The rules presented in the article were just: "Don't mess anything up, and do it with permission by the land owner. If you plan to plant a ton, ask pros if that'll mess anything up."
"In England, you would not need planning permission to plant less than two hectares (20,000 sq metres) in a low risk area, it said."
How do you expect one determines an area to be low-risk? To do so requires assessment from all stakeholders who could deem it not to be low-risk.
Woodland Trust:
> In England, planning permission isn’t needed if your project is under 2ha and in a low risk area. Check your area using the Forestry Commission land information search.
https://www.woodlandtrust.org.uk/plant-trees/advice/where/
Map browser: https://www.forestergis.com/Apps/MapBrowser/ (via https://www.gov.uk/guidance/use-the-land-information-search)
Then enable the Forestry Commission > Targeting and Scoring > Low Risk Areas for Woodland Creation layer.
At the very least, if your plan is to just beg forgiveness, it would give you a better argument that you thought it was acceptable and at least tried to comply.