6 Commercial Groups Pelargonium 1) P. X hortorum - zonal or common 2) P. X hortorum – seed 3) P. peltatum – ivy or hanging basket Dr. Terri W. Starman 4) P. X domesticum – Martha Washington HORT 429 5) Pelargonium – scented, 48 kinds Greenhouse Crop Production 6) P. floribunda – cascade

In addition to the Pelargoniumthe Geranium genus contains many ornamentals used in gardens

Cultivars Family and Origin

• Shades of red, pink, salmon or white • Geraniaceae • Flowers can be single or double • Pelargonium genus has 250 species • Petals can be round to serrate and wide to • South Africa narrow • Mediterranean climate of Cape Province • Foliage can be variegated • Dry, hot habitats, rocky, sandy • 15-20% wholesale value of bedding plants • Cuttings vs. hybrid seed

Uses Propagation

• Porch boxes • Asexually until 1960s • Ground beds • Hybrid Seed • Large pots • ‘Nittany Lion’ from Penn State was the first • Hanging baskets seed propagated cultivar • Potted plants • Tissue culture • Standards • Today, growers purchase rooted or unrooted cuttings

1 Asexual Propagation Sexual Propagation

• Root in oasis strips, rock wool, peat -pellets • 6000 seeds/oz. or final pots • Plug trays are automatically sown • Rooting hormone – dust don’t dip • Mist “as needed” • Bottom heat at 70-750F • Seeds are lightly covered with vermiculite • Mist – keep to a minimum • Light enhances germination • Full light • Transplant 31 to 50 days after sowing or • 12 to 21 days 23 to 37 days after removal from the germination room

Flowering Control and Dormancy Temperature

• Day neutral • Optimum for zonal is 68 / 630F day / night • FI and FD rate dependent on total light • Leaf unfolding rate peaks at 760F energy (intensity X duration) at appropriate temperatures • Temperature drives flower development i.e. from visible bud to opening of first • Juvenility may exist with some cultivars of seed geraniums, minimum of 15 nodes to floret flower • Optimum for ivy is 680F day and night for • Leaf area determines rate of FI in seed compact growth or 75 / 610F day / night for geraniums stem elongation

Light and Water Nutrition Varies with Development Stage

• Light drives flower initiation Seedling Well-rooted Flower in Final • Zonals like 3500–5000 fc (700–1000 color weeks µmol?s-1m-2) • Ivies like 2500–3000 fc (500–600 µmol?s- 1m-2) • Adapted to dry conditions and well-drained 100-150 250 ppm 150 ppm 50 ppm soils ppm • Water stress is sometimes used to control growth and hold plants back

2 Nutrition Cycocel

• High requirement for Ca and Mg • Hastens flowering • Low EC • Increases branching • Decreases stem • pH 5.6 – 6.0 for zonals elongation • pH 5.3 for ivies • 1500 ppm • Too low pH causes Fe and Mn toxicity • Causes marginal leaf chlorosis i.e. yellowing • Symptoms are stunting, necrotic spots and • Apply lower concentration leaf edges, chlorosis of lower leaves more frequently to reduce • To prevent raise media pH above 6.0 problem

Insects, Diseases and Spacing Physiological Disorders • Pot to pot until leaves overlap • Relatively insect free • 4-inch pots on 6 to 7-inch centers • Susceptible to numerous diseases • 6-inch pots on 8 to 9-inch centers • Bacterial leaf spots and blights • Disbud to encourage vegetative growth • Xanthomonas compestris is very serious (not in book but it works on cutting and other wilt diseases geraniums) • Culture indexed plants are used to provide • Ivies need 4 to 5 cuttings/10-inch basket cuttings • Ivy geraniums get edema

Ralstonia solanacearum Race 3 Postharvest Biovar 2 • Usually sold with at least one flower • Southern Bacterial Wilt (SBW) • Cuttings and potted plants susceptible to • Confirmed by USDA -APHIS ethylene in shipping • Spread in water • Seed geranium flowers shatter during shipping • Pathogen of potatoes • STS applied 14-21 days prior to shipping • Regulated by federal quarantine reduces shatter but predisposes plant to • Inspection, quarantine, disposal, clean-up Pythium • Traced to stock in Kenya • Unpack ASAP and maintain adequate water and • Symptoms are leaf yellowing and wilting from light in retail the bottom of the plant up then total collapse

3 Ralstonia solanacearum Xanthomonas compestris

Symptoms start at the Symptoms are bottom of the plant and more random work their way up throughout the plant

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