What's the best way to water a garden automatically?

The simplest and cheapest option is to use drip hoses. You get those perforated hoses (or irrigation tapes) that stretch between your plants and leave a faucet running at low flow. Works well for vegetables and it's easy to adjust depending on what you need. The problem is you have to be there to turn it on and off, unless you put a timer on the faucet.

If you want something actually more automatic, then you're getting into electronic timers. They attach to the faucet and let water run for however long you program it, once or multiple times a day. It's not very expensive and saves a lot of work. There are battery-powered models (cheaper) and wired models (more reliable). You just need to calibrate the minutes and the time of day right based on the heat and what plants you have.

For people who want the real deal, there are smart irrigation systems with soil moisture sensors. The system detects when the soil is dry and waters automatically. Takes more effort to set up initially but then it's all automatic and you save water. Yeah, it's more of an investment, but if you've got a big garden it's worth it.

If you want something more practical, honestly, an automatic timer hooked up to your faucet is a game changer! Stick it on there and set it to water at whatever times you want, without having to worry about whether the water's actually on or off. People sometimes overlook this detail, but watch out: if you live somewhere with irregular water supply or low pressure, the system might not work right - in those cases it's worth investing in a battery-powered or solar-powered system that works independently of the faucet!

Do you want something that actually works or are you willing to tinker with it every day? If it's the former, it's really worth investing in a drip irrigation system with an automatic timer - those controllers you attach to the faucet and program to turn on at specific times. It costs more than a simple soaker hose, but the difference is you can actually go on vacation without worrying, whereas with the faucet left open you risk overwatering on cloudy days or letting things dry out when it gets hot. A lot of people start with the manual method and end up switching to a timer after a few frustrating growing seasons.

Combining drip irrigation with a timer is really the way to go, but there's one detail that makes a difference: using a controller that lets you set multiple watering times per day. At home I have a small garden bed and I programmed it to water early in the morning (when plants use it better) and in the late afternoon, instead of one long watering that ends up waterlogging everything. It costs more than just using a hose, but the water savings and how much better the plants do make up for it.

There's one thing that usually goes unmentioned: before you invest in automation, test your garden soil to find out how long it takes to dry out between waterings, because different soil types absorb water differently and that changes everything when you're programming the timer. That way you can set it up without wasting water and without letting your plants suffer.