My dad won't be around for the next two days, so he asked me to water the plants outside twice a day, morning and night.
この場合、次のような言い方ができますよ。
ーMy dad won't be around for the next two days, so he asked me to water the plants outside twice a day, morning and night.
「父が今日から2日間留守にするので、父に1日2回朝晩、外の植木の水やりを頼まれた」
twice a day, morning and night で「1日2回、朝晩」と言えます。
ご参考まで!