A food item, all decked out with all the little goodies, deluxe style. Usually meaning vegetables, but not necessarily so. The opposite of plain. Frequently something that has been dragged through the garden has so much other stuff on it that the original or basic item is burried and lost. Sometimes used for a fast food "vegetarian" hamburger that consists of a bun, condiments and everything else - but no meat.
Usually used to mean adding all available items, especially with a hamburger, pizza or omelette. A hamburger with onion or a slice of tomato isn't dragged through the garden. A hamburger with tomatoes, lettuce, onions, mushrooms, olives, green peppers and sprouts is.
"You want cheese on that hamburger?"
"Give me cheese and drag through the garden!"
I ordered a cheese omelette, but this is a drag through the garden special.