This means:
“If a particular plant unexpectedly grows in your garden, don’t pull it out because it may have useful or beneficial qualities.”
Breakdown
“Never uproot” = don’t pull the plant out by its roots.
“This plant” = the headline deliberately doesn’t name the plant, creating curiosity.
“If it appears in your garden” = the plant may grow naturally or unexpectedly.
The post suggests there is a good reason to leave it alone, perhaps because it benefits the soil, attracts pollinators, provides food for wildlife, or has some traditional use.
Tone
This is gardening clickbait. It hides the plant’s identity and the reason for keeping it so that readers are encouraged to click.
A simpler version:
“If this plant grows in your garden naturally, here’s why you might want to keep it.”
