Asparagus is a species-rich plant genus with the botanical name Asparagus from the asparagus family, the mention of which makes every gourmet go into raptures. Since the most popular species, the Asparagus officinalis, is one of the most valuable and expensive vegetables of all, only a Croesus could afford this royal treat every day. However, a practiced hobby gardener is not impressed by this, but simply grows asparagus in his garden himself. The following instructions for growing, caring for and harvesting contain numerous recommendations, hints and tips so that the cultivation of this culinary gift from Mother Nature succeeds right from the start.
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Before you start growing the asparagus, you have to decide which asparagus plants you prefer. Although the genus includes several hundred species of asparagus, there are only a few high-quality varieties that are grown in the local regions. Basically, asparagus is a perennial, herbaceous plant whose short rootstock, the rhizome, can overwinter in the ground. The buds form on the upper side of this rootstock in autumn, from which the much sought-after sprouts, the asparagus spears, develop in spring, which – depending on the variety – are white, green or purple. Since green and purple asparagus are grown a little differently than white asparagus, the choice of variety is the top priority. Some of the most well-known asparagus varieties are presented below:
Ramires – white asparagus
- very early variety
- good head and stem qualities
- uniform growth, white and straight
Gijnlim – white asparagus
- highest quality
- very early budding
- upright pole of medium thickness
- suitable for early foil cultivation
Huchels Schneewittchen – green asparagus
- a classic variety
- delicate and aromatic
- easy cultivation
Burgundine – purple asparagus
- beautiful eye-catcher on the plate
- loses its color when cooked
- so sauté in olive oil
- is served as an accompaniment to white asparagus
Cumulus – new breed of white asparagus
- absolute top quality
- noble, thick, pure white sticks
- slightly sweet aroma
- beautiful, closed heads
All asparagus varieties are available as seeds or annual young plants in specialist shops. The seeds can be obtained from the red berries of the female plants that appear in autumn. Caution! The red berries are not suitable for consumption and cause severe stomach pains even in small quantities.
The selected bed for growing asparagus should have a sunny, airy, southern or southwestern exposure. The soil quality is best if it is slightly sandy, loose and permeable to water. Under no circumstances should there be a risk of waterlogging at this point. Since a well-prepared bed that offers these conditions can be used to grow asparagus for 12 to 15 years, it is worth the extra effort to determine the pH value including the nutrient content of the soil. In order to determine whether the ideal pH value is between 5.5 and 6, soil test kits are available from specialist retailers and cost around 5 euros. The cultivation of the asparagus takes place in these steps:
- Thoroughly clear the bed of stones and weeds. Then loosen the soil deeply.
- Dig a trench 40 cm deep and 20 cm to 30 cm wide. A cord stretched between pegs is used for orientation. The excavated material is piled up next to the ditch.
- Fill the trench with a 10 cm layer of well-rotted compost, topsoil or manure. Spread a part of the earth over it; about 5 cm thick. The bottom of the trench is then at a depth of 25 cm.
- The young plants can be planted in the ground from mid-May, when there is no longer any danger of ground frost and the temperatures have exceeded the 15° mark. These are available in nurseries, specialist shops or online shops. If buds have already developed, they should be handled with extreme care, because the asparagus spears will develop from them. The young asparagus plants are placed in the ditch at a distance of 20 cm, with their root system being spread out like a spider. Contact with the compost must be avoided at all costs. When all the young plants are in the ditch, another thin layer of soil follows so that all the buds are covered. If another row of plants is created, the distance is about 150 cm.
- Fertilization is required immediately after planting. A handful of complete fertilizer spread over 2 running meters of the asparagus row is more than enough.
- Another layer of soil is spread over the manure. Then water lightly and leave the trench in this half-open position for the time being.
- In the weeks and months that follow, the asparagus plants grow, poking through the soil and weeds are regularly removed. In proportion to the growth, the ditch is filled with more and more soil until it is flush with the surrounding surface at the end of the year. In June and August, a dose of complete fertilizer is given, as in May.
Asparagus harvesting is therefore not yet possible in the planting year. Rather, initially only the herb grows upwards, which in November, when it has dried up completely, is cut off just above the roots with rose scissors. Up to this stage of cultivation, all asparagus varieties are treated the same. The following spring, a mound of earth is heaped up to a height of 20 cm over the white asparagus varieties, because only a lack of light causes the white colour. This step is not necessary for the green and violet varieties.
Asparagus on asparagus fails
As much as the successful hobby gardener wishes to plant new asparagus in the same bed after the first cultivation of about 12 years, the chances of this project succeeding are extremely slim. Crop rotation, i.e. renewed cultivation at a different location, is unavoidable. This replanting problem has been known for decades. The cause was previously assumed to be that asparagus places such high demands on the soil that after 10, 12 or 15 years it is simply too exhausted to produce further high-yield harvests. The true cause has only recently been determined. In replanted beds, the roots of young plants are attacked from the start by a specific type of mold, Fusarium oxysporum. The lateral roots rot and the fleshy main roots turn brown.
With good care, the year of planting will be followed by at least 10 years of standing, in which the harvest yield is constantly increased. The following information must be observed:
- In the spring, loosen the bed soil and straighten the mound.
- Spread out an asparagus foil for more warmth and fewer weeds.
- Nevertheless, weeds that appear immediately.
- Fertilize three times in the first year.
- From the second year, fertilize twice with a double dose.
- Always water plentifully and avoid waterlogging.
- Check regularly for insect and fungal infestation.
- Completely get rid of the dead weed every year.
- Do not dispose of in the compost due to the risk of pathogens.
- Additionally fertilize with potash magnesia in February before the new mound is poured in.
- White asparagus varieties must always be covered with a mound of earth.
- Alternatively, build over it with a black foil tunnel 30 cm high and 50 cm wide.
If, after 12 to 15 years, the asparagus spears become thinner and thinner, this is the signal for replanting, which will certainly be even easier thanks to years of experience.
The start of the harvest depends on the weather. As a rule, it can start from mid-April. In the first year it is advisable to harvest only one asparagus spear per plant. In the second year, the harvest takes place over a period of a maximum of 5 weeks. From the third year, the harvest runs normally until June 24th, St. John’s Day. The reason for this exact limitation of the harvest time is that the plant then has at least 100 days before the first frost to gather fresh strength for the next year. This period can only be exceeded if an asparagus bed is harvested for the last time.
The popular white asparagus is harvested twice a day during the main growing season, in the early morning and late afternoon. At this time, the evaporation losses are significantly lower than, for example, at midday under blazing sunlight. There are now mechanical harvest wagons for the foil-covered mounds of earth, which lift the foil over a length of 2 meters each, but the main work – cutting the asparagus – is still done by hand. The following tools are required:
- Asparagus knife (curved at a 30° angle)
- Asparagus trowel (similar to a bricklayer’s trowel)
When the earth wall rises slightly in white asparagus and small cracks can be seen, the asparagus spear is carefully exposed with spread fingers and pricked as deeply as possible. The resulting hole is immediately filled with moist soil, which is smoothed out with the asparagus trowel. It is imperative to ensure that the dam flank holds securely. With green asparagus, the only difference in the harvesting process is that it is not under a bank of earth. The harvested asparagus spears are collected in the basket and washed as quickly as possible, so that they are then stored in a cool, damp and dark place until they are eaten.
pests and diseases
Probably the most important pest is the asparagus fly, which not only fears hard-working hobby gardeners, but also spreads fear and terror in commercial cultivation. She is particularly interested in young plants. There the females lay their eggs in the spring, from which the larvae hatch after 3 to 4 days and devastate the young asparagus plants. Since no natural enemies of the asparagus fly have been discovered so far, insecticides are used, but only in plants where no harvest takes place and in the year of planting. Environmentally conscious hobby gardeners recommend cutting off and burning infested shoots immediately. As a preventative measure, insect nets can be stretched over the beds, which are particularly fine-meshed.
Asparagus rust, a fungal disease, is also particularly difficult for the asparagus plants in the first three years. The leaves and shoots change color and the entire plant dies. So that it doesn’t get that far in the first place, the plants should be placed as airy as possible and not in a wind-protected location. In addition, affected parts of the plant are removed immediately.
The vernacular has been saying for centuries: ‘Don’t forget to eat asparagus for seven weeks until St. John’s Day.’ Thanks to modern cultivation techniques, such as asparagus foil or the foil tunnel, which are also available to dedicated hobby gardeners, the delicious white, green and purple asparagus spears can be harvested and enjoyed from mid-April to June 24th. Anyone who heeds the most important requirements for cultivation and care will have home-grown asparagus on their plate for up to 15 years from the first year; a culinary highlight that is hard to beat.