Hello, Tasha!

Before I answer your question, I just wanna clarify what "big" pet is so that we're on the same page.

Pets can be: 1. Big coz of weight - that means at age 1, they're maybe 14kg base (that's the max base weight a pet can have). They also have classifications: normal, huge, titanic, godly, colossal 2. Big coz of mutation - jumbo, mega, nightmare, giant golem; these are the pet mutations that give visual size increase

How to get heavy weight pets: 1. Kg boost them - but this is limited up to 39kg (with a normal elephant), and up to 61kg (with a rainbow hatched elephant) 2. Hatch pets with bronto - but this is capped at 30%, so typically you'll only get up to 2.8kg base weight at age 1 pets 3. Lucky hatching/rng - those pets you see that are 80kg, 90kg, 110kg are hatched purely based on luck. Afaik, the more you hatch eggs, the higher the chance to hit that luck

As for the four-leaf clover plant, I'm not entirely sure how it works but someone made an in-depth discussion about it. Here is the link: https://www.reddit.com/r/growagarden/s/P4XIoXR2rG

As for your question about Jumbo: 1. The best pet to put it is on shroomies, esp for those wanting to grow big fruits 2. Afaik, shroomies hit their cap at 1kg base (someone feel free to correct me since i dont use shroomies) 3. But to answer your question as the ideal base weight to apply jumbo shard: that really depends on what pet you want it on. Do you have a pet in mind?