How do you get purple jewels on June’s journey?

Purple Diamonds can be attained without purchase the following ways: 1. remove rocks and dead trees from newly opened land, 2. exchange regular bushes with friends (removing a red bush gives you 5 diamonds, blue gives 3, green gives 1), 3. send Jack's plane on a diamond delivery, 4. opening pink star boxes (1:10 odds of getting 20 diamonds), 5. getting a reward in suitcases after playing a hidden object scene, 6. completing a Help Wanted task that has a diamond reward, and 7. earning diamond prizes in a Detectives Needed key-collecting challenge.

You can buy them. Or as you acquire more space you'll be gifted diamonds for clearing the land; if you get gift plants from others you can turn them in for diamonds. Sometimes you'll win diamonds playing a level.