Garden structure software?

I’ve probably got the wrong title for this thread, but I couldn’t think of anything better. I’ve been restructuring my garden and want to make notes about what is planted where. The garden area is about 50 m x 35 m, but the lawn is not much more than 7m x 2m. There is a shed and a greenhouse, but as you can tell, the majority is borders and trees. I want to be able to catalogue what I have planted and where. Thus far I’ve only been able to use the back of rolls of wallpaper, but that’s no good when you go to a garden centre. Equally, I prefer to spend my money on plants not software so would really appreciate frugal but tried&tested suggestions.
Thanks