This section is from the book "Commercial Gardening Vol3", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
To succeed in forcing Strawberries for profit, it is essential in the first place to secure good strong plants. It is waste of time and money to force weak plants, and the results from such can never be satisfactory from a financial point of view.
To secure vigorous plants, the best way is to put out in early autumn a certain number of young plants for the production of runners early in the following year. Plants that are allowed to carry a crop of fruit first, produce runners not only later but also less vigorous. The bed should be placed as near the water supply as possible, to save work in watering.
As soon as the flower trusses appear in spring they should be pinched out. All the energy of the plant will thus be directed to the production of runners, of which there will be a good supply, as a rule, about the end of June.
For layering the runners, small 60's (2^-in. pots) are the most suitable.
No crocks need be used in these for drainage purposes, and any ordinary good soil will do for filling the pots, pressing it down firmly, but not making it hard.
A single layer should be placed in each pot, and may be kept from shifting by placing a stone on it, or by pegging it down with a cheap hairpin (100 for Id.) The method adopted by the writer is to pass a piece of raffia about 3 in. long round the runner stem just behind the crown, give it a twist, and press the ends into the soil with a blunt dibber. It is quickly done, and long before the raffia decays the runner will be well rooted and fit to sever from the parent plant. Only one layer should be made from each runner; those growing beyond should be pinched off unless stock is very short, when two layers from each runner may be taken.
The runners should be kept well supplied with water, and at the end of a month or so they will be well rooted and ready for moving into fruiting pots. These should be 32's (6 in.), as smaller ones do not give satisfactory returns, and entail more labour in watering. The pots should be clean and well drained, with a layer of crocks over a stopper in the bottom. The soil should consist of 3 parts of good rather light loam, and 1 part of well-rotted manure, such as may be obtained from an old mushroom bed. Add a sprinkling of soot, and mix the whole thoroughly a few days before using. The compost should be protected from rain, as it is very injurious to pot the plants into wet, sticky soil.
In potting, the crown of the plant should be kept well up, and not buried lower than the surface, and the soil should be made very firm round the roots with a good ramming stick, leaving, of course, sufficient space on top for watering.
After potting, the plants should stand on a good hard bottom in an open sunny situation, and should not be crowded close together. Attention must be given to suppressing weeds and runners, thus allowing each plant to concentrate its energies in making good crowns.
Water must be given in abundance, and when the pots are becoming full of roots weak manure water may be given with great advantage. The drainings from the stable, well diluted, are as good as, if not better than, any artificial manures, and the cost is much less.
Before severe frost sets in, the pots should be plunged in ashes, or some litter should be put between them, to prevent them from being cracked by frost. It used to be thought necessary to put the plants in cold frames, or make them into stacks with ashes between the pots; but this is quite unnecessary labour.
Unless for a special object very early forcing is not very profitable. Although prices may be high there is only a limited demand for the fruit, and the plants will not bear such heavy crops as they would later on. The first batch of plants should be brought into the houses early in January, and if a continuous supply of ripe fruit is desired, batches should be brought in every three weeks. They are best accommodated in a house by themselves. In most places, however, shelves in early Peach houses and vineries are utilized for the purpose of growing Strawberries.
The plants should be syringed when the other occupants of the house require it; but in naturally damp houses, without stone or brick floors, syringing is not necessary.
When the plants are first brought in, allow them to stand for a few days to dry; also see that the drainage is good, and make each plant firm in its pot. When the bloom trusses appear, spread a layer of well-rotted manure on the shelf and stand the pots on it, pointing all the trusses of flower to come one way towards the light.
The plants will soon root into the manure through the drainage holes, and the flower trusses will be thrown well up from the pots.
At this stage a pinch of some good fertilizer to each plant will be found very beneficial. When the plants are in flower the atmosphere should be kept in a buoyant condition by opening the ventilators a little, and the flowers should be fertilized with a camel-hair pencil or rabbit's tail, doing this when the pollen is dry, generally about midday. When a sufficient number of flowers have set to ensure a good crop, the others should be cut off" at once. This will concentrate the energies of the plant into swelling the fruits.
Before the fruit gets too heavy to bend the stems, the trusses should be kept up by running a string on a few sticks along the front of the row of plants. This will be found much better than tying each plant up separately. Where, however, several rows are grown on a stage, it is better to tie each plant up.
The soil must not be allowed to get dry, and the plants should be well fed at alternate waterings with some good stimulant, and all syringing and damping should cease as soon as the fruit shows signs of colouring.
Gathering is best done when the fruit is quite dry, and if it has to be sent by rail, pack in shallow boxes, one layer deep only. The fruit should not be allowed to get too ripe, and should be graded into best and seconds, which will be found better than mixing large and small fruits together.
If the fruit is sold locally, it may be packed in 1/2-lb. punnets with a lining of fresh leaves to make the "berries" look attractive.
A good paying crop of strawberries can often be secured from plants without any fire heat whatever. The plants should be put into the houses or in pits at the beginning of March, and allowed to grow on naturally. Ripe fruit will be available just before the outdoor crop comes in, and if the weather is hot prices sometimes run very high.
Instead of putting the plants into their fruiting pots in August, they may be planted out on a piece of open ground in rows about 2 ft. apart. They must be watered if necessary, and all weeds and runners kept under. Under these conditions the plants will make good crowns, and they should be lifted and potted in March, or they may be planted direct into pits, within 12 in. of the glass, to allow of the fruit trusses being tied up and exposed to the sun. A stake on each side of the plant, and a string round, will be found the best and quickest method of supporting the fruit. On a hot day in May water will be necessary twice a day, in the morning and afternoon, and any neglect of supplies will soon show.
Should the plants, when under cover, be attacked by green fly a fumigation with tobacco will be found the best remedy, taking care not to do it when the plants are in full flower, or some of the organs may be damaged, and the flowers fail to set well. Red Spider will sometimes attack the plants, especially if they are allowed to suffer from lack of water and feeding.
Should mildew appear on the plants, sulphuring the pipes when hot will be found the best remedy; but this cannot be applied if the Strawberries are growing with plants that are tender and liable to injury. In this case dissolve 1/2 oz. of sulphide of potassium (liver of sulphur) in 1 gall, of water and syringe the plants with it, using a very fine spray and wetting every part. If thoroughly done, one application is generally sufficient, and as the price of sulphide is only about Is. per pound the cost of this remedy is very small.
Years ago, Keen's Seedling, La Grosse Sucre'e, Viscomtess Hericart de Thury, President, Sir Chas. Napier, and Sir Joseph Paxton used to be the varieties grown for forcing, but they are now all superseded by Laxton's Royal Sovereign. It is safe to say that practically no other variety is now grown under glass for profit. It is found to be a good "doer " in every way, and each plant will produce twice as much fruit as the old Keen's Seedling used to.
La Grosse Sucree is a good variety for very early work, especially in the vicinity of towns, as it sets well under adverse conditions; but the fruit is not so large, or of such a bright attractive colour, as Royal Sovereign; and it is the same with strawberries as with apples - the colour helps to sell them.
President is a good Strawberry for cropping and flavour, but will not stand very early forcing; and Paxton was always subject to attacks of mildew. The average weight of fruit from forced plants should be about 1/2 lb. each, and individual berries often weigh 2 oz. under the best conditions.
Very early fruit is sometimes sold at a very high figure on special occasions, but the days of high prices are gone. There is too much selection for consumers now - when peaches, plums, pears, apples, and grapes in almost endless variety can be procured all the year round - to induce them to give fabulous prices for strawberries. Still, however, with an average price of about 3s. per pound there is some profit to the grower, as a heavier weight is produced per pleat; and once stock is obtained there is no great outlay except for labour, as the pots will last several years, and the plants are often grown on shelves where nothing else will succeed. For several months, when the plants are once plunged outside, no attention is required, and a market can generally be found if the fruit is first class. There is always room for the best on top, and that is where the " Sovereigns " are to be found. [a. j. b.]