By Dr. Mercola
When you see asparagus standing tall and proud in neat displays at your local grocery store, you might have a hard time imagining how it is grown. It may seem even harder to imagine you could grow it in your own vegetable garden.
While growing asparagus takes patience — about three years to be exact, to ensure vigorous growth and plant maturity — it is not as difficult as you may think. All the preparation and hard work you do initially will be richly rewarded when you harvest those first tender shoots. If you are planting a garden and would enjoy a versatile vegetable that is packed with vitamins and minerals, and delivers important health benefits, you most definitely should consider growing asparagus.
Why Asparagus Is so Good for You
Dubbed as a "feel-good" vegetable because of its mood-boosting potential, asparagus is a superfood you may want to consider not only eating more often, but cultivating in your garden. It's a nutritionally balanced vegetable that is loaded with vitamins A, E and K. One cup (180 grams) of cooked asparagus contains just 40 calories.
Asparagus is also a good source of vitamins C and B, including folate. Folate helps your body make dopamine, norepinephrine and serotonin, which is why asparagus is thought to support your mood. Claims that asparagus protects against cancer are based on its high level of glutathione, a potent antioxidant. It also contains rutin, a bioflavonoid (plant pigment), which protects your small blood vessels from rupturing. It also may protect against the damaging effects of radiation.
Asparagus boasts healthy levels of copper, iron, magnesium, selenium and zinc, to name a few of the minerals it contains. It also supports your digestive health, thanks to the presence of insoluble and soluble fiber, along with inulin, a prebiotic that acts as food for the beneficial bacteria in your gut.
Finally, researchers have uncovered a natural angiotensin-converting enzyme (ACE) inhibitor in asparagus that appears useful for lowering your blood pressure. A 2015 study1 revealed a new sulfur-containing metabolite known as asparaptine, found in asparagus spears, which, according to the authors, acts as a "new ACE inhibitor."
Interesting Facts About Asparagus
More than just the look of asparagus is unique: Check out these interesting facts about this harbinger of spring.2,3 First, you may not be aware of asparagus' status as one of only a few garden-grown perennial vegetables. You need only plant it once. Cared for properly, it will return faithfully year after year, sometimes for decades.
Second, it's important to know asparagus plants are monoecious, which means they can be either male or female. The difference is in their leaves and seed-bearing ability. Female plants are the seed bearers, featuring flowers that have well-developed, three-lobed pistils. Male blossoms do not bear seeds and are noticeably larger and longer.
Third, although green asparagus is most common, purple and white varieties also exist. Purple varieties tend to have less fibers than green asparagus, and they also boast a higher sugar content. You may wonder how white asparagus is produced, especially because it is actually the same plant as green asparagus.
The only difference is it is grown covered to inhibit the process of photosynthesis. If you've ever wondered why white asparagus is much higher priced than green, now you know. The labor involved in the blanching process drives up the cost. Notably, in continental Europe, due to its short growing season and high demand, white asparagus commands a premium price and is often slathered with vinaigrette or hollandaise.4
For the Highest Yields, Try a 'Jersey' Variety
Most avid gardeners would agree that it is nearly impossible to select bad asparagus. In particular, varieties with "Jersey" in their name, which indicates they were bred in New Jersey to be all male, will produce higher yields.5 That said, since asparagus is long-lasting, it's important you select a variety that is well suited for your area.
In the U.S., asparagus grows best in hardiness zones 4 to 9.6 Mother Earth News7 recommends Guelph Millennium for cold climates and Apollo and UC-157 for warm climates. Gardeners in zones 4 to 6 enjoy a wider selection of varieties, including Jersey Giant and Jersey Knight. Other popular choices include:8
- Brock Imperial: a high yield variety
- Mary Washington: rust resistant and the most commonly found variety
- Princeville: does well in warmer climates
- Purple Passion: a sweet purple variety
Tips on Choosing a Spot for Asparagus in Your Garden
When making a plan to grow asparagus, carefully consider the following:9,10
- Height: Since asparagus plants grow quite tall — as high as 5 feet (1.5 meters) — make sure you plant them in a location where they will not overshadow smaller neighboring plants
- Location: Due to its perennial nature, asparagus will come back on its own year after year, possibly for 15 to 20 years — making it a somewhat permanent fixture in your garden
- Soil: Asparagus thrives in lighter, compost-rich soil that drains well; a soil pH in the neutral 6.0 to 7.0 range is ideal
- Space: Allow about 4 to 5 feet (1.2 to 1.5 m) for each plant, although in the early years the plants won't spread out much; once established, however, you will be surprised at how much space they will fill
- Sun: While asparagus can tolerate some shade, you can help minimize disease and ensure more vigorous plants by placing them in direct sun; insufficient daily sunlight will result in thin spears and weak plants
You also should be aware of the two options you have when planting asparagus: using seeds or 1-year-old crowns.
How to Plant Asparagus From Seeds
According to Rodale's Organic Life,11 while starting asparagus from seed takes patience and a few extra steps, seed-grown plants are cheaper and unaffected by transplant trauma. You can buy a whole packet of asparagus seed for roughly the same price you'd pay for a single asparagus crown. Seed-grown asparagus plants are heartier, generally out-producing those started from roots.
If you grow seeds, you will also be able to selectively discard female asparagus plants and cultivate an all-male bed. Male plants generally produce higher yields than female plants. Plants can be started from seed about four weeks before the last expected frost. In northern climates, you can start seedlings indoors in late February or early March. Sow single seeds in biodegradable pots and place them in a sunny window.
Early on, you may need to use bottom heat to maintain the temperature of the pots at 77 degrees F (25 C). When the seeds sprout, you can lower the temperature by about 10 degrees. When the danger of frost has passed, plant the seedlings 2 to 3 inches, or 5.1 to 7.6 centimeters (cm), deep in a nursery bed. Once tiny flowers appear, use a magnifying glass to weed out the female plants and transplant the males to their permanent location in the garden.
Growing Asparagus From Crowns
Most people, especially anyone new to growing asparagus, will find it easier to use crowns.12,13 If for no other reason, using crowns will eliminate the year of tedious weeding that often accompanies starting asparagus plants from seed! Crowns, which are readily available in the spring, have the appearance of an old string mop.
When selecting crowns, choose ones that are fresh and firm, not mushy or withered. Skip the 2-year-old crowns due to the transplant shock they've likely experienced. Besides, they generally do not produce any quicker than the 1-year variety. Purchase the crowns only when you are ready to plant them, and plant them immediately, if possible.
Digging a trench is the most common way to plant asparagus crowns. Your trench should measure about 8 to 10 inches (20.3 to 25.4 cm) deep and 18 to 20 inches (45.7 to 50.8 cm) wide. Place it at the center of the garden bed. This is the best time to work any available manure or compost material into the soil. Rodale's Organic Life suggests soaking the crowns in compost tea for 20 minutes prior to planting for improved results.14
Spread the roots out on the bottom of the trench. Be sure to space them 12 to 15 inches (30.5 to 38.1 cm) apart to ensure they will have room to grow. Cover each plant with 2 to 3 inches (5.1 to 7.6 cm) of soil, and water well. As the plants begin to grow — about two weeks later — add more dirt. Continue adding dirt on a regular basis to cover the asparagus until only a small portion of each shoot is exposed above ground and the trench has been filled completely.
Maintaining Your Asparagus Garden Bed
The keys to a successful annual crop of asparagus hinges on how well you maintain your garden bed. The following activities will help ensure your success:15,16,17
|Weed rigorously around the plants, especially in the early years, to prevent weeds from choking out the shoots and reducing your yields|
|Apply mulch around the plants to retain moisture, for winter protection and to help reduce the presence of weeds|
|Water regularly during the first two years after planting; later on, when the plants have deeper roots, watering will be less critical|
|Fertilize by top-dressing with a liquid fertilizer, such as compost tea, in both the spring and fall; some also suggest a dose of fertilizer in mid-spring due to the heavy-feeding needs of asparagus|
|Remove and destroy the fernlike foliage prior to the appearance of any new growth because it is known to harbor diseases and pest eggs, such as those from asparagus beetles|
|Heap up soil or mulch over the bed before shoots emerge if you desire white asparagus|
|Cut plants to the ground each year, preferably in the fall, but most certainly before new growth starts|
Pests That Can Ruin Your Asparagus Crop
Your No. 1 threat to a good asparagus crop is the asparagus beetle,18,19 which will chew on spears in spring and often attacks summer foliage. These beetles are characterized by their metallic blue-black shells, which feature three white or yellow spots. They measure about one-quarter of an inch (0.64 cm).
Asparagus beetles lay dark eggs along plant leaves, which hatch into brown or light gray larvae featuring black heads and feet. You can remove them by hand or control them using a dust or spray. When removing beetles by hand, do so early in the morning when it's too cool for them to escape by flying away. Other potential pests include the 12-spotted asparagus beetle, which is reddish brown and bears six black spots on each wing, and the asparagus miner, which is known for the zigzag tunnels it makes on stalks.
What You Need to Know About Harvesting Asparagus
One of the hardest parts of cultivating asparagus is waiting for your first harvest. Here's what you need to know about harvesting this tender vegetable.20,21,22
During the first two years, because the plants need to put all their energy into establishing deep roots, gardening experts recommend you do not attempt a harvest. In year three, you can harvest finger-sized spears that are about 8 inches (20.3 cm) long for a period of four weeks. In the fourth year, you can harvest spears for up to eight weeks. Harvest in early spring, every third day or so.
When the weather turns warm, depending on production, you may need to cut your asparagus twice a day. For best results, use a sharp knife to cut asparagus spears at, or directly below, ground level. Refrigerate cut asparagus promptly. Blanch spears prior to freezing. Pickling is another option.
The Best Part of Growing Asparagus: Eating It!
Not only is asparagus crunchy, flavorful and succulent, but also, it is good for you. Undoubtedly, the best part about growing this tasty vegetable is eating it! Tender asparagus spears are a welcome addition to every meal. Light cooking, such as steaming for eight to 10 minutes, increases the bioavailability of asparagus' healthy compounds.
For breakfast, asparagus is wonderful when added to an omelet. At lunch, you can add raw or lightly steamed asparagus to a salad. For dinner, serve asparagus grilled, roasted or steamed as a compliment to any grass fed, organic meat or, my personal favorite, wild-caught Alaskan salmon. For a flavorful and healthy side dish, try my Roasted Asparagus and Fennel recipe.
No matter how you serve it, asparagus is a superfood that I highly recommend become a mainstay on your shopping list. By the way, you'll be happy to know asparagus contains low levels of pesticide residue, which means you can safely purchase and eat the conventional type.
Finally, if you notice an unusual odor after eating asparagus, most likely when you urinate, do not be alarmed. According to WebMD,23 only roughly 25 percent of the population possess the special gene that can detect this particular smell. If you are one of those who can, don't worry, while it may be a nuisance, there is no cause for alarm.