Certified Professional Horticulturist (CPH) Practice Exam

A likely reason for a customer's potted ivy to stop growing is that the plant has become rootbound. When a plant becomes rootbound, it means that the roots have fully utilized the available space within the pot, often growing in tight circles around the edges and bottom. This can restrict the plant's ability to absorb water and nutrients effectively, leading to stagnated growth.

In container gardening, especially with fast-growing vines like ivy, regular repotting is essential to provide fresh soil and ample space for root development. Noticing signs of rootbinding, such as roots emerging from drainage holes or a lack of new growth, indicates that the plant is in need of a larger pot or that it should be divided to promote healthier growth.

The other options do have their own issues but are generally less common as direct causes for growth halt. Mites might affect health but are more likely to stunt growth through general stress rather than outright stopping it. Fertilizer residue can lead to salt build-up, which may affect growth, but it typically does not cause an immediate cessation like rootbinding does. Static cling from Styrofoam beads could possibly affect moisture retention or aeration but is unlikely to be a significant factor when compared to root issues.