How do you "negoaite with a sim-eating plant"?

Plant something that will change to into a monster plant. You can find those plants with a special green monster symbol on the picture of the Seeds.

First off, you have to own a garden. Click on the garden and a sidebar should pop up with all different types of Seeds. Look for a green triangle with a monster inside of it right above a box of seeds (only certain plants have the ability to be sim-eaters). The shortest amont of time you will have to wait is 45 minutes if you have unlocked the lettuce plant. Click on a box of seeds and wait for them finish growing. Once thier done, they should have a button on top of them, click on that and the button should spin between the plant symbol and the monster symbol. If you land on the plant you will harvest money but not complete the objective. That would make you restart this process to finish the objective. If the button lands on monster then you have created a sim-eating plant. Click on the plant and then click "negotiate". Also please don't worry about the plants actually eating your sim because they don't eat the sim. Once your done with negotiating then you have completed the objective!

First off, you have to own a garden. Click on the garden and a sidebar should pop up with all different types of Seeds. Look for a green triangle with a monster inside of it right above a box of seeds (only certain plants have the ability to be sim-eaters). The shortest amont of time you will have to wait is 45 minutes if you have unlocked the lettuce plant. Click on a box of seeds and wait for them finish growing. Once thier done, they should have a button on top of them, click on that and the button should spin between the plant symbol and the monster symbol. If you land on the plant you will harvest money but not complete the objective. That would make you restart this process to finish the objective. If the button lands on monster then you have created a sim-eating plant. Click on the plant and then click "negotiate". Also please don't worry about the plants actually eating your sim because they don't eat the sim. Once your done with negotiating then you have completed the objective!