all plants will help with the exp, it's the solvant that will make a difference.

keep the columbine, mountain flower, burgloss and huuh... hmm. wait for some German speaking fellow to say wich ones for future useful potions , keep the nirnroot for later daily quests and use anything else to level up. the higher the solvant, the higher the exp. That said, discovering traits will do most of the leveling job.

You'll get 3 solvants for your skill level with the daily quests as a reward (see boards in towns). Sometime you'll have to give 3 back for these quests too. As some solvants may be difficult to find at low level if you overlevel your craft skill compared to your char, you may want to buy 5-10 on the market to start with these quests then you'll have enough untill you even need these potion level.

you'll be able to use better solvants by adding points to the skill, but don't worry, overall alchemy is one of the easier crafting skill to level up. Just pick up everything and craft anything you can... and cherrish the columbine.

Edit : and yes, for other addon research use the Advanced option to search in the description too. By default it does search only in the title, and mostly outdated addon are using the perfect name now . Good remark.