One of our customers, Julie, wrote to us to share a story about growing up as an Army brat. Nearly every time her family moved, her mother would prepare and plant an asparagus bed at their new home. "There was a lesson in all the hard work," said Julie. "Mom told us that we might not reap the rewards, but another family would." Julie and her brother later figured out that their mother's gardening tradition was a metaphor for their family's commitment to military service.
Now that she's grown up, Julie's set down roots of her own, both literally and figuratively. She, her husband and three kids have lived in the Portland, Oregon area for nearly a decade, and the pride of her garden is her thriving asparagus bed. Of course, to honor her mother, she started it from seed.
Why should you start from seed?
Asparagus is a perennial plant that can be grown either from seeds or from transplanted crowns. Crowns provide a shortcut for gardeners but may harbor one or more diseases from their parent beds, so it's important to get them from a trusted source. There's nothing worse to a gardener than putting in the effort to prepare the right spot, only to have sickly plants emerge from tainted crowns!
Seeds may require more patience but are less expensive than crowns. If you really like the delectable shoots, or if you want a larger harvest for your family or market garden customers, starting your asparagus from seed allows you to nurture the strongest, healthiest individual plants, saving time and money down the line.
Seeds are more efficient to transport and store, making it easier for you to select from catalogs who only offer disease-resistant varieties.
Crowns are susceptible to transplant shock, and many gardeners swear that once established, seed-grown asparagus outperform those from transplanted crowns.
There's no reason you can't plant a bed with crowns, and another from transplanted seeds started at home. Maintaining separate beds allow you to protect your investment in time and money. If one bed begins to have issues with pest or disease, you still have the others. Overall, though, asparagus plants are long-lived. You can expect bountiful harvests from established beds from their fourth year through their 15th, with some gardeners maintaining or inheriting beds half a century old!
Where to plant asparagus
Remember how Julie told us that her mother planted asparagus nearly every time they moved? This member of the lily family thrives in zones 3-8. In areas with long periods of humidity, fronds and shoots are more susceptible to foliar diseases. Asparagus is native to cool, breezy coastal climates.
Here are some tips to make sure you get the best yields:
- Select a site in full sun to partial shade where plants will get at least eight hours of sunlight each day during the growing season.
- It's best to set up your beds on previously uncultivated soil since young asparagus is susceptible to buildup of pests, fungi, and bacteria.
- Asparagus fronds can reach 10 feet in height, so be sure you choose a site that won't shade out the rest of your garden.
- Dress up south-facing walls or fences, or partition off areas of your garden with these, bright green, delicate fronds. Each row needs about two feet of growing space, but as the plants mature, they'll take up more horizontal space above the ground as they "fluff out".
- You'll want to check with your utility companies before digging avoid damaging buried power, sewer or water lines. Never plant anything but grass on top of septic drain fields!
Preparing your beds
Asparagus plants are heavy feeders that prefer a soil pH between 6.5 and 7.5. You'll want to provide soil rich in phosphorous, potassium and nitrogen, so it's a good idea to test your soil and make amendments as necessary.
- Remove any sod and weeds from your selected spot, with a good buffer zone. You want to eliminate competition for your asparagus in their earliest years, and developing crowns don't like to be disturbed by aggressive weeding and cultivating.
- Once you know you won't cut power to your entire neighborhood with your gardening efforts, dig a trench 6-8 inches deep. You'll place your transplants about every 12-15 inches, and rows should be 15-24 inches apart to allow good air circulation and access for you and your gardening tools.
- Mix excavated soil with aged compost and soil amendments in a wheelbarrow or on a tarp before returning it to the trenches.
- If you're preparing your beds the fall or late winter before your inaugural planting, cover with seed-free straw or groundcover until you're ready to transplant.
- Yes, you can plant asparagus in raised beds! Be sure to construct them from durable, untreated materials as your plants could outlive the planters. Follow spacing guidelines above when building your raised beds; we like to build them about 10-12 inches high to ensure proper drainage and accommodate root growth.
Don't be put off by the effort involved in properly preparing your asparagus beds. If you do it right once, you can reap the rewards for a long time to come.
Starting and transplanting seeds
While it's possible to plant asparagus seeds directly in your new beds if you live in a frost-free area, we recommend starting your seeds indoors in late winter.
Ready to begin? Soak your seeds water at temperature water for 12 hours to speed up germination. Plant them in sterile soil in newspaper pots (here's a video) and place them in a sunny spot with a heating mat to keep temperatures at about 75°F until they've sprouted. Keep soil moist with a spray mister, avoiding new shoots as they emerge.
Upon emergence, lower temperatures to between 65-70°F. Once the plants are about a foot tall and all danger of frost has passed, you can either transplant the seedlings to a protected "nursery bed" or to their permanent location. Note: Male plants tend to outperform female plants. You can learn to tell the difference here; this is the growth stage at which you will want to cull females and any struggling seedlings.
Caring for your asparagus
You'll want to mulch your beds in their first years to prevent weed growth. As asparagus matures, its spreading root system does a good job crowding out weeds.
Keep your beds consistently moist (but not waterlogged) the first two to three years. Soaker systems placed under mulch don't drench foliage and make sure the root system is getting the water it needs.
Add liquid fertilizer each spring and fall, and cover beds with straw for winter after asparagus foliage turns brown and wilts. Remove straw and dead plant matter before new growth begins the following spring.
When (and how) to harvest asparagus
Patience, darlings. Patience. You won't want to begin harvesting asparagus shoots until their third season, and even then, don't be greedy! You want the new crowns to get as much energy from the leafy part of the plant as possible, and as you know, the asparagus we harvest for the table are the emerging stalks.
Asparagus provides one of the earliest harvests of the year. Two-year-old beds can be sampled lightly if you just can't wait. When your third- or fourth-year beds are producing abundant, healthy shoots, harvest any spears between 6 and 10 inches tall. It doesn't matter if you use a clean, sharp knife or snap the shoots at their bases, as long as you don't cut below the soil line or nick neighboring plants. Always clean your hands and tools in between plants to prevent disease transmission; this is especially true when cutting stalks with a knife. Leave behind any shoots taller than 10 inches, and do not harvest after June 1; your plants need to recover to feed their roots for their dormant period.
You can store asparagus for up to five days in your refrigerator's crisper drawer if you first wrap them in a damp paper towel. After that, they lose their crispness and optimal flavor.
Avoiding pests and diseases
Perennial plants are stuck in one spot, so the pest and disease cycle can't be broken by crop rotation. This is why it's important to select the best seed stock, use clean tools and maintain care in watering, mulching and fertilizing your asparagus beds. The phrase "prevention is the best medicine" could have been coined with asparagus in mind.
Cull any young plants that are underperforming, and watch out for signs of pests and diseases common to asparagus.
Consider companion plants that repel asparagus pests. Tomatoes and basil fend off asparagus beetles, and in turn, asparagus deters nematodes that harm tomatoes. Many asparagus-friendly herbs prevent common garden-damaging insects such as aphids and mites. Our favorites include dill, comfrey, and coriander. As always, marigolds along borders act as colorful sentries against pest invasion.
Asparagus does well with rhubarb planted in between its rows; both are perennials that prefer their root systems be left alone, and these plants don't seem to compete for soil nutrients.
Our favorite varieties
Mary Washington is, quite literally, a perennial favorite. This heirloom variety grows 5-7 feet tall and produces bright green, flavorful stalks.
Jersey Knight is a prolific, hardy hybrid variety known for a higher tolerance of humid conditions. They're also known for producing more male plants than female.
Jersey Giant produce the largest spears, and the tallest, most spectacular fronds.
Pacific Purple asparagus is perfect for gardeners who prefer a milder flavor. True to its name, the bright violet hue of this variety is a hit with kids!
Invest in your garden and your health
Don't let a season pass without starting your very own asparagus beds. It's worth the effort to get them started, and with minimal effort, you'll have a flavorful addition to your menu and a stunning backdrop for your vegetable or ornamental garden.
Think of the highly-nutritious, vitamin-rich asparagus shoots as a delicious bonus; this will help you get through the first years of anticipation!