Asparagus Overview & Top Tips
- Long-lived perennial plants produce for years, but only if they are planted properly.
- Plant new crowns 4-6 weeks before the last average frost date.
- No harvesting spears the first or maybe 2nd year. Plants must be established first.
- Allow all spears to grow into ferns. Removing in the fall after killing frosts.
- Prevent weed competition by hand cultivation and utilizing compost or mulch.
- Plant 10-20 crowns per person in the household, to have enough for good harvests.
Asparagus - Female vs Male Plants
- Types: Many varieties and hybrids exist. Asparagus are dioecious, meaning there are separate female plants and male plants. Many named hybrids are predominantly male plants.
- Female plants like 'Mary Washington' can produce seeds and seedlings.
- Male selections produce no seed, allowing more energy to go into spear production. Generally, male selections produce thicker spears and plants produce more consistently in optimal conditions, which is why male varieties are preferred by commercial growers.
Asparagus Planting Instructions
- Asparagus crowns should be planted within days of receiving them as soon as soil can be worked or about 4-6 weeks prior to the last average frost date. Do Not wait until after your last frost date to plant.
- Dig a trench 12-15 inches deep and about 12 inches wide in well-drained soil.
- Blend ample amounts of organic material blended with the natural soil. Remove competitive weeds, especially perennial rooted types.
- A phosphorus fertilizer like superphosphate fertilizer (0-20-0) or Espoma® Bone Meal (4-12-0) is beneficially blended in at the time of planting. An application rate of 2.5 to 5 lbs. per 100 sq. ft. is recommended.
- After digging the trench and amending the soil, backfill the trench about 1/3 full, mounding the soil higher in the middle.
- Place crowns right side up, with roots spread out over mounded backfill, and cover with only 3-4 in. of soil, then water thoroughly.
- As new shoots appear and grow, additional soil mix will be carefully added to eventually fill the trench.
NOTE: Do Not fill the entire trench to the top, as this will be too deep.
- When the crowns sprout, grass-like thin spears will grow. When those reach 2-3 inches tall, you will then carefully cover them with more soil. As shoots continue to grow, keep adding soil until the trench is full.
NOTE: First-season spears must be left to mature into ferns.
- Asparagus plants gain sustainable energy from growing into ferns. Once those ferns naturally brown out from frost in fall, they can then be cut off down to the ground.
- Planting two to three beds of asparagus will ensure harvestable crops each season from alternating beds. While you harvest from one bed the other bed can grow and rest.
Asparagus Planting Companions
- Do not plant next to - Alliums (leeks, garlic, onions) or Potatoes
Asparagus Harvesting Tips
- Never harvest spears that have diameter smaller than a ¼ inch. (approx. #2 pencil)
- At harvest, spears should be at least ½ in. diameter.
- If spears are not large enough, let those spears grow into ferns again.
- The first season harvest is recommended for about 2 weeks.
- Each season after you can extend the harvest by adding about a week.
- The health, production and vigor of the patch will dictate how long to harvest.
Asparagus Fertilizing Tips
- Top-dress asparagus beds in early spring and again in mid-summer after harvest with 2 to 3 inches of aged manure or fresh compost.
- For side-dressing, use 1-2 lbs. of Espoma® 10-10-10 fertilizer for a 10 ft. row along each side.
- Then cover that with a good mulch product like clean straw or marsh hay.
- Grass clippings can also be used as mulch to help retain moisture and suppress weeds, but do not apply them more than 2 in. thick, and never use clippings from lawns treated with any "Weed & Feed" products.
Asparagus Troubleshooting Guide
Issue: Spears growing too thin.
Cause: Over harvesting or lack of adequate nutrition.
Solutions: Stop harvesting. Allow spears to grow into ferns to build up more energy again. Have soil test done to assess soil nutrition properly and thoroughly. Make fertility adjustments according to soil test results.
Issue: Yellowing leaves.
Cause: Poor drainage, and/or over-watering.
Solutions: Avoid issues by improving soil drainage prior to planting. Once planted and established all you can do is allow soil to dry more between waterings.
Issue: Brown, weak or spongy spears.
Cause: Typically caused by frost in early spring, or later in season can be sign of fungal issues.
Solutions: Watch weather closely and cover newly emerging spears with frost cloth or cover will with clean straw to protect against potential late frosts. Root rot or fusarium can cause problems on established beds. Ensure proper drainage to avoid rot issues. Fusarium is stubborn, incurable soil-borne disease that must be tested for. Send samples to university plant pathology lab if suspected, but also starting a new asparagus patch in totally new location.
Issue: Brown, crooked, or hooked spears.
Cause: Frost as mentioned, windy conditions or asparagus beetle damage.
Solutions: Cover spears if frosts threaten. Plant patch in location with good air circulation, but not windy exposed spot. Common asparagus beetles feed starting around May and can discolor, distort, and cause hooked spears. Adult beetles to watch are black with white spots. Some beetles are orange with black spots, these types do not damage. For control deploy floating row covers to prevent access to emerging spears or apply pesticide products with active ingredient called Spinosad, like Captain Jack's Deadbug Brew®.
Issue: Pale-colored to whitish spears.
Cause: Light discoloration can be caused by spider mites feeding. White with spotting on spears can be due to crown rot.
Solutions: To double check for spider mites, flick spears over clean piece of white copy paper. If mites are present, they are easy to see against white paper. Treat spider mites with Safer® Insecticidal Soap. Plants with confirmed crown rot should be dug and destroyed, as there is no cure. Verify symptoms with your local agricultural extension office or university plant pathology lab to be certain.