биҳӣ

биҳӣ: quince

Аз меваҳо биҳӣ хеле дер гул мекунад ва дер мепазад.
Among the fruits quince blooms late and ripens late.
Биҳӣ қариб дар ҳама ноҳияҳои Тоҷикистон парвариш меёбад.
Quince is grown in almost all of the districts of Tajikistan.

Bonus:
Quince is also called себи биҳӣ.
You can read more about quince on Tajik wikipedia: биҳӣ.
To make this word an adjective, add the suffix гӣ.
мураббои биҳигӣ: quince preserves (jam)

тарбуз

тарбуз: watermelon

Тарбуз хеле болаззат буд.
The watermelon was very delicious.
Тарбузро зимни табобати артрит, фаромӯшхотирӣ ва камхунӣ истифода мебаранд.
They use watermelon in the treatment of arthritis, memory loss and anemia.

Bonus:
Need to practice your fruit and nuts vocab? You can do it at Memrise: Tajik Fruit and Nuts.
Here is a short funny video about somebody buying a watermelon: Тарбуз ту ширинаӣ?
Tajik idiom: тарбуз аз бағал афтидан = ноумед шудан (to drop one’s watermelon = to lose hope).
For example, if you thought you were going to get some money, but then you realized that you wouldn’t you could say, “Тарбуз аз бағалам афтид.”
Read more about the health benefits of watermelon here: Тарбуз.