Plant seeds in a light seed-starting mixture, 1/2 inch deep, indoors, 10-14 weeks before last frost date. Asparagus seeds do take a while to germinate – we’ve found that 90% of will emerge within the first two weeks, with a few stragglers that pop up as much as 4 weeks after planting.
After all danger of frost is passed, plant your asparagus seedlings in a well-prepared bed. You want a location that gets full sun, with rich, well-drained soil. A raised bed, that’s had a generous layer of organic compost added, is absolutely ideal.
As you separate your seedlings, you’ll be surprised at the very impressive roots under those spindly and almost-ethereal little spears! Set each plant 2-3 inches deep, and space plants about 2 feet apart in each direction. Give them a nice thick layer of mulch, and a good watering.
Maintaining a good level of moisture for young plants is important as they’re getting established, but you also don’t want them to sit sopping wet for long periods of time. This is why selecting a rich and well-drained area for the asparagus bed is so important. A good heavy layer of mulch around the young plants will really help keep the moisture level ideal, as they’re getting established.
You won’t harvest any spears this first year, or even next year. So for now, you’re just keeping them weeded, watered, and mulched. In the late fall, as you’re prepping your garden beds for winter, you can cut down the spears that will have grown up and gone to seed, and add them to your compost heap. This is a good preventative measure, to help keep pests like the asparagus beetle from overwintering among the young plants.
By the third year (two years after planting out your new seedlings), you should be able to start cutting some of the larger spears. You’ll want to leave the smaller spears to grow up and fully frond out, so that they’ll feed and support the root system. If you continue to side dress with good compost, and mulch the beds each fall, always allowing some of the smaller spears from each plant to fully grow and mature, you should have a robust bed of asparagus plants, that will provide abundant harvests for years to come.