This section is from the book "The Florists' Manual", by William Scott. Also available from Amazon: The Florist's Manual.
An early Easter is always a blessing to a man who grows bedding plants, for just before Easter he is fearfully crowded, and has to exercise all his wits to keep things from spoiling, and one of the principal crops that needs attention is the geraniums. Then they are shifted into the 4-inch pots, from which they are bedded out. The February struck plants get a 3-inch as soon after the others as possible, and make good bedding plants that sell to late customers, and if you get 50 cents per dozen less than you do for your fine 4-inch plants they pay well.
We are always successful in getting our geraniums in full bloom from May 15 to June 1, and believe that geraniums are grown nowhere finer and better than they are in this city. We believe this is largely because we use a rather heavy loam. The only fertilizer is about a fifth of sifted hotbed manure, in which there can be little ammonia, but it keeps the soil open. We pot firmly, as firmly as we can, ram the soil down with our fingers, and this, we believe, is an important point in getting them to flower.
If you are a market grower, and your customers will forget where they purchased their geraniums, you can add a 5-inch pot of bone flour to every wheelbarrow load of compost. It will make the geraniums jump. But if you fill flower beds year after year for a good customer, don't use the bone flour; there is no need of it and plants thus stimulated will not do so well when bedded out as those grown without this fertilizer.
The treatment described above will do for all the geraniums of the zonal, rose leaf, variegated and bronze sections. The tricolor and more slow-growing varieties of the variegated and smaller scented kinds we prefer to put in the sand and give them 5 degrees more heat during winter and a richer and lighter compost.
Speaking of composts, we used to have occasion to buy some geraniums to fill late orders, and the compost they were in looked like black rappee snuff, a light sand and at least half old rotten manure; loosely potted, loose at the neck, almost needing a stake; this is the very reverse of what is right. There would surely be plenty of leaves on such plants, but a poor flower, and such stuff makes poor bedding plants.
Mme. Salleroi is so distinct in its habit that it would be waste of room to propagate it in the way we do the strong growing zonals. We lift before frost as many plants from the ground as our needs demand and pot in 4-inch or 5-inch pots just as they are lifted, and store away in some light, cool house. In January we cut them up and every shoot is a cutting which roots most easily in the sand. In the crowded state of our houses before the bedding out begins we put the variegated zonal, bronze, sweet scented and Salleroi sections into a mild hotbed. Put into the beds by middle of April they make fine plants by bedding time, in these varieties it is leaf growth you want, and they are greatly benefited by the action of the ammonia on their leaves.
The ivy-leaved section used so largely in our baskets, vases and veranda-boxes we treat entirely different. We leave them out of doors as long as safe from frost, and even if you should feel that a frost is coming it is no great job to cover them or to pull the plants up and take them into the shed to be made ready for the cutting bed next day. A few dozen old plants will give you an immense lot of cuttings, and always put them in the sand, which by this time of year is probably a little warm with fire heat.
We keep them in 2-inch pots till New Year's, then shift into a 3-inch; and the demand for these beautiful plants is so great for our veranda-boxes that we have to shift many of them again into a 4-inch. Their drooping habit makes them awkward to grow on a bench when of any size, so we have to put them on 10-inch shelves, a row hanging over on each side.
The ivy-leaved section are beautiful plants and when their roots are confined they continue to flower a long time, but when planted out in good soil they grow so freely that blooming ceases.
In winter you are seldom asked for geranium flowers, or not enough to warrant your devoting any bench room to them, but you are frequently called upon for a geranium plant in flower, and it is just as well to have some. Should you not sell them they will make a fine lot of cuttings in February.
Select a few hundred healthy young plants in May of the free blooming varieties and put them aside as sold. When the rush is over shift into 5-inch and grow along in a light house, with the pots plunged in some material to keep them from continually drying out; here is where the portable shading would come in so good. A coldframe would do as well with the glass tilted up back and front, and then you can shade from 10 o'clock till 4 o'clock.
Keep the buds always picked off these geraniums during summer, and in August, if they are worth it, shift again, into a 6-inch pot. If you allow the buds to come up after middle of September you will have some very cheerful, bright plants that are very attractive. These plants if wanted to flower freely should have a night temperature of 55 degrees, and the lightest bench you have.
There is a lesson to be observed about these common geraniums. If we give them more than 45 degrees at night and 55 to 60 degrees at day with our imperfect light and want of ventilation, for we can only give air to a limited extent, the plants will run up to leggy, useless plants, but out of doors in a night temperature of 70 degrees, and during the day perhaps to 90 degrees, they do not run up, they grow into sturdy, stout plants. So the nearer we can come to perfect light and air with those plants (roses, carnations, etc.) that we ask to flower in the winter instead of resting, the greater success we shall have.
There are scarcely any insects that trouble geraniums, and it is a great thing in their favor. Tobacco smoke does not hurt any of them, and only the scented-leaved section is ever troubled with aphis. Too close proximity to hot-water pipes will sometimes produce red spider, but that should not occur. It is a great treat to me to water a batch of geraniums that are on the dry side, and they should be allowed to get so. Then they seem to relish the soaking they get.
It would be useless to publish a list of varieties, as sorts wear out and new ones are constantly taking their places. Neither am I acquainted with a long list of varieties. It is very unwise to grow a great variety. A dozen of the best semi-doubles, half a dozen single, half a dozen of the ivy-leaved section, and a few of the standard variegated and bronze, will fill the bill for the man who has flower beds to fill. Last year the demand for geraniums was larger than ever, and although we had double the quantity of S. A. Nutt over any other, we were sold out of it long before the rest, showing that you want a large quantity of the very few leading varieties, and proportionately smaller quantities of the rest. We find at present that the following sorts suit our business best: