Trees, hedges, native grasses and shrubs: the kinds of plant you'd probably consider "weeds" in US suburbia. Within cities, there's https://en.wikipedia.org/wiki/Terraced_house, and there are villages in amongst the fields and forests of rural areas.
Even in Belgium, one of the highest density countries in the EU, most existing and newly built houses are semi-detached, with about twice as much semi-detached + detached houses as there are terraced houses.
In France, terraced homes are rather uncommon outside the North close to Belgium, and old city centers. In fact, I don't even know if we have a name for detached houses, as far as I know they're just called "a house" while a terraced house is a "city house".
So I don't have the numbers for all of the EU but I don't think most homes are actually terraced homes in the EU.
And people do have grass lawns, but only where grass actually grows without too much care needed. Where I come from on the coast grass doesn't grow well on the sandy ground and lawns are uncommon, but a few kilometres inland if you don't do anything you get a mostly-grass lawn, with a lot of clover, daisies and often orchids growing in it.
