Getting Level ten merely gives you the ability to put an omni seed in the ground, you'll have to do the opportunity that starts with deliver 10 excellent produce to the diner, then you'll want to grow cheese for the next one in the chain, then I think it's steaks they ask for, so you'll want to grow those, when you turn that in, you'll have the ability to get the omni seeds that level ten gardening lets you plant.
As far as I know, there's no way to hurry or force these opportunities to show up, just keep the skill slot open, and keep your hand by the phone. They will call eventually, but it took my gardener 3 days away from becoming an elder to get the second one, so they don't come quickly in my experience.