Planting Asparagus Seeds: A Comprehensive Grow Guide
Growing asparagus from seed is an exercise in patience.
After you’re done planting asparagus seeds, it will be a long wait before you can harvest any actual asparagus spears to eat — the third year after starting the seeds!
This is why most people plant developed asparagus crowns instead.
However, starting asparagus from seed is considerably cheaper and not a bad way to start a second asparagus patch.
Planting Asparagus Seeds
Asparagus, a valuable perennial vegetable, is hardy to Zone 2 and a favorite among gardeners for its nutritional value and flavor. This guide delves into the comprehensive steps to cultivate a successful asparagus patch from seed.
Asparagus seeds are best started indoors under grow lights and should not be transplanted outdoors until they are 10-12 weeks past germination (sprouting), and all danger of last frost has passed. Asparagus seeds can take 2-8 weeks to sprout — plan accordingly!
If you’re looking for a comprehensive grow guide on planting asparagus crowns, check out my detailed article on how to grow asparagus from crowns.
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Understanding Asparagus Needs
Asparagus is a perennial vegetable. After your asparagus patch is planted and established, it will continue to come back every year with minimal inputs from you for at least 15 years and potentially over 20 years.
That’s a big commitment and a lot of delicious food that will feed you and your family well before nearly anything else in the garden has even started growing.
This means that the site selection for your asparagus bed is crucial.
Selecting the Ideal Location for Your Asparagus Bed
Sunlight and Space: For optimal growth, asparagus demands full sun. The chosen site should provide uninterrupted sunlight throughout the day.
Asparagus Ferns: After harvest, your asparagus will grow 3-foot high ferns that are crucial to the health of the plant. Make sure your chosen site won’t shade out other plants and vegetables.
Soil Quality: Well-drained soil is a prerequisite for healthy asparagus. Enrich your soil with organic matter. Sandy soils are preferred for their drainage capabilities, which can prevent root diseases.
Planning for Longevity: Asparagus is a long-term crop. Choose a spot where it can grow undisturbed for years, considering the future spread of the plants and the maintenance of the asparagus bed. Does any part of your garden flood and hold on to water?
Preparing The Asparagus Bed
Asparagus thrives in well-drained soils with a pH level between 6.5 to 7.0. It cannot tolerate extremely acidic soils.
The plant can grow in heavy, medium, or sandy soils if the soil is well-drained and does not retain water after rain.
If possible, add anywhere from 1 inch or more of finished compost over the site where you intend to plant your asparagus seedlings.
The best time to add compost to your garden is the fall before you plant your vegetables. This keeps the soil microbes fed and happy. Asparagus is no different.
And asparagus thrives in a no-till garden, too, where the roots and complex food soil web underneath are disturbed as minimally as possible.
Prepare the future bed by removing all grass and perennial weeds. You can lay cardboard over grass, followed by compost or a mixture of soil and compost.
Then you can add an additional layer of organic mulch on top of the soil-compost to help keep weeds away and to further feed and enrich the soil as the matter breaks down — grass clippings, hay, straw, etc. all work, and my article on the best mulch for asparagus covers this topic in detail.
If your soil is extremely heavy and compacted or very poor quality — no problem.
Plant root crops like radish, turnips, or tillage radish in the fall before you transplant your asparagus.
Let the winter frost kill these crops and do not pull them out; they should be allowed to rot in the ground, which will break up the soil while enriching it with organic matter as it rots and dies.
This is also a great technique if you don’t have access to enough good compost.
Planting Asparagus Seeds — Start Indoors
Start seeds indoors during the winter months and through spring under grow lights.
Soil temperature for germination is 70–85ºF (21–30ºC), and the soil temperature is crucial for successful and timely germination.
Start by soaking your asparagus seeds for 2-3 hours prior to planting them.
Use high-quality soil for seed-starting or even finished compost. I love using a brand with leaf mold and worm casings for nutrition and adequate drainage.
Plant 1 seed per 2-inch (5cm) pot, about 1/2 inch (1cm) deep. Keep your pots in a warm place until germination, and be patient, as it can take 2-8 weeks to sprout, depending on your soil temperature.
A heating mat might come in handy here but make sure it is not too hot.
Asparagus seeds don’t need light to sprout, but the plants must be given access to proper grow lights as soon as they do come up.
Keep the grow lights directly above the plants by about 1-2 inches for 16 hours and raise them gradually as the baby asparagus plants continue to grow.
Keep soil moist, but do not keep it drenched or let the tray underneath become waterlogged.
Hardening Asparagus Seedlings
You must wait until your asparagus seedlings are 10-12 weeks old and all danger of frost has passed.
Then, hardening your delicate asparagus seedlings is necessary to acclimate them to life in the harsh outdoors where wind, rain, and storms are possible.
Begin by taking your tray of seedlings outside and leaving them outdoors for an hour or two in a warm but shady spot shielded from any harsh winds or rain.
Each day gradually increase their exposure to the outside world and sunlight.
In the first few days, avoid the sun at its peak to avoid any chance of leaf burn.
Hardening off your asparagus should take about a week of daily exposure.
Transplanting Asparagus Seedlings
Handle the seedlings with care to protect the developing root system.
Space asparagus seedlings 18 inches (45cm) apart in rows 3 feet apart (1 meter).
Transplant each plant in a hole 4 inches (10cm) deep and gradually cover the crown with soil as it grows.
You can also dig a trench at this depth and transplant.
For thicker spears, once they start to develop, space 12-14 inches (30-35cm) apart and set buds 6-8 inches (15-20cm) in the hole.
For thinner spears, space 8-10 inches (20-25cm) apart with the buds 4 inches (10cm) deep.
You do not need to fertilize if you added significant amounts of compost the season before.
In our organic no-till garden, we do not use any fertilizer beyond the finished compost from our kitchen scraps and animals.
If you choose to fertilize your bed, do so after transplanting and in the future years after harvest and again in the early spring with a complete organic fertilizer.
Asparagus needs 1 inch (2cm) of water per week.
In late fall, trim the ferns down to 2 inches (5cm) and dispose of cuttings to avoid future disease and insect problems. You can opt to chop-and-drop the ferns too, or simply compost them.
Harvesting Asparagus Grown From Seeds
Planting asparagus seeds means you will not begin to harvest any asparagus spears until year 3 after transplanting. And that first year of harvesting will be a light one to avoid damaging the plant and stunting its growth and future output.
The first year is crucial for the asparagus seedlings as they establish themselves in the asparagus patch. It’s a period of significant growth and the first season in their new outdoor environment.
In the second year, the asparagus plants focus on building a sturdy root system. Avoid harvesting any new spears this year to allow the plants to mature fully.
In the first year of harvest (year 3), pick a few spears from each plant over a 2-3 week period.
Cut only the fattest spears off, doing so right at ground level when they are 6-10 inches (15-20cm) long.
When thin spears begin to emerge, do not harvest them, but leave them alone to grow into big fronds nourishing the roots.
With each successive year, the harvest lengthens to a maximum of 6-8 weeks and you can harvest more and more.
By year 5, your asparagus patch started from seed and will be producing a bounty of asparagus spears.
Understanding the Nature of Asparagus Plants
It’s important to note that asparagus plants can be either male or female.
Female asparagus plants may produce seeds, potentially leading to overcrowding in your asparagus bed.
Some gardeners opt to remove female asparagus entirely. This is another pitfall of planting asparagus seeds — there is no way to tell the males and females apart and separate them before you put in the work and time.
The easiest way to distinguish between male and female asparagus plants is to look for the round berries (seed pods) that form from female flowers on the ferns. Then you can choose to remove those plants.
How Many Asparagus Plants Per Person
10-20 asparagus plants per person is optimal, depending on how much space you have and how much you love to eat asparagus. Consider if you plan on sharing, canning, freezing, or fermenting your asparagus to enjoy after the spring harvest and err on the side of caution by planting more.
Check out my detailed article on how many asparagus plants per person to help you decide.
Companion Planting Asparagus
There are numerous companion plants for asparagus to choose from.
Some maximize growing space by providing an additional food crop, and some help enrich the soil and keep weeds at bay.
My top choices are strawberries and bush beans, and you can read more in my article on companion planting asparagus, which will explain it in detail while outlining what not to do.
Mulching Asparagus
From living mulches like clover to organic material like wood chips in a back to Eden garden method, my article on the best mulch for asparagus covers this topic in detail.
I like to use a combination of materials readily available on the homestead.
The benefits of mulch cannot be overstated, and I use mulches extensively in my vegetable garden.
Asparagus Pests
Be vigilant against asparagus beetles, the most common pest affecting asparagus.
Other pests include aphids and cutworms. Check for damaged plants, eggs, misshapen, and stunted leaves. Regularly inspect your asparagus patch for signs of damage and disease from pests and act accordingly.
Photo Credit: Envato Elements.
More Asparagus Articles & Guides
- How Many Asparagus Plants Per Person?
- How To Grow Asparagus From Crowns (Complete Guide)
- The Best and Worst Companion Plants for Asparagus
- The BEST Mulch For Asparagus {Protect Your Asparagus Patch}
Final Thoughts
Embarking on the journey of planting asparagus seeds is a commitment to several years of careful nurturing. Each step is vital for a successful and rewarding asparagus patch, from preparing the asparagus bed in a location with full sun and well-drained soil to the meticulous care of asparagus seedlings in their first year. Your efforts will culminate in the joy of harvesting fresh, delicious asparagus spears for many seasons, making the patience and diligence well worth it.
