Asparagus Spears Thin: Young Crowns plus Overharvest
Asparagus spears thin as a pencil often come from young crowns, long picking or weak ferns the year before. Utah State University Extension advises stopping harvest once most spears are smaller than a pencil, while University of Minnesota Extension notes ferns build the energy for next year’s spears.
The short answer
Thin spears mean the crowns are short on stored energy. Utah State advises stopping harvest when most spears are smaller than a pencil in diameter. University of Minnesota Extension notes ferns make the energy stored for next year’s spears, so let them grow all summer. Young beds need time before a full harvest.
Why are my asparagus spears skinny?
Utah State lists stresses such as overcutting, drought plus weed pressure among the causes of small, skinny spears. Minnesota notes male plants grow more but smaller spears, while female plants grow larger ones.
| Cause | Sign | Fix | Source |
|---|---|---|---|
| Young crowns | Thin spears early on | No harvest until year 3 | Utah State |
| Overharvest | Spears thin late in the season | Stop when most are below pencil size | Utah State |
| Weak ferns | Fewer, smaller spears | Let ferns grow after harvest | Minnesota |
| Weed pressure | Small, skinny spears | Weed by hand plus mulch | Utah State plus Minnesota |
| Male plants | Many smaller spears | Normal for male hybrids | Minnesota |
When should asparagus harvest stop?
Minnesota advises harvesting until June 30. Utah State advises stopping when the majority of spears are smaller than a pencil, often by early to mid June. It suggests 4 weeks of harvest in year 3, 6 weeks in year 4 plus up to 8 weeks after 5 years.
How do ferns affect spear size?
Minnesota notes the fern creates energy that is stored underground for next year’s spears. Cutting too long gives the fern less time to refill the crowns, which shows up as thin spears next spring.
How to: step by step
- Note the bed’s age before setting harvest length.
- Stop picking once most spears are thinner than a pencil.
- Let ferns grow through summer.
- Weed the bed by hand or with shallow cultivation.
- Feed after harvest as a soil analysis advises.
- Mow dead ferns in fall plus mulch 2 to 3 inches deep.
Troubleshooting
Thin spears in a new bed: immature crowns. Utah State advises no harvest until year 3.
Spears thin late in harvest: the crowns are spent. Stop picking for the season.
Skinny spears after a weedy summer: weeds compete for water plus nutrients, per Minnesota. Weed early plus mulch.
Small spears with yellowing ferns: Utah State links small, skinny spears to root rot plus stress. Ease off overwatering plus overcutting.
For plant stress see the effects of environmental stresses on weed plants, underwatering cannabis plus mulch for cannabis. Kind Seed Co also stocks cannabis seeds.
Sources
- Growing asparagus in home gardens, University of Minnesota Extension
- How to grow asparagus in your garden, Utah State University Extension
- Asparagus, Clemson Cooperative Extension HGIC
- Asparagus officinalis (asparagus), NC State Extension Gardener Plant Toolbox
FAQ
How many years before asparagus spears thicken?
Utah State advises no harvest until year 3, then 4 weeks that year, 6 weeks in year 4 plus up to 8 weeks after 5 years. Minnesota advises starting harvest two years after planting crowns or three years after seed. Spears gain size as crowns build reserves.
Do male asparagus plants grow thicker spears?
No. University of Minnesota Extension notes female plants grow larger spears, while male plants grow a greater number of smaller spears. Male plants also live longer plus produce more spears overall. Utah State lists Jersey Giant plus Jersey Knight as all male varieties with large spears.
Should an asparagus bed be fertilized?
Minnesota advises adding nutrients only as a soil analysis calls for, with compost or manure in early spring or after harvest in late June or early July. Clemson advises a yearly top dressing of compost. Utah State advises feeding in early June or after harvest ends.
Can a weedy asparagus bed recover?
The sources give no recovery time, but weeds compete with asparagus for nutrients, water plus light, per Minnesota. It notes hand removal works well plus advises shallow cultivation less than 2 inches deep. Utah State advises adding 2 to 3 inches of mulch each year.
How long does an asparagus bed last?
University of Minnesota Extension notes a well planned bed can produce for 15 years or more. Clemson notes plantings are highly productive for 7 to 8 years before gradually declining. Picking lightly in young years plus letting ferns grow each summer help beds last longer.
