My point just now is that for me, the factor that eliminates something from the Next Action list doesn't need to be "can't do it until I do X" or "can't do it currently, period" but can also/instead be "not gonna do it because higher priorities will crowd it out."
If you're doing pure GTD, that should really be something that eliminates it from the project list too.
Projects are, first and foremost, outcomes you're committed to that require more than one action step.
And that's really the key - "outcomes you're committed to". If you know you won't be doing it, then it stops being something you're committed to - and it stops being a project.
In this situation, I would say that "garden" is an area of focus. Now you brainstorm projects related to that area of focus, and do the thinking about what you're going to do with your garden.
You decide that of your 15 beds, you want to plant 15 types of flowers, one per bed. So now you have a bunch of projects like:
Bed 1 - Petunias
- Buy soil (Due March 19th)
- Buy seeds (Due March 19th)
- Start seeds indoors by late March (Due March 20th)
- Prep bed
- Transplant seeds to outdoor bed
The first two are next actions, and they go on the list now - unless you know there's going to be a great sale in February, in which case you'd schedule them for later. When you're at the garden store, you can knock out dirt + seeds for your whole garden in one fell swoop.
The third is a deferred task, since you've decided to do it in late March. It might become a workable "next action" on March 13th. Throw it in the tickler file, or use your computer software to defer it. The fourth can be done whenever the weather is amenable, which you'd probably set a date for - or at least a date for making a smarter decision. You could defer that with the seed starting tasks. And the fifth is actively blocked until the seeds grow, so that's indeterminate - but based on experience, you could punt that out into the future as well. Maybe to April 30th.
If you use the list like this, you'll always have a solid "next actions" list of things that will move projects forward, your thinking will be reflected in your system (i.e. you'll get the seed planting / transplant reminders at appropriate time), and you don't have to constantly re-think things.
If you don't want to think it over until later, maybe you just kick a "plan garden" task out into late February. You can do the thinking then, and plan appropriately.
But the idea is that you *first* commit to some sort of action, *then* use the system to help you do the actions you've specifically committed to.
Have fun with your garden.