Easier Gardening for Seniors
Raised Beds

Middle-aged backs easily get stiff and sore if they're not given the proper care. Waist-high raised beds are one way to eliminate bending altogether. With tall raised beds, seeding, weeding and harvesting are a snap. But beds that are only 1' or 2' off the ground can make gardening easier on the back too.
Vertical Gardening

Cucumbers, squash, melons, beans and many other vegetables grow well when trellised. Patrolling the garden for bugs, spraying and harvesting are all easier when everything is within close reach.
Kneeler Stool

A kneeler stool has a thick foam pad that's comfortable on the knee joints. And it has hand grips that make it easier to get up from a kneeling position, since you can use your arm strength to help you stand. Once you're up, flip the kneeler over and it becomes a comfortable stool to sit on while tending your plants.
How to Kneel

When you squat down in the garden to weed or do other chores, never let your heels lift up off the ground: that puts a strain on your ligaments. Instead, keep your heels on the ground. If that's not comfortable, try kneeling with just one knee down.
Proper Pruning

Prolonged pruning can be especially problematic if you hold your hand incorrectly or if you don't have a good pair of pruners. When you're pruning, always hold your hand so your wrist is in a neutral or straight position. Grip strength is strongest in this position, and you have to use less exertion to cut or prune. Never bend your wrist down at an angle: you not only lose strength but you're also more likely to develop tendinitis.
High-Quality Pruners

Ergonomic pruners, which are specifically designed to be easy on the hands, often have comfortable handles and gears that make cutting easier. Some handles actually rotate as you cut, which reduces the strain placed on your hand muscles.
Make sure you get pruners that are the right size for you. Test for length by holding a closed pruner in your hand. The handle should stick out about a half-inch below your little finger. Test the width by placing them in your hand with the pruners open. With one handle in the crook of your thumb and your hand comfortably extended, your little finger should extend about a 1/4" beyond the other handle. If you can't reach the handle with your fingertip, your hand won't be able to rest properly between cuts.
Even with good tools and equipment, it's important to take breaks every now and then and to rotate tasks. Alternate pruning with raking every 15 minutes or half-hour, or alternate hoeing with hand-weeding so you're working different sets of muscles.