When Does Asparagus Grow? (Plus How Much You Can Harvest)


Are you looking for information on when asparagus grows and how much you can harvest?  It is helpful to know when plants grow as you plant your garden, so I’ve put together some information on this topic.

So, when does asparagus grow?  Asparagus spears start to grow up from the crown in early spring when soil temperatures reach 50 degrees Fahrenheit (10 degrees Celsius).  They continue to grow throughout the spring and summer.  Asparagus spears only stop growing in fall after frost kills them.  Usually, you harvest asparagus during late spring, in May and into June.

Of course, the amount of asparagus you can harvest depends on many factors, such as plant age.  In this article we will take a closer look at:

  • when asparagus grows
  • the best time to plant asparagus (there are two methods you can use!)
  • how much asparagus to expect from your harvest (it depends on the age of the plants!)

Let’s get going.

When Does Asparagus Grow?

According to Wikipedia, asparagus is perennial, which means that it lives longer than two years.  In fact, with proper care, asparagus plants can live and produce a healthy harvest for decades!

asparagus plants
Asparagus is perennial, meaning it will come back year after year – sometimes for decades!

The roots of asparagus grow underground, and the crown grows at ground level.  Both of these parts survive the winter each year, while the spears die back in the fall after frost.

When Should My Asparagus Come Up?

According to the Old Farmer’s Almanac, the stalks (spears) of asparagus begin come up from the crown when soil temperatures reach 50 degrees Fahrenheit (10 degrees Celsius) in the spring.

You can harvest from a mature plant (older than 3 years) for 6 to 8 weeks, usually during May and June.

Asparagus spears continue to grow during summer and into fall.  The tips of asparagus spears eventually “open up” and start to look like ferns as they mature.

These ferns have two purposes.  One purpose is to “go to seed” in an attempt to reproduce and make more asparagus plants.

asparagus
Asparagus ferns produce energy for the plant to store in the roots for next year’s growth.

The other purpose is to make energy for the plant by photosynthesis.  The energy from the ferns is stored in the roots and crown, to be used for making next year’s spears.

For this reason, you should not harvest too much from your asparagus plant.  Otherwise, it will not have enough energy to make next year’s spears (more on this later).

Does Asparagus Return Every Year?

Yes, asparagus will return every year, since it is perennial.  The roots and crown of the plant will survive the winter, even in freezing temperatures.

However, frost kills asparagus ferns (spears), which will start to turn yellow and brown as they die.  Cold and frost causes the plant to go into dormancy for the winter.

You can cut back the foliage on an asparagus fern after it turns brown.  However, don’t cut the foliage while it is still green, or you will deny the asparagus some of the energy it made!

What is the Best Time to Plant Asparagus?

You have two options when planting asparagus.  You can either:

  • start them from seed indoors and transplant outside later (more difficult and time-consuming)
  • buy crowns and plant them

Let’s take a look at both methods and when to use them.

Best Time to Plant Asparagus Seeds

According to the Oregon State University Extension, asparagus seeds germinate best at soil temperatures of 75 to 80 degrees Fahrenheit (24 to 27 degrees Celsius).

If you start asparagus from seed, you should start them indoors 10 to 12 weeks before you transplant outside.

According to the Old Farmer’s Almanac, the best time to transplant asparagus is just after the last spring frost.  You can use this tool from the Old Farmer’s Almanac to find the frost dates in your location.

For example, in Boston, MA (close to where I live), the last spring frost date is April 10.  Let’s say I want to wait until April 15 to transplant outside, to be safe. 

Let’s also say I want to start asparagus seeds 12 weeks before I transplant.  Then I need to count backwards 12 weeks (84 days) from April 15.

This leaves me with a date of January 20 to start my asparagus seeds indoors.   To check the math: 10 days in January, 28 days in February, 31 days in March, and 15 days in April gives me 10+28+31=15 = 84 days.

Just remember that when you start asparagus from seed, you will need to wait another year for a harvest!

Best Time to Plant Asparagus Crowns

If you decide to buy asparagus crowns, you should plant them as soon as the soil can be worked in the spring.  (This means wait until after the soil is no longer hard from frost, so that you can dig easily).

Asparagus crowns are more established than seedlings, so they will produce a harvest sooner.  You can buy asparagus crowns from a seed company such as Stark Brothers.

When you choose asparagus plants, ask for 1 year old crowns.  Older crowns may be damaged or diseased.  They will also be more difficult to transplant successfully.

How Long Does Asparagus Live?

According to the University of New Hampshire Extension, asparagus can produce spears for 10 years or longer!

In fact, the University of Massachusetts at Amherst suggests that asparagus plants can live and produce spears for 25 years or more!

Of course, this assumes proper care for the plants and restrained harvesting of spears.  If you don’t care for your plants or harvest too many spears, then they may succumb to disease or produce poorly.

How Much Asparagus to Harvest?

As mentioned earlier, you need to be careful about how many spears you harvest from your asparagus plant.

If you harvest too many, the plant will be left without enough energy to make next year’s spears.  The plant may even succumb to disease if it does not have enough energy to stay strong.

asparagus
If you harvest too much asparagus in a year, you will get fewer spears the next year, especially from younger plants.

You should not harvest anything from your asparagus plants for the first year or two.  Remember to add an extra year if you start your plants from seed!

This gives your plants time to store energy (in the roots and crown) to establish themselves.

Here is an outline of how much to harvest from asparagus plants, based on age:

  • 1st year: no harvest.  Let every spear grow into a fern.  These ferns will store all of their energy in the roots.  (Make a short-term sacrifice for a long-term gain!)
  • 2nd year: harvest for up to 1 week.  Let most of the spears grow into ferns so they can store their energy in the roots.
  • 3rd year: harvest for 2 to 3 weeks.  After that, let any remaining spears grow and store their energy for the future.
  • 4th year and later: harvest for 6 to 8 weeks.  After that, let the rest of the spears grow and store energy.

According to the University of New Hampshire Extension, you should harvest asparagus spears when they are 6 to 8 inches (15 to 20 centimeters) tall.

You can also look at the thickness of the spears to decide when to stop harvesting.  If the new spears that emerge are less than 0.5 inches (1.25 centimeters) in diameter, then leave them alone.

For a mature plant, you will usually begin the harvest in May and end in June (6 to 8 weeks).  Asparagus does not store for long, so be sure to eat it fresh and plan some meals around it during harvest time!

How Much Asparagus do You Get from One Plant?

As mentioned earlier, the amount of asparagus you get from one plant depends on its age.  You can get much more asparagus from a mature plant (older than 3 years) and not have to worry about weakening the plant.

The amount of asparagus also depends on whether the plant is male or female:

  • Female asparagus plants put some of their energy into producing red “berries” (containing seeds).  As a result, they have less energy to produce spears.  You can learn more about the red berries on asparagus plants in my article here.
  • Male asparagus plants do not produce berries.  As a result, they put all of their energy into spears to make more of them.  In fact, male plants can produce up to 3 times as many spears as female plants!
asparagus berries
Female asparagus plants produce red “berries” that contain seeds. This helps the plants to reproduce, but it costs energy. This means fewer spears from female plants.

The Old Farmer’s Almanac suggests that you can expect about 0.5 pounds of asparagus from each foot of row of plants.  This assumes that you space the plants 18 inches (45 centimeters) apart.

For example, let’s say you plant a row of asparagus that is 15 feet (180 inches) long.  That means you will have 10 plants, spaced 18 inches apart.

Harvesting 0.5 pounds of asparagus spears per foot, times 15 feet, would give you 7.5 pounds of asparagus for the season.

Another rule you can use is to plant about 6 asparagus plants per person (or more if you like asparagus!)  Of course, the plants will produce more as they mature beyond the first few years.

Does Asparagus Regrow After Cutting?

Yes, asparagus does regrow after cutting.  It will continue to send up new shoots (spears) until it runs out of energy or enters dormancy due to frost in the fall.

However, if you harvest too aggressively, your asparagus plant will not have enough energy to produce many spears next year.  Young plants will also fail to develop the root system and store the energy they need.

Should You Let Asparagus Go to Seed?

Yes, you should let asparagus go to seed.  It is perfectly normal for this to happen.

It is also necessary, since asparagus ferns need to grow and make energy.  This allows the plant to store enough energy to make next year’s spears.

Remember that asparagus plants can easily grow to a height of 7 feet (1.5 meters) tall!  You can learn more about the size of asparagus plants in my article here.

When asparagus ferns grow this tall, they often start to bend or fall over.  This is more common in windy conditions.

You can let them fall, or you can support them or cut them back to keep it from happening.  For more information, check out my article on how to prevent your asparagus plants from falling over.

Conclusion

Now you know all about when asparagus grows.  You also know when to expect a harvest, and how much to take each year.

I hope you found this article helpful.  If so, please share it with someone who will find the information useful.

If you want to read some of my most popular posts, check out the “Best of GreenUpSide” page here.  Enjoy!

~Jonathon

jonathon.david.madore

Hi, I'm Jonathon. I’m the gardening guy (not guru!) who is encouraging everyone to spend more time in the garden. I try to help solve common gardening problems so that you can get the best harvest every year!

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