IT would be difficult to distinguish entirely between hardy annuals and half-hardy annuals, since many plants fall into either group according to the district in which they are being grown. Any annual may be regarded as half-hardy if it is better cultivated during the first few weeks of its existence in the shelter of a frame, or in the greenhouse.
It is a common practice to sow half-hardy annuals direct in the open ground, waiting until after the frosts have ceased before the seeds are sown. This method does not allow for so long a season of growth, and is therefore not recommended where it is possible to raise seedlings under glass.
Where the seeds are sown direct in the garden they are treated in exactly the same manner as the hardy annuals, except that they usually do not transplant well as the shock of transplanting gives a set-back to the plant so that it is later in reaching maturity. This would mean, in some cases, that flowers would not be produced before the arrival of the first autumn frosts.
Compost for seed-boxes. Seed-boxes and pots should always be filled with specially prepared soil. It is waste of good seed, labour and time, to use sour or lumpy garden soil in which the seedlings cannot develop properly. That is why gardeners prepare various composts or soil mixtures, and keep them at hand in readiness for different seeds and plants.
The soil used must be open and porous, and for this reason it should contain plenty of sand. If the seedlings are of a type that will only remain for a short time in the box, the soil need not be rich; but if they are to remain for a couple of months, as in the case of some of the seeds sown in February or March, the soil must at least be rich enough to support them during this time.
Old decayed leaves which have been stacked in a heap for some time and then well rubbed through a sieve are very useful for enriching soil which is to be used for seed sowing. They should always be added to the soil used for sweet peas; but if the plants to be raised are likoly to damp off (for instance, China asters are very liable to this disease), it is better to omit decayed leaves or any other form of manure from the compost used for the seed boxes. A little lime and old soot added to the soil will both sweeten it and make it in a better mechanical condition for seed sowing.
Filling the Boxes. Boxes or pots used for seed sowing must be well drained. The shallow wooden boxes which most nurserymen use for bedding plants are generally well enough drained because the bottoms fit imperfectly. If they are not, holes should be drilled to allow for the escape of surplus water. Over the drainage holes a few crocks, concave side downwards, can be arranged to prevent the holes getting blocked. A layer of decayed leaves all over the bottom of the box is often used, and serves the double purpose of retaining moisture and preventing the soil from being washed through the bottom of the box.
The prepared compost is then put into the box, using just enough to fill it before the soil is pressed down. Use a flat piece of board to make the soil firm. This will press the soil down to about half an inch below the rim. Sow the seeds thinly all over this prepared soil; or, if preferred, use the edge of the board to make shallow indentations across the soil of the box, so that the seeds can be sown evenly. The method adopted depends entirely on the size of the seed. Some can be sown individually, each one being pushed a little way into the soil, while others are more easily scattered over the surface.
The seeds should be just covered in the case of fine seed, and for this either dry sand soil or pure sand can be used. If the soil i9 thoroughly soaked after sowing it I will probably not be necessary to water again until the seedlings appear, but they should be examined daily, and water must be given if the boxes are becoming dry. The seed-boxes also should be shaded from very bright sunshine until the seedlings are up, and as a rule it is best to keep them quite close. If pots and boxes are stood in a cold frame the lights can be left closed, and straw mats or sacking can be used over the glass to keep out the light.
Should it be undesirable to keep the frame close because of other plants that are being sheltered in it, cover the individual boxes and pots with odd sheets of glass and pieces of brown paper. The glass should be raised daily, and any surplus water that collects on it should be wiped off.
Pricking out. Seedling. Of half-hardy annuals are pricked out in the same manner as already described for hardy annuals, bat as the work is usually done in March or April, when it is still impossible to plant oat in the open ground, the half-hardy seedlings must be pricked out into boxes or into the soil of the cold frame, to grow on and form plants for bedding out later. It is usually sufficient to allow two or three inches between the plants at this stage. Some plants are bettor pricked out singly into thumb pots to avoid disturbing the roots seriously later on.
Towards the end of May or the beginning of June, the plants will be transferred to the open ground, but this must not be done in a hurry as plants, like human beings, object to sudden changes of temperature. As the plants are growing they should be inspected from time to time, and if they show any tendency to become tall and leggy, more ventilation should be given. In fact the lights of the cold frame should be left off entirely, except during spells of heavy frost or rain.
Another way of preventing the plants from becoming tall and straggly instead of short and bushy is to pinch them back when they have made four or five pairs of leaves so that side-shoots develop. In any case, during the last week or two before they are planted in the open ground they must be allowed to become gradually accustomed to open-air conditions. At first the light of the cold frame shoiud be removed entirely on the warm, sunny days, being replaced at night.
After a few days of this treatment the lights can be left off during the night, except when there is a likelihood of frost. Then the boxes can be lifted from the cold frame, stood on the garden path, and in the course of another week ib will probably be safe to put the plants out into the beds and borders. Any frosts occurring during the period of hardening-ofi must of course be guarded against, but when once the plants have become acclimatized, there is usually not much difficulty.
Their further treatment in the borders is exactly the same as that of hardy annuals. Perennials Crown as Annuals A PART from the true annuals – which normally die after flowering – thereare a number of perennial plants, which are generally treated by the gardener as annuals because they bear better flowers during their first season, or because they are not hardy enough to winter in the open borders, and it is easier to raise them from seed than to keep the old plants during the winter.
Of course, the common Snapdragon ia a good example. This is perfectly hardy in some gardens, but on cold soils and in ex-posed places it does not winter well outdoors. It is therefore more commonly grown under glass from seed sown early in the year. This is also a better method for obtaining young plants of uniform height. As the plants are really perennials, how- ever, it is also quite feasible to keep them from year to year in sheltered gardens or to increase them from cuttings of side shoots.
It is possible now to obtain Snapdragon seed which comes fairly true to type, and new seedlings are therefore quite suitable for bedding out and for colour schemes; but where it is desired to increase the stock of a particular plant which may be of an unusual colour, cuttings are taken and rooted in the autumn.
This causes slight confusion at times in connection with Exhibitions and Flower Shows, where amateurs are puzzled as to the class in which they should show their flowers. The Royal Horticultural Society issues a ruling on this point which most local Flower Shows now recognize.
When grown as annuals these plants are treated in the manner already described, and destroyed after flowering.