Rose seedling production and pruning techniques
I. Seedling production. Modern rose seedling production all uses the single-node cutting propagation method, or the graft-cutting propagation method to produce seedlings. (1) Single-node cutting: Cuttings are taken from second-grade cut flower branches, cutting single-node stem segments with plump axillary buds from the branches as cuttings. About 0.5 cm of stem segment is left above the axillary bud, ...
I. Seedling production
Modern rose seedling production all uses the single-node cutting propagation method, or the graft-cutting propagation method to produce seedlings.
(1) Single-node cutting
Cuttings are taken from second-grade cut flower branches, cutting single-node stem segments with plump axillary buds from the branches as cuttings. About 0.5 cm of stem segment is left above the axillary bud, and a 2 cm stem segment is left below the axillary bud. Then the base of the cutting is dipped in acetic acid powder, and it can be inserted into the mist propagation bed.
The most important equipment in the mist propagation bed facility is the mist controller; commonly used ones include the balance-type control switch, or the timer control switch. The former's misting interval changes with the transpiration rate, making it more convenient to use. The latter requires adjusting the misting time at any time according to weather changes.
In soilless media or rockwool cultivation methods, because the root growth environment can be controlled, cut flower cultivated rose seedlings mostly use cutting seedlings. But for general soil-based cut flower production, grafted seedlings are still used as roses for cut flower cultivation.
(2) Graft-cutting seedling raising
The graft-cutting propagation method can be divided into the following types according to the grafting method:
1. Side-graft cuttage method
Both the scion and the rootstock are single nodes with leaves; the scion is grafted in an insert-graft manner onto the other side of the abdomen below the rootstock's axillary bud.
2. Tongue-graft cuttage method
A 10 cm long rootstock segment has its leaves removed and axillary buds cut off first, then at the top of the branch a scion segment with two axillary buds and leaves is grafted using the tongue-graft method.
3. Saddle-graft cuttage method
The rootstock is an internode segment, and the scion is a stem segment with leaves; the joint is made by manual cleft grafting, or by machine forming a saddle-shaped notch and tenon shape, and then joined.
4. Bud-graft cuttage method
The rootstock is an internode segment, and the scion is a dormant one with leaves, grafted using the "T" budding method. Apart from requiring one extra grafting procedure compared with single-node cutting propagation, the graft-cutting propagation method uses exactly the same cultivation facilities, equipment and cutting methods.
II. Pruning
The purpose of pruning, besides controlling plant height and facilitating cut flower harvesting work. Renewing the main branches to maintain normal cut flower yield, as well as regulating the cut flower production period, all depend on superb pruning techniques. General pruning work can be divided by pruning purpose into three items: plant establishment, renewal pruning, and production period regulation.
(1) Plant establishment
Newly planted plants, although they will still bloom, have slender and short branches with small flowers and few petals, and are not suitable as cut flowers. The pruning work at this stage, besides cutting off dead branches and diseased branches at any time, should also remove buds at any time to avoid wasting nutrients in the plant. Until stout branches develop from the base of the plant and are pinched to form main branches, these slender branches are gradually cut off.
(2) Renewal pruning
Roses belong to shrubs; after the main branches are cut for flowers, their growth vigor gradually weakens over time, so at intervals the old main branches must be eliminated while cultivating new main branches, to maintain growth vigor and maintain plant yield. When pruning, first cut off the old branches with weak growth vigor, keep 3~5 of the youngest main branches per plant, then shorten the retained main branches to 120 cm in height. This promotes the plant base to grow new main branches.
(3) Production period regulation
The cut flower length of roses and the number of days required from pruning to flowering are closely related to the node position of pruning. Flowering branches developed from low-node axillary buds have more nodes, longer branches, and higher grade, but require more days from pruning to flowering. Conversely, the higher the pruning node position, the fewer nodes the flowering branches developed from axillary buds have and the shorter the branches, but the fewer days required from pruning to flowering.
III. Disease control
In protected cultivation of rose cut flowers, apart from powdery mildew, other diseases are very easy to control. The most effective control method for powdery mildew is to pay attention to field sanitation, ensure ventilation, and prune overly dense branches. And in cold, humid seasons, that is, seasons with fog or dew, use chemicals to prevent the disease.