Hi Mathew. I had a large Coffee plant once a few years ago and the way your describe the sticky leaves sounds like scale? Just a guess? Check out the link below and see if that might be the issue? Good luck!

Here is a link that might be useful: Sticky leaves...

Are you sure it wasn't guttation? That's when some of the fluids inside the plant seep out. Sometimes plants will do that when they've been watered heavily.
It's harmless.

Here is a link that might be useful: Wiki article on Guttation

Matthew..inspect ALL parts of your Coffee tree. I don't think Coffee Arabica is toxic. the worse that can happen is a skin rash, which is rare. Rash might be myth.

Look for brown spots that can be scraped off, white, cottony sacs, and fine webbing.

Depending on size, take your Coffee plant to the sink/shower and hose foliage w/o wetting soil.

Determine whether the sap is from an insect or guttation. If it is an insect, the sooner it's treated, the better.

I too dislike water-retentive soils..especially for house plants. Seems more and more of this 'crap' is being sold. I don't like that they add fertiilzer either..what can we do about it? Write to soil company's, complain. It's a start. Toni

Thanks for your answers. I THINK it is guttation. I have had scales before - on my weeping fig - and what a nightmare that was, so I've seen scales, and I checked my coffee plant and it is scale-free, as are the rest of my plants in that room.

I'm keeping my eyes open but it appears it was my over-watering that did it, with that moisture control stuff (which is now augmenting my garden soil)!

Thanks again!

Matthew. Guttation won't cause problems, Scale will.

Anytime you suspect or want to prevent Scale, add one cap of Fish Emulsion to a 16oz or so spray bottle. Spray all parts of the plant.

FE is basically an organic fertilizer, but prevents and kills Scale.
Don't know if you fertilizer in winter, but by spraying w/FE, your plant/s will get a foliar feeding, too.
Since FE is organic, it won't burn roots or leaves.

Take my word, it works.

One word of caution. FE has a fishy odor that will last 2-3 days, indoors.
There's an unscented FE, but I've never tried it, so don't know if the smell is truly covered. Still, it's worth a few days of odor opposed to finding a zillion Scale Bugs.
Since it's organic, the odor will not harm you or pets, unlike chemicals types. Toni