packaging, water them and provide appropriate shade if necessary.

(2) Growing medium: Choose the best mixed medium: 55-70% high-quality coarse peat, 20-25% perlite. Heavy clay soils require the addition of 5-10% vermiculite and 5-10% soil to increase cation exchange.

(3) pH value: Climbing series: 5.2-5.7; zonal geranium series: 5.7-5.9.

(4) Fertilization: Perform a complete soil test every two weeks after planting. The initial soil analysis report should be: 150 ppm nitrogen, 200 ppm phosphorus, 200 ppm potassium, 100 ppm calcium, 50 ppm magnesium, 30 ppm sulfur, 1.0 ppm iron, 0.7 ppm manganese, 0.3 ppm zinc, 0.15 ppm copper, 0.3 ppm boron, 0.05 ppm molybdenum. After planting, apply a formula fertilizer containing 200 ppm N with irrigation water (combined with 3/4 oz SubdueMaxx/100 gal). The first watering should not be too wet, so that the roots have enough oxygen to root quickly. After 5-10 days, 300 ppm N can be used. During the first two weeks, geraniums should be grown in a relatively dry medium. Temperature: Regardless of light conditions, the optimal temperature for the first four weeks is 21-22°C (depending on pot size). Daytime 21°C, nighttime 17-18°C will cause leggy growth, few branches, and affect root development.

(5) Light: For the first two weeks after planting, the optimal light level is 27-32 klux, then increase to 37-48 klux.

(6) CO2: 1500 ppm during the first four weeks can promote growth.

(7) Pythium: Use 3/4 oz SubdueMaxx once every 3-4 weeks. The frequency of use depends on the amount of watering and leaching. Pay attention to this disease at planting time.

(8) Growth regulators: To obtain a well-branched plant shape, growth regulators must be used to control growth. Use 750 ppm CCC. For vigorous growth, use 750 ppm B-9 or, if necessary, a 750 ppm mixture.

3. Flowering Production

(1) Greenhouse climate management: Generally speaking, even under low light, the temperature should not be lowered, because this will lead to delayed growth, affect root development, and increase the chance of root and leaf diseases, as these diseases are mainly caused by high humidity.

Temperature: The optimal day/night temperature is 21-22°C (depending on pot size). An average temperature of 20°C is better for slower-growing crops. The greater the day-night temperature difference, the longer the internodes and petioles, the larger the leaves, and the fewer the branches. Within a certain range, high daytime temperatures and low nighttime temperatures can save heating costs, but will reduce flower quality. Negative DIF can be applied when the plant is mature, and can be maintained for 3-7 weeks depending on pot size. The duration of negative DIF application depends on growth and elongation rates.

Light: Optimal light for the zonal geranium series is 37-54 (maximum) klux; for the climbing series, 32-43 (maximum) klux. For climbing series hanging on benches, especially in the second stage of growth, they are often placed in a stronger light, hotter, and more humid environment for better growth. For the IVIES series, if rooted cuttings are pinched 2-3 weeks after planting, the growing period is usually 4 weeks longer than the zonal geranium series.

Humidity: To control gray mold (Botrytis), it is very important to maintain low humidity through sufficient air movement. When heating, ventilation and high nighttime temperatures can effectively reduce gray mold infection and ensure the production of high-quality geraniums. The optimal humidity should be below 75%.

(2) pH value and fertilization: pH value should be continuously tested and corrected. The climbing series is 5.2-5.7, and the zonal geranium series is 5.7-5.9. Perform a medium test every two weeks. Adjust the EC value once a week, and measure the medium EC value once every two weeks. From 4 weeks after planting to the end, the EC value should be: 250 ppm nitrogen, 30 ppm phosphorus, 350 ppm potassium, 150 ppm calcium, 70 ppm magnesium, 50 ppm sulfur, 2 ppm iron, 1 ppm manganese, 0.4 ppm zinc, 0.2 ppm copper, 0.4 ppm boron, 0.06 ppm molybdenum. Leach with water before transport, and if possible drench with SubdueMaxx to reduce root diseases and prevent drying out during transport. To prevent salt accumulation, each fertilization should have 15-20% leachate. Different fertilizers have different effects on soil pH and plant vigor. For example, 15-15-15 and 20-10-20 can be used for rapid growth and lowering pH, 15-10-30 for slow growth and slightly lowering pH, and 15-5-15 containing Ca and Mg for raising pH. Based on soil analysis, micronutrients Mg and Ca should be applied once every four waterings. Fertilization schedule: At the beginning, for rapid rooting, geraniums should be grown in a relatively dry medium. Then move to a moist medium (not too wet). Generally speaking, watering should be done when the pot weight drops to half of the saturated water weight, to ensure proper plant development. By growing plants in a dry medium, growth can be reduced, branching and flowering potential can be decreased to maintain a compact plant shape. The fertilization schedule should be adjusted according to light, temperature, humidity, and different developmental stages.

(3) Disbudding and shaping: To achieve the best branching and complete growth, disbudding is very important until 3-4 weeks before transport (depending on temperature and light). If flower buds are few, simply pinch them off; if they are larger, remove them from the base of the peduncle. The disbudding time for plants should be determined according to the variety's @#@136@#@ time, and should be completed 4 weeks before transport. This will ensure plant vigor and 50% of flowers open at the time of sale. Another major advantage is that it ensures the plant has many large flower buds that can develop into flower clusters. At 5 weeks before flowering, for larger potted flowers (6.5 inches or larger), pinch off 1 to 2 dominant shoots (those that are not ideally controlled). This is particularly useful for varieties with uneven growth. Removing old leaves and overly dense leaves from the center of the plant allows light to penetrate and increases internal stem development, reduces the occurrence of gray mold, and makes the plant fuller at the time of sale.

(4) Spacing: During growth, pot spacing should be adjusted according to plant size, so that leaves do not overlap each other.

(5) Pests: Control before flowering, mainly controlling thrips, aphids, and red spider mites.

(6) Diseases: Mainly control bacterial wilt, Pythium, gray mold, and geranium rust.