Rose Cutting Selection and Rooting Promotion | Hormone Optimization Techniques to Achieve 80% Success Rate

Propagating roses via cuttings is an attractive method for many enthusiasts, as it allows you to obtain new plants that inherit the distinctive characteristics of the variety you admire. Especially in the case of discontinued varieties or rare varieties grown only by local growers, cutting propagation becomes the only means of preservation. However, when you actually try it, you may find that the success rate is lower than expected. The typical rose cutting success rate is said to be around 30–50%, but in fact, through careful selection of cuttings and optimized use of rooting promoters, achieving over 80% success rate is entirely possible. This article explains scientifically-based practical techniques.

Scientific Criteria for Rose Cutting Selection

The first key to cutting propagation success lies in selecting branches to use as cuttings. Merely judging by whether a branch "looks healthy" is insufficient. There are several specific physiological characteristics that ideal cuttings should have.

The first condition is "semi-hardened stage stems." Not new shoots that are still green and soft (softwood cuttings), nor completely brown and hardened stems (hardwood cuttings), but rather stems in the intermediate stage are optimal. If you try to bend it, it doesn't snap with a clean crack, but there is some resistance—this is the guideline. At this stage, the stem has accumulated appropriate levels of plant hormones such as auxin, which are necessary for rooting. In completely hardened stems, auxin concentration decreases, making rooting difficult. Conversely, in completely soft new shoots, auxin concentration is high, but the tissue is fragile and unable to withstand environmental stress, making the cuttings prone to rot.

Next in importance is harvesting from "new shoots immediately after flowering." Immediately after a rose flower has bloomed, you will notice new lateral branches extending from below it. This new growth is undergoing a transition from reproductive to vegetative growth—a period of most active cell division. Even on the same stem, cuttings harvested during this period show a clear difference in rooting rate compared to those harvested at other times. Cuttings taken from new shoots 5–10 days after flowering often achieve over 70% rooting rate, whereas at other times the rate remains below 50%.

Internode length is also important. The ideal length is approximately 10–12 cm, including 3–5 nodes counting from the top. Cuttings that are too short lack sufficient nutrients, while those too long result in large wasteful energy consumption during the period until roots emerge. Thickness is also a guideline—approximately pencil-thickness (3–5 mm diameter) is optimal.

Cutting Pretreatment and Optimal Selection of Rooting Hormones

Once cuttings are harvested, proper pretreatment must be performed rather than immediately immersing them in rooting promoter. Cut approximately 3–4 cm from the base at an acute angle (approximately 45 degrees) with a knife to maximize the cut surface area. The knife must be sterilized with alcohol each time to prevent bacterial infection. It is important to process the cut while fresh—immersion in rooting promoter within 30 minutes of harvest is ideal. As time passes, the cut oxidizes and water absorption capacity decreases.

Remove all leaves from the lower portion of the cutting, retaining only 1–2 leaves from the upper portion. This minimizes water loss from transpiration until roots form. For the leaves you retain, trimming them to about half their size is also effective in minimizing transpiration.

Selection of rooting promoter is a major factor influencing success rate. Among commercially available main products, there are three types.

The first is liquid-type containing IBA (indolebutyric acid) as the active ingredient. This has a fast absorption rate and concentration adjustment is also easy. For roses, 1000–2000 ppm concentration is effective. Liquid types are effective with just a few seconds of immersion, and the risk of overdose is low—these are clear advantages.

The second is powder-type hormone products. By lightly coating the cut with powder, the hormone acts over an extended period. If too much powder is applied, it can actually inhibit rooting, so the trick is to apply it thinly. Powders are highly portable and suitable for fieldwork.

The third is naturally-derived hormone products (e.g., cinchona bark extract). Their action is gentler than synthetic products, and they are often better suited to delicate varieties like roses. People with allergies can also use them easily—these are genuine advantages.

Cutting Environment and Staged Root Formation Management

After inserting the cuttings into the substrate, the first two weeks are most critical. During this period, relative humidity should be maintained at 85–95%. This humidity range can be achieved by misting 2–3 times daily or using a small humidifier. However, if humidity exceeds 95%, mold becomes likely to develop, so it is important to ensure adequate air circulation.

At the same time, maintain temperature at 20–25°C—this is ideal. In high-temperature environments, cuttings are prone to rot before roots form, and at low temperatures, hormone action becomes sluggish. At 25°C or above, microbial activity becomes active and rot risk increases sharply.

Standard substrate is equal parts small-grain akadama soil and vermiculite. This offers an excellent balance of water retention and drainage, making it optimal for rose cuttings. By sterilizing (heating) the substrate beforehand, you reduce pathogen risk.

From week 3 onward, gradually reduce humidity and progressively increase oxygen supply to the root system until new leaves emerge from the new roots. Reduce misting frequency by one application per week, gradually reducing relative humidity from 95% to 70% from week 3 to week 5. By properly managing this process, you can achieve a high success rate of 80–85%.