What are the factors affecting the emergence rate of autumn-sown flower seeds?
Autumn is the sowing season for many flowers. Biennial or perennial herbaceous flowers cultivated as annuals or biennials, such as snapdragon, dianthus, daisy, and corn poppy, along with open-ground flowers like cineraria, cyclamen, and gloxinia among greenhouse flowers, as well as flowers that easily lose germination capacity after seed harvesting such as delphinium, African daisy, primula species, and begonia species, are all suitable for autumn sowing. To improve the emergence rate of autumn-sown flower seeds, one must first understand some reasons affecting the emergence rate of flower seeds, so as to take corresponding measures and handle them properly.
1. Problems with the seeds themselves
Currently there are many flower seeds on the market, and some packaging is quite elaborate. When purchasing, whether domestic or imported seeds, please pay attention to the production date and shelf life marked on the packaging bag. Do not buy seeds that do not indicate the production date and shelf life; expired seeds have mostly lost their vitality and will not germinate or emerge.
In addition, when purchasing seeds, one should have a basic understanding of them, for example, knowing whether the seeds bought are annual or biennial flowers or perennial flowers, and whether they are spring-blooming or autumn-blooming. According to common knowledge, seeds sown in spring generally bloom in summer and autumn; seeds sown in autumn generally bloom in the following spring and summer (except woody flowers). If this is reversed, it is very difficult to achieve the expected flowering purpose without certain cultivation equipment. Purchased seeds, especially flower varieties that have never been cultivated before, should be given heightened attention.
2. Inadequate seed treatment
Different flower seeds should adopt different treatment methods: for seeds that germinate easily, the soaking method can be used. For example, salvia seeds soaked in warm water at room temperature 40°C for a day and night, rinsed clean, can then be sown. Hard seeds such as asparagus fern, tree peony, orange jasmine, crape myrtle, and winter daphne are best first soaked in hot water at 40°C for about 48 hours, then sown into potting soil, and after 20-30 days they can sprout and grow. For species with a short dormancy period that germinate easily, such as pearl plum and redbud, soaking in warm water at 40°C-60°C for 24-48 hours allows direct sowing. Some flowers such as lilac, wintersweet, and some autumn-sown herbaceous flowers require a certain period of low-temperature (0°C-10°C) treatment to promote after-ripening, break the dormancy of the seed embryo, and germinate.
The method is to mix the seeds with sand at 60% humidity, then put them into a plastic bag, tie the opening tightly, place it in a flower pot, and then bury the pot together in open ground at a depth of 40cm-60cm; alternatively, place the seeds in a refrigerator at 3°C-5°C for 60-90 days, then take them out in spring and sow. They can also be sown in autumn, allowing the seeds to pass through natural freezing outdoors in winter and germinate and emerge in the following spring. Some flowers such as fringetree, viburnum, and peony have seeds with the characteristic of double dormancy of radicle and hypocotyl, that is, their radicles need to pass through a high-temperature stage of 25°C-32°C for 1-2 months or longer to break dormancy. For such seeds, before sowing they must be mixed with wet sand and undergo a period of high temperature, then transferred to low temperature; after high-temperature treatment, sowing in spring will allow them to germinate and emerge quickly.
3. Ignoring the suitable temperature conditions for seed germination
The germination of dry seeds requires not only certain moisture conditions but also a certain suitable temperature. For example, the suitable germination temperature for sweet alyssum must be 5°C-20°C, the suitable germination temperature for African daisy must be above 20°C-25°C, and the suitable germination temperature for primrose must be within the range of 15°C-18°C. Temperatures too high or too low will affect the emergence rate of flowers, especially causing seed moldiness and rot, greatly reducing the germination rate and seedling survival rate.
4. Unreasonable sowing time
Seeds that are relatively small with loose, thin outer coats, such as those of chrysanthemum, asparagus fern, garden balsam, crape myrtle, and trumpet vine, are suitable for late spring sowing; seeds that are relatively large, have hard outer coats, or contain oil, such as those of Chinese rose, rose, pomegranate, kumquat, and southern magnolia, are suitable for autumn sowing. Seeds that are relatively small, have thinner outer coats, and require high temperatures should be sown promptly after maturity, such as cyclamen, cineraria, and amaryllis, which should all be sown in early autumn. Dianthus, pansy, golden melon, and corn poppy should be sown in late autumn.
5. Problems with sowing quality
Flower sowing has two methods: open-ground sowing and pot sowing. Whichever method is used, the soil is required to be loose and aerated, with fine particles, hygienic and non-toxic, rich in humus, and moderately acidic or alkaline fertile soil is relatively better. This is conducive to seed emergence.
Sowing methods include broadcast sowing, drill sowing, and hole sowing. Before sowing, water sufficiently; after sowing, cover with plastic film or cover the flower pot with a glass sheet to help preserve moisture and prevent the soil from becoming too dry, which would affect seed germination and emergence. The sowing depth should preferably be about 2.5 times the diameter of the flower seed grains. For tiny seeds such as cockscomb, August chrysanthemum, wax begonia, and cineraria, mix the seeds evenly with fine sand or soil powder before scattering. During the period of seed germination after sowing, attention should be paid to spraying water to maintain moisture, but spraying should not be excessive, to prevent lowering the soil temperature or rotting the seeds and the fibrous roots of seedlings, which is unfavorable for improving the emergence rate.
6. Ignoring the effect of light
The sensitivity of seeds to light can be divided into light-favored seeds, light-averse seeds, and neutral-light seeds. Light-favored seeds require a certain amount of light for germination, while for light-averse seeds, light has a certain inhibitory effect on seed germination; their classification is not absolute. Light-favored seeds are generally small in size, and after sowing need not be covered with soil or only lightly covered; for light-averse seeds, cover only until the seeds are no longer visible, and for slightly larger seeds, the covering soil thickness is 2-3 times that of the seeds.
After flower seeds are sown, light can increase soil temperature and induce seed germination, and is especially important for seeds to break through the seed coat and put out roots and sprouts. It not only affects the emergence rate of seeds but is also directly related to whether good, strong seedlings can be grown. Therefore, from sowing to transplanting, it should be a process from darkness to weak light and then to natural light, and the light needs of flower growth should be met as much as possible according to the different sowing, germination, and emergence stages.