Asparagus can be grown in just about every state of the U.S. It is even grown in areas of Hawaii that lack the frost to force the plants into dormancy. The following is what you need to know to have a successful crop of this beloved perennial vegetable. We cover choosing the location to enjoying your harvest—and everything in between.
Location! Location! Location!
When choosing the location for your asparagus bed, think and plan carefully. Being a perennial, your asparagus bed will most likely be producing for a minimum of 15 years. Take a walk around your property at different times of the day, noting the sunny and shaded areas. Don’t despair if you work during the week and are a sports-parent on weekends. Just use one of our inexpensive light meters to test various parts of your property to determine the number of hours of sun it receives.
The recommended amount of sunlight to grow asparagus is 7 to 8 hours a day. Morning sunlight will be essential and 6 hours should be considered a minimum. If you live in an area of the country that has sweltering hot summers, such as Arizona, you might want to plant where your asparagus plants get shaded in the late afternoon. If you do not have an area that is shaded in the late afternoon, consider putting up a shade cloth for those days when you know your asparagus plants may be suffering.
It is also a good idea to look at the surrounding vegetation and landscaping. If you have young trees on your property, take into account how tall and wide those trees will be 15 years from now. Shrubs, bushes and even other vegetables, such as corn and tomatoes, can block the life-giving sun from your asparagus plants.
If your options are limited due to space or sunlight requirements, consider planting your asparagus as a border plant. You will only be harvesting the choicest spears, allowing the remainder to mature and develop the ferny headpiece that is critical to energizing the crowns for next year’s harvest. They are quite beautiful, turning golden in the fall, and can be the perfect airy-looking border for taller annuals or perennials.
Asparagus can also be planted in a raised bed, allowing for at least a 12-inch depth. Otherwise, the process is the same.
Prepping the Bed & Watering
Now that you’ve chosen where to plant your asparagus plants, it’s time to prepare the bed. Many gardeners will do this in the fall, prepping, adjusting the pH and feeding the bed in preparation for spring planting. However, you can be just as successful by doing a good job prepping your bed in the spring. We do recommend that you prepare the bed before ordering or buying your asparagus crowns, though. Our crowns are fresh, which means they were harvested just shortly before you will be receiving them; the quicker they are in the ground after you receive them, the better.
The first order of business is to check the pH level of your soil. Asparagus plants prefer a soil pH right around 6.5 to 6.8. You can fudge a little on each side of those numbers, however, if your soil is too alkaline or too acidic, your asparagus plants will not grow as well. An inexpensive soil testing kit can determine the pH quickly, or you can take a soil sample to your local University Cooperative Extension office for testing. You also might check with your county’s agricultural services. Our GHS Guide to Soil and Soil Testing, Part 1, will provide you with some pH basics.
Then, if you are starting from scratch, you will have to till the area that you will be planting. If there are grass and weeds present, loosen the soil with a shovel or with one pass of a tiller and get rid of as much of the grass and weeds as possible. The cleaner the bed to start, the less weeding and maintenance later on. You will also want to discard any rocks and then till the soil to at least 12 inches. Tilling with several passes should ensure that large clumps have been broken up and that there will be adequate aeration throughout the soil for your new asparagus plants. The well-prepared bed will enable the roots of your asparagus plants to reach deep and establish well.
The final step, just before planting, is to dig a trench, 6 to 8 inches deep, in which to plant your asparagus crowns. If you will have more than one row, the recommended distance between rows is 4 feet. If pinched for space, 3 feet will work, but never plant the rows less than 3 feet apart. This leaves you room to walk between the rows for harvesting and also allows adequate air circulation to dry the ferns after it rains. Leave at least 8 inches between each plant in the row if you are pressed for space, though the best results will be achieved when planting them 12 inches apart.
This is also a good time to decide how you will water your asparagus plants. The most recommended way is with a drip system or soaker hose, both of which are fairly easy to install and make more economical use of your water. This method also does not keep those ferny tops wet. Having your water source determined in advance keeps you from running to the store for hoses or sprinklers when you realize you need to water your freshly planted crop. Admit it—we’ve all been there!
Choosing Your Asparagus
Most people will opt to grow asparagus from crowns, rather than seeds. When growing from seed, you will get a mixture of both male and female plants. Female plants tend to be a bit lankier, not producing the plumpest spears that are the most desirable and palatable. They also produce seeds, which creates a situation where your asparagus bed can become too crowded. Over-crowded asparagus is not happy asparagus! The ferny tops must be able to dry out, which requires adequate air circulation so that disease does not take hold. Male plants, on the other hand, produce more flavorful, stout spears and will not result in the additional work of “weeding” seedlings or the female plants out of your asparagus patch.
So, we recommend buying male asparagus crowns. The crowns are one year old plants that have been carefully harvested, along with their roots. They will appear dried out, but you can rest assured they are very much alive—just dormant.
Planting Your Asparagus
Whether you prepare your bed in the fall or in the spring, you should not plant your asparagus plants until springtime. In fact, even if you till, feed and amend the soil in the fall, wait until the spring to dig the trenches. Otherwise you will end up re-digging the trenches before you plant.
Our asparagus crowns are grown and harvested fresh just before shipping. Being harvested as soon as the ground is soft and dry enough explains why we do not ship our asparagus crowns until late spring. This should allow you plenty of time to prepare your bed as needed and have everything in place for when your asparagus crowns arrive on your doorstep.
Just before planting, you should soak the crowns in water for a period of 15 to 20 minutes. This will give those roots a badly needed drink and give them a bit of a jump-start on growing. Now, just lay the crowns in the trench, at least 8 inches between crowns, though 12 inches is highly recommended for the best performance. Then cover the crowns with only 1 to 2 inches of soil and water gently. Asparagus plants usually start sprouting when the soil temp reaches about 50°F, so you should be seeing those pretty green shoots within about 2-3 weeks of planting, depending upon where you live. Once you see the first shoots, you can again cover them with a couple of inches of soil, repeating the process until the trench is completely filled. View our short video on How To Plant Asparagus to see how easy it really is!
Feeding and Over-Wintering Your Asparagus
When first planting your asparagus crowns, we recommend Hi-Yield Triple Super Phosphate be sprinkled in the trench just before planting. With an NPK value of 0-45-0, this soil amendment is pure phosphorous. Due to the way asparagus grows and its perennial nature, you do not want to feed with nitrogen, which tends to spur quick plant growth. When it comes to asparagus, slow, strong, healthy growth is best. Phosphorous, on the other hand, enables the transfer of energy throughout the entire plant, encouraging the healthiest root growth. It is also essential to the process of photosynthesis. Your asparagus plants will use the most phosphorous while the spears are first forming, and then again, when flowering, so another moderate application of phosphorous is prudent when the harvest is complete and the ferny tops are appearing.
Fall is the next time you will want to pay particular attention to your asparagus bed’s nutritional requirements. Some gardeners choose to leave the ferny tops throughout the winter, cutting them back in the spring, but we recommend cutting your asparagus plants back to the ground right after the first frost. The reason for this is that fungus can grow, even in the winter, when the ferny tops don’t get a chance to dry out. It is also wise, if you know you’ve got fungus on those tops, not to compost them, as the fungus can over-winter and be passed along to anything you use that compost on.
Once you’ve cut them back, cover the whole bed with 1 to 2 inches of well-composted manure or compost and sprinkle with Triple Phosphate or Bone Meal, which will leach down to the roots, providing that springtime pick-me-up as the soil warms and the spears start to grow again. This layer of compost will not only feed the plants but will help to insulate them. In the spring, the spears will grow right through that healthy layer. The same will hold true in places like Hawaii that don’t experience frost, except that once the ferny tops have been in place about 4 months, you will want to cut the asparagus plants back to the ground and treat them the same as if they were growing where winter occurs.
Harvesting Your Asparagus
This is one of the most common questions we get. How do I harvest my asparagus?
As our crowns are already a year old when you receive them, you may not have to wait another year to start harvesting, though you should harvest prudently this first year so as to allow your asparagus bed the time to become well established and healthy. When harvesting you should only harvest the spears that are more than 3/8 inch in diameter (about the size of your little finger), allowing the smaller spears to develop that ferny top, which will, in turn, provide energy back to the crown, resulting in a larger diameter spear the following year. Your first two harvests should be limited to the first 2 to 3 weeks, allowing the asparagus crowns to continue to develop for the healthiest and longest living asparagus bed. From the third year on, you will most likely be harvesting every other day when the asparagus spears are between 4 and 8 inches tall, and for a period of 6 to 8 weeks, depending upon your geographical location. The weather will also determine your harvest. Asparagus is a cool weather crop and one of the first vegetables to be ready for harvest. Don’t pick the asparagus spears if they are no longer tight at the top. Just let those open to display the ferns that will perpetuate next year’s harvest. Nothing goes to waste!
When it comes to actually picking, many people will just snap the asparagus spears at ground level, but we suggest that you invest in an asparagus knife and cut the spears 1 to 2 inches below the top of the soil. The reason for this is two-fold. First, there is less chance that you will damage the plant by pulling as you snap the spear; and second, that layer of soil helps to protect the crown after the spear is removed. It is also much quicker and easier to harvest with an asparagus knife and it results in a longer spear.
Also, do not believe the myth that the larger asparagus spears are not as tender. What IS true is that as the spear grows both in height and in diameter, the part below ground and sometimes about an inch above the ground will get a little tougher. Simply use a paring knife and cut off the tough part, leaving the tenderest part of the spear for your enjoyment. Just throw the part you cut off into the compost bin or feed it to the chickens.
Enjoying and Preserving Your Harvest
In our opinion, the best way to enjoy asparagus is grilled. You can grill it on foil, but having a pan with close-set holes to place over your grill will result in the best flavor. Simply spray the spears with a bit of olive oil and season with garlic, sea salt and pepper and then grill to perfection! Of course, that’s not the only way to enjoy asparagus and we invite you to share your favorite recipes with us here or on our facebook page.
You can preserve asparagus by canning, pickling, freezing or drying.
Drying – Dried asparagus can be processed in a food dehydrator and then added to soups and stews throughout the year. You should wash the spears thoroughly and halve the largest spears. Either steam them 4 to 5 minutes or blanch in water for 3.5 to 4.5 minutes. Dry 4 to 6 hours in a dehydrator or oven. Of course, the drying time depends upon the initial moisture content of the asparagus tips and the type of dehydrator used. A conventional oven can take twice as long, while a convection oven with the fan going should take about the same length of time as a dehydrator. You will want to use perforated trays and allow 3 inches of clearance between the top and the bottom of the oven. Cheesecloth stretched over baking pans or over a frame will usually yield the best results, as it is guaranteed not to react with the asparagus and provides exceptional air circulation. Set your oven thermostat at 140° to 150° and prop the door open a little to allow moisture to escape. The asparagus tips are dry when they are leathery looking and brittle. Store in serving-size portions in airtight containers in a cool place and use in casseroles, stews and soups as needed.
Pickling – is self-explanatory and one of the most preferred methods of preserving asparagus. Due to its low acidity, asparagus requires a pressure canner for canning but can be processed with a water bath canner when being pickled.
Freezing – is one of the simplest means of preserving your asparagus in a close-to-fresh manner. Simply blanch small spears not more than two minutes and larger spears not more than three, then put in freezer bags or containers, removing as much of the air as possible. If you vacuum seal, you can skip the blanching process, keeping the texture fresh and the spears that gorgeous, just-picked green.
Canning – is preferred for long-term storage. Asparagus has low acidity, so it is necessary to utilize a pressure canner. You can either cut the spears to fit quart jars, or cut in smaller pieces, similar to green beans. Be sure to use a spatula to squeeze the air bubbles out of the jars before applying the lids and then process at 10 lbs. of pressure for 25 minutes.
We hope this answers all of your questions about how to start, establish and enjoy your own long-lived asparagus patch. In our opinion, nothing, absolutely nothing, beats the flavor of fresh, home-grown asparagus tips. The longer the spear is off the crown, the more the flavor and even the texture deteriorate. Eat it fresh or process it quickly. Store-bought asparagus tips, whether fresh, canned, frozen or dried, just can’t compare.