Lemon tree disappears

What would cause my prim potted lemon tree to disappear when viewed at certain angles against my windows, and what can I do to fix it? The windows are very heavily decorated, with lots of fine architectural detail, if that matters.

I've noticed the edge of my prim hair does it too, when I stand in the window...

Alpha textures will cause that at times, one reason I got rid of some of my rugs. Made certain items transparent beyond what they should be.

The alpha glitch.
Fundamentally, two semi-transparent surfaces near each other do not sort correctly, and it's fairly random, depending on viewing angle which will be rendered on top.
It's a known problem, and you can't really prevent it, except for being careful where you place things with transparency.

It is a well-known problem in 3D rendering, and despite looking like a totally stupid bug since it's obvious to humans what should be on top, it's actually not a trivial thing to calculate for a computer, in particular when two semi-transparent surfaces intersect. The twitchy behavior you see is a tradeoff between the quality and some immensely demanding calculations, opting for speed since it must be calculated realtime for any possible surface somebody may create in SL.

if you must have items in front of the window, try keeping them as far a way as possible, there is a semi work around too, which uses a script to paste the texture to the prim, it's available for free on the scripting forums, it works well for me, but its not guaranteed.

Dekka can you give a better idea of this scripts name so I can search it up. I suck at searching and am not finding it.

Me too please,just been rooting around but can't find it.I hate alpha and try to avoid it whenever possible.But sometimes it's a must.

I'll also draw the attention to this Jira entry: https://jira.secondlife.com/browse/VWR-6713 , which is a request for an "on/off" transparency in addition to the graded semitransparency we have now, which would render correctly and work well for things like windows.

Someone from Shelbyville took it?

Joking aside, it does sound like the notorious alpha-sorting issue. It's even worse when it causes banlines to appear inside your house, or parts of your hair and clothes vanish. Other than trying the solutions given, changing the layout of alpha'd items in relation to windows seems to be the best bet.