You are in Ogden, Utah, I suggest taking a walk in the mountains. Get out of town, away from the concrete. Walk up into the "hills". You will find seed, or maybe seedlings, and can work with these for free, and they will be perfectly adapted to your climate.
You can get permission to collect on private land, if you take the time to find the owners. State forests and National forests are land set aside for eventual commercial use, and permits can be obtained to collect trees in these areas. Similar with BLM properties. Parks and Wildlife Preserves will never issue collecting permits.
Railroad right of ways and power line right of ways are technically off limits for collecting, but depending on where they are located tend to be loosely enforced. A right of way through a Nature Preserve would definitely be off limits, a right of way through BLM territory might receive no attention.
Hike around, locate possible collecting locations, Then investigate. And in general, most places, seed from the wild is essentially fair game. Though definitely read all posted signs and park rules.
Even a neighbor's back yard can have "weed species" sprouting in their flower beds. Get friendly with your neighbors. Look over their garden fences. Many desert shrubs have good potential as bonsai due to their tolerance of short episodes of drought.
