A Complete Guide to Growing Asparagus (From Crown and From Seed)

 

Asparagus is a gourmet harvest worth waiting for. The delicate spears are a celebration of early spring, with a taste reminiscent of welcomed cool rain and greenness all around. Asparagus is a pleasure to grow and an event on the table, whether it’s grilled, sauteed, served with lemon and butter or a rich, creamy hollandaise sauce — and that’s if they even make it to the kitchen. There is nothing like a fresh asparagus spear, broken off and munched right on the spot. 

Growing From Seed vs. Growing From Crowns

It takes three to four years to harvest asparagus after sowing the seeds — an extra year compared to starting from crowns — so it requires patience to start a bed from seed. However, planting the seeds will save you money and often results in healthier plants and better production. 

Start your seeds indoors in January or February. They’ll appreciate a soil temperature of 70 to 85 degrees in order to germinate. The temperature can be lowered to 60 to 70 degrees after they sprout. Once all danger of frost has passed, plant your asparagus seedlings outside, keeping them well-watered all season long.

You may opt to instead plant asparagus crowns. Most of them are second year crowns, meaning they’re one year ahead of planting from seed. With crowns you will see your first small harvest two years after planting (though we recommend waiting to harvest heavily until the following year after that). 

Where Can You Grow Asparagus? 

Asparagus grows best in growing zones three through eight, as they need cold enough temperatures during winter to go dormant and recharge for the following growing season. You may find success in warmer temperatures but the plants could produce less overall, stop producing sooner, and require more fertilizer and care. If your fronds aren’t completely dying back in warmer growing zones, cut them back yourself in the fall. 

Planning for Asparagus

Location

The best time to plant asparagus is three years ago. But if you didn’t do it then, now is the next best time! One of the most important aspects is choosing a location that will be your asparagus plot for the next 15 to 20 years. Asparagus will tolerate partial shade, however we recommend picking a spot in full sun with well-draining, loose soil. Heavy clay soils should be conditioned ahead of planting with the addition of leaf mulch or straw and then finely tilled. Finally, if you’re unsure about your soil pH, get your soil tested to make sure the soil isn’t too acidic. 

How Many Plants? 

Each crown can produce a half of a pound of spears per year once they are fully established. It is generally recommended to plant ten to twenty crowns per asparagus-loving adult in your home. While that may sound like a lot, this quantity should ensure that you’ll have enough spears for a meal from a single harvest. Gauge your plantings accordingly! 

Planting Asparagus

Asparagus crowns are usually planted 12 inches apart in rows spaced five feet apart. Dig a trench eight inches deep that is about four to six inches wide. Lay the crows in the trench with the roots fanned out and buds pointing up. Cover the crowns with a few inches of soil. As the plants begin to grow and push through the soil, cover them with another inch or two. Continue covering the crowns as they grow until the trench is filled with soil. When transplanting seedlings, plant them 12 to 18 inches apart, being careful not to disturb the roots. 

Growing Asparagus

While growing asparagus takes patience, it is a fairly low maintenance plant. After planting, keep your plants well-watered throughout the growing season, ensuring they get one to two inches per week (similarly to other garden vegetables). Fertilize your asparagus twice a year with a balanced fertilizer (5-5-5 or 10-10-10 will do the trick) right before the harvest window and again right after. 

Other than that, you can take care to make sure your asparagus bed stays weed-free and well-watered and your plants will thank you with a harvest each year. Because you won’t be harvesting for the first couple of years (more on that below), you’ll end up with what we call asparagus fronds, the flower-to-seed development of the plant. Leave them there throughout the growing season and cut them back in the spring before the plants start sending up new stalks. They can also act as winter protection, as in colder growing zones we recommend mulching your bed just to make sure your asparagus doesn't freeze. 

Patience is Key

When growing crowns, do not harvest in the first year. The following year, harvest very lightly, slowly increasing the rate at which you harvest year after year until you’re harvesting for a full eight weeks. If you’re starting from seed, don’t harvest in the first two years. This will pay off in later years when your plants are well established and can produce heavily. 

Pests

The two most common asparagus pests are Common Asparagus Beetle and Spotted Asparagus Beetle. Start watching for them in the spring, just as the stalks are beginning to emerge. They spend the winter in debris, so removing the fronds before the stalks come up will help to reduce their numbers. Pick off any beetles you may find, dropping them in a bucket of soapy water. Gently wipe off any eggs you see on the stalks with a damp rag and brush larvae to the ground where they will likely die before climbing back onto the plants. If you have a severe infestation, an application or two of diluted neem oil should help keep them at bay.

Harvesting Asparagus

You’ve waited so patiently and now it’s time to harvest! Watch in the early spring for stalks beginning to emerge from the ground. Take note, in the event of a spring freeze, stalks should be covered with newspaper, leaves, or other mulch to protect them. They can tolerate cool temperatures well but freezing temperatures can ruin them.

In order to harvest, snip the stalk off of the crown at soil level. Enjoy them fresh or cooked and leave some stalks to mature fully at the end of every harvest season. While asparagus is best eaten fresh, they can be put in a jar, tips up, with about an inch of water at the bottom and kept in the refrigerator for up to four days. Cover the tops with a plastic bag just for good measure.

Companion Planting With Asparagus

Companion planting with asparagus can help with pest control, nutrient needs, and maximizing space in the garden! Especially with a year-round crop that only produces two months out of the year, you’re going to want to use this space in other ways. This is where companion planting comes in.

Once established, you can interplant many annual herbs and flowers among your asparagus crowns. This helps to manage weed pressure and pests throughout the growing season on what otherwise would appear to be an empty bed. 

Dill

Dill is a cool weather culinary herb that could be added to the garden around the same time as your asparagus is coming up! This is great because this highly aromatic plant attracts Lacewings and ladybugs that eat pests which may attack your asparagus. 

Cilantro

Cilantro is another cool weather herb with shallow roots that won’t disturb your asparagus as it’s producing. Cilantro will bolt when the weather heats up and produce gorgeous white flowers that attract beneficial insects. 

Nasturtiums 

Nasturtiums are most often planted after the harvest window of asparagus. Their vibrant color and strong scent repels asparagus beetles that are making their home in your asparagus bed to wait until next year. A crop of nasturtiums might just run them out of town! 

Basil

Predatory wasps love basil and are one of our favorite beneficial insects in the garden. 

Strawberries

While not an annual, strawberries can actually make a great companion plant for your asparagus, with a few stipulations. Plant your strawberries at least one year after your asparagus crowns or starts. Allow your asparagus time to get established before adding another crop on top of them. Further, we recommend planting your asparagus at least ten inches deep to avoid these two crops competing for nutrients. While strawberries have shallow roots, you want to ensure that these two perennials aren’t battling for the same resources. Strawberries make a great companion plant to asparagus as they creep along the ground, providing ground cover which helps avoid weeds as well as trapping moisture in the soil. 

What Not to Plant With Asparagus

Alliums

Alliums like garlic, leeks, and onions will compete for the same nutrients as asparagus and ultimately slow each other's growth. 

Beans

It’s not exactly known why, but it is accepted that beans will stunt the growth of asparagus, slowing down their establishment over time. 

Potatoes

Both potatoes and asparagus are planted deeply into the soil which means, if they’re planted together, they’ll be competing for space and nutrients. Neither crop will produce well in this environment. 

Common Mistakes When Growing Asparagus

Mistakes happen in the garden all the time, and while that is perfectly okay and part of the process, here are some common mistakes you can avoid ahead of time! 

Planting in the Wrong Soil

Heavy clay soils that stay waterlogged will cause your crowns to rot. It really can’t be said enough how important it is to plant your asparagus in good, well-draining soil. 

Planting Too Deep or Too Shallow

Crowns that are planted too shallow are more prone to drying out or getting damaged by frost. Those that are too deep may not sprout at all! Be sure to plant them eight to ten inches deep.

Harvesting Too Early

While we know the temptation of harvesting those first spears, it’s so important to allow the roots to get established before you start taking from the plant. Harvesting too early will inhibit long-term growth and production. 

Overharvesting

Asparagus plants need resources to replenish their reserves in order to thrive the following year. Each time you harvest, be sure to leave a few stalks to turn into fronds so that the plants can continue to grow. In the first year, don’t harvest at all. In the second year, take no more than a third of the spears available per plant. And as the years go on, the amount you harvest can increase, but should never be 100% of the spears produced. 

Ready to get growing? We recommend asparagus to the grower that will enjoy the challenge and the wait. The few years of establishing these remarkable vegetables are nothing next to the 20 year gourmet garden you will have outside your door!

This article was updated on 4/18/2024.

	Article Written by: Hannah Gibbons
	About the Author: Hannah Gibbons, an employee at Sow True Seed since 2020, has nearly a decade of experience in the agricultural industry. Their passion for environmental education and regenerative agriculture has been the cornerstone of their work, aimed at making gardening accessible to all.