Sowing Seeds in Pots and Boxes and Transplanting

Seeds can be sown into pots, seed pans or boxes. Sheets of glass and pieces of paper (newspaper will do, but thick brown paper is better) are needed to cover the receptacles until germination takes place. The glass is placed over the soil to prevent rapid drying out and lessen the need for frequent watering, and the paper is placed over the glass to exclude light and provide the ideal conditions for germination.


Hygiene is most important. Pots or pans that have already been used should be well washed and scrubbed. New pots should be soaked in water for several hours before use, to allow the clay to absorb as much moisture as possible, otherwise new pots will absorb the moisture from the potting medium and the plants will suffer. Some good time before they are needed, treat seed boxes with a wood preservative such as Cuprinol, which will not only preserve the wood but also act as a disinfectant. Do not use the commercial grade of solignum.


It is very important to provide good drainage. Fill the seed pots to one-third of their capacity with clean crocks and give seed pans a good layer of crocks over the drainage holes. On top of the crocks, use clean moss, dried leaves or loam fibre to prevent the soil clogging the drainage holes. With seed boxes a layer of large crocks over the space between the bottom boards is all that is needed, but the bottom of the box should be covered with leaves or fibre before the box is filled with soil.


The seed compost should be an open sandy mixture, consisting of two parts sifted loam and one part each of peat and sand, to which a fertilizer has been added to ensure the health and growth of resulting seedlings. This fertilizer should be composed of 1-1/2 oz. Superphosphate and 3 oz. Ground chalk or lime for each bushel of soil. Home-mixed composts should be sterilized by steam or chemically by formalin. John Innes composts, which are sterilized composts ready mixed to a formula, can be bought from horticultural nurserymen or nurserymen for seed sowing and for potting.

Fill the receptacles with compost to within 1 in. of the top, moderately firm the compost with the fingers(not thumbs) to get an even surface, and finally level it with a patter or firmer (a flat, circular piece of wood nailed in the centre to a short length of broom handle) or the base of another pot. Then water the pots with a watering-can fitted with a fine rose, or stand them in an old galvanized bath or similar container, and fill the bath with water to just below the rims of the pots. Allow the water to rise through the soil and moisten the surface, then lift out the pots and allow them to drain. A thoroughly moist soil before planting provides the best conditions for germination and prevents the need for frequent watering while the seeds are germinating.


The actual sowing is governed by the same rules as for outdoor sowing. Scatter flat seeds — like those of lilies, hippeastrum or amaryllis and grevillea — thinly and evenly over the soil, and press each seed gently on one side with a pencil or pointed stick to set it on edge. This ensures better germination than if the seeds are allowed to lie flat on the soil. Afterwards, gently cover the seeds with fine, sandy soil and firm the surface.

All seeds sown under glass should be sown thinly. Overcrowded seedlings are prone to ‘damping off’, a disease caused by a fungus that spreads rapidly over the surface of the soil, attacking the lower part of the stems and causing the seedlings to collapse and rot. Any seedlings that are allowed to become thin and drawn are apt to succumb to this disease, which can also be caused by a damp atmosphere and general lack of light and air in the greenhouse.


Watch carefully for the appearance of the seedlings and, as soon as they are plainly visible, remove the glass and paper. At this stage light and the normal air conditions of the greenhouse or frame are essential.

Avoid draughts, as a current of cold air can do a lot of harm and even result in the loss of the seedlings. Shade the seedlings from strong sunshine during the hottest part of the day to prevent them from flagging. Unnecessary exclusion of light is harmful and can only result in spindly growth, so make sure that the shade is supplied by outside blinds or by something erected inside the house well above the seedlings.


If cold frames are used and the seeds are sown in pots, pans or boxes, the procedure is much the same as already described, the only difference being that there is no artificial heating and therefore the germination and growth of the seedlings is slower.

Much depends on the quantity of plants required, but if the seed bed is carefully prepared and the frame is properly ventilated, a great variety of plants can be propagated in this way. The advantage of a cold frame is that the operation is more controlled than when an outdoor bed is used, because there is little interference from the weather and pests, and a much earlier crop can be obtained.

When sowing early crops of vegetables, such as lettuces, carrots or radishes, in a frame, sow the seeds directly into a bed of soil with a reasonably firm, fine tilth, prepared in much the same way as an outdoor seed bed. Seed drills can then be drawn from back to front of the frame, or the seeds can be sown broadcast. A frame can also be used in late summer to raise seeds of biennial plants such as pansies, double daisies, sweet Williams, forget-me-nots and similar flowering plants.


The next step is the transplanting of the seedlings or, as it is called when done under glass, the pricking out. Do this as soon as the seedlings produce their first true leaf, when they will be large enough to handle. The first ‘leaves’ to appear are the cotyledons or seed-leaves, and their shape is normally simple and more or less rounded. The true leaves appear with a stem from between the cotyledons and can easily be recognized by their more intricate shape, which varies according to the plant, and may be smooth or hairy.

The first transplanting needs to be done carefully, because the seedlings can easily be damaged by careless handling when young and tender. Prick out into boxes or pans filled with a light, sandy compost. Use a small pointed stick or dibber in one hand to make the hole in the soil, pick up the seedling with the other hand and place it carefully in position. Then gently firm the soil round the roots with the dibber. For very small and rather delicate seedlings, such as those of the begonia, a small V-notched stick made from a label can be used to lift up the tiny seedlings and place them in the holes. Space out the seedlings evenly, allowing about 2 in. between them in the row and 3 in. between each row.

To ensure that the operation checks the growth of the seedlings as little as possible, always prick out seedlings into damp soil and do the work in the green-house or in a warm potting shed.

Grow on the seedlings in their boxes under the same conditions and gradually accustom them to more and more air until they are ready to withstand outside conditions.

Most seedling plants can grow in their boxes until the leaves touch, but at this stage it is wise either to pot them singly or to transplant them into outside beds or borders.

05. September 2013 by admin
Categories: Gardening History, Plant Biology, Top Tips | Tags: , , , , , , , , , , , , | Comments Off on Sowing Seeds in Pots and Boxes and Transplanting


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