Are you willing to wait a couple of years for a crop that keeps coming back for 15 years or more? That's the deal asparagus offers, and it's one of the best deals in the vegetable garden. In this guide, you'll learn how to grow asparagus from seed, how to plant and care for a new bed, and when you can finally start picking those tender spring spears.
Why grow asparagus?
Asparagus is a perennial, which means you plant it once and harvest it year after year. A well-kept bed often produces for 15 to 20 years. Fresh-cut spears are sweeter and more tender than anything you'll find at the store, and they're one of the very first things ready to eat in spring.
It's also very cold hardy, thriving in roughly zones 3 to 8. Here in Minnesota, zone 5a, asparagus is right at home.
Should you grow asparagus from seed or crowns?
You can start asparagus from crowns (year-old root clusters) or from seed:
- Crowns: Give you a light harvest about a year sooner, but cost more and offer fewer varieties.
- Seed: Costs far less, avoids transplant shock to crowns, and gives you many more plants. Expect your first light harvest in the third spring.
If you're patient and planting a big bed, seed is a very economical way to go.
How to start asparagus seeds
- Soak the seed. Asparagus seeds have a hard coat. Soak them in warm water for about 24 hours before sowing.
- Start indoors. Sow seeds about 1/2 inch deep in individual pots about 10 to 12 weeks before your last spring frost.
- Keep them warm. Seeds germinate best at about 70 to 85°F and can take 2 to 8 weeks to sprout, so don't give up early!
- Give them light. Seedlings look like thin, feathery grass. Grow them under lights or in a very sunny window until planting time.
How to plant an asparagus bed
Choose your spot carefully, since this bed will be there for years. Asparagus needs full sun (at least 6 to 8 hours a day) and loose, well-drained soil. It prefers a pH of about 6.5 to 7.5.
- Prep: Clear every bit of perennial weed and grass first. They're very hard to remove later. Work in plenty of compost or aged manure.
- Trench: After your last frost, dig a trench about 6 inches deep.
- Plant: Set seedlings about 12 to 18 inches apart in the trench, in rows about 4 to 5 feet apart. Cover them lightly with soil.
- Fill gradually: As the ferns grow through the summer, slowly fill the trench until it's level with the surrounding soil.
Caring for asparagus
- Water: Keep young plants evenly moist, about an inch a week, especially in their first two years.
- Mulch: A thick layer of straw or shredded leaves keeps weeds down. Weeds are the biggest threat to a young bed.
- Feed: Spread compost over the bed each spring.
- Leave the ferns: Let the ferny tops grow all summer. They feed the roots for next year. Cut them back after they turn yellow-brown in late fall, or leave them over winter to catch snow.
When can you harvest asparagus?
This is where patience pays off. For seed-grown plants:
- Years 1 and 2: No harvest. Let every spear grow into a fern to build strong roots.
- Year 3: Harvest lightly for about 2 to 3 weeks.
- Year 4 and beyond: Harvest for about 6 to 8 weeks each spring.
Cut or snap spears when they're about 6 to 8 inches tall, before the tips start to open. Stop harvesting once most new spears are thinner than a pencil. That's the plant telling you it needs to rest and grow ferns.
The best variety to start with
Mary Washington is a classic heirloom that's been a garden favorite for about a century. It's reliable, cold hardy and produces thick, deep-green spears with purple-tinged tips. If you're planting one asparagus bed for the long haul, this is a great choice.
Plant it once, enjoy it for years
Asparagus asks for a little patience up front, but very few crops give back so much for so long. Start a few seeds this winter, and in a few springs you'll be snapping fresh spears for dinner. Our seed is non-GMO and USA grown, and I pack every packet by hand here in Minnesota.
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