I ordered a seedling online and it arrived at my house with wet leaves that were half rotten.
この場合、次のように言えると思います。
ーI ordered a seedling online and it arrived at my house with wet leaves that were half rotten.
「苗木をネットで注文して、家に届いたら葉っぱがべちょべちょで半分腐ってた」
to order ... online で「ネットで…を注文する」
a seedling で「苗木」
half rotten で「半分腐った・腐りかけた」
ご参考まで!
"The seedlings became moist and sticky."
"the seedlings" 「苗が」
"became ~" 「〜になる」
"moist" 「蒸れて」
"sticky" 「べちょべちょ」
"The seedlings that I ordered online became moist in box and the leaves were sticky rotten and damaged."
「苗木をネットで頼んだら、箱の中で蒸れて葉っぱがべちょべちょに腐ったり傷んだりしてました」