This section is from the book "The Gardener's Monthly And Horticulturist V22", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
In the Gardener's Monthly for February 1880, page 44, Mrs. S. E. P. inquires as to the best method of cultivating and flowering Mande-villa suaveolens. It should be remembered that in its native country the Mandevilla attains a growth of over forty feet in length, and therefore it cannot be grown and flowered in pots to any great perfection. Although I do not cultivate the Mandevilla as a pot plant now, 1 have grown and flowered it very well, and my method of treating it as a pot plant may be of benefit to Mrs. S. E. P. About the middle of April I turn the plant out of its pot, and remove the greater part of the soil, and also cut back some of the roots, if there happens to be many of them. I then repot it in the same pot, using ordinary potting soil with a good portion of well rotted stable manure, and then place it in a warm light place, and water carefully until it commences to grow. About the 10th of May I plunge it out of doors to a trellis, and at the same time I form a basin around the pot so that it can be watered when necessary. This basin I fill with coarse stable manure, - this prevents the plant from becoming dry so soon after it is watered.
After it is plunged it requires a bucket or two of water once a week, and the branches must be looked over occasionally and tied up, as they are liable to be broken off by the wind while young. If it grows as it should it will commence to bloom about the middle of July, and continue until frost. After the first light frost take up the pot, cut off all weak and unripe wood, and place it in the green house. It can also be placed under the shelf, if care be taken not to let it get too -wet; if allowed to get too wet it will rot. It can be wintered very well in a warm dry cellar with a little attention. My plant was in a sixteen-inch pot, and was over twelve feet in length after being cut back, and was repotted every Spring. But when planted out in a well-prepared border in the greenhouse, the soil composed of ordinary potting soil with a good portion of well-rotted stable manure. When the roots as well as the branches are allowed to ramble at will, there the Mandevilla will be seen in all its beauty, laden with large bunches of snow-white, delicious scented flowers. The Mandevilla requires considerable space to run over, as it is of exceedingly rapid growth, and the young shoots should on no account be stopped.
It commences to grow about the end of March and flowers from July to October. After it has ceased flowering, all the weak and unripened wood should be cut out, but all the strong and well-ripened wood should be left. While growing, it requires an abundance of water, and should receive a good watering of liquid manure water at least once a week. The Mandevilla is unfortunately very subject to the red spider and the mealy bug, and in planting, it should be placed in such a position that it can be freely syringed, which should be done every other evening, at least during the summer months. The Mandevilla belongs to the natural order Apocynacese, and is a native of Buenos Ayres, from which country it was introduced by H. J. H. Mandeville.