Carefully placing an artfully-shaped bonsai tree on your desk will make you the envy of your coworkers who see it during Zoom video calls. To keep it healthy and on display long-term, you need to choose the tree species carefully. 

Here's a list of species that can thrive indoors. They're adapted to constant moderate temperature, low-humidity and low-light conditions, and often native to mid-elevation dry tropical forests.   

Portulacaria afra "Dwarf Jade"
Since this plant is more like a succulent than a maple of pine tree, it's a lot tougher and adaptable to a variety of conditions. You can water it only once per week or even less; the leaves will shrivel and start to look wrinkled when the plant has been short on water. It will tolerate low-light conditions for a long time, but if you see it starting to slow down or branches look unhealthy, put it outside for a month or two during spring or summer to get more sun.  Native to South Africa, where it's called Spekboom, the leaves are small and shaped like a jade plant. This is why it’s sometimes called dwarf jade, even though they're not closely related. See below:

Ficus benjimina "Standard Ficus"
This particular Ficus species is sold as a standard houseplant shape, but can also be shaped into a bonsai tree. The large glossy leaves give it a slightly untidy appearance as a bonsai, but allow it to grow in lower light conditions than many other species.

Ficus nerifolia "Willow Leaf Ficus"
This small-leaf Ficus is a bit more finicky about conditions. It will happily live inside for six months at a time, but if you want it to grow faster, take it outside during hot and humid weather for a while like the Dwarf Jade. Leaf drop in Ficus is common when conditions change, so don’t be alarmed that a few turn color and drop off after you move it. Look for new reddish buds emerging from between leaves or on the branches or trunk.

Grewia occidentalis "Jasmine Star Flower"
This is another South Africa native with lovely flowers that last only a day or two but the plant makes them profusely under the right conditions. You'll get more flowers and growth if you set it in a sunny spot near a window. 

Ideal Conditions and Best Practices to Maintain Indoor Bonsai Health

Anytime you’re growing a plant indoors and you start to see signs of stress, it’s a good idea to think about the growing conditions and change them up. If you’re growing Ficus indoors and having problems, try placing the plant in a warmer location. If you’re growing Jasmine Star Flower and not getting flowers, try giving it more sun.

Natural Light: Ensure your tree has access to natural sunlight. Aim for 6-8 hours per day. optimize the light. Depending on your location the angle of the sun may change significantly through the year (and through each day, too.) Move your bonsai around weekly or monthly to make sure it’s getting good light. If light is strongly from one direction, be sure to rotate the tree every couple weeks also. 

Water: Watch the soil and only water when it starts to dry out. Actually push a finger down into the soil to ensure it's not just drying on top, but below the surface as well. Watering from above flushes salts from the soil that can build up over time, and watering by soaking makes sure all the soil gets completely wet. Alternate the two methods for best results. 

Humidity: Indoor species tend to be tropical, and thus do well in humid environments. Don't keep your tree near a heating or air conditioning vent.    

Fertilizer: use nutrients like DynaGro, Miracle Grow or a time release like Osamcote. These are all salt-based fertilizer that will not cause odors, and will give your plant lots of nutrients to keep growth going. 

Pests: Keep your eye out for anything that looks like a tiny insect - black bumps, green bumps, white flies, aphids and the like. Spray them or wipe them off and use a contact-spray insecticide (there are different kinds for different species.)

Dormancy: if you choose to keep a non-tropical plant inside for a while, it’ll usually do fine. But, make sure that you give it some cold dormancy. Junipers can be placed outdoors for winter where temperatures will not drop below 28 degrees Fahrenheit. Or you can keep them in your unheated garage or another space where it is cold (30-45 degrees Fahrenheit) but not freezing for a couple months in winter. Some plants go dormant based on temperature and others go dormant based on day-length; to be safe, provide both cold temps and short days for these plants at the same time - during winter.  

Advice on Keeping Juniper Bonsai Indoors