I have lived in several different places in my adult life, and at each residence, I planted a flower garden. Some of my gardens thrived all summer and some became scraggly early in the season. It was the amount of time needed to maintain the flower garden that I failed to consider. I discovered that the size of the flowerbed is only one of the factors that determine how much time it takes to maintain it. I also discovered some shortcuts to reduce time spent maintaining my flower garden.
To reduce the time spent watering the garden, use a soaker hose with a timer attached to the faucet. To cover my gardening area, I used four soaker hoses. First, I attached a splitter to the faucet. I then attached two timers to the splitter so I could set two different watering schedules. To each of the timers, I attached sets of soaker hoses (two hoses connected end-to-end). The timers I chose were inexpensive and do require manually twisting a dial to start the flow, but it then turned off the designated time. Apply 1 to 2 inches of mulch around the flowers. Mulch, like pine chips or leaf mold, helps to retain moisture and block weed growth.
I suspect some of my fellow gardeners will shake their heads at this piece of advice, but if time tending to a garden is a factor, skip using fertilizer. In the beginning, I used a liquid fertilizer dispersed with an attachment to the garden hose. After a couple of years, I skipped that step to save time and money. What I noticed is that the flowers were not significantly different from when I used fertilizer in the past, unlike the television commercials that showed tremendous changes in a fertilized plant.
Snipping off dead blooms encourages flowering plants to create more blooms. Faded blooms left on the stems convert to seed leaving a less attractive plant; but the seeds drop to create more plants the following season. For the best of both worlds, deadhead flowers until late summer and then stop to allow faded blooms to seed. Another choice is to go with flowering plants that do not require deadheading such as impatiens or Knockout roses.
Tall plants, like hollyhocks or peonies, tend to droop from the weight of the blooms. The easiest way to avoid dealing with drooping plants is to buy plants that do not require staking. My solution for dealing with drooping garden flowers was to buy decorative support, like a metal obelisk frame, that remains over the plant year-round.
Perennials benefit from being dividing about every four years. Dividing involves digging up the root ball and cutting or pulling apart the root ball into three or more sections that are then replanted. When I found that lifting a large root ball from the ground was more that I could handle, I came up with a shortcut. Instead of digging up the whole root ball, thrust a shovel into the center of the root ball to lift out half (or less) of the root ball, divide it, and replant. The next year, I go back to the same root ball and cut out another portion of it.