Is this a Cowplant that you grew from a seed that you obtained in the game via game play or one you got from debug? Items gotten from debug (like fruit trees, if I remember correctly) can have behavior limits that they would not normally.
I don't think your Cowplant, or any other plant for that matter, will advance at all in quality, condition, or growth while in inventory. Plants have also got a certain time of day that any advances kick in, and your Sim/you need to be on the lot live playing for this to happen.
You could try to debug/reset the Cowplant and see what happens?
When you try to add the Cowplant to the household inventory do you drag it there? Another method is to grab it with the hand/selector tool then hit delete to get it into the household inventory. If you haven't tried both of those methods you may want to try the method you haven't tried yet.
I'm not a huge fan of Cowplants (long, slightly funny story), but I did save mine in the gallery (under the username SheriGR, I think the room is called something like 'Unwanted Cowplant'), so if you want to try experimenting with it you are welcome to download it from the gallery. I have done some amount of adding and removing my Cowplants from inventory in the past, but it almost sounds like your Cowplant has become bugged or something. I also believe I have a Cowplant seed in a room in the gallery that I obtained in gameplay, so if this happens to be the issue either of those items may work better for you?
@myrdsiexy @Angelyne22 Interesting. I just tested from a different room I had that also had a Cowplant seed, and I tried over a two Sim-day period to reproduce the issue and couldn't. I was able to move both the full-grown Cowplant and the young Cowplant that sprouted from the seed into my Household Inventory by dragging or by the select-and-delete method both on the 1st and 2nd day after I planted them. I was then able to drag them each back into the lot. I will ask a few friends if they have seen the issue in their game also.
Do you, by any chance, have as much space around the Cowplant (with no items on the ground, walls, etc) as it's green footprint requires? And do you have it in a large planter or directly in the ground? I only ask this as I have had Cowplants &/or their seeds disappear before if their didn't have the required space.
I only had the two cowberries, so I couldn't try it again
