The oldest known plants are cyano bacteria (sometimes called blue-green algae) that are 3,500 million years old. They are ( exactly the same species is still alive today) tiny, .001mm (.00004 inch), one celled things that live by photo-synthesis, a kind of pond scum actually. Despite their tiny size they have left some big fossils, there were a lot of them for a long time, and for a long time they were the only plant there was, just floating around by themselves. When they died they settled to the bottom and over time turned into thick layers of stone called stromatolites, the largest individually distinct stromatolite weighs 6 tons. A tiny moss like plant, appeared on land around 450 million years ago . Somethin' that looks more like a plant, they have 'leaves' or at least fronds, the ferns appeared about 400 million years ago. The ferns left some very pretty fossils, BTW. Mosses and ferns reproduce with spores. The oldest seed plants showed up 350 million years ago, they were gymnosperms, there is no real flower and the seeds do not form inside an ovary or fruit. Pines and other conifers are gymnosperms they have cones instead of a nut or fruit. The oldest flowering plant is 140 million years old. It was recently discovered in China. Actually it had been discovered years ago but the fossil sat around before somebody took a good look and discovered what it really was. It wasn't much of a flower, it didn't even have anything like petals, but the seed developed inside an ovary that became a fruit. The oldest fossils with something that can be identified as tiny petals are 90 million years old. Some actual "full sized" complete flowers that really look like flowers are about 50 million years old. They don't smell like flowers though, unless you get them wet, then they smell like, well, wet rocks.

If they are the oldest fossils on record, they cannot be more than approximately 10,000 years old. Many scientists date fossils according to how old the geological layer is that they are found in. However, when asked how they know the age of the geological layer, they state that they know by the age of the fossils found in that layer. This is circular reasoning, with absolutely no scientific basis. Fossils cannot be dated using Carbon 14 methods, and there is no place on the earth where every geological layer is found intact in the same place. Therefore this negates the assumption that we can date the age of these layers, or the fossils found within these layers, by using one to date the other.