Hello Deeds,
Found the following for cuttings of the Buddleia colvillei Kewensis. Good luck ! ;D
PROPAGATION - Outdoors: Seeds can be sown thinly in February or March in pots or pans of sandy soil and placed in a greenhouse that has a 50º F temperature. Seedlings of B. Davidii that are raised in a heated greenhouse will flower within 7 or 8 months. Named varieties must be increased by cuttings. Cuttings that are made from half-ripe or semi-woody side shoots, 5 or 6 inches long, can be inserted in a closed cold frame, or outside under a hand light in July or early August. Cuttings that are made from the mature shoots of the year, 12-18 inches long, are taken off with a thin "heel" of the old wood at the base and inserted in a sheltered border outside or in a frame in late September or October.
Greenhouse: Cuttings of young shoots, 3 to 4 inches long, are taken as soon as the plants are through flowering. They are cut off just below a joint or node with a sharp knife. Remove their lower leaves and place them in a propagating case filled with sand or vermiculite. They should be shaded from direct sun and protected from drafts. When their roots are 1 to 2 inches long, they can be potted separately in 2½- or 3-inch pots that are filled with sandy soil. Keep them shaded for a few days, after which, they should receive full exposure to the sun and air. The night temperature in the greenhouse should be 45º-50º F and the daytime temperature should be 5-10 degrees more. When they are established in those pots, they are transplanted into larger pots, 4 to 5 inches in diameter. At this potting, and later on, a rich, loamy soil should be used consisting of the following ingredients: two parts of good loam, one part of peat moss or leaf mold, one part of coarse sand, one-half of a part of dried cow manure, and one pint of bone meal added to each bushel of the soil mixture. Keep repotting the plants into progressively larger containers until August or September, which should be the last potting. The final pots should be 7-10 inches in diameter for the first-year plants. Plants that are more that a year old will need larger containers. Pinch the
