Why are my asparagus spears thin?
Written by
Julia Anderson
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.Thin asparagus spears can be one indication of a stressed plant. I found that out the hard way during my first harvest. My over-picking of Year 2 spears resulted in spindly Year 3 spears. Thin spears typically indicate one of three obstacles; exhausted root systems, nutrient deficiencies, and/or overcrowding. Addressing these concerns early will help with productivity once again in the bed you are tending.
Soil Nutrition Fixes
- Apply fish emulsion weekly for 1 month
- Mix 1 cup wood ash per plant (potassium boost)
- Test soil pH, adjust to 6.5-7.0 with lime
Root Division Steps
- Dig up 5+ year crowns in early spring
- Split with sharp knife (3+ eyes/section)
- Replant 24" apart with compost
In order to reduce the harvest period to 6 weeks maximum to prevent thin spears. After I limited the harvest from 8 to 5 weeks, my Zone 5 bed really recovered well afterwards. Some additional quick pointers: After harvesting, fertilize with a 10-10-10 (1 lb per 100 sq. ft.), mulch with straw between feedings to retain moisture.
Annual Maintenance
- Test soil every 2 years
- Replace 25% compost annually
- Remove female plants (berry producers)
Harvest Adjustments
- Stop when 30% spears <½" thick
- Never cut below soil line
- Disinfect tools between plants
Baby plants can take 3+ years to reach a productive maturity. If you harvest too soon, that will make them permanent weaklings. My neighbor has a 15-year-old bed that still produces ¾" spears, because she waited until Year 4 to begin harvesting. Track the growth of your plants in a journal: Adequate and healthy crowns will put on 2-3 new spears each year until approximately year 8 when they will peak at maximum growth potential.
Read the full article: How to Grow Asparagus: Expert Tips for Perennial Success
