If you love asparagus and want to grow some yourself, waste no time in getting started. Even with the best of care, an asparagus bed won’t hit its stride for several years. Growing asparagus requires patience but male plant, is the payoff worth it. Although it takes up to three years to really get going, this perennial plant will produce a bountiful harvest year after year for up to 20 or 30 years. In addition, the plant itself is quite attractive with a long feather-like top that turns a warm golden hue in the fall and makes a powerful statement in your garden.
Native to Western Europe, asparagus does best in areas where the ground freezes in winter or there are dry seasons. In wet and warm areas such as Florida and the Gulf Coast, it is difficult to grow this plant because it is just too moist. If you live in the USDA planting zones 2-8, you can plant asparagus and expect a generous return for your time and energy.
In the old days, gardeners were told to prepare an asparagus bed by digging an 18″ deep trench and then backfilling it with a mix of compost and soil. Thanks to plant breeders at Rutgers University in New Jersey and elsewhere, today’s improved varieties of asparagus are less work to plant (6″ to 12″ deep is adequate) and produce almost twice as many spears per plant. The production increases are due to the fact that these hybrids are all-male cultivars, so no energy is wasted producing seeds. They also don’t produce baby asparagus plants, which can compete for space and nutrients. So forget about Martha Washington and the old asparagus varieties. Most of the new varieties are also resistant to two common asparagus diseases: fusarium rot and asparagus rust.
Growing and Planting Asparagus from Crowns
1. Purchase The Crowns
Asparagus is dioecious, meaning it has male and female plants. Female plants produce seeds—the little red berries shown here—that can reduce the yield of the plant, as energy is put into seed production instead of back into the root system.
It’s possible to grow asparagus by seed, but most farmers and gardeners leave this part to a professional nursery because the seed is so finicky to germinate. Instead, buying asparagus ‘crowns’ (a technical term for the dormant roots) is recommended.
The dormant crowns are available at local garden centers for a brief window in early spring, after the ground thaws, but before the crowns start sprouting. If you miss that window, it’s still possible to order them online from nurseries farther north. Some growers keep asparagus crowns in their walk-in cooler to prolong dormancy so southern gardeners running late on the garden season have something to plant. For the biggest crops, purchase all-male plants. In cold climates, look for Jersey Giant or Jersey Knight. For climates that don’t have deep winter freezes, UC 157 is a good choice.
2. Prepare the Site
Once established, asparagus will produce spears for 20 or more years, so choose the site wisely. Because it can grow very tall, many gardeners plant it on the north or west side of the garden where it will not shade other vegetables. Asparagus grows best in full sun and in loose, well-drained soil, non-acidic soil. Work 3″ of composted manure and other organic amendments into the top 12″ of the bed.
- Remove any existing vegetation from the planting area, including roots.
- Loosen the soil to a depth of 6 or 8 inches over the entire planting area with a tiller or digging fork.
- Spread 2 to 3 inches of compost over the planting area and mix it into the soil.
- If your soil is acidic, add sufficient lime to bring the pH up to 7 and mix it into the planting area*
- Dig a trench 12 inches wide by 12 inches deep where the crowns are to be planted. Rows of asparagus should be at least 2 feet apart, allowing two rows to fit in a 4-foot wide bed.
- For every 8 feet of row space, you will need about a wheelbarrow filled two-thirds of the way with equal parts of the excavated soil and compost.
- Add three cups of all-purpose organic vegetable fertilizer into the soil/compost mixture. To give the asparagus an extra boost, add a cup or two of greensand (an all-natural fertilizer that is high in potassium) to the excavated soil in the wheelbarrow and thoroughly mix.
3. Plant the Crowns
- Spread the contents of the wheelbarrow evenly along the length of the trench.
- Form conical mounds about 6 inches tall every 18 inches along the base of the trench with the soil/amendment mixture.
- Place one crown on top of each mound with the roots splayed out in every direction.
- Cover the crowns with two inches of soil (filling in the spaces between each mound, as well).
- Water deeply at this time.
Note : As the spears develop, gradually fill in the trench by adding an inch or two of soil at a time. Do not cover the foliage, only the shoots. Once the trench is completely filled in, fertilize lightly with slow-release 10-10-10 and mulch the bed well to prevent weeds. Water the plants regularly the first season to get them established.
4. Continue Filling and Watering
- As the asparagus grows, continue to fill in the trenches with the remaining excavated soil.
- Keep the asparagus bed moist, but not soggy throughout the first growing season.
- Spread a layer of mulch over the bed to help conserve moisture and reduce weed germination.
5. Learn the Harvest Schedule
Do not harvest any spears during the first year. Let all the spears develop into ferny plants, as this allows the plant to develop a vigorous root system. In year two, harvest asparagus spears for just two weeks. After that, let the spears develop into plants. In year three, harvest spears for four weeks. In year four and thereafter, harvest spears for six to eight weeks.
6. Harvest the Spears
Spears are ready for harvest when they reach 7″ to 8″ tall and still have tightly budded tips. Use a pair of pruners to cut the asparagus spears just above the soil line. Don’t cut below the soil line. Early spears will be rounded and plump, nearly as wide as a thumb. As the season progresses, the spears get smaller. When the spears are thinner than a pencil, it’s time to quit harvesting and let the ferns grow.
7. Cut Back the Foliage
In the fall, after the plants have turned brown and died back, cut them down to ground level. This prevents insects from overwintering and encourages healthy, pest-free asparagus plants in the spring.
Bent spears are caused by insects feeding or damage from cutting adjacent stalks. The damaged stalk grows normally on the side away from the wound, causing the spear to bend.
A well-drained bed will have minimal disease problems. Black and red asparagus beetles can be a challenge, damaging the foliage and weakening the roots. Usually you can control them with hand picking. Just drop them into a bucket of soapy water.
male asparagus seems to have a benefit over female. In fact, male asparagus is favored so much more that there are now new hybridized male asparagus plants that produce larger yields. Some of these include Jersey Giant, Jersey King and Jersey Knight. If you want the largest spears, these are your best options. These newer hybrids also have the added benefit of being cold tolerant and resistant to rustand fusarium. If you have planted an older variety or are unsure what sex your crowns are, wait until they flower to make a distinction. Then if you want, you can remove the less productive female asparagus and replace it with more productive male crowns.
Asparagus Beds in the Fall & Winter, How to prepare your bed for a great crop next spring