As a sign of winter thawing, asparagus is the first vegetable to break ground in the spring. It pushes up green spears from the still-sleeping garden with impressive strength and encourages us to look forward to a new season of growing. Asparagus is unlike other vegetables we grow from seed. It takes patience and understanding of its growth requirements, but once planted in your garden, you’ll look forward to spring and a delicious asparagus harvest for years to come.
A patch of asparagus can continue producing tender spears for over 20 years. It takes patience to get it started, and you’ll be tempted to eat it too soon. But we’ll walk you through the asparagus seed starting process so you can enjoy a delicious harvest that increases year after year.
How to Grow Asparagus From Seed
The best part about growing asparagus from seed is that you can take time to do it right and give it the best growing conditions. Once your asparagus plants are established, you will be rewarded with a reliable and delicious harvest every spring.
Before you plant your asparagus seeds, consider where you will grow them. The initial investment you put in now to pick the perfect location and prepare the soil will make all the difference.
Tips for fail-proof asparagus seed germination
1 - Soak seeds.
Soak asparagus seeds for a few hours or overnight before planting.
2 - Sow seeds.
Sow asparagus seeds ½” deep in seed starting mix.
3 - Warm the soil.
Asparagus seeds germinate best in soil that is 75-85ºF. You can use a heating mat indoors.
4 - Keep seeds moist.
Use a humidity dome if starting seeds indoors.
5 - Be patient.
Asparagus seeds can take 10-56 days to germinate.
Once asparagus seeds have sprouted, the soil temperature can be 60-70ºF. Keep the soil moist but not waterlogged. Watering from the bottom will help prevent damping off.
These dainty-looking seedlings will be sending out strong root growth. If you started seeds in small growing cells, you will need to pot up to keep the roots from becoming root-bound in the containers.
Once all danger of frost is past, you can transplant your asparagus seedlings to their outdoor location.
Transplanting asparagus seedlings
Some gardeners will transplant their asparagus seedlings into a sandy location that is a temporary spot. This temporary spot will allow them to easily transplant the crowns the next year to their permanent garden location in late winter or early spring.
When transplanting asparagus seedlings outdoors, take time to harden them off so they aren’t shocked by the change. Allow a week to acclimate them, and start by placing them outdoors for one hour.
Before transplanting, prepare the garden soil. Asparagus can grow in a variety of soils but will do best in loamy soil that is rich in organic matter. You can test your soil for texture, pH, and nutrients. Amend with compost before planting.
Space asparagus plants about 12” apart. Rows should also be at least a foot apart.
How to Grow Asparagus Plants for Years of Harvest
There are some simple rules to follow to successfully grow asparagus plants for a healthy harvest year after year. Plant asparagus in full sun with well-draining soil. Always protect the crown, fertilize as needed, and prune once a year.
Asparagus needs full sun to grow those delicious spears. The ferns will gather up all that solar energy and store it to come bursting up in spring. If the plants don’t get enough light, there won’t be energy to produce more spears. At a minimum, asparagus plants will need 7 hours of daily sunshine. Once the plants start growing ferns, they can get several feet tall. You will want to keep this in mind when choosing a location so that you don’t shade out other crops.
Put the effort into making your soil a great foundation since this will result in a better harvest for years. Loamy soil full of organic matter will allow the roots to grow deep and the shoots to emerge easily. Asparagus can grow in a range of soils as long as it drains well. A pH of 6.5-7 is best. Raised beds are an excellent spot for growing asparagus. You want soil that says evenly moist but never waterlogged. You don’t want the crown to drown. Which brings us to the next vital piece of growing asparagus.
Protect the Crown:
The crown of an asparagus plant is critical for all growth. This is where all the roots and spears emerge. Each year, the crown will grow bigger. To protect the asparagus crown, keep it from drying out, freezing, or drowning. In cold growing zones, you will need to apply 4 to 6 inches of straw mulch to keep the crowns from freezing.
Applying fertilizer at the right times will ensure a healthy crop of asparagus. Phosphorus and potassium can be added when planting. A balanced fertilizer of 10-10-10 is usually a good choice. You can test the soil to know what nutrients might be low. Once the crowns start sprouting new spears, you can add nitrogen fertilizer.
Since asparagus grows for 15+ years, it will be beneficial to test your soil every three years and amend it as needed. Compost tea and leaf mulch are great for adding on top since you don’t have to disturb the crowns and roots.
Watering throughout the growing season is vital. Asparagus plants need about one inch of water a week. After harvesting your asparagus spears, continue watering the plants, and don’t let them dry out. You are helping to grow next year’s harvest. Once the ferns have died off, you can discontinue winter watering.
A simple yet essential part of growing asparagus is pruning every year. The best time to prune is after all the ferny growth has turned brown. This is usually in the winter. It’s important to prune and not wait until spring so that you can cut it back before new spears emerge. To prune your asparagus plants, cut back the dead ferns to 1-2 inches above the ground.
When pruning, you can also remove female asparagus plants. Both male and female plants produce spears, but female plants put more energy into producing seeds and have thinner spears. Also, the seeds can grow over time, creating a crowded asparagus patch. However, you can always dig up crowns and share them with gardening friends or transplant them to other locations.
New asparagus spears will emerge as soon as the ground warms up in the spring. These spears can grow fast, up to 2 inches a day.
Harvesting asparagus correctly is vital for next year’s growth and subsequent harvests. Your first harvest will be three years after planting asparagus seeds.
In the first year, the seedlings are developing a vigorous root system. In the second year, the crowns are growing. The third year spears will grow, but let them develop into ferns. Those ferns will capture the sun's energy by photosynthesis and store it up for next year’s harvest.
In the first year of harvesting asparagus, it is recommended that you only harvest spears for one week. Then, let all the rest of the spears grow and develop into ferns.
In the second year, you can harvest for 4 weeks. The following year, six weeks. After that, you can harvest for eight weeks.
You will always want to stop harvesting at eight weeks to allow the ferns to grow and store energy for next year.
Asparagus spears can be harvested when they are 6 to 10 inches tall. Check every day because they can grow as fast as 2 inches a day. Usually, they are at least as big around as your finger. If they are thinner than a pencil, it is best to allow them to develop into ferns.
Use a sharp knife to cut off spears at the soil level.
You don’t need to divide asparagus plants. But you can divide crowns to share plants with other gardening friends. Do this in winter or very early spring before new growth sprouts.
FAQs about Growing Asparagus
How long does it take to grow asparagus from seed?
Asparagus seeds will germinate in 10 to 56 days. Soaking the seeds before planting can speed up the process. Once the seeds have started growing, you should wait until the 3rd spring before harvesting any spears. This will give the asparagus plants a thriving root system for better harvests every year.
How hard is it to grow asparagus from seed?
It’s not hard to grow asparagus from seed. It just takes patience. Once you have given it the right conditions and a few seasons of growth, you will have a dependable harvest for years.
Do you start asparagus seeds indoors?
You can start asparagus seeds indoors or outside. When you start asparagus seeds indoors, you can control the growing conditions. This is helpful to ensure seeds germinate and the seedlings get off to a good start.
Why didn’t my asparagus come back?
Over-harvesting asparagus can prevent your plants from growing new spears the next year. Always leave some ferns to grow so they can store up energy for another spring crop. Another possible reason for asparagus to not come back is if the crown died from being too cold or from damage caused by insects or disease.
Are there male and female asparagus plants?
There are female and male asparagus plants (dioecious). Both male and female asparagus plants produce edible spears. But female asparagus plants will put a lot of energy into making seeds and have thinner spears. If this matters to you, you can remove female plants. When they start producing seeds, you can tell which are which.
Is asparagus healthy?
This popular vegetable is an excellent source of folic acid, vitamins A, C, and B.
What is white asparagus?
White asparagus stays white because of “blanching.” This is a process of growing the asparagus and covering the emerging spears so they don’t get any sunlight. It results in an interesting but less nutrient-dense vegetable.
Solutions for asparagus pests and diseases
Aphids can be a problem, as they are with most garden plants. Use neem oil and other natural methods to deal with them.
Asparagus beetles will feed on the tender spears and ferns. Start looking for them as soon as the spears emerge. You can pick them off and drop them into soapy water. Look for eggs and pupae, as well as adult beetles. You can also apply neem oil as a pesticide.
It is possible and rewarding to grow asparagus from seed! It takes patience not to eat those first spears, but you will be richly rewarded for your labor. Don’t be intimidated by the wait time. Growing asparagus isn’t hard; it’s just a matter of timing. Once the soil is prepared and you know how to fertilize, prune, and harvest, you’ll enjoy the effort for years to come.
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