Snapdragon is a starter plant and doesn't require any skill I'm pretty sure. Wild plants need to be full grown to harvest. They can only grow if you're on the same lot and that can take several trips.
A community garden works best when the plants are full grown already so you don't have to wait. That's why I grab them from the gallery for community lots. Once you harvest the plant, you may need to return the next day right before 5am for it to bloom again but it won't take much time since the plant is already mature if that makes any sense. Unfortunately there's a gardening glitch EA hasn't fixed and may never fix where plants can revert back to dirt. I don't know what triggers it. It always seemed random in my game.
There are 32 harvestables that can be collected in the base game and 61 more were added with content packs, with a current total of 93. They are collected through finding them in the wild, grafting, or purchasing seed packets from the computer or garden plot and planting them. The harvestables from content packs are often found in the corresponding world of the pack that introduced them.
Since Seasons, all plants will start growing every 5:00 AM and will have reached their maximum number of crops for that day at 5:30 AM once they are fully grown. The update made it very difficult to measure the growth rate of each plant. Some plants always mature after the same number of hours, with others the hours vary greatly.
via Sims Wiki Sims 4 Gardening
