This section is from the book "The Florists' Manual", by William Scott. Also available from Amazon: The Florist's Manual.
This handsome tropical foliage plant is not so largely used as it was ten years ago. A change of fashion in flower gardening will account for this. A return to less formal style and the larger use of flowering plants lessened the popularity of the coleus; still there will always be some demand for them. Ver-schaffeltii is a variety raised from Blumei, which species is also the parent of the thousands of varieties that have been raised, disseminated, and many now forgotten. The coleus as a bedding plant is finely suited to our warm summers, and those that have not seen it struggling along, dwarf and scrubby looking, in the gardens of North Britain, don't realize what a grand plant we have in this tropical herb.
In climates where they make but a poor growth out of doors they are appreciated as decorative pot plants, for which they make fine specimens. They can be pinched and tied to most symmetrical forms and for pure beauty of form and color are as handsome as any plant. But here, where we see them growing so luxuriantly outside, they are not appreciated as pot plants, unless it be for filling up in the summer and fall. It would not be at all difficult to start with a 4-inch plant in February and by the following October have a plant six feet across and as even in outline as an umbrella, but few would stop to admire it. They would only remark or reflect: "How long it must have taken John Smith to grow that plant!" The plant is not worth the pains.
To digress a moment. To me it is no pleasure (simply a bore, in fact) to see an elephant on a tub, a horse waltzing, or a dog walking on his hind legs. I feel very tired if it lasts long, and instead of being amused by such monstrosities am continually thinking how many weary days and weeks it must have taken to teach these lower animals the tricks. That's all there is in it; it shows the patience and untiring perseverance of some men; the result is nothing when attained. I will go a long ways to see a dog chasing a rabbit or a fox, a horse's neck stretched out to pass the winning post first, or an elephant pulling a ten-ton cannon and showing his majestic strength, and it's about the same with this specimen coleus. It only shows the patience ana skill of the workman; the result is meager after all the labor and cost.
To obtain a good stock of coleus for bedding purposes it is better to carry over a few each of the leading varieties in pots during summer, say in 5-inch or 6-inch pots. If you should have a cool spell in October and November, when firing but little, the fair-sized plants can stand it, but small plants in 2-inch pots cannot. By starting these plants in good, strong heat after New Year's you will soon get plenty of cuttings. As is known to every florist, the coleus roots most easily in sand the year around, and in the months of March and April, when you are doing your heaviest propagating, a bottom heat will save several days.
Coleuses are sold cheap and must be raised expeditiously or there will be no profit. We endeavor to have several sizes. The largest are in 4-inch pots. Perhaps these have been stopped at least twice, their cuttings having been used for propagation. The 3-inch pot plants were stopped once and the smaller plants in 2 1/2-inch pots had the top pinched out. We find customers want different sizes. Some are willing and able to pay for the largest plants; others think the smallest plants just as good. " They grow very fast, you know." We keep on propagating to the middle of May.
I have seen, in fact I have had, a poor lot of coleuses, for sale at the end of May, just when they should be looking fine, and the reason was I thought it a saving to buy no more fuel after the end of April or first of May, and perhaps to add to the trouble had some whitwash on the house. A sudden drop in temperature with a cool, damp house is the very worst thing for coleuses. They lose their leaves, grow decidedly smaller, and instead of showing their fine colors, all assume a brown paper appearance. Full sunlight and heat is what they want and must have.
I must refer once more to the hotbeds. There is no place like them to grow good bedding coleus. They need not be built up as if you were growing cucumbers in the month of March, but one foot of solid stable manure with four or five inches of loam or refuse hops on top and some clean glass over them will produce in three weeks a better bedding plant than you can make in ten weeks inside. Have a big batch of cuttings so that they are ready to pot off middle of April. By first of May they can go into the hotbed in 3-inch pots, and that is their finish. One more great advantage is that on warm days toward bedding out time you can remove the sash, which finely prepares these tropical plants for their next and last move.
We use coleuses of several varieties for veranda boxes and vases. They always do well. The only trouble with them is that they grow so freely that if allowed they will smother the geraniums, the flowers of which are always looked for.
Any light loam with a third of sifted rotten manure will grow coleuses, and if we wish to hurry them along we add a quart of bone flour to every bushel of compost.
Mealy bug is about the only greenhouse pest that troubles the coleus, and if it has been a gardener that had charge of the hose, that would not be seen. A proper use of the hose will keep them down; if it does not, use the kerosene emulsion in the mildest form, and if your plants are very bad throw them away and start with a clean lot.
Verschaffeltii I can remember very well watering as a rather choice exotic about the year 1863. It is by long odds still the best of them all, and Golden Bedder is such a fine golden yellow that nothing is equal to it in its color. If you grew 5,000 coleuses for bedding plants, 2,500 should be Verschaffeltii, 2,000 Golden Bedder, and the rest your own fancy. For vases, etc., the fancy sorts are useful. We have long since neglected to keep record of the names of the fancy coleuses, and grow only half a dozen that are most distinct and keep their color and markings outside in the broad sun.