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Every Single Thing You Need to Know About an Indoor Greenhouse

Legend has it that a physician told Emperor Tiberius that he should eat one cucumber a day to stay healthy. The ancient Roman engineers and scholars then had to solve a problem: how do you manage to grow plants all year round?

And that’s when the first known greenhouse was made.

Greenhouses have been popular ever since, especially now when people are more than ever eager to do some gardening and grow sustainable food in their own homes.

Here’s everything you wanted to know about indoor greenhouses.

Why Get An Indoor Greenhouse?

Having an indoor greenhouse gives you a ton of benefits, whether you just want to pluck an occasional basil leaf for your manicotti and a bunch of arugula for your salad, or want a splendid indoor garden for you to grow vegetables and flowers all year long.

Not everyone is blessed with a backyard though, and for people in apartments, an indoor greenhouse offers all the benefits of true gardening.

An indoor greenhouse is great because:

It’s Easy To Move

If you need to move house, you can easily take your indoor greenhouse apart and relocate together with the plants.

It Can Be Built Anywhere

Maybe the climate where you live isn’t ideal for vegetables, or your growing season is too short, or your backyard sees too little sunshine. Maybe the soil is not suitable for greens. Having the greenhouse inside solves all these problems.

Protects Your Plants

Not even heavy rain, wind, or snow can harm your herbs and greens in an indoor greenhouse.

It’s Easier To Monitor

You can regulate the temperature, humidity, as well as easily check your plants for diseases and pests when the greenhouse is close at hand.

Starting a garden is a good bonding time. The things that you can learn from it by just slowing down, watching how nature grows and works and learning the responsibilities of being out there to tend to the garden.


Jessica Jasnoch, Retail Manager at Earl May Garden Center

Where To Place Your Indoor Greenhouse

You should place your greenhouse where your plants could get plenty of sunlight, like next to a south-facing window or a patio door. [1]

You can also add lighting from a grow light to your greenhouse instead, but keep in mind that sunlight is always best for plants. If you can, at least make a combination of the two, so your plants don't grow on artificial lighting alone.

The ideal spot also needs to be humid and warm.

You also have to consider the size. Once you know what plants you want to grow, you’ll know the size you need, and eventually where to put your greenhouse. 

Best Plants For An Indoor Greenhouse

Indoor greenhouses really let you broaden the variety of plants you can grow inside. If you plan ahead and prepare the right conditions, only the ceiling’s the limit. [2]

Herbs

Herbs are definitely the most popular variety for growing inside. They don't need much care and don’t take long to grow. If you’re just starting to grow indoors consider getting a few shots of:

  • Basil
  • Chives
  • Mint
  • Oregano
  • Parsley
  • Rosemary
  • Thyme

This is a great time to start a herb garden on a sunny windowsill. Hardier herbs like thyme, rosemary, and sage can do well outside this time of year but will work equally well indoors. I'd also recommend basil, parsley, or cilantro for indoors. Herbs are basically a triple threat: You get a nice-looking plant that grows quickly, they smell terrific, especially when you blend multiple types of herb plants, and you can use them.


Joe Ferrari, Founder of Tend Greenpoint

Vegetables

Your indoor garden can also save you money at the grocery store. A minute ago they were in the garden, and now they’re on your chopping board. Vegetables to consider include:

  • Avocado
  • Carrots
  • Cucumbers
  • Hot peppers
  • Lettuce
  • Radishes
  • Spinach
  • Tomatoes

Fruits

You’ll have the best chances with fruit plants that don’t take up much space such as strawberries, and other shrubs from the berry family. These can easily give you a healthy snack all year long:

  • Gooseberries
  • Grapes
  • Figs
  • Lemons & limes
  • Mulberries
  • Oranges

Flowers

With indoor greenhouses, even growing orchids may become an easy thing. Just keep enough space for each plant, and you can also grow beautiful ones like:

  • Chrysanthemums
  • Fuchsias
  • Hostas
  • Marigolds
  • Peace lilies
  • Roses

Determining The Size Of Your Greenhouse

The size of your indoor greenhouse depends on several factors, like the available space, location, and the kind of plants you want to grow.

If it’s just a few herbs and a couple of cherry tomato stalks, a mini-greenhouse made with 5” x 5” grow trays would be enough.

On the other hand, if you want leafy greens, large flowering plants, or even small trees like avocados, you’ll need to take their size into account and do more planning.

If you’re short on space, you can even go vertical, with a five-foot-tall, tiered greenhouse.

How To Build Your Own DIY Indoor Greenhouse

Materials

Frame

For the frame, you need something sturdy to support the weight of the whole structure. [3]

Wood — A great option for indoor greenhouses because it can look great in your home. You can cut it and shape it relatively easily and make the frame you want. This “warm” material is also a great insulator. However, keep in mind to use treated wood, as too much humidity can make it rot.

PVC Pipes — Another material that make building a DIY greenhouse indoors a breeze. With plastic, you don’t have to worry about humidity and warping. Still, PVC pipes aren’t as sturdy as steel, so if you plan for a tiered house, you may want to use something stronger.

Galvanized Steel — Strong and won’t break the bank. Galvanized means coated with zinc, so you don’t need to paint or treat it against rust. Steel, however, isn’t as easy to cut as wood or PVC pipes. Also, keep in mind that it’s much heavier than the other two options. 

Glazing/Covering

When you’ve chosen the frame, you need to find the covering which will allow for plenty of sunlight to get through.

Glass — A go-to material for indoor greenhouses covers. It definitely has a lot of perks — it’s easy to maintain, doesn’t wear out easily, gives a nice appearance, and lets plenty of light to pass through.

On the other hand, glass can be expensive, and hard to install if you do it yourself. Finally, if you have playful kids or “hyperactive” pets, you’re probably reading the other options now.

Fiberglass — Has all the benefits of glass plus it’s durable. It’s lightweight so you can install it much easier and allows a lot of light inside. However, after about ten years, it can turn yellow unless you give it with a new coat of UV protection resin.

You should place your greenhouse where your plants could get plenty of sunlight, like next to a south-facing window or a patio door.

Film Plastic — Often used to make indoor greenhouses. There are many types of plastics, and the amount of light they let through depends on the type you choose. This is by far the cheapest option but needs much more maintenance and replacement, as it damages more easily.

Environmental Factors

Sunlight or Grow Light — Sunlight is essential for growing plants, so you should place the greenhouse somewhere it gets the most sunlight throughout the day. Grow lights can help, but can’t replace natural light.

Grow lights are great for winter but keep in mind that they can add up a lot of heat. Make sure you use them with a timer so you don’t pop the corn while still on the stalk.

Temperature — Growing plants generally need a temperature range between 65-75°F (18-23°C). [4] Your home probably falls into this scope, but it’s good to have an easy option to control the cooling or heating in indoor greenhouses.

To make it warmer indoors, you can use tea lights or a small electrical heater. Most plants grow best when nighttime temperatures are 10 to 15 degrees lower than daytime temperatures, so make sure to lower the temperature at night with a small fan, which can also make for air circulation.

Humidity — It’s hard to escape the change of seasons, and even inside your home, plants “feel” that something’s happening outside. To prevent them from losing leaves or turning brown due to low humidity, you should get a humidifier. If not, just make sure to mist the plants at least once a day.

Water and Nutrients — For your plants to flourish, the soil should best be moist but not soggy. As your indoor greenhouse will probably be within your reach, it’ll be easier for you to check the moisture. Unlike outdoors, the amount of nutrients your plants can draw is limited indoor, so you’ll need to make a bit of compost or add organic fertilizer all year round.

Supplies

The frame and covering apart, you’ll need a few supplies to get your indoor greenhouse up and running. Once you’ve chosen pots or trays, decided on the type of soil and fertilizer, you need to get:

1. Grow Lights — These can be of great help in winter months when there’s little sun, especially inside. They also help if you plant flowers that like high-intensity light.

For me, I use these 70W LED Grow Lights from SANSI.


2. Fans — Use them to lower the greenhouse temperature and improve air circulation.

The one that I use in my own indoor greenhouse is this Schaefer Versa-Kool 12" Deep Guard Greenhouse Circulation Fan.


3. Heater — If the temperature, on the other hand, drops too low, a small electric heater like the Bio Green Greenhouse Heater is more than welcome.


4. Hygrometer — If you can see that the humidity level is low, then it’s probably too late for your plants. You should avoid this by adding a small stick-on hygrometer like this Govee Hygrometer + Thermometer.


5. Thermometer — Without a reliable thermometer you’ll be pressed hard to guess the exact temperature inside your greenhouse.

You can use the Govee Hygrometer as well because, fortunately, it's also a thermometer. This means that you can save more since you don't have to buy a separate thermometer anymore.


6. Watering System — Can make your daily maintenance really easy. An automated watering and misting system like the MIXC Mist Irrigation Kit and Plant Watering System is really useful when you go away for a week or two.

Cost

So, are all the homegrown vegetables and herbs worth the cost of the entire home gardening thing?

Yes, without question.

Keep in mind that a lot of these supplies are optional, and it’s you who decides how much your greenhouse is going to cost. A mini-greenhouse for annuals and herbs can be made for less than $10, and there are 4-tiered indoor greenhouses that are sold for as little as $30.

How To Get Started

  1. 1
    Decide what and how many plants you want to grow, as this will help you determine the size of your indoor greenhouse.
  2. 2
    Next, find a sunny spot in your home where the greenhouse won’t stan in people’s way. Then, find the supplies for the frame and covering and start building it. 
  3. 3
    Lastly, add the pots or trays, and fill them with growing medium, and you’re ready for planting.

Most plants grow best when nighttime temperatures are 10 to 15 degrees lower than daytime temperatures, so make sure to lower the temperature at night with a small fan.

PRO TIP: It’s always better to plant seeds than cuttings as this way you won’t bring any insects into your home.

Use the first few weeks to install optional supplies and adjust the conditions inside the greenhouse.

Best Indoor Greenhouses

If you don’t have the time or materials to build your own indoors greenhouse, you can easily pick one up from the store. I trust Outsunny for this since they’ve been a reliable manufacturer of greenhouses for a long time.

Outsunny 39" Aluminum Vented Cold Frame Mini Greenhouse Kit

Just about one meter long and wide, this indoor greenhouse is ideal for those with no garden and little available space.

Aluminum is one of the best materials for frames, so you don’t have to worry about rust with this one.

The features I like the most are the winged roof openings that allow me to easily reach every plant. Most of the time I just prop them a few inches open for better ventilation. 

A single Outsunny 51 Inch Aluminum Vented Cold Frame Mini Greenhouse Kit

PROS

  • Lightweight
  • Perfect for indoor gardening
  • Fits almost anywhere
  • Excellent heat retention

CONS

  • Somewhat tricky to put together

Outsunny 6' x 3.5' x 5' Outdoor Portable Walk-In Greenhouse

Although listed for outdoors, you can still use it as an indoor greenhouse. This greenhouse is a good one if you want to bring your outdoor flowers inside or extend the growing season when the temperature plummets.

Also, the sturdy transparent plastic cover has a zippered front door which you can roll all the way back for maximum ventilation.

A single Outsunny 6' x 3.5' x 5' Outdoor Portable Walk-In Greenhouse with Clear PVC Cover

PROS

  • Powder-coated steel frame
  • Rust-resistant
  • Great for vertical trays
  • Durable PVC cover

CONS

  • Only 4’9 tall
  • Tricky to anchor indoors

Outsunny 51" Aluminum Vented Cold Frame Mini Greenhouse Kit

This versatile indoor greenhouse allows you to plant and use vegetables, flowers, and herbs all year round. Transparent polycarbonate panels have UV 30 protection, so you don’t have to worry about your plants getting sunburnt.

On sunny days, you can easily move this greenhouse out on the deck or your garden — but best keep the lid closed to keep the pets and other furries out.

For me, the best selling point is the compact size — you can fit this greenhouse into every room. 

A single Outsunny 51 Inch Aluminum Vented Cold Frame Mini Greenhouse Kit

PROS

  • Portable
  • UV 30 protection

CONS

  • Limited instructions
  • Not much width with 27”
  • Not suitable for heavy plants

Outsunny 71" Aluminum Vented Cold Frame Mini Greenhouse Kit

Even in winter, you can keep going green with this lean-to-shaped indoor greenhouse.

The roof swings open all the way, so you can easily check what’s going on inside or ventilate if it becomes too hot for your plants.

Speaking of hot, this indoor greenhouse has great heat retention so you’ll rarely need to turn up the heater. Drop the roof down and you can even leave the greenhouse outside for a whole day, and no squirrel or bird will get any smarter. 

A single Outsunny 71 Inch Aluminum Vented Cold Frame Mini Greenhouse Kit

PROS

  • Plants are easy to access
  • Rust-resistant

CONS

  • Takes more time to put together
  • Requires a flat surface
  • Zip ties are recommended for security

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Outsunny 5.9’ L x 3.0’ W x 3.0’ H Portable Mini Greenhouse

With this spacious house-shaped indoor greenhouse, you’ll forget the last time you went to the grocery market.

It’s PE mesh grid cover is UV resistant, and has two large door flaps that roll up with ropes. This way, you have plenty of room to check on your indoor garden and give each plant the care it needs. 

A single Outsunny 5.9’ L x 3.0’ W x 3.0’ H Portable Mini Greenhouse - 2 Large Zipper Doors Garden Planter

PROS

  • Great ventilation

CONS

  • Not fully sealed
  • Requires a flat surface
  • Zip ties are also recommended for security
  • Could be too large for smaller apartments

Conclusion

An indoor greenhouse is a sustainable and inexpensive way of growing plants at your home all year round.

Whether you want to make the growing season last longer, keep fresh herbs close to your chopping board, or have beautiful flowers ready at all times, having your greenhouse indoor makes it all easier.

Indoor greenhouse kits come in all sizes and shapes, but you can DIY one that perfectly fits your apartment and your indoor gardening skills.

Or if you don’t have the time to make your own, you can always get yourself a ready-made one. I recommend the Outsunny 39" Aluminum Vented Cold Frame Mini Greenhouse Kit for this.


References

  1. https://extension.unh.edu/resource/how-site-greenhouse-receive-most-sun
  2. https://www.gardeningknowhow.com/special/greenhouses/unheated-greenhouse-growing.htm
  3. https://homeguides.sfgate.com/framing-material-greenhouse-53157.html
  4. https://extension.umaine.edu/gardening/manual/propagation/plant-propagation/

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