With many methods of propagation, you need to control the environment the plants are growing in to ensure successful results.
There are two environments that you need to consider – the aerial environment around the leaves and stems and the rooting environment.
The aerial environment includes temperature, humidity and light levels.
The rooting environment includes temperature, moisture, aeration and acidity/alkalinity (pH).
For successful propagation of the vast majority of plants, there needs to be an environment that minimises water loss from the plant, the correct temperature within the plant’s normal range, good overall light – but not too strong to cause scorching or excessive drying out, and a warm, moist compost/soil with plenty of aeration, the correct amount of nutrients and within the correct pH range.
Whereas most hardy plants can tolerate a wide range of environmental conditions, ‘softer’, half-hardy or non-hardy plants need better-regulated conditions and usually won’t survive without some sort of environmental control, especially during cooler/colder weather.