Clematis are heavy feeders, though will also do fine without extra fertilizer. I have sandy soil, so am constantly amending with compost and fertilizer similar to tomato fertilizer. A top dressing of compost and dry fert in March + regular liquid feedings throughout the season up to August is my usual routine.

I would do a dry or granular fertilizer topdressed in March and no more until after blooming. Then I would do the liquid fertilizers after the first bloom until no later than the middle of August maybe even stop beginning of August to let them get ready for winter.

That seems to be a lot to me :-) I fertilize once in spring.....that's it. And sometimes the fertilizer is not exactly "fertilizer" out of a box or bag but bunny poop (when I still raised bunnies) or compost. I don't find clematis to be excessively heavy feeders. I DO have decent soil but it is not exceptional and not nearly as good in my new garden as in the old (20+ years of amending) but the clematis -- and all the other plants as well -- thrive without excessive fertilization. But then I tend not to pitch in a lot of additivies of any kind to my garden. Compost is my mulch and nutrient source of choice.

Three tablespoons is a lot if they are small.....

I do not use liquid fertilizer on my clematis and am surprised to read that others do. I thought we were all using organic rose/tomato fertilizer here and alfalfa and compost or manure.

When I say liquid fertilizer I am talking about alfalfa tea, Sea Tea, or Fish Emulsion only. Not all at the same time either! It depends on what I have on hand.
My soil has been improving, but it's no where near what it will be a few years down the road. I do use manure in the fall, and I have just started a compost bin, so that'll have to wait until the compost is ready. Then I will be using mostly just the compost.
When you are just starting out or so, you do not have access to all those wonderful additions right off the bat all the time, and you have to work with what you can.
My soil test indicated I have plenty of phosphorous and potassium, but low nitrogen. So, hence the additions.

Those are all organic liquids that aren't even close to being as strong as Miracle Gro. That is what I thought everyone here was doing. Thanks for clarifying. :)

I only feed the ones that have competition from neighbor's tree roots other than top dressing the entire yard with compost every year.

My Clems in heavily worked and amended beds with no tree roots have thrived with no added fertilizer other than compost.

Clems crammed in between tree roots in unamended clay soil have all struggled and need the extra fertilizer.