Garden tours

"College tour" companies, and of course charities that run gardens often create money-raising land-vacation-packages that visit (in some cases) otherwise private gardens. These tend to be pricey, but it's "all done for you." Your question opens the door to vast amount of reading and internet research, sometimes with websites that aren't translated. And you have to vet each place to see if it's worth the time and money to get there.

Could you post a clearer request, please? Have you ever been to Europe before? What is your daily hotel budget (as a way of discussing your feelings about cost.) How many people, any age or disability issues? Are you simply looking for a list of likely gardens? Or are you hoping someone will give you a complete itinerary for one or more of those countries?

As it happens, we had a short stay in London in September, 2019, and prioritized the very famous (but not that large) Sackville-West garden at Sissinghurst Castle. We undertook it "independently", which wasn't that hard. But by public transportation, it was a full-day out from London, and still cost close to $100 per person. But it's a really famous destination, and a must for us, after many trips to England.

Google will be full of options for garden focused tours, or ask your local horticultural society if anyone can recommend. I really like to meander and take time, so would prefer to tackle them on my own. Paris alone has numerous to visit including Rodin Museum and Gardens. Add Versailles and Giverney and you can spend days with Paris as a home base.
If you have NetFlix or a PBS membership, review Monty Don's Gardens of France and Gardens of Italy. I started planning a trip to Italy with his gardens in mind, but they are not quite as accessible as indicated. However, a car and driver, or private guide for the day could bring the more of the way gardens closer. I've signed up to receive regular newsletters from this group newsletter(at)grandigiardini.it which describes numerous gardens throughout Italy.

I loved an independent trip to Andalusia region of Spain and every city had gardens accessible - often via the private house museums like Palacio des los Duenas in Seville; as well as the Alcazar, Granada and so many more.
Joining the National Trust in England/UK gives reduced entries to many of the stately protected homes and gardens.
Look at gardenvisit (dot) com that lists gardens for visit around the world, as well as tours available.
I love adding gardens to my tours but I'm not sure I can make it the primary focus of a tour abroad. Too many other hobbies and interests.
Enjoy!

I think we could have you more if you gave us specific towns, villages or cities you plan to visit in each country.

If going to London, visit Kew Gardens and the Chelsea Physics Gardens, that is where I am headed next year. I too am a huge fan of going to gardens!

I have been to Monet's Gardens outside of Paris and they are wonderful. I can't wait to return!

I think I can give more suggestions if I knew where you are planning to actually go as each country is very large to visit.

Agree we need more info, but this resource might give you some ideas:
https://www.ahsgardening.org/gardening-programs/travel-study

And when (month, time of year) are you going? That can make a difference in what people recommend, as some gardens are only open or at their peak certain times of the year.

Teaton - For classic garden tours from the countries you have listed, here are some to consider.

Spain:

Jardín Botánico Marimurtra located in Girona, Spain

https://www.marimurtra.cat/en/

Granada (Alhambra gardens)

https://andhereweare.net/a-stroll-through-the-generalife-gardens-at-the-alhambra/

Ireland:

Powerscourt Gardens located in South Ireland - Enniskerry, County Wicklow, Ireland

https://powerscourt.com/gardens

England:

Wrest Park located in Silsoe, Bedfordshire, England

https://www.english-heritage.org.uk/visit/places/wrest-park/?utm_source=awin&utm_medium=Affiliate&utm_campaign=Affiliate&awc=5928_1575666217_4f356ffbb50c867bee0978a0139911ed&utm_source=awin&utm_medium=Affiliate&utm_campaign=Affiliate&awc=5928_1575666217_4f356ffbb50c867bee0978a0139911ed

Fountains Abbey & Studley Royal Water Garden - Fountains Abbey and Studley Royal Water Garden, Located at Ripon HG4 3DY, United Kingdom

https://www.nationaltrust.org.uk/fountains-abbey-and-studley-royal-water-garden

France:

Claude Monet Gardens - Giverny, France

http://giverny.org/gardens/fcm/visitgb.htm

Veau Le Vicomte Chateau - Located in the Loire Valley at 77950 Maincy, France.

https://www.youtube.com/watch?v=BYItH-sXA44

https://vaux-le-vicomte.com/en/decouvrir/the-french-formal-garden/

P.S - The Chateau Versailles Gardens is also another top destination to tour just outside Paris.

http://en.chateauversailles.fr/discover/estate/gardens

Hi Teaton,
A friend of mine has used Martin Randall Tours for home and garden tours (at the very least, the itineraries should help with planning and ideas.)

https://www.martinrandall.com/houses-and-gardens