Asparagus is a low-risk, permanent horticultural crop.
When to Plant
The best time to plant asparagus is when soil temperatures rise in spring. For the Northern North Island this is in mid September to mid October. In the South Island the best time is from early October. Planting asparagus any earlier than this often results in death of plants through frost damage or diseases associated with wet cold soil.
What to Plant
The best variety of green asparagus to plant is Pacific 2000. This has better quality spears, tastes better and beds of Pacific 2000 last longer than older varieties like Jersey Giant or Mary Washington.
The new Super-sweet variety of Purple asparagus Pacific Purple is also very popular.
Plant one year old crowns in a well drained, sunny location.
Asparagus likes deep soil that is well drained and free of compaction layers. The best soil is a sandy loam, loamy sand or free drained volcanic soils.
Asparagus also likes plenty of organic matter so dig well rotted garden compost or mushroom compost into the soil prior to planting.
A high pH (6.0-6.5) is preferable as well as high levels of phosphate. Lime (either dolomite lime or hydrated lime) and superphosphate should be dug into the soil prior to planting. Spread the fertilizer on the soil surface and deep dig to bury the fertilizer to the depth that most root growth will occur ie below 15cm depth.
Make sure the site is free of perennial weeds before planting.
How to Plant
Open a trench approximately 20cm deep with a flat bottom approximately 20 cm across. Plant the crowns down one side of the trench placing each crown 20 cm apart. Plant another row of crowns along the other side of the trench but in the gaps of the first row. This gives a staggered double row with about 10 plants per m length of row.
Do not fill the trench but cover the crowns with 5cm of loose soil. This will ensure the crowns get away to a good start. During the following summer and autumn slowly fill the trench with soil as you hoe any weeds on the sides of the trench.
By the following winter, the trench should be filled with soil and the soil surface should be flat again.
Fern Removal in Winter
Once the fern has completely died off and turned brown, cut the dead fern off at ground level and either compost it or burn it. The stalks that remain at the soil surface can be buried with soil or compost to help them rot down. This makes picking the following spring much easier.
Normally this is two years after planting the crowns. However, if the crowns grow well in the first year and spears emerge that are 15mm in diameter or bigger these can be picked one year after planting the crowns. Normally this "bonus harvest" season will only last 10 days to 2 weeks.
Normal harvest starts two years after planting. The season usually lasts 3-5 weeks. The following years it will last 6 to 8 weeks and the year after that it will last 8 to 10 weeks.
A well kept garden bed planted with the recommended variety will last up to 20 years with some beds in New Zealand lasting up to 58 years.
Where to Buy Crowns
Aspara Pacific sells asparagus crowns to home gardeners throughout New Zealand. Contact us to place an order and we will courier the crowns to you when soil temperatures are suitable for planting.