To be fair, very little of the Downton gardens are showcased in the series. We see alot of the lawn and trees, etc. but not the manicured, stylized garden.

The potting shed is the classic illicit trysting place - that and the stables of course.

For those who haven't seen Season 1 or 2 yet, this recap from pbs is excellent. It hits all the important plot points and it's hilarious.

http://video.pbs.org/video/2312271318/

And this is about Highclere Castle, the setting for the fictional Downton Abbey. Great history, colorful family some surprises. Totally worth watching for DA fans.
http://video.pbs.org/video/2320059755

Great recap here too! http://pulpbitchin.wordpress.com/2013/01/11/down-with-downton-part-iv/

And there is a season 1 recap for anyone more severely behind the times. :)

Yeah watching season 3 at the moment, I don't remember ever seeing (that is, noticing) the hedge garden at all... The massive tree out front with the seat underneath however... siiigh. Screenshot -> http://imgur.com/CDznz

Season 2 in a nutshell: WWI comes to Downton Abbey- literally. Lady Sybil takes a nursing course, Matthew goes off to the Somme, William the footman joins him. Mr. Bates' evil wife turns up like a bad penny to make life miserable for him and Anna. She threatens to go to the press about Mary's Turkish affair.Mary decides to marry some Rupert Murdock-esque publisher in order to cover up the death of the Turkish ambassador in her bed. The publisher buys off evil Mrs. Bates then makes Mary an ultimatum: she can't back out of the wedding or he will expose her. Gasp! Matthew meets Lavinia while on leave and gets engaged. Matthew and William are in a horrible explosion. William is fatally wounded. He wants Daisy the Kitchen Maid to marry him as his dying wish to leave her a widow's pension. She feels guilty because she doesn't love him but goes along with it anyway. Matthew is paralyzed from the waist down. The doctor says he will never father children. Sob! Downton Abbey is turned into a convalescent home for WWI injured officers. Edith finds her calling in life as a social organizer and administrator of the convalescent home. One of the injured officers knocks up Ethel the maid. She has a little boy. The officer refuses to acknowledge him. The officer is an only child of an aristocratic family. He dies in the war after he is returned to the front. Ethel decides to confront the officer's parents with the bastard but they rebuff her. Then they relent. They want the child but not Ethel. She refuses and sinks into poverty. Matthew comes home, Mary keeps him company. I wouldn't call it nursing, exactly. This is Mary after all. Sybil and Branson the chauffeur fall in love and decide to run away and get married. Matthew tells Lavinia, his rich fiancé, to forget about him. She goes away initially but comes back. Mary still loves Matthew but respectfully steps aside. Matthew gets feeling back in his feet. He is able to walk with a cane. He has a dance with Mary where he confesses his love. Lavinia overhears. She comes down with the Spanish Flu and tells him to be happy before she dies. Mr. Bates' evil wife is found dead from poison in her tea. Mr. Bates suspects he will be accused of her murder because it is the poison he gave her even though it looks like suicide. He hastily marries Anna. They share a night of passion in a spare room at Downton Abbey. The cops come to take him away shortly afterwards. There is a trial. He is convicted by Mrs. Bates' letter to a friend where she says she had a dreadful fight with the accused. Mr. Bates gets the death penalty but with Matthew's help, it is commuted. Matthew blames himself for Lavinia's death and won't reconcile with Mary because of the guilt he feels. Somehow, he gets over it. Mary girds her loins and tells the publisher to go ahead with the scandal. She is planning to visit her American relatives to ride it out. Sybil and Branson are convinced by Mary that eloping would be a mistake. They confront Lord Grantham about their plans. He doesn't take it well but eventually relents when he sees how dedicated Branson is to Sybil. Sybil and Branson go off to Dublin to be married in a private understated ceremony. At the end of the season, Lady Grantham gets a note from Sybil saying she is pregnant.
Mary is prepared for the scandal, she finally tells Matthew about the Turk. Matthew asks her if she loved the dude. She says it was lust and just a spontaneous foolishness. Matthew says there's nothing to forgive. He realizes he can't live without her. At Christmas time, he proposes to her outside the Abbey on a snowy evening. It's all quite romantic. {{sniff}}
On with season 3.

*wipes tear*

Highclere favorite garden place is featured often on "Downton Abbey," the huge old evergreen trees with their spreading lower branches.

We have a sort of similar property near to us in Suffolk, England-- The Ickworth House. The grounds are incredible, and my favorite part is the Victorian kitchen garden.
If you're interested, I have a photo-filled post about it : http://and-here-we-are.blogspot.co.uk/2012/11/backyard-surprises-ickworth-house.html

It's a pity they don't show the gardens more in the show--something that wonderful should be admired often!
Ashley Erin Mayer