How to Start Asparagus Plants from Seed
Starting asparagus plants from seed is easy, but slow, as far as waiting for the seedlings to germinate and getting to harvestable shoots. Start seeds about four months before you intend to transplant seedlings into the garden, or, you can keep asparagus seedlings in small containers for one year before transplanting them outdoors.
Asparagus seedlings germinate quickest in a temperature range of 75ºF to 85ºF (24ºC to 29ºC). They germinate, more slowly if directly sown into the garden when soil temperatures are approximately 60ºF (15.5ºC). Once seedlings are growing in the greenhouse, you can reduce the temperature to between 50ºF and 60ºF (10ºC to 15.5ºC), but the plants will progress more slowly the lower the temperature.
Start seeds in the greenhouse by planting one seed per cell in a planting tray or small grow pot at a depth of ½ to ¾ inches (1.3 to 1.9cm) deep in sterile soil mix. Keep pots warm and in full-sun during the day until germination occurs in about 3 weeks, and keep soil moist but not soggy.
When sowing the seeds directly, first prepare a permanent asparagus bed, then sow seeds ½ to ¾ inches (1.3 to 1.9cm) deep in rows 3 to 4 feet (.9 to 1.2 meters) apart, spacing the seeds about 6 inches (15cm) apart in the rows. After germination, thin the seedlings to a spacing between 12 and 18 inches (30 to 46cm) apart.
As the seedlings grow, water them every few weeks with a nitrogen fertilizer, such as diluted fish emulsion, but be careful not to give the young plants too much nitrogen, as this can decrease root growth while stimulating vegetative growth.
Advantages of Starting Asparagus from Seed
Some advantages of starting asparagus plants from seed are:
- It is less expensive than buying crowns and easier than digging up asparagus roots from somewhere else.
- You can grow your asparagus crop completely organically.
- You can grow a variety of asparagus which may not otherwise be available.
Planting out Asparagus Grown from Seed
When seedlings are 12 to 14 weeks old and frost danger is over, transplant seedling to the asparagus bed, or, keep plants growing in pots until the next spring.
When transferring the seedlings into the soil, first dig a trench, just as you would for planting asparagus crowns, and place the seedlings into a mound in the middle of the trench, covering them carefully with soil until they are planted slightly deeper than they were in the tray or pot.