Asparagus is a perennial vegetable which can reach heights of 5′ and is grown for its edible stems. It can take 2–3 years to establish a new asparagus stand, but once you’ve done that, you can expect to harvest it each spring for up to 20–30 years. Originally native to Europe, northern Africa, and western Asia, it’s now grown around the world. It prefers climates with cool winters and will die back each year, sprouting new stems and feathery stalks of leaves in spring. There are usually male and female plants, with males producing yellow or white flowers and females producing smaller flowers followed by berries that will ripen to red. Because it originated near the sea, it’s more tolerant of saline soils than most other vegetables or weeds.
Jersey Supreme is an excellent variety of asparagus that’s highly resistant to cold and thus will produce a week or two earlier than most other varietals. After waiting two years for growth, that may not seem like a lot of extra time, but once you taste these stalks, you’ll be happy to have your spears popping up as early as possible! As an all-male variety, the Jersey Supreme plant also directs all of its energy to stalk production instead of stalk and seed production and tends to have higher yields than dioecious varieties.
Seed Depth: 1″
Space Between Plants: 12″
Space Between Rows: 15–18″
Germination Soil Temperature: 50–70°F
Days for Germination: 10–15
Sow Indoors: Start your seeds indoors 3–4 months prior to the average last frost.
Sow Outdoors: Transplant seedlings outdoors as soon as the soil can be worked. If planting seeds directly outdoors, wait until all chance of frost has passed.
Vegetative: It is recommended that you start your asparagus plants from crowns since you’ll need to wait an extra growing season (3 years instead of 2) before you start harvesting if starting from seeds. Asparagus can be grown from crowns with large (but not tightly packed) roots.
Prefers somewhat cooler weather and won’t grow well once temperatures are consistently over 75°F, so the best time to plant is in the early spring in most climate zones. It’s possible to grow asparagus in zones warmer than USDA Zone 8, but if soil temperatures do not reach below 50°F, the plant cannot become dormant, which is a necessary stage in its life cycle. Dormancy may be induced by withholding irrigation; however, choosing when and for how long to withhold water will vary based on your location’s weather and climate patterns, so this is not recommended for novice gardeners.
Natural: Prefers full sun but will tolerate partial shade in hot weather.
Artificial: As asparagus likes full light but doesn’t care for too much heat, fluorescent bulbs placed approximately 1′ from the plant tops will help your seedlings thrive. Keep plants under your light source for 10–12 hours per day until ready to transplant.
Soil: Prefers sandy or loamy, well-drained soil. If soil does not drain well, consider planting in beds or mounds. A pH of 6.0 to 6.5 will keep plants healthy and nourished.
Soilless: Grows well in soilless mixes with good drainage such as those that contain perlite, vermiculite, or rock wool.
Hydroponics: Will thrive in a hydroponic system in media such as coco coir or gravel paired with a drip system.
Water: Requires moderate levels of water. Although asparagus likes consistently moist soil, it does not like to be in standing water, so be sure to plant in well-draining soil. Water regularly within the first two years. Following this time period, plants will require less watering, but be sure to keep an eye out for limp spears as this can indicate dehydration.
Nutrients: Although not required, a balanced nitrogen, phosphorous, and potassium fertilizer can help plants grow, particularly in the earlier stages.
Foliar: Spray with a compost tea both in the fall and spring to help the plant grow.
Pruning: Beds can be cut back either in the fall, after all the foliage has died, or in the spring. There are two varying schools of thought on when to cut: advocates for fall pruning say it keeps pest populations down, while those who advocate for spring pruning say ferns keep the plants protected from frosty weather. Whichever season you choose, cut the plant’s ferns down to about 3″ above the soil and cut off the crowns of any remaining stalks to encourage new fern growth in the following season.
Mulching: Healthy cuttings from pruning your beds can be left around your plants in order to add nutrients back into your soil. If using a mulch to keep soil moist and pest populations down, use a medium that’s lighter so as not to smother your spears. Straw or grass clippings are both suitable media in this regard.
Companions: Grows well with dill, carrots, tomatoes, parsley, basil, and parsley. Avoid onions, garlic, chives, leeks, and potatoes.
Harvest: Do not harvest your asparagus until it has become established (at least 2 seasons). To harvest, wait until stalks reach 6 to 12″ and either cut or snap off near the bottom of the stalk. Leave the leaves to help the plant grow stalks the following year. Leave thin stalks on the plant to grow into ferns in subsequent seasons.
Storage: Will keep in the refrigerator for 1 to 2 weeks. Do not wash until you are ready to use.
Seed Saving: To save asparagus seeds, remove the tops of your plants with the berries still attached once the berries have turned bright red. Hang these stalks upside down in a paper bag in a warm, dry location and wait for the berries to start falling off. Once this occurs, remove the remaining berries from the stalks by hand. Soak the berries in warm water for a couple of hours and then extract the seeds from the berries. Lay seeds out on a cookie sheet in a warm, dry location for up to two weeks until completely dry. Store in a sealed container.
Preserve: Can be frozen by trimming the base of stalks, blanching, and placing in freezer bags. Pickled asparagus spears are also a tasty way to keep asparagus throughout the off-season.
Prepare: To prepare stalks, trim the bases to take off the tough sections. Spears should then be rinsed and steamed, baked, or boiled.
Nutritional: Contains significant amounts of fiber, antioxidants, and the vitamin(s) K and B. It also contains a trace amount of many minerals including magnesium, potassium, phosphorous, zinc, copper, and calcium.
Medicinal: Has historically been used for decreasing cholesterol and digestion problems such as constipation and irritable bowel syndrome. Some studies have furthermore linked the plant to increasing urine production and the treatment of urinary tract infections.
Who says pickling is just for cucumbers? Try this Pickled Asparagus recipe for a tasty, crunchy snack!