As far as I know, I had thought the new Forge hooks allowed for plants to grow when loaded by a chunkloader. However my automatic Peat Bog/Forestry system relies on the growth of peat/trees to self-supply. The engines appear to be working, but no peat is growing to replace the used fuel used in the peat-fired engines which are being kept loaded by the chunkloader. Pretty sure this is a bug, but if not, consider it a feature request to allow plant growth when loaded by chunk loaders. EDIT: Normally I switch my farms off overnight, but accidently left it on and it worked. Appears to be fixed. Perhaps a Forge update fixed it?