This section is from the book "The Florists' Manual", by William Scott. Also available from Amazon: The Florist's Manual.
The trailing V. major with its variegated form, is one of our most useful trailing or drooping plants. The long drooping growths seldom flower, but the short, erect growths do. The flower is, however, of little consequence. Plant out a sufficient stock of young plants in the spring. They make a great growth in any good soil.
A Bed of Vinca Rosea.
Put in cuttings in September. The cuttings should not be made of the hardest part of the stems, and should always be of two eyes, as we depend on growths from the bottom eye. We like the propagating bed for these cuttings. They root rather slowly, but surely. Keep in 2-inch pots till January in any cool house and then shift into 3-inch. As they grow they will need the edge of the bench, or the edge of a rose or carnation bench, so that their long growths can hang down.
Some growers lift up the plants from the field in October and stand on the edge of the benches. They make fine decorative plants for some occasions, as their numerous growths will be several feet long. In February the large plants are divided and potted into 3-inch or 4-inch pots.
The young growths are troubled with greenfly. Any soil and any cool house will grow them, and they need little light till they begin to make their growth in early spring. Use good rich soil when shifting from 2-inch to 3-inch, as you want them to grow fast.
Vincas are most useful and popular vase and veranda-box droopers, and plants in 3-inch or 4-inch pots with several long drooping growths are always in demand in late spring. I should say the demand for them is always in excess of the supply. Another plan to give you for these desirable plants is to plant out a number of plants from 2-inch pots. They propagate most easily in spring; the end of June is early enough to plant out. and you can put them six inches apart. In October lift them, cutting off the tops to within three or four inches of the ground and pull to pieces or divide the plants till you can get each division into a 2 1/2-inch pot. These will winter on any cool light bench, and in February will be sending up a number of strong shoots from the roots. They can then be shifted into 3-inch or 3 1/2-inch pots and given a place on the edge of a bench. These will make splendid useful plants for your vases. A large effective growth in the smallest possible pot is the desired object with a vinca.
Vinca minor, often strangely called myrtle by our people, is perfectly hardy. Where grass won't grow in shady city lots it covers the ground finely. It can be divided and planted either in spring or fall and will quickly cover the ground.
Vinca rosea is a very different plant and requires a warm house in winter. It makes a pretty greenhouse plant, but its chief use with us is in the flower garden, where it makes a very pretty bed, and a change from the high colored geraniums. It can be easily raised from seed sown in January and grown on in a light, warm house, and needs an occasional pinching to make the plants bushy.
Plants can also be lifted and after New Year's cut back, when you will get young growths which root freely. Don't plant out till frost is surely past.