I’m sure you can
I don’t think you re allowed... I checked the website and the lunch are allowed for big group that reserved in advance (like school trip) - I doubt you can bring in sandwich, the garden offers restaurant as well.
yes, great way to save a few bucks
I did not see anyone checking your bag for food and water at the entrance when I was there. My family brought their own water bottles and snack, so I don't see why you cannot bring your own sandwiches. I like their food served in the cafe though and as most food in Montreal, it is relative inexpensive comparing with other major US cities.
According with their FAQ's:
Can I take a picnic to the Garden?
Unfortunately, the Montréal Botanical Garden’s official policy does not allow picnics on site, except in areas that are designated for meals (the meal area at the Insectarium, as well as the picnic areas situated in front of the Lion statue and at the Frédéric Back Tree Pavilion). The restaurant’s patio offers outdoor tables, and you can eat a meal there brought from home.
Please note that alcoholic beverages, chairs, coolers and blankets are not authorized inside the Garden. Only alcoholic beverages purchased on site can be consumed at the Garden’s restaurant, on its patio and in the meal area of the Insectarium.
You can also start with a visit to the Garden and then enjoy a peaceful picnic at Maisonneuve Park. Afterwards, you could always come back to the Garden to continue your visit. Just let the attendant at the gate know that you’ll be coming back and he or she will stamp your hand as proof you have already paid for admission when you return. If you need to leave the Garden and use a parking lot, use the Insectarium’s lot (the second traffic light east of Pie-IX, near Maisonneuve Park).
Yes you can bring your lunch. There are benches throughout the garden where you can sit, eat and enjoy the ambiance.
Yes, you can eat your sandwiches (food you bring) in a cafeteria which has tables for people who bring their own food
Yes. They don’t check your purse or anything. That would be a very good idea actually.
Get quick answers from Montreal Botanical Gardens staff and past visitors.