Stop cutting when most of the spears coming up are thinner than a pencil. That is the plant telling you its reserves are spent. Spears you have already cut last longest at 32°F to 35.6°F in air close to saturated, and they fade quickly outside that range.
Keeping it, and for how long
What temperature keeps asparagus best?
The UC Davis Postharvest Technology Center sets the target in its asparagus fact sheet: an optimum temperature of 0°C to 2°C, which is 32°F to 35.6°F, with relative humidity of 95 to 100 percent. That is nearly saturated air. The sheet adds that high humidity is needed to prevent desiccation. A spear is a young, wet shoot, and it loses water fastest through the cut end.
Both edges of that window bite. Above 10°C (50°F), the sheet says, spear toughening occurs rapidly. A spear left on the counter on a warm afternoon is already getting stringy by evening. At the cold edge, freezing injury is likely at -0.6°C (30.9°F) or lower. The spears take on a water-soaked look and then go extremely soft. Most gardeners know this as the bundle that looked fine in the fridge and turned to mush in the pan.
Look at how little room there is. The gap between “stays crisp” and “freezes” is barely more than a degree at the cold end. At the warm end, the spears have about 14 degrees of slack between the top of the optimum range and the point where toughening takes off. Those spears have the best chance in a fridge that holds steady near 32°F to 35°F and never touches the freezing line.
How long will cut asparagus keep?
Any number of days you see quoted for fresh spears is a ceiling, reached only when the temperature and humidity above are both met from the moment of cutting. Miss on either one and the days shrink. Spears cut on a warm morning and left on the porch while you finish the row have already used some of their time before they reach the fridge.
So treat the clock as short. Cut in the cool of the morning and get the spears cold within the hour. Cook or eat them soon after, since the best flavor and texture come from the freshest ones. A garden is the one place where “same-day” asparagus is easy, and the shortest route from bed to plate is the best storage method there is.
Cold, wet and quick also covers the freezer question. The freezing-injury warning applies to fresh spears held in the fridge, not to spears you blanch and freeze on purpose. A fridge that drops below the freezing line is simply a fault, and it ruins a bundle.
Where in the house that actually is
Which fridge shelf comes closest to the optimum?
A household fridge is usually set warmer than the top of that range, and the door runs warmer still. Every time the door opens, that shelf takes the room’s air first. Skip the door for asparagus.
The coldest, most stable spot is generally the back of a lower shelf, or the crisper drawer if it holds steady. Cold air blowing straight from a vent can freeze produce, so if lettuce near the back wall ever turns glassy, keep the spears a few inches forward. An inexpensive appliance thermometer set on that shelf for a day tells you the real number. Many fridges sit a few degrees off their dial setting.
How do you get 95 percent humidity at home?
A fridge is a drying machine. Its cold air is dry, and it pulls moisture out of anything left uncovered. Reaching 95 to 100 percent means building a small, wet pocket around the spears. There are two ways to do it, and they work the same way: keep the cut ends wet and the tips from drying out.
- Stand the bundle upright in a jar or glass with about an inch of water under the cut ends, and loosely cover the tips with a bag.
- Or wrap the cut ends in a damp paper towel and slip the whole bundle into a perforated or loosely closed bag.
Standing the butts in water is the step to keep. Skip it and the spears lose water through the cut ends faster than anywhere else, and they turn limp and woody. Change the water if it clouds. Keep the bag loose so condensation doesn’t pool on the tips.
Common questions
When do I stop cutting asparagus each season?
Watch the spears. When most of the new ones are thinner than a pencil, stop and let them grow into ferns. Early in the season, spears come up thick. As the bed tires, they thin out. The cap on the cutting period grows with the bed’s age: four weeks in the first harvest year, six the next, then eight. Frost can still arrive late in the spring. The reference station’s last 32°F frost falls between May 7 and May 18 (the 30 to 70 percent probability band), and at higher elevations frost can come in any month. The reference station has about 130 frost-free days at 6,000 feet, so season extension helps more than a calendar date does.
Can I cut a few spears before the third year?
No. Asparagus is planted as crowns in 8-inch furrows in early spring and is not harvested until year 3. After that, a bed produces for 10 to 15 years. If you want the bed to last that long, the first two years belong to the plant. Growing Asparagus in Wyoming covers planting and the early years in more detail.
What should I do with the plants after the last cut?
Let the remaining spears grow into ferns and leave them standing. Summer rainfall at the reference station comes to about 5.8 inches across June, July and August (2.16, 2.11 and 1.52), and August is the driest month. That is what the region can usually expect, and a rain gauge in your own bed settles the question. Soil changes the answer. The state’s representative soil, the Forkwood series, is a well-drained loam to silt, but your own garden may differ, so a soil test is worth the small cost. Will Wyoming Soil Hold an Asparagus Bed for Fifteen Years? goes through the drainage question. Ferns are also where pests show up, which What Eats Asparagus in Wyoming, and When covers.
Which variety should I plant?
Your county extension office can tell you what local gardeners have had success with, which matters more than a catalog description when the bed has to last for 10 to 15 years.