AMES, Iowa – Geraniums are popular flowering plants for beds, borders, containers, hanging baskets and window boxes. Plants are traditionally grown from cuttings.
In recent years, however, seed-grown hybrid geraniums have become available, according to Richard Jauron, Extension horticulturist at the Iowa State University Extension.
The new seed-grown hybrid geraniums possess excellent vigor, heat tolerance, disease resistance and are free-blooming.
Geraniums are fairly easy to grow from seed. However, they are rather slow growing. Sow seed in early to mid-February to produce flowering plants for spring. Flowering occurs approximately 12 to 16 weeks after sowing.
Suggested seed-grown geraniums for Iowa include varieties in the Orbit, Elite, 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.)
Commercially prepared mixes, such as Jiffy Mix and Redi-earth, are good germination media. You also can prepare your own medium by mixing equal parts sphagnum peat and vermiculite. During germination, damping-off of geranium seedlings can be a serious problem.
Containers used for starting seed should be clean and provide for adequate drainage. Previously used containers should be washed in soapy water, then disinfected by dipping in a solution containing one part chlorine bleach and nine parts water.
Fill the container with the germination medium to within 1 inch of the top. Firm the medium lightly, water thoroughly and allow it to drain for 1 or 2 hours.
Geranium seed is fairly large, but somewhat expensive. Carefully sow the seed thinly and uniformly in rows and cover with about one-eighth inch of medium. After sowing, thoroughly water the medium with a fine mist using a rubber bulb sprinkler or by partially submersing the container in water.
To ensure a uniform moisture level during the germination period, cover the container with clear plastic wrap. Set the container in a warm location. The temperature of the medium during germination should be 75 degrees. Do not set the covered container in direct sunlight.
The high medium temperatures that may occur in direct sun may inhibit or prevent seed germination. With favorable temperature and moisture levels, the geranium seed should germinate in 7 to 10 days. Remove the plastic covering as soon as germination occurs.
Using a well-drained commercial potting mix, transplant seedlings directly into individual 3 to 4-inch-diameter pots when the first true set of leaves appear. Handle the small seedlings by their leaves since the small, thin stems break easily.
Insert seedlings to the base of the seed leaves or cotyledons when transplanting.
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.
With inadequate light, the geraniums may become tall and spindly. Pinch out the shoot tips of spindly plants to encourage branching.
Ideal growing temperatures for geraniums are 70 to 75 degrees during the day and 60 to 65 degrees at night.
Thoroughly water geraniums when the soil surface is dry to the touch. Fertilize every two weeks with a diluted fertilizer solution. Harden or acclimate the plants outdoors for 7 to 10 days before planting into the garden.
Plant geraniums outdoors when the danger of frost has passed. Generally, mid-May is a safe planting time for geraniums.
When starting plants from seed this winter, don’t forget geraniums. While most gardeners purchase their geraniums from garden centers in the spring, growing them from seed is easy and fun.