ASPARAGUS (Asparagus officianale)
Introduction
Asparagus as such grows in the wild in the dry subtropical region in the country. It is
collected by farmers and brought to the market and sold for high price compared to other
vegetables. However, Dasho Rimpoche first introduced the cultivated variety of
asparagus crop in Bhutan around 1971 (personal communication). It was first tried in his
garden and some plants were planted at Ramtokto in HM’s orchard. Later on the
Department of Agriculture undertook the task of multiplication at Semtokha. Though
there had been asparagus planted in Paro earlier, it was only during 1989 that NASEPP
undertook to multiply the crop commercially.
Asparagus is a perennial vegetable grown for its young shoots. The young shoots are
called spears. Asparagus is a high value crop with an economic lifetime of 10 to 12 years;
the plants can be productive for 8 to 20 years, and a dozen plants, well grown, would be
sufficient for an average family. It is a rich source of vitamin A, B, C and amino acids.
Asparagus is also a labour-intensive crop and makes high demands on the farmer in terms
of soil management. Asparagus can be grown under a wide range of conditions from subtropical through the temperate conditions. The variety Mary Washington, currently the
only variety available from Druk Seed Corporation, is suitable for mid and high hills up
to 3000m.
Plant characteristics
Asparagus is a perennial crop belonging to the Liliaceae family. The plant is either erect
or climbing. Cultivated species are usually erect and herbaceous. Wild species are
climbing and woody. Individual asparagus plants are male or female. Male plants are high
yielding but it is impossible to distinguish them until they are one year old. Male flowers
are yellowish green and conspicuous. Female flowers are less conspicuous and are
pollinated by bees. Fruit is a 3 celled berry and red as it matures. Within the berry are 3 to
6 seeds. Seeds are large (3 mm or less in diameter) rounded at the base but more or less
flattened on one side, black in colour.
Climate
Asparagus is a cool season crop and therefore thrives best in the cool temperate climate. It
also thrives well in the dry sub-tropical climate. Good quality spears with higher yield are
obtained when the temperature range is 18-25 degree C.
Site selection:
 Very exposed sites and frost pockets should be avoided
 Choose a plot of land that has never been used for asparagus production before.
 Choose a sunny site sheltered from strong winds.
 The soil should be properly drained and avoid marshy areas.
 There should be irrigation facilities.
 Look for a pH of around 6 (optimum is 5.9)
Handouts prepared by J. Gyeltshen for the 6th batch AG trainees 21 April 2000
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Propagation
Asparagus is propagated through seeds or vegetatively by means of crowns. Crowns are
referred to that part of the plant that gives rise to new shoots. Asparagus crowns are
grown from seed planted in a well-prepared seedbed where the plants are allowed to grow
for one full growing season before being planted in the permanent bed. The quickest way
to establish asparagus crop is to plant 1-year old crowns, normally obtained from Druk
Seed Corporation. One-year old crowns are far better than 2 to 3-year old crowns that
take longer to recover from transplanting although the crowns may be larger (The Royal
Horticultural Society, London, 1981).
Seed rate/planting material requirement
For a production field of one hectare, about 25,000 plants are needed (about 10,000 plants
per acre). At a germination rate of 80 to 90 %, 65% of the seeds will become usable
plants. If 1 kg of seeds contain an average of 40,000 seeds, an amount of 1 kg seed is
required for 1 ha i.e. 400 gm per acre (IHDP, 1994).
Planting preparations:
 Remove all weeds.
 Plough in autumn so that the soil can reposition in winter.
 Plough as deep as possible to obtain a deep layer of rootable soil. Please note that as a
general rule, more rootable soil means a longer production life, depending on soil
type.
 Apply approximately 30 tons of organic manure per ha in autumn, before ploughing.
Some dolomite limestone may be applied to increase pH and the magnesium level.
 Consider sowing a green manure crop during winter too improve soil structure.
Nursery raising
Prepare raised nursery bed of standard size after incorporating enough organic manure or
fertilizers such as suphala at the rate of 5 kgs per 100 sq meters. Sowing time is from
February to March. Soak seeds in warm water (32 deg C) for 3 -4 days to hasten
germination. Sow the soaked seeds in rows at a distance of 10 cm (4 inches) from seed to
seed within a row and with a row-to-row distance of 30 cm (12 in). Sow in moist soil at a
depth of 1.5 to 2 cm; under dry and windy conditions, depth may be increased up to 5 cm
(2 inches). As asparagus seed is very expensive (each seed roughly costs about Nu.5) use
precision sowing; put each seed separately into the soil at the above distances. Sow in
moist soil at a depth of 2 cm.
Germination time is 6 weeks. Make sure to irrigate in case of dryness and keep the
nursery free of weeds. The germinating seeds will be ready for transplanting in the main
field after one year at the nursery bed.
Druk Seed Corporation can provide one-year old plantlets (crowns). Using these will save
one year. However, they are not always available, and the seeds have the advantage of
transporting easily to remote areas.
Handouts prepared by J. Gyeltshen for the 6th batch AG trainees 21 April 2000
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Production field
Prepare trenches of 15 cm (6 inches) depth and about 50 cm (20 inches) width. The
distance between the inner edges of two trenches should be about 1 m. Trenches of 20 cm
depth and 30 cm wide are also recommended (Royal Horticultural Society, 1981). For
land that is on a slope it is advisable to make trenches horizontally along the slopes in a
fish bone pattern depending on the steepness of the slope.
The trenches need to be filled with top soil (5 cm), bone meal and other organic manure
at a ratio of 50:50.
Plant selection and preparation
Since asparagus has an economic production life of at least 10 years, it is very important
to use only the best quality plants. Follow these guidelines:




Plants should not be badly damaged, as this can cause disease.
Remove any rotten or diseased plants and plants with very soft or dead roots.
Plants should be uniform, not a mixture of very heavy and very light plants.
Plants should have sufficient roots (approximately 20)
Before planting drench the plants in a fungicide solution, e.g. 20 g carbendazim per 10
litres water. Drench the plants for 15 minutes in this solution (not shorter, but certainly
not longer!). Plant them immediately after drenching. Make a new fungicide solution
when the previous one is too polluted with sand.
Transplanting
Transplanting of one-year-old plantlets or crowns should be done in spring, roughly from
March to May, when the plants are still dormant. Do not transplant during a frost period.
The soil should be moist during planting. Make sure the time between uprooting and
planting is as short as possible to prevent plants from drying out. Single row planting is
recommended with a plant-to-plant distance of 25 cm. The plants can also be grown at a
spacing of 45 cm; closer spacing gives higher yield, while wider spacing gives thicker
spears. The distance between rows to row is 150 cm. Approximately 25,000 plants are
needed for 1 ha at the above planting distances. (10,000 plants per acre).
The crowns are laid carefully on the bottom of the trench on a 10 cm mound and covered
with 5 cm of fine soil. When planting, put the heads of the plants in the same direction
and spread the roots as much as possible so that the plant can get water from a larger part
of it’s surrounding. Cover the plants with soil can irrigate. Be sure to irrigate frequently
during dry weather. The trench is filled and raised gradually during the season as the
shoots grow to 15 cm above the ground level.
Handouts prepared by J. Gyeltshen for the 6th batch AG trainees 21 April 2000
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Maintenance
The plot should be weed -free before the spears start growing and during the harvest
period. But it is advisable to keep the soil free of weeds during the whole growing season.
No chemical herbicides should be applied during the harvest periods.
Mulching with pulled weeds or other organic material between the rows is advisable. This
will keep the soil moist ands d also control the weed growth.
During November and December when the ferns turn yellow they are cut to the ground
leaving a stump of about 5 cm. During February -March before the spears come out, soil
should be put on the crown to make a ridge. If long spear is preferred 5-8 cm of soil can
be pulled up over the stumps. Before the harvest period starts, make small mounds over
the plants of about 10 cm height and 20 cm width. This will support the spears later and
will facilitate the harvest.
Irrigation and drainage:
Especially in the first two years, proper water management is vital for asparagus. Make
sure the soil contains enough water, at deeper layers as well as higher. Irrigate frequently
before the harvest period in case of dryness, to stimulate the growth of young spears. This
will also prevent the soil from forming a thick crust, which will have a negative influence
on spear growth and quality. After finishing the harvest, in case of dryness, irrigate to
stimulate shoot growth for a healthy crop. Make sure the excess water can drain off the
field easily during wet season.
Fertilisation:
During the production years, the main elements required are nitrogen, phosphorus and
potassium. Nitrogen can best be applied after the harvest period, although sometimes the
dose of N and K is split into two half before the growing season and half after it. When
using organic manure, this should be applied in autumn, after the removal of stems. In
general, if FYM is applied, the dose of chemical fertilizers can be kept fairly low.
Some general recommendations are given below. However, fertilization strongly depends
upon the soil conditions and structure, and will have to be defined individually for each
plot.
FYM 15 tons/ha (6000 kg /acre)
N
100-180 kg/ha (40-72 kg/acre
P
50-100 kg/ha (220-40 kg/)
K
100-180 kg/ha (440-72kg/acre)
Crop protection:
The main disease of asparagus in Bhutan is Fusarium wilt/ crown rot. This disease is
characterized by the production of weak, spindly spears in spring. Shoots may exhibit
yellow coloration and some vascular discoloration. Roots can be rotten and discoloured
(red violet colour). Stems infected may exhibit fusarium lesions near the soil line. These
will take the form of a white growth that will cover the whole stem near the soil line.
Control: Direct control unknown. Ensure proper drainage and disinfect planting material.
Handouts prepared by J. Gyeltshen for the 6th batch AG trainees 21 April 2000
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Any pesticide should be applied only after harvest is finished.
Since the presence of the soil fungus Fusarium Oxysporum is very specific to asparagus a
rotation system of 20 years is recommended.
Also after the crop has turned completely brown in autumn, cut all the ferns at the soil
level, collect them and burn them outside the production field to erase possible pests or
diseases.
Harvest
Asparagus can be harvested from the third year (that is the second year in the production
field). Harvest time in general will be from April to June, depending on the altitude and
weather conditions. The first spear should not be harvested and should be left to develop
bushy fern-like stems. In the first year after planting only few spears should be harvested.
As soon as the spears attain a height of 8-12 cm they should be cut about 6-7 cm below
the soil surface. Spears coming after July should not be harvested and left to develop
ferns in order to develop their reserves for the next year’s crop.
For a three-year-old crop, the harvest period should not be longer than 4 weeks.
Harvesting can be done two to three times a week. Stop harvesting after six to eight
weeks and allow the spears to develop into ferns. This way they will form nutrition for
the next year’s reduction. Preferably the harvesting should cease during the period of
vigorous growth. Yield for the next season will strongly depend on the quality of shoots
left to develop into ferns for next year.
Asparagus is kept best upright and while packing leave some space on the top of the
cartons to accommodate the after harvest growth. Optimum condition for storage is at 2
O
C and a relative humidity of 95%.
Grading and packing:
Spears can be graded into three diameter grades and two quality grades. The best quality
spears are straight and undamaged. Diameter grades are:
Small
4-7 mm
Medium
7-13 mm
Large.
>13 mm.
References:
1. The Royal Horticultural Society, London (1981). The Vegetable Garden
Displayed. Pp 57-59.
1. IHDP, MoA, Thimphu ( ) Asparagus
2. Factsheet MoA and Fishery, Ontario, Canada
3. NASEPP - Farm Manager, Tenzin Wangda (personal communication with Chhimi
Dorji)
4. Shanmugavelu, K.G. (1989). Production Technology of Vegetable Crops. Oxford &
IBH Publishing Co.Pvt ltd.
Note:
The above information are mainly drawn from References 1 and 2 and partly adapted
from Chimmi Dorji,s handouts. Reference 3 & 4 are as cited in the same handouts.
Handouts prepared by J. Gyeltshen for the 6th batch AG trainees 21 April 2000
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