Planting asparagus seeds is an exercise in patience, but one of the most rewarding of all garden tasks. Asparagus seeds germinate slowly, and the crowns take three seasons before they can handle being harvested. However the grower’s patience is generously rewarded by early season harvests of asparagus with a flavour not to be found on store shelves anywhere. You will wish you had planted a bigger asparagus bed!
Moderately difficult. Requires patience!
Season: Cool season.
Zone: Hardy to Zone 2
Start seeds indoors during winter through spring under bright lights. There will be no harvest from these these long-lived perennials until 3 years after transplanting, so be patient. Soil temperature for germination: 21–30ºC (70–85ºF).
Soak seeds for 2 hours. Plant 1 seed per 5cm (2″) pot, 1cm (½”) deep. Keep in a warm place. Be patient: they can take 2-8 weeks to sprout depending on soil temperature.
Transplant when seedlings are 10-12 weeks old and danger of frost has passed. Space 45cm (18″) apart in rows 1-2m (3-6′) apart. Transplant each plant in a hole 10cm (4") deep and gradually cover the crown with soil as it grows. For thicker spears, space 30-35cm (12-14″) apart and set buds 15-20cm (6-8″) in the hole. For thinner spears, space 20-25cm (8-10″) with the buds 10cm (4″) deep.Fertilize after harvest and again in the spring with 1-2 cups of complete organic fertilizer per 3m (10′) of row, worked in lightly. Asparagus needs 2cm (1″) of water per week. In late fall, trim ferns down to 5cm (2″) and dispose of cuttings to avoid future disease and insect problems.
It’s important to not harvest until the third year so that plants can become established and strong. Then harvest over a 2-3 week period. Cut the fattest spears off at ground level when they are 15-20cm (6-10″) long. When thinner spears begin to emerge let them to grow into big fronds to nourish the roots. With each successive year the harvest lengthens to a maximum of 6-8 weeks. Store in the refrigerator wrapped in a damp paper towel.
In optimum conditions at least 75% of seeds should germinate. Usual seed life: 2 years.
Diseases & Pests
Rust, fusarium wilt, and fusarium stem and crown rot can all be problems. Using seed started in sterile soil instead of purchased plants, and planting in soil that has no history of disease will keep asparagus plants healthy.
Asparagus beetles can defoliate the ferns of the asparagus plant. They overwinter in the top growth, so thorough removal of the fronds in the fall (after they have died) is vital. In a small garden, simply hand-pick the voracious insects.
Encouraging beneficials like ladybugs reduces aphids. Aphids are usually found together on growing tips (look for the sooty blotches they leave behind).
Companion planting is a cornerstone of organic gardening. Carefully choose companions to reduce your need for pesticides. Plant asparagus seeds or crowns with asters, basil, cilantro, dill, cilantro, marigolds, nasturtiums, oregano, parsley, peppers, sage, and thyme. Asparagus repels nematodes that attack tomatoes, and tomatoes repel asparagus beetles. We have a full list of companions to consider.