Have you ever wondered what causes the difference in the diameter of asparagus spears, and whether the thick or thin asparagus is better? It has been widely reported that the thinner asparagus spears are the better, more tender version. However, that is not always true.
Table of Contents
Asparagus Plant Structure
To start off this discussion, let’s review the different parts of the asparagus plant.
- Crown – This is the part of the asparagus plant where new spears are created (the part of the plant that we eat), and from which the roots grow. Each new asparagus spear grows from a bud that forms on the crown. There are never two spears that grow from the same bud, so as the asparagus plant ages (and as long as the underground crown is not damaged from harvesting, insects or diseases), the crown grows larger and larger as more buds are created.
- Spear – Each piece of asparagus that grows from a bud is referred to as a “spear.” If the spear is not harvested in time, it will mature into a vegetative form of growth called a “fern.” The fern will grow large and produce lots of vegetative growth, which will photosynthesize to produce “food” to nourish the underground crown.
Below, you can see the crown of a 2 year old asparagus plant. When planted, the crown is always planted beneath the soil line. However, in this picture, you can see the structure of the crown and how the asparagus spears grow. You can also see where the soil line is located because everything above the soil line is green, and everything beneath the soil line is white.
How do Asparagus Plants Grow?
Asparagus plants are perennial plants, meaning that they grow for multiple years/growing seasons. Once they are planted in the ground, they will produce approximately:
- 15% of their total yield during year 2
- 60% of their total yield during year 3
- Up to 100% of their capacity from year 4 and onward
How Long Does the Asparagus Growing Season Last for?
When asparagus plants reach their full growing potential, their growing season lasts approximately 50 days, with harvest taking place each day. These plants can grow successfully this way for up to 8–12 years. When harvested tonnage from a field declines, a grower will normally deep chisel the field, and re-plant the asparagus field or rotate the field into another crop type.
How to Tell When Asparagus Spears are Mature & Ready for Harvest?
The spear diameter does not reflect the maturity of the asparagus spear, the tips do. The spears need to be harvested when they are mature or just a bit over-mature to still be marketable, meaning that the spears’ tips must be tight and firm, and not feathery or open. Timing of harvest, postharvest precooling, proper packaging and proper handling are required for the spears to make it to the store in the proper condition. See here for a guide on the different asparagus maturity stages.
You can tell the maturity of the spears by looking to see how tightly closed the tips are. For example, in the picture below, you can see that the scales on the tip of the spear on the left are tight and closed, while the spear on the right has continued maturing and is over-mature for fresh consumption.
Which is Better: Thick or Thin Asparagus?
The answer is that all sized diameter spears can come from the same plant, so there is no clear answer as to which is better. Throughout the growing season, spears continuously shoot up from the crown. Each spear shoots up from a separate bud, so no two spears will come from the same bud or be the same. When they do this, it can result in any size diameter. However, once you get near the end of the harvest season, it will be hard to find any of the larger jumbo and colossal spears (up to 1″ in diameter) because the crown has already expended most of its energy producing the larger spears during the initial stages of the season. For the specifics on how asparagus are graded, you can see the USDA Shipping Point and Market Inspection Instructions for Asparagus.
In the example below, you can see how the spears grow up out of the ground. All of the plants that were planted in this field were planted at the same time and have all been harvested at the same time throughout the growing season. However, there is no clear designated diameter.
When harvesting, the workers select spears that are the appropriate height and at least a certain diameter, while making sure not to cut too far below the ground to where they will damage the crown of the plant. When doing so, all of the following spears can be harvested from the same field at the same time. (Click here to see the full asparagus harvesting and packing process!)
The two asparagus spears in the middle are the common spears you find at the grocery store. The two larger examples to the far left and the far right are jumbo and colossal spears (13/16″ – 1″ in diameter) and are sold as a specialty product. If you take a look at the spears from another perspective (see below), you will see something unexpected. The thinnest spear is the most mature, which you can see based on tightness of the tips.
How to Pick the Best Asparagus?
You should look for a tight tip on the spear instead of the spear diameter. Also, check the bottom of the spears to ensure they are not shriveled, severely wrinkled, or not reasonably green.
Chefs normally select a specific diameter asparagus for a specific dish. For example, jumbo/colossal for steak dishes, and pencil spears for salads. There is a different specification for every preparation!
Regardless, make sure you prepare and consume your fresh asparagus as soon as possible after purchasing! Consumer tip: cut 1/2″ off the bottom of your asparagus bundles when you arrive home. This will reveal a fresh, green bottom of the spear. Then, place the bundle inside a large glass and add approximately 1/2” of water. Asparagus is very vascular and will absorb the provided moisture, similar to freshly cut flowers! This quick and easy measure will ensure a much fresher, longer-lasting and tastier bundle of asparagus at preparation time!
Special Thank You!
I would like to send a big thank you to Eric Sorensen, who helped contribute to this post. Eric is an agronomist with 40+ years’ experience in agricultural production/research, fresh produce wholesale and retail distribution, training, education, foreign consulting and possesses a renowned passion for all aspects of agriculture! He is also one of the greatest supporters of The Produce Nerd!
I would also like to thank JMB Produce and Mister Spear for letting me come and take pictures of their products to share in this post! JMB Produce is an asparagus shipper, and Mister Spear is a specialty supplier of the jumbo and colossal asparagus spears.
If you enjoyed this post, please share it!
You might also enjoy reading:
Really informative! I didn’t know any of this information about asparagus and always thought thinner was better. I’m curious as to how we can avoid asparagus that is woody/stringy making it unpleasant to eat/chew.
Thanks!