Use Fewer Perennials
They are very high maintenance. If an existing perennial border is left alone, the fittest plants will survive (though crowding out the delicate ones in the process.) The tough perennials may get overgrown and not flower optimally, but some will still bloom. Just enjoy them in all their imperfection for with infirmity, age or indolence comes the unfortunate necessity of resigned acceptance.
Use More Flowering Trees and Shrubs and Ground Covers
Shift from perennials and annuals to low care ground covers that don't require bending. For flowers, increase the use of low maintenance flowering shrubs and trees that don't require special care or pruning once they're established. With careful planning, there can always be something in bloom.
Plan for a Succession of Bloom
Walk around your garden and your neighborhood and see what you like in late winter. Then look around again in early spring. Write down the varieties of plants so you'll remember. Then do this each month of the year. Soon a plan for your own Succession of Bloom that will work in your neighborhood will take shape through your lists. In northern areas, a Succession of Bloom might consist of magnolia, weeping cherry and PJM rhododendrons for April. Crabapples, azaleas, lilacs, dogwoods and early rhododendrons for May. Late rhododendrons, Kousa dogwoods, Japanese lilac trees, and bush roses shine in June. In July, fill tall flowerpots with annuals and maybe even tomatoes and herbs. In August rose of Sharon and hydrangea flower.
Get Help with the Heavy Digging
Hire a professional to plant new shrubs and trees. Don't even think of doing it yourself! It's very hard work, but once they're in, it will be much easier.
To simplify weeding and watering, mulch deeply. Have someone put mulch where you want beds to look neat. If possible, have them first put on a weed barrier layer such as perforated black plastic or weed fabric. Then cover the weed fabric with wood chips for a better appearance.
Herbicides for Weeds
And there are times when herbicides are useful, so don't hesitate if you need them. One trick is to attach a paint brush to a 3' long stick. Then dip the brush in a small bucket of the herbicide and "paint" it on the weeds to kill them. No bending needed, just patience.
A permanently set up sprinkler or soaker hose is most useful, so when it's dry all that's needed is a turn of the faucet. If even turning the handle is too difficult, invite someone to tea and have them turn it on, have tea and then turn it off. Delicious pastries and eclairs help.
For less impaired gardeners, an easy to pull garden wagon makes chores seem easier. Long handled tools that eliminate bending, especially ones that weed or cultivate are useful when kneeling isn't possible any longer.
Use long acting, slow release fertilizer in pelletized form that can be sprinkled about and not dug in. While it may not be the most sophisticated gardening technique, it works. For northern climates, there is pelletized fertilizer that lasts 3 months. For southern climes, one can use those that last for 9 months.
Condense High Maintenance Areas
The most important thing is to make the high maintenance areas smaller. Put them into small spaces, like right near the back door where one can see the flowers and care for them without great effort. Or where one can see them out a convenient window. Which brings us back to big, tall flowerpots. For easy flowering put a big flowerpot, filled with styrafoam where you want some flowers. And when bare spots develop in the pots, just buy another little flowering something and stick it in. During winter, if the pot looks bare, try some cut pine branches. They'll last a couple of months.