Asparagus is the most worry-free perennial plant there is for the home gardener. If you have bought some lately, then you know how expensive it is. In order to fully cover how to grow asparagus, we will be talking about bed preparation/selection, transplanting, harvesting, mulching, and propagating of the asparagus. After the initial investment, you can propagate your own asparagus seeds and increase your crop very easily. Be sure you order your plants from a gardening supplier you trust. You can order asparagus seeds (www.rareseeds.com/precoce-dargenteuil-asparagus) or crowns (plant roots ready to go in the ground), it just depends on how you want to get your bed started. Be sure to plant them in the place you want them to be because once planted, they will produce for 20-30 years and repeat transplanting is not good for any plant.
The first step in learning how to grow asparagus is to understand that it is a perennial vegetable grown for its delicious young shoots. It is rich in B vitamins, vitamin C, calcium, and iron. Asparagus is one of the first crops ready for spring harvest. We started cutting ours in early March. It had produced quite a few spears before I realized it was even up. I actually found it by accident when I was checking the mulch level of the garden in preparation for spring planting. It was a welcome, delicious surprise!
Asparagus plants are monoecious (I had to look it up) meaning each individual plant is either male or female. Some varieties of asparagus, such as “Jersey Knight” and “Jersey Giant” produce all male or primarily male plants, so they’re more productive. Male plants yield more harvestable shoots because they don’t have to invest energy in producing seeds. If a higher yield is your goal, then you should choose an all-male variety, but even then you may get a female or two. We planted Jersey Knight and of the 15 I planted, three were female. This is fine with me since I have learned to propagate the seeds to increase my plot. We still have a high enough yield for us. If you prefer an heirloom or purple-stalked variety, you may like “Purple Passion.” With an all-male variety, 25 plants are usually adequate for a household of four; double the number of plants for standard varieties and if you are an asparagus lover, you may want to triple that. We started out with fifteen for the two of us about four years ago and this year I am transplanting about 30 more that I started from seed. Since I started them from seed, it will be two to three years before I can harvest from them.
You will find that fresh-picked spears are far more tender and tasty than store-bought ones. The flavor doesn’t even compare. Asparagus thrives in just about any area where you have freezing in the winter and a dry season in the summer. The mild, wet regions of Florida and the Gulf Coast are about the only places where it’s difficult to grow asparagus and even there it is doable with a little work and ingenuity.
Bedding is an important consideration for how to grow asparagus. Asparagus needs loose, compost–rich soil. It does best in lighter soils that warm up quickly in spring and drain well; standing water will quickly rot the roots. It can withstand some shade, but it really prefers full sun. You want to be sure your site is in an area where it will not be endangered when you cultivate your garden. We planted ours directly in our garden at the far end, so as not to interfere with other gardening tasks. It is always in the direct sun and produces abundantly from March until around the end of September. It slows down around that time and I usually let it rest a while without harvesting it; then I cut it off at the ground in late October or early November, depending on temperature and its health. In hindsight, I wish I had gone with raised bed gardening. When I next increase our plantings (by propagating my own seeds), I will put the new ones in a raised bed next to the garden. Some people do soil tests and amendments based on the recommendations of university and government studies. I do not do that and in all my years of gardening, I have never had an issue. We mulch and add compost and organic fertilizer from our farm.
You want your planting bed about four feet wide and to remove all weeds and roots. You will plant your crowns in the middle of your bed and you’ll want to add plenty of aged manure or compost. Pretty much like you would any bed preparation. Asparagus has a strong root system that spreads as much as six feet horizontally and can go six to eight feet down.
I am sure you have noticed I don’t say “planting” asparagus, I say “transplanting.” The distinction is important when learning how to grow asparagus. Asparagus seeds have to be planted so deep that it impedes their development, so seeds are started (just like any other seed) in cups and then transplanted to the garden. Remember, while you can order seeds or crowns, the bed preparation is the same.
For crowns, dig a trench 12” deep down the middle of your four-foot row. Plant crowns 1’ – 2’ apart in it. Cover the crown with about two inches of soil. As shoots emerge, cover them with another two inches of soil, continuing this pattern as the plants grow, until the soil level reaches the top of the trench. In very sandy soils, you will probably be okay filling in the trench when you plant the crowns, but you must be sure your soil is “very sandy.” Trenches should be four feet apart. Plant in spring or, in milder climates, late fall/early winter.
Starting asparagus from one-year-old crowns gives you a year’s head start over seed-grown plants. Two-year-old crowns may seem enticing, but they tend to suffer more from transplant shock and by the time they recover, they won’t have produced any faster than one-year-old crowns.
I have been asked about transplanting or moving mature crowns to a different location by people learning how to grow asparagus. While technically this is possible, my advice on that idea is, forget it! Crowns more than two years old are generally huge and it is very difficult to get them out of the ground in one piece. The transplant shock is very great for these more mature crowns and the end result is that the moved crowns usually die. Even if they don’t die immediately, you are probably moving, along with the crown, the root rot organisms that almost always infect them. In their weakened condition, the crowns will fall victim to the disease more quickly.
Asparagus is a heavy feeder so, while you will harvest some without it, your yield will be greater if you spend a little time and effort fertilizing your bed. In Carla Emery’s Encyclopedia of Country Living (my go-to for all homestead questions), you will find detailed information. She says manure is best and compost second best. I have my bed mulched four to six inches so I really don’t spread either in there. I add water to wood ashes and pour that over it. It produces well for us.
Do not harvest your asparagus the year you plant it and, preferably, the year following planting. The asparagus plant needs to grow and establish a healthy crown and it will need all of its energy to do that. You can harvest lightly the second year, but it is best to allow most spears to set ferns (the spears will become ferns as they develop) so that energy is put into developing stronger plants. They need to put all their energy into establishing deep roots. During the third season, harvest lightly leaving some to set ferns. By the fourth year, you can extend your harvest to the full season. “Lightly harvest” means you take only the shoots that are 1/2” or greater in diameter.
Harvest spears when they are four to six inches high and just before the scaly section at the tip begins to open (see the first picture above). As the weather warms, you might have to pick twice a day to keep up with production. Cut asparagus spears with a sharp knife or snap off the spears at, or right below ground level with your fingers. They will snap off at the woody portion. I prefer to cut mine at ground level.
It is best to harvest in the early morning since hot sun makes them tough. You should check your bed at least every two days. I go to mine every day and almost always get some. You must harvest every spear of appropriate size or your plants will produce flowers and this will stop further shoot production from that crown (root). An established bed can be harvested until late fall (like mine), but the first few years of harvesting, say years four to six, you should let the spears set ferns after about 12 weeks of harvest. I know this sounds like you will be missing out on some good eating, and like most gardeners, I hate to let fruit sit in the garden unharvested, but it will benefit you in the years to come. Remember, you will be harvesting from your bed for at least 20 years!
Whips are the tall slender spears and are generally higher in fiber and so tougher to eat than thicker spears because most of the fiber in asparagus is in the skin. You can harvest these also. The larger spears are more tender than the slender whips. If you notice the number of spears in a harvest drops off dramatically, or if the spear diameter drops, you may want to consider ending harvest early. These are good indications that the crown is experiencing some stress.
Remember, the fern is the “factory” that supplies energy to the crown and storage roots for the next year’s crop and it takes a great deal of energy to perform this task. Throughout the post-harvest growing season, keep your ferns healthy by never pruning or cutting them back. You don’t want a lot of new fern growth towards the end of the season so you need to stop any fertilizing and watering early to late fall, depending on your area. Later in the south (as I am). I usually let them rest after September.
Just a side note: I used to think white asparagus was a variety, but it is really just the very young spears before they green up in the sun. Some people like them because the flavor is milder. We really don’t care for it since we prefer the flavor of the mature spears.
Weed control is very important in successfully growing asparagus. This is especially so in the first couple of years after transplanting, when the young crowns are at their most vulnerable. Four to six inches deep is how to lay mulch in this scenario. Don’t mulch your very young plants. They may have trouble growing through it. I spread just enough leaves around my young ones to keep them from over exposure to heat and keep some moisture in.
How to Grow Asparagus From Seed
Starting or increasing your asparagus patch from seed takes a little patience, but there are advantages. Seed-grown plants don’t suffer from transplant shock like the roots (crowns) grown at the nursery. Seeds are considerably more cost efficient. You can buy a whole pack of seeds for the cost of one crown and if you save your seed from your existing bed, they are free. As I have already said, I am experimenting this year with this process. So far it has been easy and productive. We will see what happens next year when/if they produce shoots. I will update you on that event! Also, most seed-grown asparagus plants will out-produce root grown ones in the long run.
I am told you can discard the females and keep the males when growing from seed, however, I am still learning and not sure how to tell them apart when they are seedlings. I am studying it on the internet, so for now, I am planting whatever sprouts and hoping for the best. I can always remove them from the bed, if I get too many females. This is the best information I have found on telling them apart, but mine haven’t “flowered:” “When tiny flowers appear, observe them with a magnifying glass. Female flowers have well-developed, three-lobed pistils; male blossoms are larger and longer than female flowers.” Still looking for a better way to tell.
I followed Carla Emery’s advice to save my own seeds and it worked well. In the late summer or early fall, when the female berries have turned red, cut the fern, leaving the berries intact on the stem, and hang it upside down in a cool, dry place. I hung mine in a room in our house where I store “things” like jars, preserved foods, and such; you know you have a place like that too. In late February, I soaked them in room temperature water for a couple of days then planted them in seed starter cups of organic soil.
Once they had a strong root system, I planted them in the asparagus bed in the garden. I have read that you should put them in a seedbed and transplant the following spring, but I wanted to avoid any root shock. Carla says that you can plant them directly to your permanent site from a seed flat when the plants are well rooted so I tried it. We will see how it turns out.
Once you cut the spears, wash them and pat them dry. Place them in an air-tight container (I use a baggie or veggie bag) in the refrigerator. They will keep fresh for about a week, so you can add to it after each cutting until you get enough to cook. Of course, this depends on the size of your family and number of plants you are harvesting from.
We like to eat it raw on our salads, or just as a veggie with our meal. We like to steam it, this takes 15-20 minutes depending on how tender you want it. Our favorite way is to put some butter in our cast iron griddle, put the asparagus in, sprinkle a little sea salt and garlic powder and sauté them until they are lightly grilled. Yum!
As I always tell you, don’t take my word as the end authority on anything. Always study it out for yourself. Experience is the best teacher. Just because it is in print and sounds good, doesn’t make it right or true. Study and see what makes sense to you and try it. There are as many ways to accomplish a farm chore as there are farmers, so just dive in and enjoy the journey!
What tips would you add to this guide for how to grow asparagus?
Originally published in the September/October 2014 issue of Countryside & Small Stock Journal and regularly vetted for accuracy.