Just like the title says.

I use both plant foods for good foliage and flowers.
All the other plants sell within 15 min, but the last plant consistantly will never sell, even when leaving the nursery up for hours.
I am just selling plants to make money for upgrades right now, and all the plants I'm selling are Daisy Ferns, so they're all the same plant.

I have the blue soil and water.
The last plant is never infested, or sick, it's perfectly healthy.
I have tried moving the plant to a different stand, and periodically lowering the price.
I have even lowered the price all the way to $1.
If I leave it up at $1, eventually it will sell, but it takes about 15 minutes.

This happens every single time I sell.
What's going on with this?

Are you being careful to prune off all dead foliage from all plants before you try to sell them? That's very often the reason that a plant fails to sell (and it's the 'last plant' left in the nursery for that reason).

If I'm sure that all plants are properly prepared for sale and reasonably priced, moving them around as they're being sold will usually result in them all of them being sold before my patience runs out.

I do remove the dead foliage, as soon as it appears.
By the time the plants bud, all the dead foliage is trimmed off.

I stop time at night, and during the day when I'm on the computer I check constantly.
I mark the times when each next event should happen, buds, maturity, seeds, and I'm careful to check on time.

I'm home on permanent disability after months of hospitalization and recovery, so I basically have little else to do right now while I'm still restricted to very limited mobility.

I played Fish Tycoon first and finished that, so now I've started Plant Tycoon.
Once Plant Tycoon is done, I was thinking of playing all the Virtual Villagers games starting with the first one.
I think it would be more fun to start at the beginning.

It seems the last plant in the nursery also takes a longer time to sell for me. Even if it is the same type of plant as all the others, treated the same way with healthy foliage and a nice show of flowers, it just seems to always take a while before it finally sells. Eventually it will sell though.

Lazuli, Have you found any of the rare plants yet? Once you find the Fabled Blue Rose you can charge the most for it. If you don't have Virtual Families I recommend it. Download the sample and see it you enjoy it.

I also have a plant that won't sell no matter what I do and wondered if anyone had found a solution recently. Unless there are "leaves" hidden on the "other side" of the plant, I don't see how that can be the problem in my case as, since it's a ball cactus, it's perfectly obvious where the leaves are. And anyway, doesn't the plant's health go down if it has dead leaves? My plant's health is always at 100%. I've also tried moving it around, lowering the price, selling it in a nursery full of other plants and so on. I've also sold several of this particular species before without problems.

Related question: do plants get too old to sell at some point, no matter their condition?

For me it's the Spotted Ball Cactus, grown in gold soil, gold water and 2 applications of fertilizer bomb. I only grow it for cross pollination and it usually ends up in the trash priced at the original $10. The nursery is fully upgraded with all six magic plants. The other plants along side it sell for $$$ like hotcakes. Go figure!