Immersive virtual reality (IVR) offers possibilities of creating a learner-centric environment that can provide more presence and engagement for students leading to an enhanced learning experience compared to conventional classroom practices. However, the potential of IVR in vocational education and training (VET) has not yet been explored in-depth, and it is an open question of whether it can effectively support learner creation in a designing task. In this paper, we present an IVR application developed to support gardener apprentices in designing gardens. Using this application, we conducted an experimental study with gardener apprentices to investigate the effect of the IVR interface compared to paper sketching and learner behavior on the proportion, composition, and creativity of the design outcome. Additionally, we investigated how it can be combined with a paper sketching activity to improve its effectiveness. Our analysis shows that the IVR interface can be more effective for the proportion aspect, but this may be limited to students that are able to use it after working with paper. In terms of the combination order, the effectiveness of IVR on the design quality was improved when it was carried out after the paper sketching and this ordering produced a more effective outcome for the proportion and composition aspects. Finally, our results show that IVR design quality is related to learner behaviors such as the time spent on designing and the number of simulations used. This study demonstrates the effectiveness of IVR applications in supporting designing skills and how effectiveness can be improved by combining it with a conventional method of practice.