I am visiting Stockholm with my mother, 78, we are staying in Södermalm. Any nice gardens to visit in the city of outside of it? We will be here till the end of August. Are there any festivales during this time?

Thank you for your help!

Bergianska trädgården (botanical garden in stockholm) is more central (sorry their homepage is only in swedish). The garden is located close to the university and the naturalhistory museum.

The city of Uppsala is not too far from stockholm it´s the city where the famous Carl von Linne worked and lived (he was the one who organised flowers and animals into different families and species). The botanical garden in Uppsala still contains plants that Linne planted and there is also a Linnegarden in Uppsala.

The medivelfestival at skokloster is 26-30 of july.
http://www.skoklosterspelen.com/ (it is possible to choose english text at the homepage)
The castle at skokloster is worth a visit the man who built it was a good warior and he plundred the castles in europe so the castle is quite rich on objects and most of the paintings etc. are the originals.

I also recommend visiting some museums
Here you can find the museums in stockholm
http://www.stockholmsmuseer.com/ (it is possible to choose english text at the homepage) Many of the museum cahrges no entrance.
The one I really like is Livrustkammaren (The Royal Armoury) it´s located at the royal castle here you can se old clothes from the royal families thru the centuries even clothes with bulletholes from when the king was killed, old wagons etc. This museum is one of the museums that doesn´t charge any entrance fee.

From stockholm there are very nice boattrips to Birka Swedens first town. It´s possible to eat at the island where birka is located but I have always had a picnic at Birka when I have been there, the nature is very beutiful. http://www.strommakanalbolaget.com/ (It´s possible to choose english text on the homepage)
They also have boattrips to Sigtuna witch is a very old and pittoresque little town.

+They have boattrips to Drottningholm where the swedish king and queen lives, there is a nice castlepark to walk in and some of the buildings are open for the public.