When is the latest planting time for asparagus?

Asparagus is one of the world's top ten famous vegetables, also known as shidiaobai or longxucai (different from haifacai——a deep-sea vegetable, which is also sometimes called longxucai). It enjoys the reputation of “king of vegetables” on the international market. Asparagus is rich in various amino acids, proteins and vitamins, with levels higher than those of ordinary fruits and vegetables. So when is the best time for asparagus?

Planting time for asparagus

The planting time for asparagus is generally spring.

Asparagus sprouts new stems 2 to 3 times or more each year. Generally, the tender stems that sprout in spring are used for eating, and their growth depends on the nutrients stored in the roots from the previous year. The growth of tender stems and the formation of yield are positively correlated with the number of mature stems and the degree of lushness of branches and leaves in the previous year. As the plant ages, the number of tender stems produced and the yield increase year by year. As the rhizome continues to branch, the clump tends to decline, the aboveground stems become increasingly thin, and the yield and quality of tender stems gradually decrease. Generally, the peak production period is 4 to 10 years after planting.

If you want to grow asparagus in the open air, raise seedlings in April and May and plant in July and August. If growing asparagus in a greenhouse, you can also raise seedlings in August and September and plant in October.

Growing conditions for asparagus

Asparagus has a relatively wide temperature tolerance. The suitable temperature for seed germination is 25-30 degrees, and the optimal temperature for vegetative growth is 20-30 degrees. Below 15 degrees, growth is slow and few tender stems are produced. Above 30 degrees, the outer skin of tender stems easily becomes fibrous and the tips easily splay open, resulting in poor quality. Above 35 degrees, growth stops.

In addition, asparagus is a sun-loving plant and requires strong light. With sufficient sunlight, it grows lush branches and leaves, and photosynthesis is closely related to temperature. Of course, high-temperature seasons are unfavorable for asparagus growth, and prolonged rainy weather also affects asparagus yield.

Also, asparagus is a deep-rooted crop, and the young stems need to be earthed up for shading, so you should choose a sandy loam soil with deep soil layers, loose and fertile texture, and rich organic matter. A pH of 5.8-6.5 is optimal.

Common problems in asparagus cultivation

1. Discoloration of white asparagus: White asparagus, used as a raw material for canning, is grown by earthing up to soften it before harvest. Generally, asparagus harvested after earthing up should be white or creamy yellow. If it is green or the tip is green-red, it is discolored. The causes of discoloration are: first, the soil is too clayey or too sandy. The former easily cracks, while the latter has large pores, creating gaps that let light through and cause the asparagus to discolor upon exposure to light; second, when soil temperature is high and dry, the earth-up soil easily dries and cracks or is too loose, and the soil pores are too large, allowing light through. To prevent discoloration of asparagus, care should be taken during cultivation to select sandy loam soil, plow and harrow carefully so that soil particles are uniform in size, maintain moderate moisture, and keep the earth-up soil uniformly firm. If ground temperature is too high, water appropriately to increase soil moisture and reduce cracking. If conditions permit, covering with black film instead of earthing up for blanching cultivation gives better results.

2. Deformed asparagus: At harvest, asparagus tender stems that are curved, uneven in thickness, or have a non-round or flattened cross-section are all deformed. The main cause is the application of undecomposed organic fertilizer or a single excessive fertilization, which burns the growing point of the tender stem or inhibits its normal development; second is high soil viscosity, many clods, and uneven firmness of the earth-up soil, which hinders the normal growth of tender stems; third is pest damage when the tender stems emerge. Control measures: plow the soil finely so that it is loose and free of stones and clods. In addition, keep the earth-up soil uniformly firm, and pay attention to controlling underground pests.

3. Hollow asparagus: Tender stems with hollow centers are hollow asparagus. It is mostly caused by an imbalance in nutrients, lack of phosphorus and potassium fertilizer, excessive application of nitrogen fertilizer during the harvest period, and excessive vegetative growth of the plant. Control method: Pay attention to rational fertilization during the harvest period, especially topdressing with phosphorus and potassium fertilizer. Do not apply nitrogen fertilizer alone, to ensure that the aboveground parts grow thick and strong.

4. Cracking of tender stems: During the harvest period, tender stems split longitudinally into brown deep cracks and cause rot. The cause is a lack of phosphorus and potassium fertilizer in the soil and excessive vegetative growth of the plant; second is a long drought followed by heavy water, causing the tender stems to expand too quickly and crack. Control measures: Pay attention to increasing the application of phosphorus and potassium fertilizer, and water evenly, avoiding alternating drought and wetness.

5. Off-flavors: Asparagus has a mild taste. Excessive bitterness or other off-flavors will affect its commercial value. The causes are contamination by pesticides and irrigation with urban wastewater, or contamination by toxic exhaust gas and industrial waste. For this reason, do not apply inorganic fertilizers when earthing up; before and after earthing up or during the harvest period, the use of pesticides and garbage fertilizer and irrigation with industrial wastewater should be strictly prohibited.