This section is from the book "The Gardener's Monthly And Horticulturist V24", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
I wish to say a few words on the cultivation of the Marechal Niel Rose "under glass," and thinking that to enter into all the minute details would take up too much space in your valuable paper, I will confine myself to a few of the most important parts.
To succeed with the Marechal Niel I prefer plants budded on the Banksia or Solfatarre, as they tend to check too rampant growth for the first two or three years, and induce more freedom to bloom by producing wood that ripens well. Also, the budded plant will grow and bloom for years, where, on the other hand, plants on their own roots make a strong watery growth, which it is almost impossible to ripen, (unless the wood of the Niel is thoroughly ripe we get but few flowers), and after a few years the plant begins to decay, and is gone before we have had a full crop of bloom from it. We must always bear in mind that the Niel wants age before it will flower freely.
Another thing we must consider - the Niel must either be grown in a house devoted to its requirements, or in pots or tubs.
I prefer the latter mode. Take good thrifty plants about March 1st. Pot them into six inch pots, give moderate heat and moisture, say 55° by night, 70° by day, shift into larger pots as they require it; in this way keep them growing until the first or middle of September. Then place outside, first plunging the pots into the ground up to the rim ; tie the top up to a trellis or let it rest on some old brushwood, or some kind of support, so that the air will have a free circulation all around the shoots. Never allow the plants to get dry so as to wilt. But be careful not to water so as to induce growth.
The plants may remain in this position until after the first sharp frost, or until about the 20th or last of October. Then take up the plants, loosen the soil on the top of the pots with a hand fork or pointed stick, to the depth of two or three inches, remove the soil and replace with a top dressing, one half loam and one-half rotten manure. Prune away all useless wood, place in a greenhouse, which keep at a temperature of 45° to 50° by night, 65° to 70° by day, for about a fortnight, then gradually raise the temperature to 55° by night, 75° to 85° by day, the latter temperature with bright sun. I do not like a night temperature of more than 55°, as I find it spoils the color and size of the buds.