Carefully placing an artfully-shaped bonsai on your desk might make you the envy of your coworkers who see it on your video calls, but to keep it there long term you’ll need to choose the species carefully.
It’s unlikely you have perfect plant conditions in your office or home workspace, most indoor environments stay at low-humidity to avoid that sticky-sweaty feeling and about 68-75 degrees F (20-22 C.) Unless you were lucky enough to have a lot of natural light in your office, you probably are under artificial lights - fluorescent, LED or incandescent. While these temperatures and lighting conditions work just fine for human comfort, they are not the ideal environment for plant growth.
Staying home or returning to work, either is a good reason to get a bonsai. Think about the species that you are going to grow first, plants that thrive indoors are adapted to constant-moderate-temperature, low-humidity and low-light conditions, which means that they are likely native to mid-elevation dry tropical forests, and live in the undergrowth. But, rather than trekking all over the Amazon mountains, let’s just go with these species:
Portulacaria Afra - (aka Dwarf Jade) Since this plant is more like a succulent than a maple of pine tree, it is a lot tougher and adaptable to a variety of conditions. You can water it only once per week or even less, it will tolerate low light and it will have no problem with the constant temperature.
Native to South Africa, where it is locally called Spekboom, the leaves are small, and shaped like a jade plant, which is why it’s sometimes called dwarf jade even though it’s not closely related.
P. afra will handle low-light conditions for a long time, but if you see it starting to slow down or branches look unhealthy, take it home for a month or two and put it outside to get more sun. (during spring, summer, not winter) The leaves will shrivel and start to look wrinkled when the plant has been short on water.
Ficus Benjimina - This particular ficus species is sold as a standard houseplant shape, but can also be shaped into bonsai. 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 - a small-leaf or “willow-leaf” ficus that is a bit more finicky about conditions. It will happily live inside for 6 months at a time, but if you want to get some fast growth take it outside during hot and humid weather for a while like the P. afra plant noted above. Leaf drop in ficus is common when conditions change, so don’t be alarmed that a few turn color and drop off when it’s relocated. Look for new reddish buds emerging from between leaves or on the branches or trunk.
Grewia Occidentalis - Jasmine Star Flower - another South Africa native, the lovely flowers last only a day or two but the plant makes them profusely under the right conditions. If you can give it a sunny spot like near a window you’ll get more flowers and growth.
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. Many people struggle to grow Juniperus procumbens ‘nana’ bonsai plants indoors because they missed the memo that this tree needs to be outside! It’s a temperate-climate plant, and grows best in full sun with lots of air movement. If you’re growing ficus indoors and having problems, try placing the plant in a warmer location. If you’re growing Grewia and not getting flowers, try getting it more sun. And if you're growing junipers, either put them outside for a while (like the entire summer) or get creative and see what conditions you can create to make them grow and thrive!
Use best cultural Practices
Watering - watch the soil and only water when it starts to dry out. 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.
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.
Light - Optimize the light. Depending on your location the angle of the sun may change significantly through the year (and each day obviously.) 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.
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 (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 F. Or you can keep them in your unheated garage or another space where it is cold (30-45F) 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.