Asparagus (Asparagus officinalis) is a perennial that continues yielding spears for 10 to 15 years in U.S. Department of Agriculture plant hardiness zones 3 through 8. If you grow open-pollinated or heirloom asparagus varieties, you can save their seeds and sow them to yield asparagus of equal taste and quality.
About Open-Pollinated Asparagus
Open-pollinated plants are more genetically diverse than hybrid plants because the open flow of pollen between plants enables them to adapt slowly to climate and growing conditions.
An open-pollinated heirloom plant has a documented history. A documented 50-year history is often the standard for an heirloom plant.
A hybrid plant, typically carrying the designation F1, was bred to have a certain size, color or other characteristic. Seeds from hybrid plants are less vigorous and will not produce plants that are identical to the parent plants.
Male and female flowers grow on separate asparagus plants, meaning the plants are dioecious. Each flower begins with both male and female sexual organs, but one sex's organs die as the flower matures.
Bees and other insects carry pollen from one plant to another. Open-pollinated asparagus plants need to be separated by at least 1,300 feet to avoid cross-pollination.
The parts of asparagus that people eat are shoots. Adult, seed-bearing asparagus plants grow up to 3 feet high and spread 4 feet wide.
Growing asparagus for seeds requires using vigorous female plants with at least one nearby male plant. The flowers of both sexes are greenish and bell-shaped.
When the plants are mature in early autumn, the female flowers yield reddish berries containing seeds.
Collect the ripe berries before they drop, and then rub them over a screen or between the palms of your hands to separate the seeds from their coverings.
Wash the seeds in several changes of water, and let them dry for several days.
Stored asparagus seeds can remain viable for three to four years. Place 1/2 cup of recently opened dry, powdered milk in a cloth bag, and place the bag on the bottom of a glass jar. The purpose of the powdered milk is to absorb excess moisture. Put the seeds in the jar, screw the lid on the jar tightly, and put the jar in a refrigerator or freezer to store the seeds.
- ‘Purple Passion’ (Asparagus officinalis ‘Purple Passion’), considered a gourmet asparagus, yields sweet, purple spears that turn green when cooked. Robust male spears grow 1/2 to 3/4 inch thick. Female spears are thinner. ‘Purple Passion’ is perennial in USDA zones 4 through 8.
- ‘Mary Washington’ (Asparagus officinalis ‘Mary Washington’), reportedly originated on the sandy coasts of the Mediterranean Sea. Do not harvest its spears until the second year after sowing the seeds. ‘Mary Washington’ also is hardy in USDA zones 4 through 8.