Seed Sowing and Planting Material
|Seed Sowing and Planting Material|
Methods of seed sowing
After the preparation of a nursery, spread the seeds on nursery beds and cover them with finely sieved rotten FYM or compost. This method has some disadvantages, as seeds cannot be placed at equal distance. This might require a large number of seeds in comparison to other methods of seed sowing.
Line sowing (shallow trenches on bed)
It is the best method of sowing seeds in a nursery. Sowing in lines improves germination and quality of seedlings. In this method, each seed gets independent space, and hence, grows healthy and vigorously. In this method, the diseased seedlings and weeds can be managed easily.
On a levelled bed, shallow trench of certain depths are made with the help of a stick width-wise, with the required spacing. This depends on the size of the seeds. Small seeds are sown at shallow depth and at low spacing between rows and vice-versa. Seeds are, generally, sown at a depth of 3–4 times of its diameter. They are placed singly at equidistant points in rows. Small seeds are mixed with sand for even distribution. The trenches are, then, covered with fine soil. The beds require light irrigation from sowing till transplanting by means of a sprinkler or a water can. Mulching of seed beds by polyethylene sheet, paddy straw, etc., helps in quick and uniform germination of seeds. Mulches should be removed immediately after the germination of seeds.
Seed sowing in plug trays
High value and hybrid seeds are preferred to be sown in plug trays (pro-trays) instead of open field nursery beds. Pro-trays are made of soft plastic having shallow plugs. These plugs are filled with planting medium. Coco peat, a by-product of the coir industry having a high water-holding capacity, is commonly used as a medium in pro-trays.
Small depressions (0.5 cm) are made at the centre of the plugs with fingertips for the sowing of seeds. The seeds are placed in the depressions and covered. Water is sprinkled by a water can to maintain moisture.
Rooting of cuttings
Many ornamental plants are commercially propagated by asexual means of reproduction. Planting of rooted stem cutting (duranta, croton, acalefa, etc.), leaves (bryophyllum) or roots (begonia) are important methods in most commercial ornamental crops. Some plants are propagated by grafting and budding, and root stocks needed for this are raised by planting the stem cutting. So, rooting of cuttings is another important method involved in vegetative propagation of ornamental plants. Cuttings are planted on raised beds, flat beds or on the side of ridges, for rooting. For budding and grafting purpose, poly bags of requisite sizes are used for rooting of root stock. Cuttings treated with hormones induce fast rooting. Sand or sandy loam is supposed to be a good rooting medium due to adequate aeration and drainage.
Potting, depotting and repotting
It refers to the transferring of plants from seed bed or polyethelene bags to pots containing potting mixture.Potting of plants involves various steps.
(i) Selection of the pot
(ii) Filling the pot with potting mixture
(iii) Placing the plant
(iv) Watering and staking the plant
Ornamental plants are grown in a variety of pots, depending on the choice and availability. Clay, cement, ceramic, plastic and other kinds of pots are used for growing house plants. However, clay pots are most popular, easily available, highly porous and cheaper. Selection of the appropriate size of pots is significant. The size of the plant and its growth habit are to be considered before selecting a pot. For specimen plant display, the pot size should be of at least 30 cm diameter.
An effective potting mixture must be light in weight and have good water-holding capacity. It allows drainage and helps in supplying adequate nutrition to plants. It must beensured that the mixture is free of insect pests and diseases. For ferns and bulbous plants, the medium needs to be highly porous, comprising coarse sand, light garden soil and leaf mould. Neem cake and bonemeal may also be used in small quantities as nutrients.
(i) Filling of pot
Selection of a pot is made according to the size and growing habit of a plant to be potted. Drainage hole at the base is made to ensure the drainage of excess water. The drainage hole is covered with pieces of earthen tile so that the rooting medium does not flow out with water. Large crocks of 3–5 cm size should be placed at the bottom of the pot to avoid clogging of the drainage hole. A thick layer of coarse sand is placed over it, and finally, the remaining pot is filled with the potting mixture. The pot must have 2.5 cm space from the brim for holding water.
A healthy rooted cutting or a plant with well-established root intake is carefully dug out from the nursery bed. It is, then, placed with the root ball of soil in the centre of the potting mixture. Fill the pot with the potting mixture all round the ball of soil. Press the mixture around the stem firmly and make it compact. Potting of deciduous house plants is done in February–March, whereas evergreen plants in July–August.
Care must be taken that the root ball of plant is not pressed too hard as it will break and damage the roots.
Water the plant gently with a sprinkler can, immediately after planting. Place the potted plant in a cool shady place for settlement. Stake the plant with a bamboo stick, if the stem is long or weak.
It is the removal of a plant from a pot for planting on ground soil, bed or in another pot. As roots are sensitive and prone to injuries, care needs to be taken while depotting a plant. It is better to depot the plant along with the soil attached to the root system. This soil, if needed, can be removed carefully after depotting.
The pot must be watered before depotting. The pot is lifted by one hand, the palm of the other hand spread over the top of the soil holding the stem between the second and third finger, and the thumb along the side of the pot. The pot is then turned upside down. If necessary, a gentle tap is given on the rim of the inverted pot against a solid base or on the edge of bench to loosen the earth ball. The whole earth ball, with intertwining roots of the plant, will come out as a single piece and kept outside carefully. Before transferring the plant in a new pot, the lower old and finer roots along with some old potting mixture are removed.
It is transferring or transplanting a plant from one pot to another. It is the planting of a depotted plant into another pot. Repotting is done with the following objectives:
Changing the existing small old pot or exhausted potting mixture to a new one.
For healthier growth of house plants, repotting and transplanting of established plants is done once in a year.
Repotting facilitates pruning of overgrown roots, which in turn ensures better survival of the plant.
(iv) Bigger size of the pot provides a larger space for root development.
Depending upon the plant type, repotting is done in February–March or just before the onset of monsoon. Cut the decayed, dead, dried or twisted roots neatly with sharp secateurs (see Fig. 3.6). The excess and old soil is gently removed from all round. The pot is filled with fresh potting mixture, and then, watering is done. Place the plant in a new pot at the same depth in the soil at which it was in the old pot.
Nursery plants: Care and maintenance
Nursery plants need care and maintenance when raised from root stock or by tissue culture technique. It is important to provide nursery plants with suitable conditions to ensure their growth and development. The following activities have been executed for the production of good quality planting material.
To protect the young plant in the nursery from intense heat and heavy rains, shade-nets or polythene nets are used.
It is a way of regulating plant population in rows and lines. During this operation, unhealthy, weak, diseased and damaged plants are pulled out to allow healthy plants to grow. It is normally performed when seedlings form few true leaves. It allows sunlight and air to reach each and every plant.
The nursery bed must be irrigated with the help of a water can. After the plants are well-established, watering should be done as per the requirement of the plants.
Weeds compete for nutrients and soil water, which results in poor quality seedling growth. They also prevent air circulation and may harbour insects and disease-carrying organisms, and hence, nursery beds should be free from weeds. Hand weeding or hand hoeing is the most common practice to remove weeds on emergence. Pre-emergence herbicides can also be sprayed on the nursery beds as basal dressing soon after seed sowing to control weeds.
Hardening of plants in nursery
Hardening of seedlings is nothing but withholding of water to nursery beds for few days before removing them for transplanting. Hardening of seedlings is necessary to prepare them for withstanding transplanting shock. It is also practised in situations where preparation of land is delayed and the seedlings become over-sized.