I would speculate whereby any transaction, operation is entirely intrastate would not be reachable by the commerce clause. Landscaping could be an example of such thing, especially since its almost entirely a service. IF the supplies/materials used in such activity were entirely of local origin, that'd be entirely intrastate commerce (subject only to local regulation and ordinance). The only wrinkle there would be if one used a phone where the phone line looped outside state lines.
However, things get pretty weird now a days (considering the global economy we're in. And Congress clearly has the power to regulate trade with foreign nations. So who knows what could be interpreted concerning anything anymore.
The biggest problem I see is that things used to be clear cut and dried, i.e., either "direct" or "indirect". What it seems like they started doing is regulating in the abstract. When one engages in abstract reasoning and philosophy all bets are off and the sky's the limit.
I've heard that in higher level mathematics courses that philosophies of mathematical truths are debated. 2+2 might not necessarily be 4 as a truth. Some of the modern physics work with charmed particles and the like start getting into Eastern religous metaphysical concepts.
Clearly in Wickard, we're no longer dealing with tangible fungible markets, but abstract concepts of national markets created by regulation of commerce. Its enough to make anybodys head spin.
Under current doctrine, it can't be purely intrastate. If the material and labor weren't available locally, you might have to seek them in interstate commerce, and they have declared that to be sufficient.
And how does that square with stare decisis?