It originally grew in coastal sand dunes. Today Asparagus Is grown In a wide variety of soil types and climatic conditions. In Western Australia Asparagus is grown from Albany to Kununarra. in sand and Karri loam. The one common factor in all locations is the soil MUST be well drained.
Asparagus is unique amongst vegetables in,that it is a true perennial cropping for up to 20 years from a single planting. A wide range of soils are suitable for the crop,but it does best in deep well drained loams. Ample water is required in sandy soils, but in other types water is not a major problem. Heavy poorly drained clay soils are not considered suitable for the crop.
As the crop is such a long term prospect, thorough preparation is both important and sensible. Ensure that perennial weeds like couch, sorell, nut grass, oxalis and docks etc are totally removed.
General: Asparagus is a herbaceous perennial plant in the south west the foliage dies down whilst the crown and root system survive until the warmer weather retums. The shoots (spears) are produced from the underground section called the crown. This is supported by a mass of fleshy storage roots. These roots are attached to the crown which is made up of many buds. when dormancy is broken (soil Temperature 8-10 C )spears grow from the buds. if allowed to develop the spears develop into tall attractive fern like fronds. The ferns produce carbohydrates which are stored in the fleshy roots, this in turn provides the substrate to produce the new seasons spears. The greater the root reserve the more spears can be harvested.
Site and Soil: The prime requirement for Asparagus cultivation is to have well drained soil. Asparagus respond well to soil structure being enhanced with application of organic matter. animal manure mixed with straw or sawdust is most beneficial. The pH level of the soil is best at a range of 6 to 6.7 especially in sandy soils. Asparagus are partially tolerant of salini1y in soil and irrigation water.
Asparagus are not as affected by wind as other vegetables but it is desirable to provide wind protection for the early spring winds which could damage newly emerged spears.
The best position for the Asparagus Plot is in a sunny well drained posit as crops in shaded sites begin cropping late in the season. Selecting a site which will increase the soil temperature early in spring will produce earlier crops.
Planting: Planting can be done from July to September. however the eartier the better.
The preferred method for the home garden is to prepare a trench 30 to 35 cm deep and 30 cm wide. Lay 10 to 15 cm well rotted manure or compost in the bottom of the trench. Add a complete vegetable fertiliser to the trench (if needed) and cover with 8 cm of good top soil to cover the fertitiser and manure. Mound the soil along the centre of the trench. Place the Asparagus crowns over the mound spreading the roots either side of the mound. Plant the crowns 35 to 45 cm apart. If more than one bed is made they should be 1.2 to 1.5 m apart. Fill in the trenches to ground level. Mulch over the Asparagus rows will help increase soil temperature and retail soil moisture.
Care: Asparagus should be fertilised with a high nitrogen fertitiser in spring prior to spear emergence and again at the end of harvest. Spear production will be promoted if the beds are kept weed free. At the end of the season cut and remove the old dead ferns. Asparagus beds should be kept moist from the first appearance of spears until the ferns have browned off.
Pests: There are a number of pests that attack Asparagus. These include
Brown headed weevil larva
African black beetle
White-headed weevil larva
White fringed weevil
Redlegged earth mite
Snails and slugs
Control measures are similar to other garden vegetables.
Harvest: Do not cut any spears in the first, year after planting from any variety. In the second year only take the first 2 or 3 spears from Mary Washington, but if the UC 157 Hybrid variety is used up to 6 orB spears can be taken. From the third year onwards all spears can be taken until mid December, when all cutting should cease, to allow top growth to replenish the ,crowns for the following season.
Spears may require cutting every second day in warm conditions, but not as frequently when conditions are cooler. Cut the spears off below soil level, usually when the spears are around 15 to 20 cm. long, but before the tips start to open up.
The tops that deveiop after cutting ceases should be allowed to remain until it turns yellow in late autumn,when it should be cut down and removed. At this stage the bed should be cleaned up and fertilised for the next season.
In subsequent years you can cut most of the spears but make sure you leave ferns to develop late in the season to ensure the crown is built up for the next season.
Eating: Asparagus looses quality very quickly. it is very important to cool spears to 1 C as quickly as possible. Asparagus will keep longer if kept moist at 1 C. Asparagus is best if eaten soon after harvest.
Tips: Try asparagus raw it is delicious or alternatively cook it for a very short time. enough only to heat it either in a microwave or steamer.
Varieties: MARY WASHINGTON 500. A reliable rust resistant variety that has been the main commercial and home garden variety for the past 30 or more years. I, is resistant to Asparagus Rust.
DC 157 Hybrid. A very vigorous hybrid variety that comes into full production a year or more earlier than older types. Rust resistant. Rapidly becoming the main variety grown.