monet's garden

I'd guess 2-3 hours would be good unless you plan to have lunch maybe at Restaurant Baudy. I am going next week and am taking the 10:19 AM train from Paris and returning on the 4:53 PM. I've been before. We stayed around 5 hours but we had lunch.

Reservations are not required on this route and your tickets will be good all day. Just be sure to validate them before boarding using the machines that are available for that purpose.

Giverney is really crowded. If you are arriving at the train station in Vernon you must still ride the bus to Giverny. I expect you will be arriving at a peak time.

The crowds are not fun but I think worth enduring. However they make it hard to advise you about how much time to spend. Several hours, I should think. There are a few restaurants in Giverney; it might be worth reserving lunch.

I hope you will have time to visit some of Monet's paintings while in Paris; there are none at Giverny. They are at the Orangerie, the Orsay (usually), and the Marmaton. Have a wonderful trip.

It depends on how busy it is and how long you need to appreciate the gardens and house. The crowds could slow you down (take longer) or put you off (cause you to leave sooner). The bus runs until 7 pm or so. Just make sure you get to the bus stop well ahead of departure time as there is often a long line.

I have follow up questions as we are going next month. I noticed that the OP is getting there in time to connect with the first bus from Vernon to Giverny. Would it still be crowded that early? Is it better to stay the night before in Giverny and be there right when it opens to avoid the crowds? Can you re-enter on the same ticket? That is, leave for lunch and come back.

I would just note several return times so you can be flexible. The buses are timed to the trains and you need to step lively when the train arrives if you want to get a seat (or place) on the bus as they fill up. When we were there, there was no second bus in sight for those left waiting. Same on return, get to the pick up point 15 minutes ahead. This is easily done on your own; it does make sense to get train tickets a day ahead so you don't have to fiddle with it the morning you go; we missed the train when the line was an hour to get tickets and had to go a different day. (I don't know if US credit cards work in the machines now; they do work on the metro -- but back then they didn't.) The train tickets are usable any day any time; just be sure you compost (validate) them before getting on the train, both directions. Often there is no ticket check, but if there is and you haven't properly validated the ticket in the machine, it is a very large on the spot fine as the tickets can be used at any time and so unvalidated they are not 'spent.' Buy two tickets - one for each direction - when you buy the tickets.
https://janettravels.wordpress.com/2010/05/25/not-so-secret-garden-giverny/
We were there on a crowded day and it didn't diminish the beauty of the place. Be sure you get tickets for the gardens ahead of time so you don't have to wait in a long line. You can enter at the group entrance with those tickets.

Thank you all. I appreciate and will use all the thoughts and opinions. We are a large group really (9) so will eat lunch there and take the entire day. I will purchase entry tickets and train tickets ahead of time to reduce our time in lines. Thanks so much

If you are able to get on that first train, you will miss some of the crowds...the next train and wave will be where most will be.

I find the best practices when visiting Giverny is when you get the Vernon, look at the schedule and note the last couple of trains, and when you take the bus, ask the driver the frequency and the last couple of buses and work this backwards. The schedule can change due to season and I find that the information online can make your visit there too rushed and planned and given the free spiritedness of the place, it is better to visit when you are relaxed. There is plenty of time to see it and so as long as you are aware of the last trains so you don't get stuck, then take as much time as you can. If you get back to Paris early, even better...but if you don't, then at least you got your full experience.

When I have gone to Giverny, I have always taken time in Rouen as well and have always had enough time.

You can find and copy the train schedules here: https://en.voyages-sncf.com/en/
I don't know if the tickets can be purchased on line and printed at home; probably not on a regional train but you can try.

PS: When I visited the on-site museum a half-dozen years ago it displayed no Monet originals although it was worthwhile looking at his contemporaries. In Paris the largest Monet collection (maybe in the world) is at the Marmottan.
https://en.wikipedia.org/wiki/Mus%C3%A9e_Marmottan_Monet

Apparently I misunderstood how to do the train to Monet's garden. Rather than reserve seats for a particular departing Paris time and and returning to Paris time, am I just purchasing open timed tickets (similar to a Metro) that I validate upon use but allow me to take any timed trains. So that if I depart Paris on the first train (815 or so) when we are finished at the gardens/lunch/etc we can return at any time train?

I think you can reserve a train and seats, but normally people buy unreserved 2nd class tickets and simply validate them (yellow machines) before boarding each way. Always keep your tickets with you. You get fined on the spot for not having your validated ticket.

Expect the bus tours to be there from about 10 am to maybe as late as 4 pm. If you can get there first thing and see the place early, or alternatively plan to be there after the most crowded part of the day, it might be a little more comfortable. I usually plan first thing in the morning for the most crowded sights but you will have to get to Gare Saint Lazare, catch about a 30 minute train to Vernon, then bus from there. It may be asking too much with a big group.

I've ridden the train to Normandie several times. Early in the morning, it's not that crowded. By 10 am, the train is packed with people heading to Vernon.

There is no need to pre-purchase your train tickets and as it is a regional train and not a TGV, you will not have an assigned seat.

You will simply buy tickets at a kiosk or window for Vernon and when you purchase it as a round trip ticket, you will be able to come back on any train. You can also use the voyages-sncf app to buy your tickets and to keep track of the schedule, but I will always just confirm the return train schedule when I arrive at Vernon and keep that in the back of my head as I visit.

And then as mentioned, you will catch a bus from the Vernon train station (which is a very small station) to Giverny and the gardens. The bus stand is clearly marked.

Yes the gardens are crowded even if you get there right when they open. The day we went there were many tour buses also arriving at opening time. We bought our return tickets at the train station. The gardens are beatiful and so worth it! We were there last week.

The train that you take to and from the gardens may be an Intercites or a TER. If it is an Intercites, you can purchase a print at home ticket online but there is still no seat assignment. If the train is a TER, you also have no seat assignment and you cannot print the ticket at home and must obtain it from a ticket machine, a SNCF boutique or the SNCF customer service reps at the station. We used an Intercites ticket to go from Paris, which I printed from home and picked up the return ticket which was on a TER at Gare St Lazare.

When I went three days ago, there were three buses meeting the train and the second one, the one I was one, left 1/2 full and the 3rd one which was completely empty stayed behind.