On birdhouses: [mounts soapbox] PLEASE do some homework on this before you put them up. They require maintenance and effort! If you don't properly install the right size/type box AND actively monitor it, you will breed non-native, invasive House/European Sparrows - they are VERY aggressive and will force out and/or kill (yes, kill!!!) native cavity nesters like bluebirds, chickadees, tree swallows, purple martins, and others. Other non-desirables like mice and yellow jackets will also take up residence in a nestbox that is not maintained. And an improperly mounted box can allow snakes, raccoons and other predators to climb up and raid the nest. I really enjoy hosting native birds, but it does require some work to provide a safe place for your birds. For tons of great info on hosting bluebirds (and some other cavity nesters), my favorite site is
the Sialis website. [Steps off soapbox]
Save seeds from your garden to grow next year and to trade.
Divide perennials and trade them for new plants.
Mulch, but don't buy it. Cardboard or layers of newspaper can be put down to smother weeds, and then covered with grass clippings, leaves or wood chips. Mulching saves time and water, and organic mulch adds nutrients to the soil. Leaves are easy to get in the fall - people even bag them up and leave them at the curb for you.
Compost. Anyone can do this, even in the city. Reduces trash, is easy, and provides the BEST fertilizer you can get for your garden.
Grow perennials from seed. It takes longer and is more work, but is MUCH less expensive than buying potted perennials. And you can trade the extras.
Garden organically. Chemicals, non-organic (petroleum-based) fertilizers, and pesticides are expensive and bad for you and the environment - they can harm or kill beneficial insects, birds and animals. Attract ladybugs, preying mantis, insect-eating birds, toads, dragonflies (they eat mosquitoes), bees (needed to pollinate your plants), and they'll take care of things like aphids for you. Also, healthy soil leads to healthier plants that can resist many pests and diseases, so you don't have to use chemicals on them. Earthworms and many other soil-dwelling critters are your friends! This may take more effort to begin with, but will save you time and money in the long run.
Root cuttings to increase the number of plants you have. Annuals, perennials, shrubs, even some trees can be started this way.
Consider putting rain barrels under your downspouts to catch rainwater.
Save plastic pots and those little packs that annuals come in to start seeds in next year. I also use toilet paper rolls cut into thirds, egg carton, clamshell packaging that things like strawberries come in, etc. to start seeds in.
Every year, invest in something like a fruit tree, strawberry plants, asparagus crowns, raspberry plants, grapevines, etc. You spread out the cost and the work over time, and make progress annually, which feels good.
If possible, make those "investment" purchases when things are on clearance in the fall. Late autumn is a great time to plant many perennials and trees, and many stores and nurseries are trying to unload them before winter. Discounts of 50% or more are not uncommon.
Make your own tomato cages with 2X4" welded wire fencing or concrete reinforcing wire. Can be less expensive and are MUCH more functional than those little hoop cages you see in stores.
Buy gardening tools at yard sales. You can often find better quality tools for much less money than in stores.
Enjoy your garden. If you don't enjoy it, you won't do it, and the savings of growing your own is lost. Put a comfy seat in the garden so you can sit and read, fill a birdbath to attract singing birds, plant some herbs to enjoy the fragrance when you walk by them, and don't forget to plant some flowers in the veggie garden - a spash of color makes an otherwise purely functional area beautiful, and you can cut them for fresh flowers indoors.
Happy gardening!
Diana