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Quick guide
- An asparagus plant can last 15 years. Choose its spot in the garden carefully.
- You can start asparagus from seed or from one-year-old roots, called “crowns.”
- Crowns grow vertically and horizontally. Planting at the right depth is important.
- Good soil moisture is important at planting for good root and fern growth.
- Begin harvest 2 years after planting crowns, 3 years after planting seeds.
- Harvest spears until the end of June, and then allow the large feathery ferns to develop.
Grow Asparagus
Is one of the earliest harvested vegetables each spring. Asparagus spears are crisp, tender and flavorful. The asparagus harvest season lasts about 6-8 weeks, from early May to late June. In the peak of asparagus season, asparagus spears can grow up to 2 inches per day, producing bountiful harvests for gardeners to enjoy.
How asparagus grows
- Asparagus is a unique crop. It is one of the few perennial vegetables.
- The edible parts of the plant are called the spears. The spears emerge from underground buds at the base of the root system. These buds and roots are called “crowns.” If spears are left to grow, they develop leaves and are called “ferns.” Asparagus harvest is only 2 months instead of the entire season, because the plants need a chance to let the ferns grow in order to recover and build up energy for the next year.
- The fern creates energy that will be stored in the underground portion of the plant to produce the following year’s spears. It is important to take care of the ferns even after the harvest is over to make sure you will have good future harvests.
Soil
Asparagus grows best in well-drained soils with a pH between 6.5 to 7.0 and does not tolerate extremely acidic soils. It can grow in heavy, medium, or sandy soils, as long as the soils must be well-drained and do not exhibit pooling water after rains. Before planting asparagus, have your soil tested to see if the soil has the right amount of nutrients for asparagus to thrive. Add recommended fertilizer based on the soil test results. It is best to add part of the fertilizer the fall or spring before planting, but about half of the phosphorus and potassium should be added at the time of planting. Nitrogen should be added after planting, once the crowns begin growing. In the absence of a soil test report, the typical garden fertilizer rate for asparagus is to apply 1 to 1.5 pounds of a 10% nitrogen, 10% phosphorus, and 10% potassium fertilizer (10-10-10) per 100 square feet before planting.
Care
Once an asparagus patch is established, it is best to test the soil approximately every 3 years and follow the test recommendations before adding nutrients. After the asparagus patch is established, fertilizer, compost, or composted manure can be added either in early spring before spear emergence, or after harvest in late June or early July. Only add these inputs if they are needed according to the soil test. Add the fertilizer alongside the row of plants and scratch it in lightly. Do not allow the tool to penetrate the soil more than an inch deep, to avoid harming the underground portions of the plants.
Types
- There are female and male plants (dioecious).
- All produce edible spears.
- Only plants with all female flowers produce red, inedible berries in summer.
- Female plants grow larger spears.
- Male plants grow a greater number of smaller, uniform spears.
- Most hybrids, are plants with only male flowers that produce no seeds.
- Plants with all male flowers do not use energy on developing seeds and fruits.
- Male asparagus plants tend to live longer and produce more spears.
- Female plants can produce undesirable weedy seedling asparagus plants.
Planting
A planting of asparagus can last 15 years or more, so choose the spot for an asparagus bed carefully.
- Choose a fertile, sunny, well-drained site with soil that holds moisture well.
- Late spring frosts can kill emerged spears, so find an area that is not exposed to frost.
- Asparagus plants have deep root systems. Avoid areas with shallow soils, or soils prone to water-saturation.
- If the asparagus bed is to be part of a larger vegetable garden, the best place is at the north end of the garden, so that the tall ferns do not shade the other crops.
- Asparagus is planted between early May and early June. Refrigerate the crowns until planting.
- Dig a 6-12 inch deep trench for the crowns to be planted into. In heavy clay soils, make the furrows more shallow (6-8 inches) and deeper (10-12 inches) for very sandy soil. As the soil is removed from the trench, set it directly to the side. It will be returned to the trench several weeks later as the ferns grow.
- The length of the trench should be as long as the number of crowns being planted. For example, if you have 10 crowns, dig a 10-foot long trench. If planting multiple rows, space the furrows at least 3 feet apart, because the plants will spread as they age.
Starting Seeds
- Choose an area of the garden as a nursery bed. Young asparagus plants will grow here for their first year. The site for the asparagus nursery should be level and have sandy soil.
- Plant seed in spring, about one inch deep, spaced 2 to 3 inches apart, within rows that are a foot apart. Seeds can take 3 weeks to germinate.
- Keep the nursery bed free from weeds, as the asparagus seedlings will not be able to compete with strong weed growth.
- Mulch the nursery bed with 4 to 6 inches of straw in late October to keep it warm during winter.
- In early April, before the plants start to grow, dig up the crowns with as much of the root system as you can, and move them to their permanent location.
Watering
- Soil moisture is important for good root and fern growth in asparagus. Even though asparagus ferns rarely exhibit obvious signs of drought stress, they need consistent soil moisture in order to stay healthy for the next year. Watering during the harvest season may also increase yields in very dry years.
- Asparagus patches should receive at least one inch of water every week. Asparagus growing in sandy soil should be watered more than once per week in the absence of rain, and heavy clay soils may not need to be watered as often. Additionally, soils covered in mulch will retain more water.
- An inch of water will wet a sandy soil to a depth of 10 inches, and wet a heavy clay soil to 6 inches.
Weeds
- Weeds compete with asparagus for soil nutrients, water, and light, so managing weeds will help support a more bountiful yield of spears. Removing weeds by hand is still one of the most effective methods, especially in smaller asparagus beds. Additional methods include well-timed hoeing, flame-weeding, cover crops, and careful use of select herbicides.
Harvest
- In spring, spears will start to emerge from the soil. The first spring, a year after planting the crowns, do not harvest any spears. Allow the spears to become ferns and build the strength of the crowns.
- The second spring after planting crowns, if the plants were strong and healthy during the previous growing season, begin to harvest when the spears are 6to 8 inches long. In the first year of harvest, only pick asparagus for two weeks. After that, allow the spears to develop into ferns.
- In the following years, harvest asparagus up to July. Some gardeners will not harvest during the second year at all, preferring to allow the plants to build more strength before finally beginning to harvest in the third year.
Storage
- Fresh asparagus is such a springtime treat that you can eat within hours of picking, but it can also kept for up to a week in the refrigerator.
- You can freeze an asparagus harvest.
- You should only can asparagus in a pressure canner.
Source: https://extension.umn.edu/vegetables/growing-asparagus#harvest-and-storage-193114
