Asparagus
Asparagus officinalis
A perennial spear bed that shelters tomatoes and shuns onions.
- Type
- Vegetable · Perennial
- Botanical family
- Mixed / other
- Foliage color
- Green
- Sunlight
- Full sun
- Watering
- Moderate
- Soil
- Deep, sandy, well-drained
- Feeding
- Feed in spring, then mulch with compost in autumn once the fern is cut.
- USDA zones
- 3a–8b
- Frost tolerant
- Yes
- Pruning
- Cut the fern down in autumn once it yellows, and never while it is still green.
- Plant out
- 14 days before the last spring frost
- First harvest
- at the last spring frost
- Harvest ends
- 100 days before the first fall frost
- Apr–Apr Spring Growth
- Apr–Jun Harvest
- Jun–Oct Growing
- Oct–Dec Leaf Fall
- Jan–Apr Leaf Fall
- Plant spacing
- 15.7 in
- In-row spacing
- 13.8 in
- Between rows
- 2 ft 11 in
- Square-foot density
- 1 per square
- Root system
- A fleshy crown with thick perennial roots
- Working depth
- 18 in–4 ft
- Can reach
- 6.5 ft down where the soil allows
- Spread
- 4–6.5 ft across, about 1–1.5× the width of the plant
- Shallowest pot
- 18 in of soil
The crown is the plant’s bank account and it is slow to rebuild, which is why a new planting is left unpicked for a season or two. Plant it at the depth it asks for and no deeper; these rot from being buried far more often than they suffer from being shallow.
The crown is a starfish of thick storage roots that goes on widening for twenty years, and the fine feeding roots run a metre or more out from it in every direction. This is why an asparagus bed is dug once, deeply, and then never dug again, and why it is left uncut for its first two seasons while the crown is built.
Figures recorded for Asparagus itself. Roots follow the soil either way: a compacted pan, a high water table or heavy clay stops them well short of any of it, and deep open ground lets them go further.
- When
- Do not cut at all in the first year after planting crowns; take a light 2-week harvest in year two, then a full 6–8-week season from year three. The season runs mid-spring to early summer (traditionally ending around the summer solstice in the UK); stop cutting on time so ferns can rebuild the crown.
- What to look for
- Spears 15–20 cm tall with tight, closed tips and about finger thickness. Once tips begin to loosen and open the spear turns woody — cut it anyway and compost it to keep the bed producing evenly.
- How to harvest
- Cut spears with a sharp knife (a serrated asparagus knife is ideal) 2–3 cm below the soil surface, or snap them off at ground level where they break naturally. Angle the blade carefully to avoid nicking emerging spears and the crown below.
- How often
- In peak season check the bed every 1–2 days — in warm weather spears can grow 5 cm or more a day. Cut every spear of harvestable size during the season, even thin ones, to encourage the crown to keep pushing.
- Storing the crop
- Quality falls off within hours as sugars convert to starch — eat as fresh as possible. Store upright in the fridge with cut ends in 2 cm of water or wrapped in a damp towel, for up to a week; blanch and freeze, or pickle, any surplus.
- Asparagus beetle A checkered orange-and-black beetle whose grubs defoliate asparagus fern, weakening next year’s spears. Hand-pick from late spring and burn cut fern at season’s end.
- Slugs & snails Slugs on the spears as they push through
- Root & crown rot Violet root rot
- Verticillium & fusarium wilt Fusarium
Beneficial predators that hunt this plant's pests — grow their favourite flowers nearby to recruit them. companion plant
- Beneficial nematodes Steinernema & Heterorhabditis spp.Hunts Slugs & snails
Microscopic worms watered onto damp soil that hunt down soil-dwelling grubs and release a bacterium that kills them within days. Timing is the whole thing: warm, damp soil and a small target grub, which means late summer for most of what they are used against.
- Centipedes ChilopodaHunts Slugs & snails
Flat, fast, one pair of legs to a segment — and a predator, unlike the slow round millipede it is constantly confused with. It hunts slugs, cutworms, springtails and woodlice by night under mulch and stones. Learn the difference and leave this one alone.
- Frogs & toads AnuraHunts Slugs & snails
A resident toad works the beds every night for slugs, cutworms, and weevils. Recruit them with water — even a sunken basin pond — plus damp shade and an upturned-pot toad house; skip the slug pellets that poison their prey.
- Garden birds PasseriformesHunts Slugs & snails
Both things are true: birds strip your currants and a brood of blue tits takes several thousand caterpillars out of one fruit tree in a fortnight. Net what you must and welcome them everywhere else — a nest box near the apples is worth more than a spray.
- Ground beetle CarabidaeHunts Slugs & snails
Fast, glossy night hunters that patrol the soil surface for slugs, cutworms, and root-fly larvae. Give them daytime cover — thick perennial edges, stepping stones, a log — and skip the tillage that wrecks their burrows.
- Hedgehog Erinaceus europaeusHunts Slugs & snails
A European animal, and worth saying so plainly: there are no hedgehogs in North America, and the ally that does the same night shift here is the toad, the opossum or the ground beetle. Where they do occur, cut a gap in the fence and skip the pellets.
- Rove beetle StaphylinidaeHunts Slugs & snails
Slim, quick beetles with short wing cases that hunt in soil and litter, taking root-fly eggs and larvae, fungus-gnat larvae, and mites. Mulch and undisturbed ground keep them resident year-round.
- Salamanders & newts CaudataHunts Slugs & snails
Damp-loving hunters of slugs, worms, woodlice and beetle larvae that spend the day under a log or a stone and work the beds at night. Companions to the toads: they want the same damp shade, the same log pile, and the same absence of slug pellets.
- Snakes & lizards Colubridae & PhrynosomatidaeHunts Slugs & snails
A garter snake works the beds for slugs and voles and a fence lizard clears grasshoppers off a sunny wall. Almost every snake a gardener meets is harmless and useful; give them a log pile, a warm flat stone and a bit of cover and they stay.
Tomatoes, Parsley, Basil, Marigolds
An asparagus bed can crop for 20 years — but you wait two years before the first harvest.
The Cottage Garden Companion — the gardener's herbarium at cottagegardencompanion.com