Parks in London are great for utilising outdoor exercise, good weather and family trips out. What you consider London depends on your definitions and willingness to travel within the nine TFL zones.
Across the districts there are localised information spots of things to do; borough dependant, finding a green space isn't hard but there are accessibility points like fees and opening times for some registered parks.
The Popular Ones
Richmond Park
This park is located on the west of the District line, with it's terminating stop being Richmond Station, accessible via South West Trains too, but you may want to catch a bus to the park as it is not directly in sight of the town centre. This park boasts a peaceful and rural experience and is free for visitors: opening times are generally 7am-7.45pm but these change depending on the season so check official websites for information. The main attraction is that this park has roaming deer. It is home to the beautiful Isabella Plantation, Pembroke Lodge and herds of Red and Fallow deer. It has children play areas too at two entrances, depending on where you enter or leave, you could make use of this suburban plain for family picnics.
Regent's Park
This Park is affiliated with the famous Primrose Hill, a hotspot for viewing sunsets across London. The park situates London Zoo and also hosts the Open Theatre from May-September. The park is free to enter and provides disabled access, toilets, baby-facilities and a few cafés, try the Garden Café for immediacy or The Honest Sausage for something heavier.
St. James' Park
South of Regent's Park, it lies in the heart of London. Close to Piccadilly Circus, it is surrounded by three palaces. It's donned with stripy deck-chairs during the hotter months and is prime spot to see pelicans. The Mall is situated here and across the year, many national celebrations take place in this famous park.
Kew Gardens
Despite an entry fee for this ground, it is historically a space of cultivation and horticultural excellence. Renowned for being London's botanical garden, it features collections and exhibitions of diverse flora and learning. You can roam the gardens and view: a Japanese Pagoda, a tropical climate zone, a small lake, a tree-top walk, the Hive installation, an aquatic room etc. Exhibitions of plants rotate to offer cultural insight, so make advantage of this by checking online what is being showcased and when. Kew Gardens also benefits from many eating facilities and children's experiences. It's a 10-15 minute walk from Kew Bridge station and roughly 7-10 minutes from Kew Gardens Tube station, on the District Line. Prices are an average of £15, children 4-16 yr/o enter for £2.50 and children under four enter for free. Concession and discounts exist for students and those with other requirements; check online for further official info.
The Other Great Parks
Perhaps not as famous as the above, the following list of parks offer green, breathing spaces when this city is just too busy. London has an energy that attracts all sorts of visitors and it's what makes the place so vibrant! This is great for finding parks as it means local authorities take pride in providing park and garden spaces in many neighbourhoods, for easy access.
Localised Parks
These parks may not have their name appear in tourist guides or TimeOut London, but they're easily findable at many London Tube Stations on the area maps provided. London's TFL staff can even point you in the direction to a local green space, if you find them at a registered Tube Station.
E.g.
Kingsbury park is 7 minutes down the high street: features basket ball courts, play area for children, large oak trees
Lampton Park is a 5 minute walk, turning right out of the station: features a rose garden, tennis courts, picnic benches and play areas.
The following link can be used to find a local park in your area:
https://www.gov.uk/find-your-local-park