Bring flowers — odd number, unwrapped, never red roses
If you bring flowers to a German home, count the stems (odd numbers only, even numbers read as mourning), unwrap them before handing them over, and skip red roses (romantic), chrysanthemums, lilies, and carnations (funeral associations).
Pick a bouquet with an odd number of stems, three, five, seven, whatever fits the size you want, and take the paper wrapping off before you hand it to your host rather than presenting it still wrapped.
Steer clear of chrysanthemums, lilies, and carnations (funeral associations) and red roses (romantic, not host-gift territory) — tulips, gerberas, sunflowers, or light-colored roses are all safe defaults.
Hand the gift over right at arrival, not on your way out — wine, quality chocolate, or flowers all work, and the timing matters as much as the item itself.
Don’t wander past the room you’re welcomed into — guests are expected to stay where they’re invited and not explore the rest of the home unprompted.
Why it matters
German gift-giving customs run more precise than "bring something nice" — an even-numbered bouquet is traditionally tied to mourning, so florists and guests alike default to odd counts without needing to think about it. Handing over a bouquet still wrapped in its paper reads as bad form, since unwrapping it in front of the host is part of the gesture. Certain flowers carry specific associations strong enough to avoid entirely: chrysanthemums, lilies, and carnations are funeral flowers, and red roses signal romantic intent, not a casual dinner-invite gift.