The Boston Public Garden? I've never been there in late April, but I would think they would have something happening?

I stumbled upon the Boston Victory Gardens last year in summer. These are private plots, I believe, but if the spring is anything like the summer display, it will make for a wonderful stroll!

Dee

Here is a link that might be useful: Boston Fenway Victory Gardens

The Arnold Arboretum? They have their own website and they have Lilac Sunday later in the season. I'm sure they would list anything else going on there.

Magnolia Trees along Commonwealth Ave are open now

The Rose Kennedy Greenway should have something early. I have seen a photo of a yellow Magnolia from that area.

There are Cherry Trees along the Esplanade that have opened about the 3rd week of April in past years.

There seem to be a lot of neighborhood gardens in the Back Bay with spring plantings.

Here is a link that might be useful: Arnold Arboretum

I love checking out the Fenway Victory gardens. There are some really cool plots there(as well as some that are decidedly neglected).

Teresa

There were a bunch of different trees (magnolias, pears, cherries, and crabs) blooming along the Esplanade and Huntington Avenue today. Quite lovely.

I'm late seeing this, but if you can get to Garden in the Woods in Framingham, it might be worth looking into. They feature local wildflowers. I'm not sure what they have flowering this early, but you could ask.

Here is a link that might be useful: Garden in the Woods