The sources behind this page do not name a single insect or animal that eats asparagus in Oregon, and they give no month for when one would show up. What they do establish is what the crop demands from Oregon ground and weather, and who gets the first bite: the gardener, and not until the third year. This page covers soil, summer water and planting dates. For the full picture, start with Growing Asparagus in Oregon.
The short answer
A bed planted this spring should still be producing in 10 to 15 years, which makes asparagus the one crop where you choose a spot once and live with it. Utah State University Extension, the only authority used here, asks for one thing from the soil: that it drains. Most soils will do, provided they are well drained. Nothing else is required of the ground.
What the state soil says
Oregon’s official state soil is the Jory series, adopted by state law. It is an Ultisol, which is an old, heavily weathered and leached soil, naturally acid and low in nutrients. The USDA records its surface layer at roughly 14 percent sand, 34 percent clay and 52 percent silt, with about 5.0 percent organic matter. The same record classes it as well drained.
That answers the main question. Despite the clay, the soil that represents Oregon passes the one test the crop sets. The surface pH averages about 5.6, slightly acid, but treat that as a description of the series and not as a target or a measurement of your yard. The extension source says nothing about pH, so no number is offered here.
When your ground is not Jory
The state soil is a starting point, not a diagnosis. Oregon spans hundreds of soil series, and a river bottom, a stretch of hill country or a lot a builder scraped and filled can behave nothing like the mapped series. The USDA figures describe the surface of the series as mapped, not a worked garden bed.
In most crops, a heavy soil is a nuisance you amend a little each season. Here it is a decision you cannot undo, because the crowns sit in the ground for a decade or more. If water lingers on your chosen spot long after a hard rain, don’t plant there. Pick higher or looser ground, or build the bed up above the wet layer. The longer discussion lives in Will Oregon Soil Hold an Asparagus Bed for Fifteen Years?. For your own number on nutrients and acidity, send a sample to a soil lab before the crowns go in.
Will the summer here water it for you?
No. Western Oregon’s summer is the dry part of the year, and the bed’s schedule assumes you will fill the gap yourself.
What June, July and August deliver
The NOAA NCEI normals for the Portland reference station show about 2.7 inches of rain across all three summer months, out of 36.9 inches for the year. June brings 1.63 inches. July drops to 0.51, the driest month, and August adds 0.54. Those are 30-year averages for one station, not a forecast, and a slope, a rain shadow or a city block can shift them.
The bed wants 1 to 2 inches every other week for its first two years, then every three weeks after that. Here is how that plays out against the rain:
- Count the rounds. A summer of about 13 weeks holds six or so every-other-week rounds, which works out to roughly 6 to 12 inches in the first two years. After that, every three weeks gives four or five rounds.
- Subtract the rain. About 2.7 inches covers a fraction of that, and nearly all of it falls in June.
- Look at July by itself. Its half inch is less than a single round at the low end.
- Add the difference with the hose or drip line. In the early years that is several inches over the season, and the figure shrinks once the schedule stretches to three weeks. This is my arithmetic from the figures above, not a published irrigation total.
- Put a rain gauge on the plot. It beats any normal.
Why heat and clay change the math
A clay surface holds water for days, so deep, infrequent rounds suit a Jory-type soil, while a sandy bed would drain through within a day. Hot days at or above 90°F pull water out faster. A single summer thunderstorm mostly runs off instead of soaking in, so a heavy shower does not count as a full round.
When to put the crowns in
Crowns go in during early spring. For the Portland reference station, NOAA NCEI puts the last 32°F freeze at around March 6 to March 21. That is the band where the odds of a freeze are between 30 and 70 percent, an average and not a promise, so a late cold night in April is still possible.
Around the frost window
Portland sits west of the Cascades. Central and eastern Oregon are high desert with a far shorter season, so do not apply this window statewide. A frost date for those areas is not published here. The finer timing question gets its own page: When to Plant Asparagus Crowns in Oregon.
The crowns go into furrows 8 inches deep. You do not fill the furrow all at once. Backfill gradually across the year, 2 inches every other month, as the plants grow up out of the trench.
Then comes the waiting. Do not harvest in the first two years or the third spring. From year 3 on, the first picking season runs 4 weeks, then 6 the next year, then 8. Stop when most spears are thinner than a pencil. That is the signal, and no calendar date replaces it.
The source names four varieties and gives only their sex. Jersey Giant and Jersey Knight are all-male. UC 157 F1 and Purple Passion are male and female. It publishes nothing on flavor or yield, and no reason to prefer one, so choose on availability.
Starting from seed instead
Seed is the alternative to buying crowns. The sources used here carry no seed-starting date and no seed harvest schedule, so none is invented. Starting from seed means raising the plants yourself first, so it is sensible to assume the first harvest lands later than with crowns.
Common questions
What eats asparagus in Oregon, and when?
The sources behind this page identify no pest and no season for one. Your county Extension office is the right place to ask what is chewing on a bed in your area. The one eating schedule published here is yours: nothing in years one and two, then 4 weeks in year 3.
When can I first pick spears?
Not until year 3, and not a few spears early. Year 3 gets 4 weeks, the next year 6, the next 8. End each season when most spears are thinner than a pencil.
How do I keep cut spears fresh?
UC Davis Postharvest lists the optimum at 32°F to 35.6°F with 95 to 100 percent relative humidity (UC Davis Postharvest Technology Center). Above 50°F, spears toughen rapidly. At about 31°F or lower, they freeze and go soft on thawing. In a kitchen, stand the cut ends in water, since moisture leaves fastest through the cut end.
Do I need to know my soil pH first?
The extension source gives no pH figure for asparagus, so there is no number to aim at. The Jory surface value of about 5.6 describes the state soil series, not your bed. A soil test gives you your own reading, and drainage, not acidity, is the stated requirement.