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Growing Geraniums from Seed
by Don Janssen, UNL Extension Educator
Geraniums have been a popular bedding plant for many years. Plants have traditionally been grown from cuttings, however, seed-grown hybrid geraniums are very popular.
The popularity of seed-grown geraniums increased because they often outperform the older geranium varieties propagated from cuttings. The new seed-grown hybrid geraniums possess excellent vigor, heat tolerance, disease resistance, and are free-blooming.
Geraniums are easy to grow from seed. However, they are rather slow growing. Sow seed in mid- to late January to produce flowering plants for spring. Flowering occurs approximately 12 to 16 weeks after sowing.
A commercially prepared growing medium is a good germination medium. Gardeners can prepare their own medium by mixing equal parts sphagnum peat and vermiculite. During germination, damping-off of geranium seedlings can be a serious problem and is caused by various types of fungi that attack the seedlings and destroy them. To discourage damping-off, containers used for starting seed should be clean and have adequate drainage.
Fill the container with the germination medium to within 1/2 to 1 inch of the top. Firm the medium lightly, water thoroughly, and allow it to drain for several hours. Sow the seed in rows 2 to 3 inches apart and cover with about 1/8 inch of medium. After sowing, thoroughly water the medium by partially submersing the container in water. When the surface becomes wet, remove the container from the water and allow it to drain. To insure a uniform moisture level during the germination period, cover the container with clear plastic.
Set the container in bright light, but out of direct sunlight. Extremely high temperatures may develop if the covered container is set in direct sunlight. These high temperatures may adversely affect seed germination. The temperature of the medium during germination should be 75 degrees Fahrenheit.
Transplant seedlings into individual containers when the first true set of leaves appears. Handle the small seedlings by their leaves since the small, thin stems break easily. Insert seedlings to the base of the seed leaves, called cotyledons, when transplanting. An excellent growing medium for geraniums consists of one part soil, two parts peat, and two parts perlite.
For best results, grow seedlings under fluorescent lights. The lights should be no more than 4 to 6 inches above the growing plants. Leave the lights on 12 to 16 hours per day. If supplemental lighting is unavailable, place the plants in a sunny south window.
Ideal growing temperatures for geraniums are 70 to 75 degrees Fahrenheit during the day and 60 to 65 degrees Fahrenheit at night. Thoroughly water geraniums when the soil surface is dry to the touch. Fertilize weekly with a one-quarter strength houseplant fertilizer. Harden or condition the plants outdoors for seven to ten days before planting into the garden. Plant geraniums outdoors when the danger of frost has passed.
University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office