Take the bottom branches of the Christmas tree, cut them to size and pin them to a ring of florists' foam with 'staples' improvised from lengths of whippy red dogwood,
add whatever the garden can provide ( in this case ivy, box, hebe, euonymous, lavender, rosemary, a couple of honeysuckle flowers, some shrub with red berries whose name I don't know, and a few pine cones) and arrange as best you can.
Voila!