The plant of Asparagus
The asparagus (Asparagus officinalis) is an herbaceous perennial, monocotyledonous angiosperm plant, member of the lily family: it is a dioecious plant, which means that bears male and female flowers on different plants. The male plant is more vigorous, precocious and productive that the female plant, but produces more thin shoots; the fruits, produced instead only by the female part, are small red berries containing black seeds.
A plant of asparagus is formed by an underground rhizome from which differ roots and buds: all this together in horticulture is technically called the "paw". From rhizomes, or roots, which grow under the ground, forming a star pattern, in April and May develop the shoots, the edible part of asparagus, consisting of a "fleshy" shoot of different sizes, with a very mild and sweet flavour.
The shoots begin to grow and develop at the end of winter, when the temperature begins to rise, that is when it gets to about 10°C, because in these conditions, nutrients begin to move from roots to buds and viceversa.
When the shoots come up to the surface, they are long, more or less thick and they have in the apical part, leaves similar to flakes.
When the shoot is not even popped out of the ground it is hite, stocky, with a rounded apex, while, when it comes into contact with light, it becomes increasingly rosy until it becomes purple and finally of a more or less intense green colour, as a result of photosynthesis.
The seeds of asparagus germinate around 20-22° C, as the minimum temperature of germination is about 10-12°C and the maximum of 34-35°C.
When the soil temperature near the rhizomes, reaches 10-12 °C, the plant begins to produce shoots. The Shoots of the plant of asparagus develop from the roots (rhizomes) that grow under the ground, forming a star pattern and are commonly called paws. Therir length varies between 1 and 1.5 metres and should be harvested when they are still tender. They have light, branched and deciduous leaves and small flowers on stalks, in part hermaphrodite and in part separated into male and female: the flowers of asparagus are bell shaped with white petals striped with green or yellow.
The flowering of asparagus starts in late June, when the ripening of the shoots is already completed, and lasts about two weeks.
The fruits of asparagus consist of red berries containing black seeds, present only on the female plants.Unlike many other fresh vegetables where the smallest and thinnest sprouts are also the most tender, in this case the largest stalks of asparagus and of other similar fresh vegetables result to be the most tender, as they have more pulp.
Asparagus is a hardy plant that grows naturally near the coast and in submontane regions, both in insular and peninsular Italy: it is able to adapt to any climate, as long as there is a great amount of brightness, and they are cultivated far from trees that shade.
Asparagus, from the point of view of the ground, has particular needs with regard to water conditions, which must always be at optimal levels for the planting of seedlings, which is performed at a considerable depth. For the cultivation of asparagus, therefore, it is preferable that the soil is loose, sandy, well-structured and well drained.
Today, in fact, asparagus is widely cultivated in sandy or even wild soils.
It is best to rotate the cultivation od asparagus with that of different cereals, while rotation with potatoes, beets, carrots, alfalfa and beans is not advisable, because these crops may be affected by root rot, disease that can be transmitted to asparagus and remain active even for 15-20 years.
The cultivation of asparagus lasts more years and requires special planting techniques that can be oriented to direct or indirect seeding. In Italy, very important is the cultivation in open field, which is possible because the plant can withstand cold weather. However, also the forced cultivation is possible, with or without heating.
Among the parasites of the plant of asparagus, the most important is the asparagus fly, an animal that digs tunnels through the vegetable, causing the death or the deformation of the shoots: the prior fight to this parasite is done through the destruction of the infested stems of the plant and the planting of new plants of asparagus in ventilated areas, while the direct struggle is based on treatments with quassia wood added to soap.
The aparagus beetle, instead, is an animal that gnaws the aerial parts of the plant: the struggle in this case consists in sprinkling the plants with lithotamnion with the favour of dew or treating the plant with rotetone.
Among the disease of the plant of asparagus, however, the most important is the asparagus rust, which appears in spring on the shoots, causing oval yellowish spots, while later, on stems, branches and leaves spread brown pustules, which produce the reddish powder, with the consequent withering of the aerial part. The prior fight to this disease involves eliminating in spring the wild asparagus and then burn the stalks in fall, to eliminate the infected spores. The direct fight instead, consists in treatments with a water-alcohol solution of propolis (150 cc.) added to Sulfar.