@tittymcswag I haven't spliced anything since the update so I don't know if there's any known bugs or like a chance reduction to get what you want or something. If your new plant is called "Spliced Plant" it should be producing three things: the two plants it was created with and one extra fruit of the thing it can make (in your case and orchid). You can this plant this extra fruit to grow a solid only-orchid bearing plant.
If that extra fruit isn't lost somewhere in your sims' inventory. I'd wait a bit longer for it to bear more fruit before harvesting to see if you can get it to grow what you need.