> Jefferson had planted opium poppies in his medicinal garden, and opium poppies are now deemed illegal
Growing with the intent to produce opium is illegal. By continuing his tradition in the museum, it was deemed a continuation of production for drugs and so probably came under scrutiny. I'm sure they could regrow a garden for decorative purposes if they actually did that and were clear about it.
https://scholar.lib.vt.edu/VA-news/ROA-Times/issues/1991/rt9...
1- `A DEA man noticed the store was selling packets of "Thomas Jefferson's Monticello Poppies."`
2- `Nobody told them to do this, but, under the circumstances, no one dared risk the threat`
> The seeds had to go, too. While poppy seeds might be legal, it is never legal to plant them. Not for any reason.