Coffee and tea grounds are great plant food, quickly eaten by worms in the garden. They are available year-round. They are particularly useful for keeping blueberry plants happy by keeping their worms continually fed. Scattered on living soil with a lot of worms, they disappear quickly; they do not keep the ground covered. Other mulch or ground cover is needed to keep blueberry roots happily covered as well.
Saving and using them can be a problem; they are very wet, and readily mold. Therefore, the key to using them is to dry them and not enclose them.
Making my beverages; I use a hand-drip; the bowl on top has a hole in it.
Coffee and tea grounds in the first drying stage, in their filter baskets. Note the tea basket is on top of previous batches with a paper towel between to wick the moisture away.
While making the next pot, the previous filter and grounds go in the bowl on top of the paper towel to continue drying. Normally, I would do this on top of the paper towel and grounds, as in the previous photo. A separate bowl is a good in-between step for multiple batches in the same day.
Grounds ready to spread in the garden.
First, after making your beverage, place the coffee filter in a cereal bowl on a paper towel to begin drying until you need to make the next batch. It will dry faster with the grounds facing up. When you make the next batch, dump the first grounds in a second bowl, and put a paper towel on top. Put the next batch in the first drying bowl to dry. Do not put either bowl in an enclosed space like a cabinet.
As you make more batches of coffee or tea, keep moving the older grounds from the first drying bowl on top of the paper towel into the storage bowl under the paper towel. When it is full, scatter it in the garden. You should not try to keep them for more than three or four days or they will tend to mold and lump together.
Another readily plant food that you can use in pots and on your blueberries is egg and milk. Both have sticky proteins that grab hold of the soil to feed it and your plants. If you make custard or French toast, for instance, you can rinse the bowl and measuring cups into another bowl and water your potted plants or blueberries with them.
The best mulch, bar none, for preventing weeds germination is leaves. Every other mulch will eventually become a seed bed for weeds; many start right out growing whatever lands on the surface. Leaves dry out quickly in the top few layers where the seeds land, so they can’t germinate. Large seeds can grow through them, but smaller seeds are either smothered beneath them or dry out on top. The next year’s supply comes along before the previous year’s leaves become a seed bed. A couple inches guards against most weeds; a foot deep will grow huge veges. Just plant large seeds or small starts into the damp leaves beneath the top layers.
A bowl of kitchen waste. Note that the bowl is small; it doesn't pay to let them pile up and rot.
If you use leaf mulch in the garden to keep weeds down, you can scatter kitchen waste in the leaves. Bananas are particularly useful for their potassium, important for root growth. They turn brown and disappear into the general mulch quickly. Fruit seeds will grow, a bonus. Be sure to remove labels; they stay bright. Don’t scatter onion or citrus peels in the garden; they take a long time to blend in and rot, and they stink when they do. They belong in the trash.