We were there in November and December and went to botanical gardens several days as my wife is a horticulturalist working for the RHS in the UK on each occasion we took a picnic coffee cold drinks sandwiches etc we did not have any problems at all and nobody said that you're not allowed to have a picnic
As far as I know, it is not allowed. There is a small office on site that may be able to provide you more detailed information.
It's a small park and such activities are not allowed
No it is not permitted.
Thanks! Your answer is awaiting moderation.