No doubt to Alan Titchmarsh’s great relief, the horticultural arm of the post-apocalypse flick is finally entering the growth phase, with the likes of Annihilation, The Last of Us and now this lightweight effort from Chinese director Lin Zhenzhao. The hubris here is that mankind has overcompensated for the desertification of the planet with cutting-edge research to promote plant growth, accidentally creating a super-species of sentient flora that has choked the Earth, and whose roving vines hunt down people to snack on. Yang Hao (Mickey He) is a bunkered-in dad…