When asparagus spears grow into tall, ferny bushes, many gardeners worry they’ve ruined the crop. In reality, this is a natural and necessary stage of the plant’s life cycle. Letting asparagus “go to fern” is how the plant rebuilds energy reserves in its crown for next year’s harvest. The key is knowing when to stop picking, how to manage the ferns, and what to do with tough, woody spears that are past their prime. This guide covers both caring for the plant and using the overgrown spears in the kitchen.
What You’ll Need
- Sharp garden shears or a knife
- Garden gloves (optional, for handling ferns)
- Compost bin or garden waste bag
- Stakes and twine (if you want to support the ferns)
- Vegetable peeler (for cooking with tough spears)
- Large pot for blanching (if you plan to cook them)
Step-by-Step
- Stop harvesting immediately. Once asparagus spears get thin (pencil-thickness) or begin to open up into fern-like growth, stop cutting them. Harvesting further weakens the crown. The plant needs those ferns to photosynthesize and store energy.
- Let the ferns grow. Do not cut down the ferny growth. This is the plant’s food factory. Leave it standing through the summer and early fall. It will grow several feet tall and may produce small red berries (if female plants) – these are harmless but not edible.
- Support the ferns if needed. In windy areas, tall ferns can flop over. Drive a few stakes around the row and run twine between them to keep the ferns upright. This improves air circulation and reduces disease risk.
- Water and fertilize lightly. During the summer, give the asparagus bed about an inch of water per week if rainfall is scarce. In early summer, you can side-dress with a balanced fertilizer (like a 10-10-10) at the rate recommended on the package, but avoid high-nitrogen formulas that promote soft, disease-prone growth.
- Cut ferns down in late fall or early winter. After the ferns turn brown and die back naturally (usually after the first hard frost), cut them to the ground. Remove all debris from the bed – this removes overwintering asparagus beetle eggs and other pests.
- Mulch the bed. After cutting, apply a few inches of compost or well-rotted manure over the crown area. This feeds the soil and protects the crowns over winter.
- For tough spears that are already picked: If you have a bunch of overgrown, woody spears, don’t compost them all. You can still use them in the kitchen. Snap off the woody base – it will break at the point where it becomes tender. Then use a vegetable peeler to shave the outer skin of the remaining spear, which is often fibrous.
- Cook tough spears longer. Overgrown asparagus is great in soups, stews, or stir-fries where longer cooking tenderizes it. You can also roast them at high heat with olive oil and salt until they’re slightly charred and tender.
- Make asparagus stock. Boil the woody ends and peels in water with a bit of onion and garlic for about half an hour. Strain and use the liquid as a flavorful base for risotto or soup.
- Freeze or pickle. If you have more than you can use, blanch the trimmed spears for a couple of minutes in boiling water, then plunge into ice water, drain, and freeze in airtight bags. Or pickle them in a vinegar brine for a tangy snack.
Common Mistakes
- Cutting ferns too early. Cutting ferns in summer or early fall starves the crown. Always wait for natural die-back.
- Harvesting too long. Continuing to cut spears after they become thin or ferny reduces next year’s yield. Stop after about six to eight weeks of harvest in spring.
- Leaving ferns on the ground. Dead ferns left on the bed harbor pests and diseases. Remove them in fall.
- Over-fertilizing. Too much nitrogen creates lush, weak ferns that are more prone to disease. Use a balanced fertilizer at moderate rates.
- Trying to eat extremely woody spears raw. Overgrown spears are fibrous and tough. They need peeling and cooking to be palatable.
Tips
- Mark your calendar. In most regions, the asparagus harvest season ends around early summer. Set a reminder to stop picking and start letting the ferns grow.
- Grow male hybrids. If you’re planting new asparagus, choose all-male hybrid varieties – they produce more spears and don’t waste energy on berries.
- Use a raised bed. Asparagus thrives in well-drained soil. A raised bed makes it easier to control weeds and moisture.
- Compost the ferns. If you don’t have disease issues, you can compost the cut ferns. Otherwise, discard them.
- Don’t harvest the first year. New asparagus plants need at least two years to establish before you can harvest. In the third year, harvest for a few weeks only.
Troubleshooting
- Ferns are yellowing in summer. This could be a sign of Fusarium wilt or root rot. Improve drainage and avoid overwatering. If the plant dies, remove it and don’t replant asparagus in that spot for several years.
- Asparagus beetles are eating the ferns. Hand-pick beetles and larvae in the morning, or use an insecticidal soap labeled for asparagus beetles. Remove ferns in fall to reduce overwintering.
- Ferns are falling over. Stake them up as described. If they’re too heavy, just let them lie – they’ll still photosynthesize, but may be more prone to disease.
- No spears next spring. This usually means the crown was weak. Ensure you didn’t harvest too long the previous year, and that you fertilized and watered during the fern stage.
- Tough spears are still stringy after cooking. Peel more aggressively, and cook longer. You can also puree them into soup for a smooth texture.
Frequently Asked Questions
Q: Can I eat the red berries on asparagus ferns?
No, the berries are not edible and can cause mild stomach upset if eaten in quantity. They are harmless to birds.
Q: How long does an asparagus plant live?
With proper care, an asparagus bed can produce for many years – often two decades or more. The key is letting the ferns mature each year.
Q: Should I cut back asparagus in the spring instead of fall?
It’s best to cut in late fall or early winter after die-back. Cutting in spring risks damaging new spears and may harbor pests over winter.
Q: Can I harvest asparagus in the fall?
No. Fall is when the plant is storing energy for next year. Harvesting then would weaken the crown and reduce next year’s crop.
Q: What if my asparagus spears are very thin?
Thin spears indicate the crown is stressed or young. Stop harvesting immediately, let them grow into ferns, and ensure the plant gets adequate water and nutrients.
Q: Is it okay to cut one or two ferns for decoration?
A few won’t hurt, but avoid cutting more than a small percentage. Each fern contributes to energy storage.