Pokémon Go ‘Glittering Garden’ event guide
From Aug. 5-8, you can find more grass-type Pokémon spawning in Pokémon Go as part of the “Glittering Garden” event.
This article references relevant content from the polygon.com website. Original article link: [https://www.polygon.com/pokemon-go-guide/2023/8/4/23820158/glittering-garden-shiny-petilil-timed-research]

Pokémon Go’s “Glittering Garden” event runs from Aug. 5-8 and features grass-type Pokémon and promotes visits to parks during the event period.
The event cuts the distance you have to walk with your buddy to earn hearts, increases the chance of finding XL candy with your buddy, and increases hatch candy and stardust by 150%.
The event also introduces shiny Petilil and Lilligant, adding them to the game’s shiny roster.

Specifically, there are some Pokémon that will spawn more often in parks depending on the day:
Alongside these bonuses is the usual stuff that comes with events, including Timed Research, Field Research, and special spawns, which you can see below.
Pokémon Go ‘Glittering Garden’ Timed Research Tasks
Rewards: 50 Venusaur Mega Energy, 50 Beedrill Mega Energy, 50 Pinsir Mega Energy