If you mean "lush" as in "abundant, green, and thriving":
* Gwyrddlas (pronounced "gwirth-hlas") is the closest word, meaning "green and lush." It describes the abundance and vibrancy of vegetation.
* Cyfoethog (pronounced "kuh-foth-og") meaning "rich" or "abundant," can also be used to describe a lush landscape.
If you mean "lush" as in "delicious, enjoyable, or pleasurable":
* Blasus (pronounced "blas-us") means "delicious" or "tasty," and is a good option for describing food or drink.
* Hwylus (pronounced "hwi-lus") means "pleasant" or "enjoyable," and can be used for experiences or things you find pleasurable.
If you mean "lush" as in "attractive, luxurious, or opulent":
* Gwych (pronounced "gwikh") means "splendid" or "magnificent," and can be used to describe something that is luxurious or impressive.
* Hyrys (pronounced "hu-ris") means "gorgeous" or "beautiful," and can be used to describe something that is attractive or opulent.
It's best to choose the word that best fits the context of what you're trying to describe.