Ask the ISU Extension Garden Experts About Geraniums, Amaryllis and Plum Trees

Growing geraniums from seed

When should I sow geranium seeds indoors?
Geraniums are relatively easy to grow from seeds. However, geranium seedlings are slow growing. Geranium seeds should be sown in early to mid-February to produce flowering plants for spring. Flowering occurs approximately 13 to 15 weeks after sowing. Suggested seed-grown geraniums for Iowa include varieties in the Elite, Orbit, Maverick, and Multibloom Series. (A series is a group of closely related varieties with uniform characteristics, such as height, spread and flowering habit. Generally, the only characteristic that varies within a series is flower color.) 

Caring for amaryllis

What should I do with my amaryllis after it is done blooming?
Some individuals discard their amaryllis after it is done blooming. However, it’s possible to save the amaryllis and force it to flower again next year. 
Proper cultural practices must be followed to successfully grow and reflower amaryllis bulbs. After the flowers fade, cut off the flower stalk with a sharp knife. Make the cut one to two inches above the bulb. Don't damage the foliage. In order for the bulb to bloom again next season, the plant must replenish its depleted food reserves. The strap-like leaves manufacture food for the plant. Place the plant in a sunny window and water when the soil surface is nearly dry. Fertilize every two to four weeks with a dilute fertilizer solution. 
The amaryllis can be moved outdoors in late May. Harden or acclimate the plant to the outdoors by initially placing it in a shady, protected area. After two or three days, gradually expose the amaryllis to longer periods of direct sun. The amaryllis should be properly hardened in seven to 10 days. Once hardened, select a site in partial to full sun. Dig a hole and set the pot into the ground. Outdoors, continue to water the plant during dry weather. Also, continue to fertilize the amaryllis once or twice a month through July. Bring the plant indoors in mid-September. Plants left indoors should be kept in a sunny window. 
In order to bloom, amaryllis bulbs must be exposed to temperatures of 50 to 55 F for a minimum of eight to 10 weeks. This can be accomplished by inducing the plant to go dormant and then storing the dormant bulb at a temperature of 50 to 55 F. To induce dormancy, place the plant in cool, semi-dark location in late September and withhold water. Cut off the foliage when the leaves turn brown. Then place the dormant bulb in a 50 to 55 degree location for at least eight to 10 weeks. After the cool requirement has been met, start the growth cycle again by watering the bulb and placing it in a well-lighted, 70 to 75 F location. Keep the potting soil moist, but not wet, until growth appears. The other option is to place the plant in a well-lighted, 50 to 55 F location in fall. Maintain the amaryllis as a green plant from fall to early to mid-winter. After the cool requirement has been met, move the plant to a warmer (70 to 75 F) location. 
Additional information about foliage and flowering house plants and succulents is available in the ISU Extension publication Indoor Plants, PM 0713. This publication includes 180 color photos and 110 plant descriptions and can be ordered from the ISU Extension Online Store at

Selecting plum tree varieties

Which plum varieties can be successfully grown in northern Iowa? 
Several hybrid plum varieties developed at the University of Minnesota are reliably hardy in northern Iowa. These hybrid plums include ‘Alderman’ (burgundy red skin, yellow flesh), ‘Pipestone’ (red skin, golden yellow flesh), ‘Superior’ (red skin, yellow flesh) and ‘Underwood’ (dull red skin, yellow flesh). The aforementioned hybrid plums are self-unfruitful. (Self-unfruitful trees cannot produce fruit from their own pollen.) A pollinator, such as ‘Toka,’ needs to be planted to pollinate the hybrid plums. ‘Toka’ produces small red fruit with yellow flesh in addition to being an excellent pollinator. 
‘Mount Royal’ is a self-fruitful European plum variety that is hardy in northern Iowa.  ‘Mount Royal’ produces small fruit with bluish black skin and greenish yellow flesh. 
Why Fruit Trees Fail to Bear, PM 1083, an ISU Extension publication available for download from the Online Store, further explains the factors affecting a tree's ability to begin and continue to bear fruit.
To ask the ISU Extension garden experts questions, call the Hortline at 515- 294-3108, Monday-Friday from 10 a.m. to noon and 1 to 4:30 p.m., or e-mail