Arduino uno with solinoid valve(Garden automation)

As a part of my Garden automation project i would like to control a solinoid(12v)valve in every morning and evening by using rtc(1307).So by googling i found two use full ways.
1)Either by using a transmitter like in this link(https://core-electronics.com.au/tutorials/solenoid-control-with-arduino.html)
2)Or using a relay(12v)
So i expect very use full suggestions regarding this along with my following faqs too
1)Currently iam using 5v adapter to power the arduino,so if i connected arduino with solinoid of 12v should i upgrade the adapter too?
2)Why everyone is suggesting 12v solinoid,while 6v solinoids are available in the market?
Expecting very usefull replay alongwith components needed and purchase link if anyone implemented before.
Thank you in advance

OK, what you need to do, is to cite (Weblink) the solenoid you have so we know how much current you need to control it.

We now use ("logic-level") FETs instead of ("bipolar") transistors - that article is not very helpful at all.

Most garden watering systems use 24 V AC, not 12 V DC so you are suggesting something non-standard and we need to know the full details before explaining how to use it.

You will always require a regulated 5 V DC to run the Arduino.

6 V solenoids would require twice the current as 12 V and correspondingly heavier wiring.

aboosidhu:
So i expect very use full suggestions regarding this along with my following faqs too
[...]
Expecting very usefull replay alongwith components needed and purchase link if anyone implemented before.

You have high expectations! Sounds actually more like a demand. Why don't you search some instructables? Many have complete lists of parts with affiliate links. Do make sure you fully understand what's going on so you can correct for the errors as you try to replicate the project.

I find it easy to find 12V power supply, rather than 6V. The lower current helps as well of course. Same for the solenoids, I've commonly seen 12V, 24V and 220V. 6V versions much less so, especially for valves that handle water pressure.