One of the questions people like to ask is if you can grow Hostas, Heucheras, and other Perennials indoors? The short answer to this question is, unfortunately, no.
The long answer is maybe, but it is very difficult. If you love a challenge, you can give it a try!
The main reason why it’s not a good idea to grow temperate perennials (perennials that need a seasonal temperature change, or a ‘winter’ period) indoors is that they absolutely require a cold, winter ‘rest’ period. This primes them for their annual cycle of new growth in spring, summer filling out, fall die-back, and winter rest.
The cells in plants secrete hormones that control their growth. Hormones also control how they grow, and when they grow. In addition, hormones are responsible for seasonal light and temperature changes that happens naturally outdoors in temperate perennials.
Basically, when you give temperate perennials a fairly unvarying temperature and light levels (like in indoors environments), their internal systems aren’t working quite right! The symptoms include a lack of vigor or being excessively stretched, pale plant stems, and a slow decline to eventual plant death.
They can also suffer from environmental stresses, due to the fact they’re in an unnatural environment. We’ve created an ideal indoor environment for human beings – we have vents that blow out heat in winter, keep it chilly in summer, made our buildings air-tight and dry (no wind or humidity!) and have developed low glare, dim lighting in the spectrums that work best for the human eye. These are, regrettably, very poor and confusing situations for temperate plants!
Now for the challenge! You can almost certainly grow just about anything indoors, but you have to modify your growing space accordingly in order to do so
Requirements to Grow Temperate Perennials Indoors
The first requirement (and frequently most important for all indoor plants) is light. Light is commonly measured in footcandles. It’s the amount of illumination the inside surface of a one foot radius sphere would be receiving if there were a uniform point source of one candela in the exact center of the sphere. It is defined as the illuminance on a one-square foot surface in which there is a uniformly distributed flux of one lumen.
The average light level outdoors on a sunny day is around 1200 footcandles.
In the shade, that drops to 350 footcandles.
Inside a room with a window, about 200-800 footcandles (depending on how close to the window you are, the orientation of the window, direct sunlight, etc).
Inside an interior office (no windows, overhead lighting) only 30 to 40 footcandles!
A desk lamp only provides 30 to 80 footcandles, directly underneath!
To acquire as much light as possible, place your plant near a sunlit window. Supplemental light is recommended as well as frequently required (especially for full-sun plants!).
If you’d like to find out exactly how much light you have in any given area, you can buy a light meter on many hobby websites and Amazon (Professional Light Meter)
Plants need special light spectrums. While humans enjoy the full spectrum or close to it, plants on the other hand can only use certain sections of the spectrum (mostly red and blue) and require more of those. Plant ‘grow lights’ are sold in many stores as well as online (here’s an example TaoTonics LED) – if you’re serious about growing plants indoors, it’s best to do your research and invest in a grow light if needed for best results!
The other most important requirement is seasonal temperature. If you want to grow temperate perennials (like Hosta, Heuchera, anything grown outdoors in USDA growing zones 1 through 12) they will absolutely need a ‘winter’ cold period. The cold period can be attained through many different ways, but it depends on the size of your plant and pot.
For the largest plants and pots, the only options tend to be either leaving them outside (covered or insulated) or in your garage over winter (if you live in the plants’ growing zone). Similarly, you can also test how cool your basement gets. By chance it does get cool enough (check the plants’ requirements, and growing zone winter temperatures), place the pots there for a cooling period.
If you live in an area where you have no winter cooling (or inadequate winter cooling for your choice of plant) I recommend sticking to smaller pots, or growing temperate plants indoors as annuals, and replacing them every spring.
For smaller plants and pots, you may be able to fit them in a fridge. To prevent drying out or excessive moisture, these plants will have to be carefully covered and checked frequently. You can always follow the same instructions for large pots, and place small pots in basements, garages, or outdoors for winter as well.
If you are prepared to cater to your temperate perennials’ needs for light and temperature, the third requirement is water and humidity.
Indoor plants require much less frequent water than plants grown outdoors. That’s because indoor plants do not transpire (water evaporation from leaves) as much as outdoor plants. That’s due to the fact they don’t have wind or breezes to ‘pull’ the moisture away. Therefore, they also tend to grow at a slower rate, so they just don’t need as much water to drive their food production system. This makes it easy to overwater indoor plants!
Make sure to always check the soil moisture levels before watering. This creates an idea of how often the plant truly needs to be watered. There are commercial ‘soil probes’ available to measure soil moisture by either electronic means or physically pulling a soil sample from lower in the pot. Here’s some examples of soil probes of the electronic variety (Dr. Meter)
and the physical variety
Symptoms of overwatering include brown leaf tips, a funky smell to the potting mix, and stem or root rot. Fungus gnats are hard to get rid of since they love overwatered plants. So if you hear small and irritating black flies buzzing around, that means no more water please!
Some plants require more moisture in the air, rather than at the roots. These would benefit from a light misting daily or frequently. You can purchase a squirter or sprayer bottles for these plants, and use as recommended for the plant family/variety. An example here (Coolrunner Vintage).
First of all, ALWAYS plant indoor plants in a soilless media mix. Your local garden store should easily carry soilless media mix. Garden or outdoor soil or dirt can frequently be problematic indoors, due to the fact it can be contaminated with insect pests and diseases. Soilless media is ph-balanced which makes the ph-balance is neutral. It has good large pores to store water or air for growth, as well as allowing easy root growth.
Garden soil (your own or purchased in bags) can tend to either be clayey (can ‘bind’ nutrients, making them difficult/impossible to access), or ‘sandy’ (refuse to ‘hold on’ to any nutrients, letting them leach out of the pot entirely). Similarly, it’s prone to compaction. Compaction makes it smaller for no pores for water or air which makes it unnecessarily difficult for roots to grow through. Make sure you’ve purchased ‘soilless potting mix’ instead of bags labeled ‘garden soil’ or ‘potting soil’! Indoors is already a hard environment, let’s make it easy on the roots!
Indoor Plant Alternatives
If temperate perennials sound like too much work indoors, there are other plants that are much more easily adaptable to indoor environments! The Tropicals! Stores often sell tropical plants as ‘indoor’ plants. That’s because their ideal habitat is quite close to our indoor environment!
Tropical plants (like Dracaena, Pothos, Ficus, and other plants native to USDA growing zone 13) require constant, fairly warm temperatures, and plenty of moisture. Many plants are able to adapt for being in the shade(understory natives)! These plants have the best chance of surviving and even thriving in an indoor environment without significant modifications. If you want to build yourself a lush, green indoor paradise, we recommend exploring these great families!
Here’s some links to articles with lists of easy-care tropical indoor plants!
(file:///C:/Users/Hostasdirect/Downloads/Lightlevels.pdf) (University of Denver, DU Portfolio – What do light levels really mean)