“Like squeezing blood from a turnip.”
“The juice isn’t worth the squeeze.”
And, for something that doesn’t involve a squeeze…
“The last mile.” (though that’s most appropriate for those familiar with shipping problems or supply chain management)
Speaking of squeezing, how about “Squeezing the last bit of toothpaste out of the tube”?
I feel that low hanging fruit are goals that are very easy to achieve. So I feel the opposite would be goals which are very hard to achieve, which is why I suggested reaching for the stars.
But all fruit is equal. Low-hanging fruit yields as much reward as fruit high up on the tree (theoretically, I’m sure someone who picks a lot of fruit will beg to differ) but the effort required to achieve that reward is least for the low-hanging fruit.
It’s not just that some goals are easier than others, but that the ratio of return to risk/effort/time/what-have-you is greater for some simply by virtue of their being easier to accomplish. Low-hanging fruit.
So the opposite of that, in my opinion, would be something that yields the same sort of return as an alternative source of reward, but requires considerably more effort.
The problem with expressions like “blood from a turnip” and the “last toothpaste in the tube” is that they describe trying to achieve something that’s almost certainly impossible and/or not all that desirable in the first place.
Low-hanging fruit are certainly desirable—they’re just easy to acquire. If you’re scraping the bottom of the barrel, you’re getting dregs, which are no one’s first choice.
As others have pointed out, a lot of this hinges on how we define “opposite.” Is the opposite of “desirable and easily achieved,” “undesirable and hard to achieve” or “desirable and hard to achieve?”
The OP mentioned that the phrase “high-hanging fruit,” while awkward, captures the desired sentiment. So it seems (to me, at least) that the OP is going for a phrase describing something desirable but not easily won.
Holy Grail.
Scaling Everest?
Best antonym pairing so far: low-hanging fruit [easy pickings for high yield] <–> the last toothpaste in the tube [lots of effort for little worth].
The smallest return-to-effort ratio is going for what you can’t have, but while that’s an idiom it’s a literal one. A related one is the forbidden fruit: going for what you can have but it’s going to be complicated and the cost will be much higher than you first thought (not that Adam and Eve had it very difficult to actually reach the fruit, but they did pay a high price for it).
Hard nut to crack.
I’ve got it!
“High-falling rock-poison.”
In Spanish I’ve heard a tí sólo te gusta Doña Inés, “you only like Doña Inés”: the novice Doña Inés is the single one of the many women wooed by Don Juan Tenorio with whom he actually falls in love, but he is unable to truly do the right thing (being too used to finish any relationship once he’s gotten his prey) and destroys both their lives. Note that there are an absurd amount of versions of Don Juan, he’s probably the Spanish equivalent of Romeo and Juliet in terms of international appeal; people know Don Quijote but he gets mentioned, not reused.
“Reach for the Moon”, or, my favorite mixed metaphor, “Rocket Surgery”.
Let’s go for the low hanging fruit and put the rest on the back burner.
“Stretch goal” may be another relevant phrase.
Low hanging fruit as a metaphor means you walk through the orchard and can simply pick it hanging in your face - you don’t have to stretch, climb trees, etc. Maximum reward for minimum effort.
I’ve seen this mentioned in task analysis as similar to the Pareto Principle’s biggest item - if you can fix 80% of your problems with one effort, then you can quickly improve your statistics. But then, the fixes for the next 20% of problems will not yield as big an improvement as easily.
These are the hard bits. the ones you really have to work for. You have to get the step ladder, keep moving it, and only get a few fruit with each trip up the ladder.
This would be tough slogging, the last mile, buried treasure (depending on the payoff). I’ll agree “scraping the bottom of the barrel” is a good idiom.
These two can be combined into one saying:
“Shoot for the moon. Even if you miss, you’ll land among the stars.” - Norman Vincent Peale
However, if one is landing among stars, that would suggest that one has landed nowhere near one’s target, the Moon.
I think the Dutch expression “laatste loodjes” nicely expresses the opposite of low hanging fruit.
Translated here as the “home stretch”
“Low hanging fruit” is a noun. The opposite must be a noun too. It refers to the easiest part of a project, usually done first. The opposite would be the parts that are the most out of reach and difficult, but that must be accomplished for the project. So it’s more specific than being difficult.
If I was speaking I might use the term " the beast" for it. “I’m going for the low hanging fruit this week, leaving the beast for later.” Also people used to say “the bitch” to refer to it.
“Sour Grapes”