Geranium is a genus containing more than 300 species, is found in both hemispheres, and is known for its beautiful flowers and use as a ground cover and weed suppressor. A true perennial geranium differs from the indoor annual Pelargonium, which has been mistakenly called geranium. Geraniums are also known as "hardy geraniums" or "cranesbill geraniums." Collecting geranium seeds can be an inexpensive means of propagating new geraniums but can take some dedication and know-how. Geraniums develop spiked seed heads, called cranesbills, which contain the seeds at the bottom of the spike. When ripe, the cranesbills split open with force, flinging out the seeds. The trick to collecting geranium seeds is correct timing and proper collection procedures.
Select a healthy plant or several healthy plants. Do not select unhealthy or leggy geraniums, as the seeds collected from such plants may not result in a hearty offspring.
Locate enlarging seedpods at the base of the flower. A darkening of the seedpod color from green to brown signifies that the seeds are ripe.
Ease a fine mesh nylon bag or a double layer of pantyhose over the seedpod and tie it to the stem with lightweight garden string. Thicker twine is discouraged as ants can crawl underneath gaps. Take care as you tie the string to avoid crushing or slicing through the stem with the string. Avoid plastic bags as these may encourage mold growth, which would rot the seeds.
Wait until the geranium seeds itself by splitting open its spike and flinging the seeds into the nylon bag. Snip the stem an inch below the nylon bag, keeping the nylon bag securely fastened.
Open the bag indoors, away from danger of wind or damp, and separate the seeds from the dried hulls. Save the seeds in a dry environment until you are ready to plant in the spring.