How To Start An Indoor Greenhouse

Learning how to start an indoor greenhouse can be a daunting task, but this article will provide a simple stepwise process to a successful indoor garden. Indoor greenhouses are great for those lacking the traditional outdoor space for a garden or for those looking for a head start on the growing season. From year-round growing to a wider variety of produce, to saving money and reducing your carbon footprint, indoor gardening has many advantages.  

Indoor greenhouse or garden systems come in large to small, tall to short allowing your garden to be as big or small as you would like. From growing seedlings to transplanting to an outdoor garden to looking for fresh homegrown produce during the winter to gardeners in apartments or in urban settings your indoor greenhouse can conform to all of these roles. Your dreams of a garden are a reality with an indoor greenhouse if you follow the tips and recommendations below.

Climate Of Your Indoor Greenhouse

When asking yourself how to start an indoor greenhouse, most of the categories below will be components of your own mini plant habitat. For this reason, picking plants with similar needs is the best idea. Lighting, temperature, humidity, and ventilation are all factors that are important to consider when starting your greenhouse. Consider investing in tools such as thermometer, humidity gauge / humidifier, fans for improved ventilation. These are not a requirement but can help regulate your plants environment and set up for success.

Location: When it comes to picking a location to start your indoor greenhouse, there are several factors to consider. Each of which need to be considered for the best success: 

Space: Select your location and this will dictate the size of your indoor greenhouse.  

Lighting: Light both natural and artificial are required for growing indoors, so placing by a window can be helpful but not required. South-facing windows are generally the best, as they receive the most sunlight throughout the day. Even if they are located by a window, if growing in the off season, you will need to supplement with grow lights as discussed below.

Temperature: Ideally temperature should be controlled, so would avoid placing it right next to a drafty window or a furnace vents. Choose a location that stays within the optimal temperature range for the plants you want to grow. Generally, most plants prefer temperatures between 60-75°F.

Humidity: Indoor greenhouses can become quite humid, so it’s important to choose a location that allows for proper ventilation to prevent mold and mildew growth. Research the plants that you are growing ideal humidity. Humidifiers can be used to increase humidity, increasing ventilation can help reduce humidity.

Accessibility: You’ll want to choose a location that is easily accessible for watering, caring, and harvesting your plants. You don’t want to have to carry pitchers of water across your entire house every time you need to water your plants, a little planning ahead will save time and energy.

Overall, the ideal location for an indoor greenhouse is a sunny, temperature-controlled room with good ventilation and ample space for your plants and equipment.

How To Water Your Indoor Greenhouse Plants

Growing plants in an indoor greenhouse has several parallels to container gardening, and when growing indoors, your plants are 100% dependent on you for watering. Correct watering plays a significant role in ensuring successful output. With limited soil volume, containers dry up faster, making it necessary to regularly check on the soil moisture levels. Most plants prefer moist soil but too much water can cause roots to rot or fungal diseases to proliferate. 

When watering, water deeply, meaning water until it begins to drip through holes at the bottom. This will ensure moisture is reaching the deepest roots.  Avoid watering until there is standing water in the pot as this will increase the risk of rot and fungal growth. 

Also avoid frequent light watering as this will encourage shallows root development that is more susceptible to drying out quickly

Water in the morning, as early as possible. This also will allow the water on the leaves to dry off during the day while the grow lights are on, as wet leaves encourage the spread of disease.

Lighting Your Indoor Greenhouse

When you are considering how to start an indoor greenhouse, correct lighting is an extremely important factor in the success of your garden. Many vegetables that can grow indoors require about 8-12 hours of “sunlight a day.” When growing indoors, it is necessary to use artificial lights to achieve the needed sunlight. Natural sunlight can augment or possibly reduce the amount of time that you need to operate the artificial lights. Trying to rely on only natural sunlight by placing on a windowsill will likely lead to “leggy seedlings” that have long stems as they try to search out more light. This can lead to stems that snap easily, reduced production or difficulty with transplanting outside as they will have more difficulty recovering from the transplanting process. 

There are several different options available for lighting. Indoor greenhouse plants will do the best under a grow light that will provide full – spectrum light, which produces both blue and red spectrum wavelengths. These lights imitate sunlight and promote the plants energy producing process of photosynthesis. There are many bulbs out there but the most popular and energy efficient would be the LED grow lights.  

LED Grow lights 

Most LED grow lights are full- spectrum, energy efficient, low head and compact making them a good choice in all indoor greenhouses. However they tend to be a bit pricer than other options, but while they may have a large upfront cost, most will be recouped by energy savings and longevity. 

Compact Fluorescent light

Another good choice for growing lights, they are compact, low heat, and inexpensive. They are not very energy efficient and tend to be a bit underpowered. They are best used when growing leafy green vegetables or starting seedlings prior to planting outdoors. 

High – Intensity discharge lights

More popular in commercial greenhouses, these lights produce impressive output, but the major drawback is the amount of heat they produce. This head production I would not recommend these bulbs for hobbyist gardening.

Soil For Your Indoor Greenhouse

When starting an indoor greenhouse, don’t overlook your choice in soil. Soil provides life to your plants as they grow. It needs to contain the proper nutrients and moisture for the plants that you want to grow. To be honest, most commercial potting soils are good choices for most plants and vegetables.

These types of soil mixes are specially formulated with a blend of organic materials, like peat moss, vermiculite, and perlite, that create the ideal balance of air and water for plant growth. They are high in nutrients which help give your plants a head start. Potting soil nutrients are limited and are used by your plant or leech from the soil with water rather quickly. Depending on how long you plan on growing indoors, you may need to consider adding nutrients or fertilizer to your soil. Do not use soil from outside and it can quickly compact, does not drain well, and can introduce pests or disease to your greenhouse.

Fertilizer For Your Indoor Greenhouse

Potting soil is preferred in containers due to its moisture retention, water drainability and being nutrient rich. Unfortunately, as excess water drains from the soil it also takes nutrients out as well. If you are just starting seedlings in your greenhouse, you likely will not have to worry about fertilizing indoors. If you plan on growing all season it is necessary to replace those nutrients. To accomplish this consider adding a slow-release fertilizer according to the directions on the packaging to the potting soil prior to planting. 

As the plants grow and through the producing phase, I would recommend intermittently adding liquid fertilizer about twice a month, again per the directions on the packaging. If you have the ability to test your soil for fertilizing or need for specific nutrients that can be done once every 1-2 months or as needed.

Balanced fertilizers are a safe bet, and have equal amounts of each macronutrient typically nitrogen, phosphorus, potassium (e.g. 10-10-10). Note that higher nitrogen content will stimulate more leaf development at the expense of fruit/vegetable production, while fertilizers with higher phosphorus will stimulate high production of roots, flowers and produce. 

When To Start Seeds Indoors

If you are planting seeds to eventually transplant to an outdoor garden, it is usually recommended to start seeds indoors 6- 8 weeks before the last frost date in your area. Based on my location, this will be around late march to early April, you can look up your last frost date on the Almanac website for timing specific to your area. If you are planning on growing the plants / vegetables indoors for their entire life span, indoor greenhouses allow you to plant year-round.

Examples Of Some Of The Best Vegetables To Start Indoors:




Brussel sprouts







Great Herbs to Consider










How to start an indoor greenhouse is just that easy! Consider these tips and you will be on your way to a successful indoor garden. Growing vegetables in an indoor greenhouse has several advantages including space saving options, allows you to grow year-round and is very convenient with lower maintenance than an outdoor garden. Indoor gardening can be a great hobby that is both rewarding and relaxing. With these advantages, why not start your own indoor greenhouse and see what you can grow in your own indoor greenhouse?

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