Da'irar aljana al'amari ne na halitta da ake samu a wuraren ciyawa, musamman a yankunan busasshiyar. Yana nufin wani madauwari na ƙasa mara kyau da ke kewaye da zoben namomin kaza, wanda sau da yawa yakan girma cikin tsari madauwari. Kalmar "da'irar aljana" ta samo asali ne daga imani cewa da'irar an halicce su ta hanyar aljanu ko wasu halittu masu ban mamaki. Duk da haka, da'irar suna haifar da haƙiƙa ta hanyar haɗakar hulɗar tsakanin ƙasa, fungi, da tsire-tsire.