Valmiki Ramayana Ayodhya Kanda Sarga 28 Shloka 22

भामिनि O lovely Sita, वने in the forest, द्रुमाः trees, कुशा काशाः च kusa grass and reeds, कण्टकिनश्चैव thorny ones, व्याकुलशाखाग्राः with tops of branches interlaced with each other, तेन therefore, वनम् forest life, दुःखतरम् is full of difficulties.

O lovely Sita there are thorny trees with branches on the top interlaced with one another. There are kusa grass and reeds. So forest life is very hard.