updated 12/06/2013 AT 9:30 AM ET
•originally published 12/06/2013 AT 10:25 AM ET
Some holiday traditions are too important to not do yourself – and when it comes to picking out a Christmas tree, Jennifer Aniston and Justin Theroux don’t put on airs.
The glamorous pair ventured out of their sprawling Bel Air mansion to personally pick out a tree – in this case a 10-ft. Noble Fir from Mr. Greentrees in Beverly Hills that Theroux paid for.
“Jen picks her own Christmas tree every year,” says a witness. “It’s a tradition for her. She’s very specific about the tree that she wants. ”
At the tree lot, “Jen was in a great mood and took her time to pick out the perfect tree,” says the witness. “Justin helped her and she found a beautiful one.”
This is the third year in a row that the couple – who have kept a low public profile for the past month – have picked out a Yuletide conifer together.
It’s part of a cherished Aniston tradition: her annual tree-trimming party for close friends and associates.
“The tree will be delivered in time for her party,” says the witness.
Says an Aniston source about the star’s tree-trimming parties, “Jen always has her personal chefs prepare great food for guests, and this is by far her favorite party to host. She always puts in a lot of planning.”
“The party will start early in the evening so children can attend,” says the Aniston source. “It’s always a family friendly event.”
“Jen and Justin looked very happy together,” says the witness at the tree lot. “She wore her engagement ring and looked amazing.”