Why should you be going to you local coffee shop? Well, beyond the need for a caffeinated hot beverage to ward off winter chill, you should be going for the FREE coffee grounds to perk up your garden.
Why use coffee grounds? Because they are rich in Nitrogen, they acidify soil (essential in Colorado where the soil and water are so basic that blueberries cannot thrive without serious amendment), they encourage worm migration into the area being mulched, they add organic matter to the soil, they are pre-shredded, as mulch they look great, and best of all they are FREE!
Map out a route to collect from multiple coffee shops in a single day to make the trip economically beneficial. My route is planned so that I add no extra distance to my after work pick up the kids and head home circuit that happens at the end of the day. In this modified course I am able to visit seven coffee houses (five of which are Starbucks). You will need to retrain your baristas to save the grounds and to double bag them for you and this may take a week or so of consistent visits but they will be happy to let you have what you need if you are kind, polite and discreet. (don't shout "THANKS FOR THE GROUNDS!!" while slinging a leaky bag over your shoulder and heading out)
Why now in the winter time??? This is the most obvious question that I am asked by the coffee house employees. The answer is more subtle than "got nothin better to do..." In fact the grounds can be applied to areas when the snow is melted and the freeze/thaw cycles will help to start incorporating and breaking down the particles into the soil amending it naturally and prepping it for the upcoming season. If your ground is completely coated in snow then save the bags by stacking them in a corner. They will freeze and keep nicely until the thaw giving you time to accumulate enough to mulch with.
This brings us to the question: How much do you need? This varies depending on many variables but I have found that a nice sized bag with about twenty lbs of wet grounds will mulch about two square feet to a depth of an inch and a half. This means that I will need to collect six such bags every day for the following month or so in order to mulch my strawberry beds, around my hardy kiwi, in my blueberry containers, and in the annual beds in the front of my house. (about two cubic yards)
Berry plants of most any variety prefer neutral to slightly acidic soil even those that are tolerant of more basic soil types and low growing berries such as strawberries, emerald carpet, wintergreen, and cranberries additionally benefit from the fact that slugs hate the coarseness and caffeine compounds in the coffee grounds.
They can be used to 'green' up your compost pile in a fall build up of brown carbon materials, and they replenish many trace minerals into the soil as they decay. Some people like to add water to the grounds in a bucket and let them steep for about a day and then pour the phase II coffee directly onto the plants such as fruit trees for a gentle nitrogen boost. I have found that more than anything this technique neutralizes the alkalinity of my water before giving it to sensitive plants such as blueberries.
Where not to use them? Use them sparingly in your general raised beds or anywhere the plants prefer an alkaline soil. Cabbages, broccoli, and other leafy cool weather greens do not like the acidity. If using them as mulch like I am I have heard that some people like to add dry crushed leaves to break up the tendency of the grounds to cake up and form a crust. (I don't worry about this as it helps with weed control.)
Even if you don't drink coffee, remember that this is an excellent resource that will become landfill if not leveraged for your own use in the garden.