Asparagus Care Through the Year: Feeding, Weeding and the Ferns

Two feeds, in the right two places

Asparagus is a hungry perennial living in the same soil for over a decade, so it needs feeding, but the timing is more useful than the quantity. There are two moments that matter: just before the spears start pushing in spring, and immediately after you stop cutting.

The second feed is the important one, and it is the one most people miss. Once you stop cutting, the plant throws up its ferns and spends the entire summer refilling the crown. Feeding at that moment goes directly into next year's spears. Feeding in autumn, by contrast, mostly washes away over winter.

Spread feed over the whole bed surface rather than in a band along the row. Asparagus roots reach several feet sideways, well beyond where the spears appear.

Weed on the surface, never with a fork

The crown sits four to eight inches (10 to 20 cm) down and sends feeding roots out in every direction just below the surface. Anything that goes deeper than an inch or two into an established bed cuts those roots, and a fork pushed in blind can slice straight through a crown.

So weeding is a hands-and-knees job, or a very shallow hoe, and it is best done often enough that nothing is ever big. A thick mulch does most of the work for you: two to three inches (5 to 8 cm) of compost or well-rotted manure over the bed suppresses annual weeds, holds moisture and feeds the crowns as it breaks down.

1. Hand-pull annual weeds while small Pull them at the seedling stage when the root comes away cleanly. A large weed pulled from an asparagus bed brings asparagus roots up with it.
2. Hoe no deeper than an inch If you use a hoe, keep it skimming the very surface. Anything deeper than one inch (2.5 cm) starts cutting feeding roots you want.
3. Mulch after the spring feed Lay two to three inches (5 to 8 cm) of compost across the whole bed once you have fed it. It is the single most effective weed control that does not involve disturbing soil.
4. Never dig the bed over There is no winter digging in an asparagus bed. If the soil looks compacted, add mulch on top and let worms take it down.

Mark the row ends with permanent stakes. Most crown damage happens in late winter when the bed is bare and nobody can see where the plants are.

Water matters most while the ferns are growing

An established asparagus bed is deeply rooted and reasonably drought tolerant, which misleads people into never watering it. The bed does not usually die of drought. What happens instead is that a dry summer stunts the fern growth, the crown stores less, and the following spring produces thin spears. The damage shows up a year later.

So the watering priority is the fern season, not the cutting season. During spear production the plant is living on stored reserves and needs relatively little. Once the ferns are up and photosynthesising through summer, that is when a deep soak in a dry spell pays for itself.

1. Soak deeply, not often In a dry spell give the bed a thorough soak that wets the top foot (30 cm), roughly once a week. Frequent light watering encourages shallow rooting on a plant that should root deep.
2. Prioritize summer over spring If you can only water sometimes, water while the ferns are growing. That is when next year's spears are being paid for.
3. Water new crowns through year one A first-year bed has no root reserve to fall back on. Keep it evenly moist through its first two summers, then relax.
4. Check drainage after heavy rain Standing water around the crowns for more than a day invites crown rot. If puddles sit on the bed, raise it before the next season.

Leave the ferns standing all summer

The fern is not decoration and it is not a mess to be tidied. It is the entire mechanism by which the crown recharges. Every week those ferns stand green is a week of sugars going down into the roots, and the height and density of the fern at the height of summer is a fair predictor of the spear crop next spring.

That means resisting the urge to cut it back because it has flopped, gone untidy, or is in the way. If ferns are falling over, support them rather than remove them. A row of stakes with twine run along both sides at two and four feet keeps a six-foot fern upright through summer storms.

1. Stake before they need it Put stakes in at the ends and middle of each row early in fern growth. Trying to lift a collapsed six-foot fern afterwards snaps stems at the base.
2. Run twine at two heights String twine along both sides of the row at roughly two feet (60 cm) and four feet (120 cm). The ferns lean against it rather than being tied individually.
3. Remove only broken stems If wind snaps a stem, cut that one off cleanly at the base. Leave everything still green and standing, however untidy it looks.
4. Watch for yellowing early Ferns that yellow in midsummer rather than autumn mean a problem: rust, waterlogging or starvation. Diagnose it while there is still season left to recover.

Female plants set red berries on the ferns. Those berries seed themselves into the bed and the seedlings compete with your crowns, so pull volunteer seedlings out while they are small.

What to record so next year is easier

Asparagus punishes vague memory more than most crops, because the consequence of any given year's management appears the following spring. Without notes you cannot tell whether this year's thin spears came from cutting too long last year, a dry summer, or a crown that is simply failing.

Keep it minimal but consistent. Four things logged each season will tell you almost everything you need within two or three years, and they take about five minutes a year to write down.

Sketch the bed once with each crown numbered. When a plant starts failing, being able to say which position it is in makes the pattern of a soil-borne problem obvious.