Is a woman in iddat allowed to go out into the garden of her house?
بِسْمِ اللهِ الرَّحْمنِ الرَّحِيْم
In the name of Allah, the Most Gracious, the Most Merciful
Generally speaking, a woman in ʿiddah is not allowed to leave her house at all except if there is a need for it, this includes the garden of her house. This need can be both physical (e.g. needs to earn an income to survive) or mental (e.g. needs to relax her mind by going outside). When her specific need has finished, she must return to her home.
Only Allah knows best
Written by Shaykh Tahsin Alam
Checked and approved by Mufti Mohammed Tosir Miah
Darul Ifta Birmingham
 Al-Mawṣulī, al-Ikhtiyār, volume 3 pg. 456