Days to germination: n/a
Days to harvest: one year after planting (see below)
Light requirements: Full sun
Water requirements: Frequent until established
Soil requirements: Deeply dug, loose, phosphorus added
Container: not suitable
Asparagus is unique among garden vegetables because it is a perennial, and an established asparagus bed will produce a harvest every year without new plantings. The harvesting timeline may seem complicated at first, but once your asparagus bed is mature, it will produce a harvest for up to 20 years without any additional plants. Asparagus is one of the most problem-free crops you can grow in your garden, and having fresh vegetables early in the spring is an added bonus.
The parts of the asparagus that you harvest and eat are the early shoots that the plants put up in the spring, usually referred to as “spears”. You pick spears for a few weeks, then let the plant grow naturally for the rest of the summer to replenish the roots. They will grow into large plants, with fine leaves like ferns.
Starting from Seed
While you can grow asparagus from seed, that’s not the usual approach for home gardeners. Plants are usually purchased as “crowns”, which are basically just asparagus seedlings with a cluster of roots and spear buds. You can usually buy 1, 2 or 3 year old crowns.
Since your asparagus bed is a somewhat permanent part of your garden, take some time to prepare it properly. Dig the soil down deeply with good compost or aged manure. A little bonemeal added to the soil will provide some extra phosphorus for healthy plants.
Check the age of your crowns when you purchase them because it will make a difference in how you harvest later on. Planting 1-year old crowns will mean limited harvest for their first two years. Larger 2- or 3-year crowns will be able to produce full harvest after their first year.
Your crowns should be planted in early spring to get your bed started right. Dig down around 6 inches for planting, and place your crown in the hole (roots down). But then just fill the hole with about 2 inches of soil, leaving your new plant in a bit of dip. You can fill in the rest of the hole the next year. Space the plants out by 1 to 2 feet between the crowns. Leave about 4 feet between rows if you are planting an entire bed of asparagus.
For the growing season in the same year you’ve planted, you should leave your new plants alone with no harvesting at all, to let them get well-rooted and established. This is the case no matter the age of your initial crowns. Leave 1-year crowns for an extra year after that.
Limit your cutting period to 2 or 3 weeks in the first harvest year. The next year, you can cut spears for up to 4 weeks. After that, you should be able to harvest your fresh asparagus for 6 weeks each year without harming the plants.
During the first couple of years, make sure to water your bed regularly. Once the plants are well established, their deep roots will make frequent waterings less necessary. Asparagus plants do not compete with weeds very well, so after the harvest period you still need to maintain the bed and keep it weed-free. Fully grown plants tend to shade out weeds.
A standard 10-10-10 fertilizer should be applied very early in the spring before the spears start to show. You can also do a second application in the fall when the ferns begin to die back.
For white or blanched asparagus, you can cover the emerging spears with mulch or dirt to keep them from turning green.
Asparagus is not suitable for container gardening because the plants are perennial and will get too large for containers within a few years. Mature plants will have roots that extend down up to 10 feet.
Pests and Diseases
Because the spears are produced so early in the spring, the plant escapes most insect pests and diseases. Rust disease can attack asparagus but you can buy crowns that are naturally resistant. If you do get rust, you’ll notice the reddish-orange fungus on the plants usually after the harvesting period, when the plant has begun to grow out.
Fungicide sprays can be used through the summer, after the spring harvest time has passed to help control rust. As long as the plants are not overwhelmed with it, it will not effect your harvest.
The fern part of the plant is also susceptible to asparagus beetles. Like the rust, it usually doesn’t become a problem in the early spring when you are actually picking your asparagus. Regular insecticides can be used in the summer months to keep the insects from killing the plants.
Harvest and Storage
You can expect to harvest 6 to 10 spears from each asparagus plant, or about half a pound. Harvesting too much will harm the plant, and you’ll get a much reduced crop the next year.
You will get your asparagus harvest very early in the spring, when the first spears come up through the earth. If you live in a warm climate, this can be as early as February.
Let the spears grow up to the thickness of your finger before cutting them off just below soil level with a knife. They’ll be around 4 to 10 inches in length. Larger spears will be tough, but should still be picked to prevent early ferning of the plant. After your harvest period ends, leave the plants alone for the summer.
In the fall, leave the ferns in place to overwinter. They help protect the plant’s roots from the cold. You can cut them back in the early spring to make room for the new spears. If you’ve had problems with insects or disease, make sure to remove all plant material in the spring to prevent re-infection.
Fresh asparagus spears do not store for very long, and you should keep them in the refrigerator until used. Only wash the spears when you are ready to cook them. Asparagus spears are usually cooked, but small ones can even be eaten raw. It’s a very good source for vitamin K, folate as well as vitamins C and A.