The one that most frequently gets recommended in Australia is "Gardenate" by Yates Gardening. It's not terrible, but it relies on one being willing to do the data entry - and I find that it's tricky to do data entry on a piece of tech with dirty hands from burrowing around in the soil.

I tried a few 'free try-before-you-buy period' programs, but again, it requires data entry and I don't have the time or mental space for working out how to put the data in and then generate what I need to know. I find I'm personally better off with old fashioned paper and pencil, even if it's not as pretty.