Preparation Before Sowing Flower Seeds and Key Points for Fertilizing in Summer and Autumn

(1) Fertilizing in summer: prevent "burning". Summer temperatures are relatively high, and most flowers grow poorly. Flowers that cannot tolerate high temperatures, such as scarlet sage, petunia, Gerbera jamesonii, and clivia, grow extremely slowly when summer temperatures are high and do not have high fertilizer requirements, so fertilization should be stopped at this time. If cooling conditions are good and the flowers can grow normally, they may be fertilized.

Flowers that are in a semi-dormant state in summer, such as Chinese rose and cyclamen, should stop being fertilized, and fertilization should begin again after temperatures drop and growth resumes; for some heat-tolerant flowers such as zinnia, Madagascar periwinkle, cockscomb, gladiolus, and sunflower, summer is their peak season for growth and flowering, so fertilizer should be applied normally. However, because daytime temperatures in summer are relatively high, fertilization should be done in the early morning or evening, and the concentration of the fertilizer should also be controlled to prevent root burn. After fertilizing, immediately rinse the flower leaves with clean water to prevent the fertilizer liquid splashed onto the leaves from burning the leaf surface; aquatic flowers such as water lilies and bowl lotus can also be fertilized normally in summer, and decomposed fertilizer can be buried in the soil at the roots, so there is no phenomenon of root burn or leaf burn.

(2) Be cautious when applying nitrogen fertilizer in autumn. However, for flowers that go dormant in winter, applying a large amount of nitrogen fertilizer in autumn will induce the growth of autumn shoots. The growth of autumn shoots will not only consume the nutrients stored in the flowers, but the growth and flowering of the flowers in the following spring will also be affected. Moreover, because the dormancy period of the flowers will be delayed after autumn shoots grow, cold damage will occur when they encounter low temperatures, so phosphorus and potassium fertilizers should be applied to winter-dormant flowers in autumn. Phosphorus and potassium fertilizers can promote the accumulation of nutrients in the flowers. This lays the foundation for growth and flowering in the following year.

It is not that nitrogen fertilizer cannot be applied at all in autumn. Flowers that do not go dormant in winter can still be given nitrogen fertilizer, and especially foliage plants should still be given fertilizer based mainly on nitrogen. However, when applying nitrogen fertilizer, attention should be paid to combining it with phosphorus and potassium fertilizers. Reasonable application of phosphorus and potassium fertilizers can improve the cold resistance of flowers. Plants that bloom in winter, such as cineraria, calceolaria, cyclamen, poinsettia, and wintersweet, are in the vegetative growth period in early autumn and should be given fertilizer based mainly on nitrogen; in late autumn they are mostly in the bud-forming period, and when fertilizing such flowers, phosphorus and potassium fertilizers should be the main type and nitrogen fertilizer secondary, because too much nitrogen fertilizer is not conducive to winter flowering.