Asparagus is the most patient vegetable most New Zealand gardeners will ever plant. Where tomatoes and lettuce return a harvest inside a season, asparagus takes two to three years from planting to its first proper picking, and even then only a light one. This isn't a plant sold as difficult; it's simply built on a different timescale, and gardeners who don't expect that are the ones who dig it back out in year two convinced something has gone wrong.
Asparagus is grown from one-year-old crowns rather than seed, since seed-grown plants take even longer to reach a harvestable size. Most crowns sold here now are all-male hybrids, bred because male plants put their energy into producing spears rather than seed, which gives a noticeably heavier harvest than the older mixed-sex varieties. Crowns go in as bare roots in a trench, backfilled gradually as the first shoots push through rather than all at once. Timing depends on region: Northland, Auckland, Bay of Plenty, Gisborne and Hawke's Bay gardeners can plant from July, Waikato, Taranaki, Manawatū-Whanganui, Wellington, Nelson and Tasman gardeners should wait until August, and everyone from Canterbury and Marlborough down through Otago and Southland should hold off until September, once the ground has warmed and the worst of the frosts have passed. Choose the spot carefully: asparagus needs a permanent, full-sun bed with free-draining soil, since the crowns resent being dug up and moved the way an annual crop would be, and they'll be there for a long time.
For the first one to two years after planting, the job is to grow fern, not spears. Every shoot that comes up should be left alone to open into its feathery top growth, which can reach around 1.5m tall and feeds sugars back down into the crown all summer. Space crowns 40cm apart, keep them in full sun with moderate, even watering, and weed by hand rather than hoeing, since the crowns sit shallow and a hoe blade will cut straight through them. Watch the ferny growth for asparagus beetle, which strips foliage through summer and is the main pest asparagus attracts in New Zealand gardens.
Resist harvesting anything in year one, and again in year two. It's the single hardest piece of asparagus advice to follow, because by the second spring there are usually spears thick enough to eat, and picking a few won't kill the plant. But it will set the crown back, and the point of the wait is to bank enough root reserves that the bed can support decades of cropping rather than a handful of seasons. A light picking is usually possible in year three. From year three onwards, established plants send up spears each spring for a defined 6-8 week harvest window, cut or snapped off at ground level once they reach 15-20cm and before the tips start to open. Once that window closes, stop picking even if spears keep coming, and let the rest grow on into fern for next year's crown.
Resist harvesting anything in year one, and again in year two.
An established asparagus plant yields around 700g to 1kg of spears a season, which sounds modest until it's multiplied across a bed of a dozen or more plants and compared with what asparagus costs at the supermarket in spring. The main disease risks are asparagus rust and root rot in soil that doesn't drain freely, which is why bed placement matters more here than for most vegetables. Tomatoes, parsley and basil are good companions nearby; keep onions and garlic out of the bed, as asparagus doesn't share space well with either.
Leave the fern standing through autumn until it yellows and dies back on its own, since it's still feeding the crown for next spring right up until then. Cut it back to ground level once it's fully brown and mulch the bed over winter. Do that consistently and a well-kept asparagus bed can keep producing spears for 15 to 20 years, which is a longer working life than almost anything else grown in a New Zealand vegetable garden. It's a slow start for a very long payoff.