Asparagus spears

How to Blanch Asparagus for White Spears

ByStephen Albert

Sharing is caring!

Blanching asparagus is an age-old technique for producing tender, mild-flavored white spears. Instead of growing in sunlight, the spears are deprived of light, preventing chlorophyll formation and keeping them pale. I’ve experimented with blanching in both raised beds and open garden rows, and it’s easier than many gardeners expect. Here’s how to do it successfully for a unique harvest.

Choose the Right Variety

While any asparagus can be blanched, vigorous, thick-stemmed varieties like ‘Jersey Giant’ or ‘Purple Passion’ produce the best white spears. Start with healthy, established crowns at least two years old for a strong harvest.

Prepare the Bed

Loosen soil and remove weeds in late winter before spears emerge. Good drainage is essential because blanching methods trap moisture, which can cause rot if the soil stays soggy.

Blanching Methods

1. Mounding Soil

  • When tips first break the soil, gently mound 6–8 inches of loose soil over the row.
  • Continue adding soil as spears grow, keeping them covered until harvest.
  • Harvest spears when they reach 8–10 inches beneath the mound, cutting just below the soil line.

2. Covering with Boards or Buckets

  • Place opaque boards, black plastic, or inverted buckets over emerging spears.
  • Ensure covers block all light but allow some airflow to prevent heat buildup.
  • Check daily and harvest spears when they reach the desired length.

Harvesting Tips

  • Cut spears before tips push through the soil or covers and begin to green.
  • Use a sharp knife to avoid damaging crowns.
  • Blanched spears are more tender but slightly lower in yield, so plan your harvest accordingly.

My Experience and Key Takeaways

In my California garden, I prefer the bucket method for small beds—it’s simple, keeps spears pristine, and avoids heavy soil mounding. For larger rows, traditional soil mounding produces consistent results. Whichever method you choose, careful timing is key to achieving crisp, sweet, ivory-white asparagus.

Asparagus Growing Hub

Start here: The Ultimate Asparagus Growing Guide: From Seed to Harvest

Planting & Establishment

Care & Maintenance

Pests & Diseases

Harvest & Storage

Kitchen & Varieties

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. Harvesttotable.com has more than 10 million visitors each year.

Similar Posts