Using leftover tea and coffee in the garden?

Not sure whether this should be in "..ancestral skills" in stead

Anyway:
I have often a little tea left at the bottom of the teapot and wondered which plants would benefit from leftover tea/tea leaves. My mother uses teawater on her begonias. And my grandmother sprinkles the used coffee powder around her roses. But I haven't been able to find anything in writing on the use of it in the garden.
What plants benefits from tea or coffee (or -leaves/-powder). And why? And which ones should I not use it for?

It annoys me greatly to waste it, when I could be doing something useful, and good for the plants, with it, but I don't want to kill them either......

You probably already know of this but in the case that you weren't aware I just wanted to bring up that non-organic coffee often has high levels of pesticide residue in it. Not sure about tea but I've heard that tea bags can often have bleach and other crap in them. Sounds like you may be using loose leaf tea though.

If you're worried, what about composting the remains? I recall a Geoff Lawton video where he comments that compost renders many toxins insoluble or something to that effect.

If you've got tea and coffee scraps that you feel safe about, I think just about any plant would benefit from them, especially coffee as it is high in nitrogen. Make sure to add water so that the concentration isn't going to burn the plants roots. My understanding is that you want it to look the colour of a weak tea solution that is semi-transparent, if that makes sense.

well i use hubby' coffe grounds and filters in my compost and my tea "grounds" as well..but I haven't really thought about the actual "liquid" left over..can't see where it would hurt to put it in the compost pile or pour it on the garden either..

Thank you for your serious answers. It is encoraging to get such good answers to my first post.

I did some more searching and found out of the following:
- Tea contains large amounts of flouride.
- Snails don't like tea leaves and coffee grounds.
- Tea are supposed be a fungicide.
- Tea contains a lot of nitrogen.

- Used tea leaves absorbs strong smells, e.g. from garlic.
- And can also be used in the cat toilet (sprinkle on top of the gravel) to absorb smell and work as a flea repellant.

So tea and tea leaves for my nitrogen using plants

(didn't really go into stuff about coffee as coffee is only drunken here, when we have guests)

Coffee grounds keep cats from using nicely dug beds as litter boxes. 

I haven't tried it myself, but I b'lieve I've read that coffee grounds can be good for blueberries, which prefer acidic soil. However, you don't want to use very much--if you were a pot a day kind of coffee drinker, that'd be way too much acid. If it's only used when you've got guests over, though, probably can't hurt to toss the coffee grounds under the blueberries.

I will confess to occasionally dumping out the remains of my coffee or tea onto the blueberry bushes when I'm having breakfast out on the deck, and they haven't dropped dead yet.