Ian Hodgson continues his course for beginners by describing the basic techniques of sowing.
On the face of it, the actual act of sowing seed seems simple enough. Surely, it's just a matter of scattering seed liberally over the surface of the compost. But many would be seed raisers have come to grief by not employing the right techniques suited to their particular type of seed. Common mistakes range from completely missing the target by holding the seed packet too high above the surface of the compost to sowing far too thickly so that young seedlings are immediately in competition with each other for space and light. Seed is expensive, particularly with many F1 hybrid stock and few people can afford to scatter it about like confetti at a wedding!
Careful sowing can prevent many serious problems occurring later on and significantly raise the number of successfully raised seed grown plants. Success also stimulates enthusiasm and so getting everything right from the word go can only make seed raising all the more rewarding.
First of all familiarise yourself with the type of seed you are sowing. The size and shape of seeds offers incredible variety from those the size of the coconut to the minute thread-like seeds of orchids and the dust-like spores of ferns. To see the latter, you will need the use of a powerful hand lens or microscope and they pose their own special sowing problems. More often than not, you will not have had the opportunity to see the size and shape of the seeds having been solely lured by an attractive colour picture on the front of the seed packet. I never fail to be in awe at the range and sheer variety of seed shapes, colours and forms, from the brightly coloured tufts of hairs on the seeds of Strelitzia to the intricate silvery mottling on the seedcoat of Ricinus, the Castor Oil Plant. Hairs, spines and barbs attached to some types of seed can make sowing and handling difficult. The juice or gum contained in berried fruit may cause dried seed to stick together. These must be loosened from one another before sowing.
It's a good idea to only open the packet when you are good and ready to sow your seed. From bitter experience, seed from opened packets is very easily spilt and it always happens to be the most expensive or scarcest seed that goes! Seed is sealed in foil packets to keep it as fresh as possible.
Opening the packet prematurely can destroy that extra protection. Before opening the packet make sure that all the seeds have dropped to the bottom end. Opening the packet with the seeds trapped at the top can result in disaster. Some companies package their expensive seeds in an inner sleeve contained inside the colourful outer jacket. Most companies repackage very fine seed in a smaller inner envelope to make them easier to handle and prevent them falling out. Try to refrain from opening fine seed packets until the last moment. Opening then unnecessarily is like opening Pandora's box, one sneeze, involuntary shake of the hand or slight gust of wind and you're lost.
First of all before you sow any seed, always obey the instructions on the back of the packet. This will give you all the concise information you will need to know about successfully raising your seeds, such as the timing of sowing, sowing depth and the optimum temperature for germination. Other information will be given if the seed has any other peculiar or individual requirements. The information is the result of years of trials and research. Ignore it at your peril.
Before commencing to sow, have all your materials prepared and ready to hand. Have compost pressed and leveled in pots and containers.
Seed should always be handled with care. Even though they appear not to be, they are living organisms. Their life processes have been slowed down to the barest minimum but nevertheless, they are sensitive to changes in environmental conditions.
As a general rule, smaller seeds have thinner, more absorbent seedcoats and so handling them directly with the fingers can damage them irreparably. The skin on our fingers exudes grease, acids and many other substances which are toxic to seeds, as well as providing a home for innumerable fungal spores and bacteria. Even light pressure when held between the fingers can bruise or damage delicate structures in the seed.
Larger seeds such as those from many trees and shrubs are usually space sown. The technique involves individual seeds being placed in an allotted amount of space. By predetermining the amount of space each seedling is allowed, overcrowding will be avoided and the seedlings will be stronger and healthier. Abnormal growth caused by overcrowding seedlings can have serious repercussions on the appearance of many slow growing or woody plants later on. Seed can be sown together in trays or half pots. Alternatively plant single seeds individually in 2½in (6cm) pots, expandable Jiffy 7 pellets, or plastic cell trays.
To sow make a hole with a dibber, to the planting depth. Drop in the seed and cover. As a rule of thumb, cover the seed with the same thickness of compost as its diameter. Alternatively place all the seeds in position in the container and then press into the compost with a flat smooth surface. Again cover the seed with a thin layer of compost. Makeshift presses can be easily made from off cuts of timber. Made to fit just inside the rim of pots and containers, they can be used to firm down both compost and seed.
The position that seeds lie in the compost can have a bearing on the success of germination. With perfectly round seeds this is obviously immaterial but to seeds which are long and flat this can be crucial. This is particularly the case with the cucumber family, the Cucurbitaceae, which has many familiar vegetables such as cucumbers, melons, squashes and of course ornamental gourds. Laid flat, water can collect behind the raised rim on the edge of the seed causing it to rot. It is best pushed vertically, sharp end first into the compost, so that excess moisture is shed.
Many seeds possess appendages to aid their dispersal, such as the wings of Ash (Fraxinus), Maple (Acer) and Hop Tree (Ptelea). For relatively small amounts of seed, the wings can be safely removed with sharp scissors, making them much easier to handle and convenient to space sow. Do not forget that many members of the Pea family, Leguminosae, require pre-treating before sowing. Hard seed coats may require soaking in warm water for a number of hours or chipping with a sharp blade to allow water to enter.
For general purposes, seed can be dispensed straight from the packet. Various techniques can be used which enable the seed packet to become the dispenser.
Firstly, open the packet by cutting off one corner or carefully slit open the entire end with a sharp knife. Turn the packet with its longest edge vertical with the open end slightly dipped. With the top index finger gently tap the top of the packet with sufficient force to vibrate the seeds out of the packet.
Hold the open end of the packet about 1-2 inches (25-50mm) above the surface of the compost so that the seeds fall where they are directed. Whilst tapping, the packet should be moved slowly and evenly over the entire surface of the container so that all the seeds are evenly broadcast.
Alternatively, the packet can be held horizontally and the bottom panel of the open end squeezed to form a 'beak' or 'V. This will help collect and direct the seeds to where they are wanted. Again, dipping the open end slightly, simply tap the top of the packet and allow the seeds to run into and off the beak.
If you don't like using packets, pour the seed into the cupped palm of one hand and sprinkle small amounts of seed with the fingers of the other hand. With practice, seed can be held in the cupped hand and allowed to fall down the wrinkles of the hand by gently twisting the wrist or tapping it with the fingers of the opposite hand. Unevenly sown seed can be relocated by moving the seed to new gaps with the point of the dibber or a pencil.
Fine seeds have their own particular problems. Many of our favourite plants such as Calceolaria, the Slipper Flower and Campanula, the Bell Flower, have very fine seeds. These can be sown by carefully opening the small protective envelope and tapping it in the normal way so that the showers of tiny seeds are spread as evenly as possible. Ensure that conditions are as still as possible whilst you are doing this. Accurate sowing of fine seed takes practice if you are to avoid overcrowding. The seed can be made easier to handle by bulking it up with an equal amount of fine dry silver sand. Mix seed and sand in a small container, stirring it carefully until it is well mixed. The mixture can then be sown in the normal way.
For the exceptionally fine, dust-like spores of ferns the following method of sowing is very effective.
Take a couple of sheets of coarse, clean paper. Stand the filled, prepared tray or pot on one and pour the fern spores in the centre of the other. Spread the spores around until the paper is covered evenly. Tap off the excess back into the packet.
A layer of spores should now be adhering to the fine fibres of the paper. Invert the sheet, so that the spores are immediately above the compost. Drum your fingers over the paper so that the spores are dislodged. Remove the top sheet and container and return any spores which have fallen onto the bottom sheet back to the packet. Before sowing any fine seed or spores, make sure that the compost is adequately moist. Once sown, pots are best soaked from the bottom.
Many plants from cooler climates and prolonged winters require their seeds to be subjected to a period of low temperatures before they will germinate. Many of these can be sown fresh during the autumn and left outdoors over winter.
Instead of sowing them directly outdoors seeds can be chilled artificially by storing them in the bottom of a refrigerator. Collected fresh, the seeds are immediately mixed into a 50/50 moist peat/sand compost and placed inside a plastic bag. Store this inside the general part of the refrigerator, there is no need to use the icebox or deep freeze.
In spring, when the temperatures are more favourable, the whole contents of the bag can be sown in the usual way.
Ian Hodgson trained at Kew.
Source of article
Growing From Seed - Autumn 1988 Vol. 2 Number 4
© The Seed Raising Journal from Thompson & Morgan