Acknowledge Dad's love of the garden with a Father's Day gift he'll use often. If Dad likes to garden efficiently, a sturdy garden cart will make his work easier. A weeding auger will let him mix his love of power tools with his love of the garden. And if your father is no longer able to get outdoors easily to work a garden plot, an indoor microgreens kit will still let him work the earth. See Resources for more info on the below-listed items.
A bicycle-wheeled garden cart is a vast improvement over a tipsy wheelbarrow. Dad will likely appreciate its stable wheelbase, large carrying capacity, and the fact that the front panel slides out to allow for easy, complete dumping of weeds, rocks, sand, dirt, logs, or anything else he can carry around the yard.
Wheelbarrows are notoriously unstable on slopes or when carrying unbalanced loads, but a two-wheeled garden cart is easy to push, even uphill or when unevenly loaded. Many brands of garden carts, like the original Vermont Carts (at CartsVermont.com), are made in the U.S.
Electric Weed Auger
If Dad likes to play with power tools, an electric weed auger is just the thing for him. These long-shafted spiral drill bits hook up to his favorite power drill and let him harness that garage-workbench energy to rid the garden of weeds.
The Turbo Weed Twister takes the power-weeder idea one step further with two spiraled fingers that reach around the weed and allow Dad to pop even deep-rooted weeds out of dense soil with the push of the power button.
Indoor Salad Greens Kit
Losing the ability to garden is tragic for elders who are confined indoors due to infirmity, or who have moved to a small apartment, assisted living facility, or nursing home. A microgreens salad kit is the perfect gift for a Dad whose fingers still itch to garden even though he's unable to cultivate a large outdoor plot.
With a small sack of potting soil, several miniature aluminum loaf pans, a couple of disposable cups for soaking seeds in water, and an assortment of sprouting seeds, Dad can grow a richly mixed, nutritious salad in about a week, with minimal space and light requirements (the seeds sprout the first 4 days in the dark, then need only minimal light on a windowsill or under a florescent bulb to green up).
Microgreen seeds are available from most large seed suppliers, or in kits complete with planting materials from vendors such as The Daily Gardener.