Cuttings will root more quickly and reliably in warm rooting mix. Keep your cuttings between 65°F and 75°F, avoiding excessive heat. If your area is too cold, consider a heating mat or cable especially designed for this purpose.
Keep the atmosphere around the cutting warm (not hot), keep the humidity relatively high (>90%), and keep the root zone temperature warm (at about 25°C).
To improve success with rooting of cuttings it is best to maintain media temperatures between 68-77°F; even cold tolerant crops such as pansy, dianthus, osteospermum, petunia, etc. prefer these media temperatures for rooting.
Most plants will not root well in full sun, so place the cuttings in a location where they will receive a 50/50 ratio of shade to dappled sunlight. For most plants, cuttings thrive on warmth and humidity, and the growing medium should be kept evenly moist but not drenched while roots develop.
Light provides the energy for callus formation and the subsequent generation of adventitious roots. At the same time, light increases plant temperature and accelerates the drying of leaves, which can quickly dehydrate cuttings.
Media is usually kept at 72-77° F while air temperature is maintained at 68-73° F. If bottom heat is not used, air temperature should be maintained between 77 and 80° F. Maintaining air temperatures lower than medium temperatures retards shoot growth while promoting root development. Excessive heat can damage cuttings.
Especially with cuttings, it's often desirable to have a cooler (5 to 10° F) air temperature than root tempera- ture, which allows the roots to grow more quickly than the shoots.
Give cuttings bright light but not sun. Keep soil moist but not wet. The cuttings should root within three weeks. Admit air gradually to wean the cuttings from their humid environment, then pot singly before outdoor planting.
Cover the Pot With Plastic
Place the container with the cutting into a plastic bag. The bag will keep the humidity high and hold in heat. Do not seal the bag completely because some airflow is necessary to prevent fungal rot.
Ideally, the temperature of the medium should be maintained slightly higher (5°F-8°F) than the air so that callus and root growth occur faster than shoot growth. To accomplish this, bottom heat- ing is required. Desirable propaga- tion temperatures are 73°F-77°F for the medium and 68°F-73°F for the air.
Time it right
It's an easy and satisfying way to increase your stock of plants. It's always best to take cuttings early in the morning, when the parent plant is still turgid, i.e. full of water.
In general, the rooting medium should be sterile, low in fertility, drain well enough to provide oxygen, and retain enough moisture to prevent water stress.
The sooner you can get your cuttings into a more normal environment with air flow and no dome, the better off they'll be. After about a week, remove the dome and monitor your cuttings to see if they begin to wilt. If they do, they're not ready to go dome-less, so try again in 1-2 days.
Lack of any one requirement can damage or kill cuttings. However, keeping them always at a very high humidity (A 34) is the most important, because: most unprotected leafy cuttings lose a lot of water within minutes, even in the humid tropics, by evaporation from their leaves (and stems);
Place your stem cutting in your vessel with enough water to cover the node. The water level will drop due to evaporation, so you should add water every 3-5 days as needed. You can watch the roots develop if you have chosen a clear vessel for your cutting.
Some plants will root in water, but cuttings will develop a better root system when rooted in a soil-less potting mix. Sand or perlite can also be used, especially for cuttings that need good drainage and may rot if kept too wet.
Controversially, I'm gonna suggest you don't water them very often. I would start with very evenly moist airy soil – water in sans cutting, and mix it round so it's not saturated at the bottom. Add your cutting, and then mist the surface thoroughly daily (trying not to get the cutting). Twice a day if it's hot or dry.
The best light cycle for rooting cuttings is generally 18 hours of light and 6 hours of darkness. Do not supply cuttings with 24 hours of light without any dark periods because this has shown to slow the rooting process down as plants root best with a sufficient dark period each day.
We recommend a photoperiod of 12-13 hours for the propagation of most annuals, especially for long-day plants such as petunia. Light Intensity. Desirable levels of light vary, depending primarily on the stage of root development.
Technically, you can transfer your cuttings to soil at any time. In fact, you can actually propagate directly into soil, however, it's much harder to do within your home. When you propagate in soil, you have to keep a good balance of soil moisture, air flow, and humidity.
Cuttings are very delicate and vulnerable so pests, disease, the wrong growing conditions, too much water or too little water can all cause them to fail.
Relative Humidity and Airflow Management
It is recommended maintaining the relative humidity in a propagation house at a minimum of 85 percent. This can be done with mist or fog systems.