I had a dream that my boyfriend was a huge old oak tree with weeping willow branches on it. The funny thing is that I didn't even think it odd that he was a tree. I was having a conversation with him. I have also recently dreamed that I was sewing patches on a jacket that belonged to him. Does anyone know what these things could mean?

I think the oak tree may relate to something you have done with your boyfriend, or perhaps how you view him?  Do you see him as a 'wise old oak' tree that you go to for advice?  The weeping willow branches adds a sad and perhaps beautiful aspect?

It could also relate to 'growth' with him.  The age of the tree may also relate to the age of your relationship.  Have you been through a lot together?

Here is what a tree as a dream symbol is said to represent from my sources:
Tree - A tree may symbolize the power of personal growth. Just as a tree blssoms in the spring so too should a person in their growth as a person. A dead tree would indicate you are lacking this quality in your life. A withered tree may symbolize a dried-up state of being, one who lives too much from the head with rigid rules taking the place of instinct.
Oak tree - Seeing an oak tree in your dream, symbolizes longevity, stability, strength, tolerance, wisdom, and prosperity. Seeing an oak tree with acorns means a promotion or increase in the social ladder.
Willow - Seeing a willow tree in your dream, symbolizes mourning and sadness.

So the dream could be addressing that wisdom that he has, as well as strength and stability, and the potential longevity, or perhaps the existing longevity of your relationship with him.  The weeping willow relates to a period of sadness or possibly mourning that he is going through.  Perhaps you are concerned that his sadness may be caused by, or perhaps may effect your relationship (a common theme I have personally seen).  The dream may be assuring you of the strength of your relationship.  Does that mean anything to you?

In terms of mending the jacket:
Jacket - Seeing or wearing a jacket in your dream, represents the image that you want to present and project to the outside world. Alternatively, it symbolizes your protective and defensive persona. You tend to distant your feelings and as a result, you may be isolating yourself. Consider also the color, appearance, and type of jacket for additional significance.

Sewing - Dreaming that you are sewing, suggests that you are trying to make amends with others. There may be a situation or relationship that needs to be repaired. Perhaps you are seeing or eating a new self-image and taking on a new attitude. Alternatively, it represents fertility, growth, and emotional maturity.

It sounds like your boyfriend is going through some hard times, perhaps relating to the outside world in the symbol of the jacket?  Perhaps he had his confidence beat, lost his job, something like that which has put holes in his defenses.  You are helping to repair his armour, or sew patches on his jacket.  The sewing symbol could have the double meaning of you trying to 'repair' something in the relationship, though you both have that emotional maturity and fertile relationship as seen in the tree dream.

Does that make sense?

Sweet dreams,
Rook