Learn how to grow asparagus from crowns and seeds. Asparagus is the most worry free perennial plant for the home gardener. If you have bought some lately, then you know how expensive it is. We will be talking about bed preparation and selection, transplanting, harvesting, mulching, propagating, and preserving asparagus.
After the initial investment of purchasing crowns, you can propagate asparagus from the seeds they produce. A crown is the plant roots that arrive ready to go in the ground.
You can save money by purchasing only a few crowns and then increasing your asparagus production by planting the seeds.
You should order or purchase your asparagus crowns from a garden supplier you trust. You can order seeds or crowns it just depends on how you want to get your bed started.
Be sure to plant them in the place you want them to be because once planted, they will produce for 20-30 years and repeat transplanting is not good for any plant.
Growing Asparagus from Crowns and Seeds
Asparagus is a perennial vegetable grown for its delicious young shoots. It is rich in B vitamins, vitamin C, calcium, and iron.
Asparagus is one of the first crops ready for spring harvest. We start cutting ours in early March.
This year it had produced quite a few before I realized it was even up. I actually found it by accident when I was checking the mulch level of the garden in preparation for spring planting. It was a welcome, delicious surprise!
Male vs Female Plants
Asparagus plants are monoecious, meaning each individual plant is either male or female. Some varieties of asparagus, such as ‘Jersey Knight’ and ‘Jersey Giant’ produce all male or primarily male plants, so they’re more productive.
Male plants yield more harvestable shoots because they don’t have to invest energy in producing seeds. If a higher yield is your goal, then you should choose an all-male variety, but even then you may get a female or two.
If you want to propagate your asparagus using its seeds, you will need a female plant.
We planted Jersey Knight and of the 15 I planted, 3 were female. This is fine with me since I have learned to propagate the seeds to increase my plot. We still have a high enough yield for us.
If you prefer an heirloom or purple-stalked variety, you may like ‘Purple Passion’.
How Much Asparagus Should You Plant?
- With an all-male variety, 25 crowns is usually adequate for a family of four.
- If you are planting a standard variety, one with both male and female plants, it will take 50 plants for a family of four.
- An asparagus lover may want to triple these numbers.
We started out with fifteen for the two of us about 4 years ago and this year I am transplanting about 30 more that I started from seed.
Since I started them from seed, it will be 2-3 years before I can harvest from them.
You will find that fresh-picked spears are far more tender and tasty than store-bought ones. The flavor doesn’t even compare.
Where Can Asparagus Grow?
Asparagus thrives in just about any area where you have freezing temperatures in the winter and a dry season in the summer.
The mild, wet regions of Florida and the Gulf Coast are about the only places where it’s difficult to grow, and even there it’s doable with a little work and ingenuity.
Soil and Sun Needs For Growing Asparagus
Asparagus needs loose, compost-rich soil. It does best in lighter soils that warm up quickly in spring and drain well.
Standing water will quickly rot the roots.
It can withstand some shade, but it really prefers full sun. You want to be sure your site is in an area where it will not be endangered when you cultivate your garden.
We transplanted ours directly in our garden at the far end, so as not to interfere with other gardening tasks. It is always in the direct sun and produces abundantly from March until around the end of September.
In hindsight, I wish I had put them in a raised bed. When I plant the ones I’ve propagated from seed, I will put them in a raised bed next to the garden.
Some people do soil tests and amendments based on the results they get. If you are new to gardening or if you like the scientific approach to the best gardening soil, this is a good way to improve your soil.
We don’t do that and in all my years of gardening, I have never had an issue. We are constantly working on improving our soils with the techniques we learned from our grandparents. We deep mulch our garden and raised beds, add compost, vermicompost, and organic fertilizer from our farm.
Prepare the Planting Bed for Asparagus Crowns
The planting bed or row should be at least 4 feet wide. Remove all weeds and roots from the bed where you will be planting your crowns.
Now is the time to add plenty of aged manure or compost as well. Pretty much like you would any bed preparation. The bed preparation is the same for seeds or crowns.
Asparagus has a strong root system that spreads as much as 6 feet horizontally and can go 6 to 8 feet down.
When to Plant Asparagus Crowns
Knowing when to plant asparagus is critical for a successful and bountiful harvest. It all depends on your growing zone. Asparagus requires strategic timing that balances soil temperature and the growing season.
Typically, the best time to plant asparagus crowns is during the early spring or late fall when the soil temperatures are around 50 to 60 degrees Fahrenheit (10 to 15 degrees Celsius), but the weather is still relatively cool. This allows the young plants to establish their roots and become hardy before the rush of the growing season begins and they face the summer heat or winter cold.
It’s essential to avoid planting too early in cold soil or too late when the soil becomes too warm, as this can hinder the plant’s development. By adhering to the optimal planting window, you can set the stage for a thriving asparagus bed that will yield delectable harvests for years to come.
We plant our asparagus crowns and plants started from seed in the fall because we feel they are stronger and healthier by the next growing season than those planted in the spring. This is because of the amount of time they have had to establish themselves.
How to Plant Asparagus Crowns
Some people say “transplanting” instead of “planting” and others, like me, use both terms. There’s a reason for both positions, but I find it is really a matter of semantics.
Crowns are roots that have been dug up and shipped for “transplanting” but most people understand this when you say you “planted” asparagus.
Asparagus seeds have to be planted so deep that their development is impeded. To get around this and have a productive propagation, seeds are started the same as any other seed in cups and then transplanted into the garden. So I don’t think it matters much which way you say it.
Once your bed or rows are prepared
- You will plant the asparagus crowns in the middle of the bed.
- Dig a trench 12″ deep down the middle of your 4-foot row.
- Trenches should be 4’ apart.
- Plant crowns 1 – 2 feet apart in the middle of the row.
- Cover the crown with about two inches of soil.
- As shoots emerge, cover them with another 2″ of soil, continuing this pattern as the plants grow, until the soil level reaches the top of the trench.
- In very sandy soils, you will probably be okay filling in the trench when you plant the crowns, but you must be sure your soil is “very sandy.”
- Plant in spring or, in milder climates, late fall/early winter.
Age of Crowns
Growing asparagus from 1-year-old crowns gives you a year’s head start over seed-grown plants.
Two-year-old crowns may seem enticing, but they tend to suffer more from transplant shock and by the time they recover, they won’t have produced any faster than 1-year-old crowns.
You need to let the asparagus put down its root system and become established before you can harvest. This will be 2 – 3 years. We’ll talk more about this in just a bit when we look at harvesting asparagus.
I have been asked about transplanting or moving mature crowns to a different location. While technically this is possible, my advice on that idea is to forget it!
Crowns more than two years old are generally huge and it is very difficult to get them out of the ground in one piece. The transplant shock is very great for these more mature crowns and the end result is that the moved crowns usually die.
Even if they don’t die immediately, you are probably moving, along with the crown, the root rot organisms that almost always infect them. In their weakened condition, the crowns will fall victim to the disease more quickly.
General Care of Asparagus
Asparagus is a heavy feeder. You will need to improve the soil quality or use an organic fertilizer.
You will probably have a harvest without it, but your yield will be far less than if you have healthy, rich soil.
In Carla Emery’s Encyclopedia of Country Living, she says manure is best and compost second best. I have my bed mulched 4-6 inches so I really don’t spread either in there. Instead, I use compost tea and add water to wood ash, and pour these over the bed. It produces well for us.
Otherwise, asparagus is relatively task free.
When to Harvest Asparagus
The asparagus plant needs to grow and establish a healthy crown which requires all of its energy. They need to put all their energy into establishing deep roots.
To help your asparagus be healthy and productive for years to come, do not harvest your asparagus the year you plant it and, preferably, not the second year after planting either.
You can harvest lightly in the 2nd year, but it’s best to allow most spears to set ferns. Uncut spears will become ferns as they mature.
During the third season, harvest lightly leaving some to set ferns.
“Lightly harvest” means you take only the shoots that are 1/2″ or greater in diameter.
By the fourth year, you can extend your harvest to the full season.
Harvest spears when they are 4 to 6 inches high and just before the scaly section at the tip begins to open (see the first picture above).
As the weather warms, you might have to pick twice a day to keep up with production.
How to Harvest Asparagus
Cut asparagus spears with a sharp knife or use your fingers to snap off the spears at, or right below ground level. I prefer to cut mine at ground level.
They will snap off at the woody portion. The woody portion is the part that is maturing and develops a wood-like texture. It is not edible.
It’s best to harvest in the early morning since the hot sun makes the spears tough.
You should check your bed at least every two days. I go to mine every day and almost always get some.
You must harvest every spear of appropriate size or your plants will produce flowers and this will stop further shoot production from that crown (root).
An established bed can be harvested until late fall, but the first few years of harvesting, say years 4-6, you should let the spears set ferns after about 12 weeks of harvest.
I know this sounds like you will be missing out on some good eating. Like most gardeners, I hate to let the fruit sit in the garden unharvested, but it will benefit you in the years to come.
Remember, you will be harvesting from your bed for at least 20 years!
Whips and When to Stop Harvesting Asparagus
Whips are tall slender spears and are generally higher in fiber and so tougher to eat than thicker spears. Most of the fiber in asparagus is in the skin. You can harvest these also. The larger spears are more tender than the slender whips.
If you notice the number of spears in a harvest drops off dramatically, or if the spear diameter drops to only whips, you may want to consider ending the harvest early. These are good indications that the crown is experiencing some stress.
The fern is the “factory” that supplies energy to the crown and storage roots for the next year’s crop. It takes a great deal of energy to perform this task.
Throughout the post-harvest growing season, keep your ferns healthy by never pruning or cutting them back.
You don’t want a lot of new fern growth towards the end of the season so you need to stop any fertilizing and watering early to late fall depending on your gardening zone. Here in the deep south, gardening zone 8, I usually let them rest after September.
Production naturally slows down around that time so I take the queue it gives me and let it rest without harvesting.
In late October, or early November, depending on the overall health of the plants and the weather, I cut it off even with the ground.
Just a side note: I used to think white asparagus was a variety, but it is really just the very young spears before they green up in the sun. Some people like them because the flavor is milder. We really don’t care for it since we prefer the flavor of the mature spears.
Mulching the Asparagus Bed
Weed control is very important in successfully growing asparagus. This is especially so in the first couple of years after transplanting, when the young crowns are the most vulnerable.
Don’t mulch your very young plants. They may have trouble growing through it. I spread just enough leaves around my young ones to keep them from overexposure to heat and keep some moisture in.
Mulch should be 4-6″ deep around mature plants. We use leaves for our mulch. Sometimes we chop them up with a mulching mower and sometimes we leave the whole.
You can also use some wood chips but be careful. They may contain bugs or fungus which could harm your asparagus. We sometimes use oak chips but that’s about it.
Some people prefer wood chips in mulch. Everyone has to decide for themselves what works with their plan and goals.
How to Grow Asparagus from Seed
Asparagus seeds have to be planted deep which impedes their development. To get around this and have productive propagation, seeds are started in cups or trays the same as any other seed. Once they are large enough to go to the garden, transplant them to the bed you have prepared for them.
Starting or increasing your asparagus patch from seed takes a little patience, but there are advantages.
- Seed-grown plants don’t suffer from transplant shock like the roots (crowns) grown at the nursery.
- Seeds are considerably more cost-effective. You can buy a whole pack of seeds for the cost of one crown and if you save your seed from your existing bed, they are free.
- Most seed-grown asparagus plants will out-produce root-grown ones in the long run.
We have had great success in increasing our asparagus bed by saving seeds and starting seedlings.
I am told you can discard the females and keep the males when growing from seed. I’m still learning how to tell them apart when they are seedlings.
So for now, I am planting whatever sprouts and hoping for the best. If I have too many females, I can always remove them from the bed.
This is the best information I have found on telling them apart: “When tiny flowers appear, observe them with a magnifying glass. Female flowers have well-developed, three-lobed pistils; male blossoms are larger and longer than female flowers.”
I’m still looking for a better way to tell.
How to Save Asparagus Seeds
I followed Carla Emery’s advice to save my own seeds and it worked well.
In the late summer or early fall, when the female berries have turned red, cut the fern, leaving the berries intact on the stem, and hang it upside down in a cool, dry place.
I hung mine in a room in our house where I store things like jars, preserved foods, and such. We don’t heat this room so it works well for tasks like this.
In late February, soak them in room temperature water for a couple of days then plant them in seed starter cups of organic soil. We mix ours from compost, sand, and soil here on the farm.
Once they have a strong root system, plant them in the asparagus bed in the garden.
I have read that you should put them in a seedbed and transplant them the following spring.
Carla said you can plant them directly to your permanent site from a seed flat when the plants are well-rooted. I wanted to avoid any root shock so I planted mine directly in the existing bed I had prepared for them. It was very successful.
The best ways to preserve asparagus are by freezing it, pickling it, or canning it.
To freeze asparagus:
- First, you must Blanch it. In a large pot bring 4 quarts of water to boil. I would suggest using filtered water so the chlorine and fluoride in municipal water supplies do not cling to the spears.
- Add up to 1 pound of asparagus spear to the boiling water and let boil for 2-6 minutes. If you have thinner spears boil for closer to 2 minutes, thicker spears go up to 6 minutes.
- You can also blanch asparagus spears by steaming them for freezing. Steam for the same amount of time as for blanching with boiling water. Follow steps 4-7 once the steaming time is up.
- When time is up, immediately remove them from boiling water and place them in ice-cold water.
- Leave them in the ice water bath for the same amount of time you blanched them.
- Drain them well on a clean dishcloth
- Place the number of spears you want for a meal into a freezer bag and place it in the freezer. They will keep longer in the freezer if you first warp them in parchment or wax paper before placing them in the bag.
- If you don’t want your spears to stick together, you can lay them on a baking sheet so that they do not touch one another and place the tray in the freezer. Once completely frozen, place them in the bag and return to the freezer. They will keep longer in the freezer if you first warp them in parchment or wax paper before placing them in the bag.
To Can Asparagus:
To make canning asparagus worthwhile you must have a lot of plants or purchase some at the Farmer’s Market to mix with yours.
You must pressure can asparagus.
- Add 2 quarts of water to a large pot and bring to a boil. If you have a lot of spears to can, you will want more water. This is to pour over your prepared spears.
- Bring a small saucepan of water to a boil and add your caps (seals) to the hot water.
- While the water is boiling, wash the asparagus spears and break off any woody portion. You can find this section by taking the spear at both ends and gently bending it. The spear will snap at the woody section. Your chickens or pigs will love the woody parts or you can add them to your compost pile.
- Cut the spears so they are not longer than 6″. This allows for the 1″ head space required in canning.
- Lay a clean, sterilized quart jar on its side. This makes it easier to slide the spears and use all the space available in the jar.
- Fill the quart jar until you can squeeze in no more asparagus spears. Put them in the jar with the tip of the spear pointing up or the narrowest end if you had to cut them to 6″.
- Do not leave a lot of room in the jar because they will shrink when processing and may float above the water when canning.
- Stand the jar upright and add 1 teaspoon real salt to each jar.
- Cover the asparagus with boiling water being sure to leave a 1″ head space.
- Place a cap and ring on each jar and close tightly.
- Process quart jars in a pressure canner at 10 pounds of pressure for 40 minutes. If you have a dial gauge canner, use 11 pounds of pressure.
- Adjust pressure and time for your altitude.
- After the time is up, remove from heat and allow the pressure to release naturally until it at zero.
- Use a jar lift to remove the jars from the canner and place them on a clean towel to cool.
- Once you have that delightful “Ping” for sealed jars, you can loosen or remove the rings to prevent rust under them which makes it difficult to get a jar open.
- If you have a jar that doesn’t seal, let it cool completely and then put it in the refrigerator. It will be good for up to a week. You can test the seal by pressing the very center of the lid. If it moves up and down when you press it, it is not sealed. If it doesn’t move, it’s properly sealed.
Our favorite recipe for Pickled Asparagus is not my own. It is a delicious way to preserve asparagus.
Once you cut the spears, wash them and pat them dry.
Place them in an air-tight container in the refrigerator. A baggie, vegetable bag, or a glass jar with a tight lid, works just fine.
They will keep fresh for about a week, so you can add to it after each cutting until you get enough to cook.
Of course, this depends on the size of your family and the number of plants you are harvesting from.
We like to eat it raw on our salads, or just as a veggie with our meal. We like to steam it, this takes 15-20 minutes depending on how tender you want it.
What’s your favorite way to eat asparagus?
I hope this helps you establish a healthy, delicious asparagus bed of your own. Have more questions? Feel free to get in touch.
As always, I’m here to help.