Will a professor always say so if they can't write a very strong letter of recommendation?

Question

I am applying to graduate school currently, and all schools I've been looking at require a number of recommendation letters. I go to a fairly small school, so I've had many repeat professors. Thus, my pool of professors to ask for letters who taught me in a relevant subject is somewhat limited.

One professor in particular I have had many classes with, and I did well in most of them. However, in my most recent class with him (last semester) I did fairly poorly. I was often behind on assignments, and while I was in communication with him and tried to work with him to catch up, he would often say things like "you probably just need to study a bit more, this material shouldn't be too hard."

There is probably some good in this. Since I did well in his classes in the past, he may be confident in my abilities and thought that I should be able to keep up in this class. This could also mean that he thought I really wasn't trying very hard. This is probably true to some extent, as I was having some personal issues last semester.

So with that said, I still felt like I had overall positive experiences with him throughout my college career, and like I said, my options were somewhat limited anyway, so I decided to ask him. I figured that if he was unhappy enough with how I did in his class last semester, he would just decline outright, or say that he couldn't honestly write an overwhelmingly positive letter.

However, he did end up accepting, so all should be well, right? Maybe I am just being paranoid, but I am kind of concerned for a few reasons. One, other professors who accepted clarified that they were willing to write a "strong" letter of recommendation for me, whereas the professor in question did not.

Another reason is the fact that I do believe he will have positive things to say about me, even if there might be some negative mixed in there. So it might be that he considers what he has to say about me positive enough to write a letter, even if it isn't all amazing.

In my research, I found this question: Should I take a "positive, but not enthusiastically strong" letter of recommendation?

So I'm concerned his letter may fall into that category of "positive but not enthusiastically strong", which, as the answers to that question point out, is generally not a good thing to have.

The last factor is that since this is such a small school, he may know that my options are kind of limited, and figures that I pretty much need his letter, even if it's not extremely positive.

Am I just being paranoid? Is it a bad idea to ask him about this?

EDIT: I was reading through more posts on this site and came across this: Difficult student would dispute every grade in the course and now wants letter of recommendation. It was a question asked by a professor, and some answerers mentioned that the OP made no promise to write a strong letter of recommendation, so they were not obligated to, despite accepting to write one. This is kind of worrisome to me, as it's clearly not implicit in acceptation to write a letter of recommendation that you are willing to write a very strong one.

Answer 1

Since you ask "always", the answer is clearly no. Some will not. Most will try to do "as well as they can" for you and not sabotage your chances, but their feeling may be hard to hide in any letter they write.

My suggestion is that you go talk to him in person and ask about his current feeling toward you ("How am I doing?") and what you might do to regain his confidence in the future ("What should I do now/next?"). Admit to any faults if they come up ("Yeah, I blew it.") and explain them if given the opportunity ("I got distracted by ..."). But don't press that if not asked.

I once disappointed my main mentor (by getting overextended and focusing on things outside math) but he still came through for me when it counted. All is not lost.

At small schools this is much more likely to be successful, actually as you are more of a person and not just a student.

Such a conversation normally clears the air if it is cloudy and leaves the person with a better sense of you and more likely to want to help. If he feels just a bit better about you after the conversation you will benefit in his "mood" when he comes to write the answer. It is the unconscious negative feelings that you want to dispel if you can.

And if you come away feeling bad "vibes" you might want to consider other options for letters.