11 Must-Know Tips To Growing Tomatoes Indoors
There’s something exciting about a fresh tomato grown in a garden. When done correctly, these plants can produce plump, juicy fruits with vibrant colors. Unfortunately, when winter sets in, your sun-loving tomatoes will struggle to thrive. It’s no wonder people have been trying to grow tomatoes indoors. And with the proper care and good artificial light, it’s possible to grow tomatoes indoors. That said, going this route is not for the faint of heart. It’s not as easy as growing leafy greens or herbs indoors.
Can You Grow Tomatoes Indoors?
The short answer is, yes, you can grow tomatoes indoors. However, unlike other houseplants or vegetation, tomatoes never truly acclimate to indoor-living; they need to grow in a way that almost perfectly matches outdoor conditions. At least 8 hours of sunlight (or grow light) is necessary, and a stable, moderately warm environment is ideal. Based on USDA Plant Hardiness Zone, thriving tomatoes fruiting are best in Zone 5,6,7 and 8.
The benefit of growing this fruit (no, not a vegetable) indoors is that the plant is shielded from harsh weather conditions and hungry pests, meaning that you might be trading one challenge for another. If you give them the time and attention needed, your house tomatoes should grow big and strong. But let’s take a look at the process of growing your tomatoes indoors. If you have what it takes, you could have amazing tomatoes all year-round.
How to Grow Tomatoes Indoors
We should start by saying that this isn’t going to be an easy process. Growing tomatoes indoors requires the correct plant variety, proper tending throughout the winter months, grow lights to achieve sufficient growth and development, pruning, and the appropriate airflow. You’ll even need to hand-pollinate your plants. In other words, to do this the right way, it will be a time-consuming project.
If you’re looking for a way to grow tomatoes inside with less of a headache, consider starting with a hydroponic unit. Some, such as the AeroGarden Bounty or Rise Garden, give you a seed starter kit, proper plant food, and even an LED that meets your tomato plant’s sun needs. AeroGarden also comes with a lattice, which works well and, in my opinion, looks nicer than a traditional tomato cage.
Steps for Growing Tomatoes Indoors
Whether you decide to grow in a planter or with a hydroponic system, think of the rewards of tomato growing indoors! A homegrown tomato is typically tastier than anything that ends up in the store, especially during the winter. So if you’re up for a challenge, follow these steps to growing your tomatoes indoors.
Step 1: Pick the Ideal Tomato Varieties for Your Space
When picking which tomato variety, there are a few variables to consider. More than anything else, you want to make sure you choose a variety that has a natural resistance to pathogens. But you also need to decide if you’re going to go with a determinate (bush) or indeterminate tomato plant (vining), which will affect the size of the tomato plant, the amount of time you’ll need to spend on care and maintenance, as well as the preferred harvest season.
How Many Tomatoes Will One Plant Produce?
The amount of tomatoes produced from one plant is dependent on several factors. Light and heat are essential, but the yield will also vary depending on the tomato plant type.
Generally speaking, there are two varieties of tomato plants: determinate and indeterminate. Determinate plants are more bush-like and tend to yield all of their tomatoes at once–– their yield is more-or-less predetermined. By contrast, indeterminate varieties sprout along an ever-growing vine, producing tomatoes all season long as the plant keeps growing larger. That said, a regular average has indoor tomato plants in ideal conditions yielding about 200 tomatoes, or 10 pounds, per season! For such a haul, I think the attention to detail is well worth it. But that’s the catch; a lot is riding on the perfect conditions you provide for your indoor fruits.
Determinate Tomato Plants
Determinate tomato plants will only grow to a specific size before stopping. This makes them a good option for container plants or anywhere with just a limited amount of space (like your living room!). With determinate varieties, you have a smaller plant that may not require stakes or a tomato cage. And while its fruits will ripen early, they will often produce all at once, meaning you have a short season.
Some indoor tomato varieties that are determinate (both hybrids and heirlooms) include the following:
- Celebrity – a hybrid variety that produces long stems/vines that can hold at least 20 fat and full tomatoes
- Silvery Fir Tree – Russian heirloom with a slight citrus flavor, growing up to 2 inches around, great for canning and juicing, and eating raw
- Tiny Tim – a type of cherry tomato that is relatively easy to grow, producing a uniquely small plant, great for window boxes or hanging baskets and small garden spaces
- Small Fry – another dwarf variety, ideal for small containers
- Totem – bred for front porches and window boxes, named for stacking up more fruit than leaves, growing just 12 to 18 inches tall
- Patio – bushy, dwarf variety growing about 2 feet tall, generally sturdy enough to not need extra support.
— Ken Goering (@KenGoering) March 16, 2021
Indeterminate Tomato Plants
Indeterminate varieties continue to produce fruit and grow throughout their season. In some cases, they can become substantial and end up looking more like bushes than tomato plants. This means you’ll need to spend more time staking and caging – often with metal rebar stakes to keep them supported. The benefit of indeterminate varieties is that you can enjoy their fruit for a longer stint of time than you would with determinate varieties. That said, if you’re planting indoors, it may make the most sense to go with a determinate variety, which can help you save on space. If you use an indeterminate tomato, consider a smaller variety, such as cherry tomatoes.
Here are some popular indeterminate tomato varieties.
- Better Boy – Guinness record holder for the amount of fruit produced from a single plant, known for superior flavor, typically ripen in 72 days
- Yellow Pear – named (quite obviously) for its yellow color and pear-like shape, bite-sized and tangy flavor
- Tommy Toe – can produce hundreds of perfectly round tomatoes, stands up well to high heat, pops when bitten
- Big Boy – large and bright red, good for slicing onto sandwiches, harvest midseason
- Early Girl – medium-sized, popular with indoor gardeners because it ripens quickly
- Pink Ping Pong – about the size and shape of a ping pong ball, slightly pink color, will need a support system
Step 2: Choosing The Right Potting Mix
You can use a standard starting mix, potting mix, or soil mix for your growing medium. The key is that your growing medium has good drainage. When choosing a potting mix, check the ingredients: an excellent blend has sand, vermiculite, peat moss, and compost. And most importantly, it drains well.
Here are some recommended commercial options for potting mixes:
- Organic Potting Mix by Perfect Plants
- Miracle-Grow Expand ‘n Gro Concentrated Planting Mix
- FoxFarm Happy Frog Nutrient Rich Potting Soil Mix
Step 3: Potting Your Tomato Seeds
When growing tomatoes indoors, you’ll likely need to grow from seed. According to the University of Missouri Extension, begin with a sterile growing medium – like a soilless potting mix or a pre-moistened seed germination medium. Take your growing medium and place it into a cell tray or a grow disk. Then place one to two seeds in each cell. Bury them each about 1/4 inch deep.
From there, mist your seeds with water and then put a plastic humidity cover over the tray to keep the moisture inside with the seeds as they start to germinate. Germination will take up to two weeks after planting. Temperature is vital during this step, with your seed tray needing to be 62-65 degrees Fahrenheit. Once again, consider using a heat mat if you’re growing them in a colder indoor space.
Once your seedling is about two inches tall, transplanting the tomato seedlings into a container is the next step. A small biodegradable 2″ pot works fine.
When the seedling is five to six inches tall, transplant it again. One common mistake urban gardeners make is putting a mature tomato plant in a pot that’s too small. It’s okay to start with a smaller pot, but once the plant is about a foot or more, make sure your container is at least 12 inches deep. This allows room for its growing root system.
Step 4: Placement: Sunny Window or Grow Lights
Tomato plants love to be in the sun. You’ll want to place them in whatever part of your home is the brightest, such as a south-facing window, a windowsill, a sunroom, or any sunny window. Our condo is more like a cave with a single-window that receives direct light a few hours a day. For us and most people indoor gardening, you’ll need to invest in fluorescent lights or grow lights to supplement the light.
The type of light your plants receive is important as well. For a tomato plant, it’s best to use a light that has bulbs that are both cool-colored and warm-colored. The warm-colored lights will encourage your plants to produce healthy flowers and begin to fruit.
Along with light, heat is an integral part of tomato development. Temperatures below 50 degrees Fahrenheit can hurt the tomatoes, while temperatures above 90 degrees Fahrenheit can harm the fruit. If you’re growing in a place that’s chilly, such as a basement, you may consider using a heat mat beneath the plants.
— Chris Holmes (@HolmesAllotment) March 17, 2021
What Is The Best Lighting For Growing Tomatoes Indoors?
The type of light your plants receive is important, and assuming you don’t have access to 8 hours of direct sunlight indoors each day, a grow light is your next best bet. However, artificial light doesn’t quite count the same as the natural stuff, so plan on giving your tomatoes 16 total hours of light every day.
Cool-colored lights (about 6500K) are best for stimulating leaves and vines but not great for flowering or fruit yield.
However, warm-colored lights (about 2700K) will encourage plants to flower and bear fruit but won’t show much leafy growth. For a tomato plant, it’s best to use a light with bulbs that are both cool-colored and warm-colored. The warm-colored lights will encourage your plants to produce healthy flowers and begin to fruit, while the cool colors will keep your vines and leaves growing healthy.
Here are a few options, depending on your setup:
Can You Grow Tomatoes Indoors With LED Lights?
LED lights are the standard for indoor grow lights, and they make it possible to grow food indoors all year round since you can fully customize your lighting needs while shielding your plants from the harsh cold of winter and the extreme heat of summer.
They increase the tomato fruit yield and quality, consuming less energy than the alternative High-Pressure Sodium light. LEDs even increase the tomato fruit yield and quality because of their generally vast range of customization. This combination of UV, white, blue, and red light simulates the sunlight a tomato plant needs. Although LED lights are safer than the sun in terms of heat damage, they will affect your crop’s temperature, which will need close monitoring–– the right temperature is just as important as the proper lighting.
What Color Grow Light Should I Use For Tomatoes?
Tomatoes need a wide range of lighting colors to grow correctly. Both red and blue, warm and cool lights are necessary for development. The cooler light is most helpful in the early germination stages, while the red aids in fruit development.
Many grow lights (utilizing what is known as a full-spectrum bulb) allow for both warm and cool lights, so don’t worry about needing many different devices. In terms of brightness, around 7000 lumens is ideal for tomatoes. Again, upwards of 9 hours of direct light is necessary for optimal tomato growth. The brightness and coloring won’t only affect what the plant is absorbing but also the temperature at which it lives and grows.
Along with light, heat is an integral part of tomato development. Temperatures below 50 degrees Fahrenheit can hurt the tomatoes, while temperatures above 90 degrees Fahrenheit can harm the fruit. A growing environment of about 70 degrees is best for long-term indoor tomato growth. If you’re growing in a place that’s chilly, such as a basement, you may consider using a heat mat beneath the plants. Here is a selection of a few good options:
Can I Leave My Grow Light On 24/7?
It might be tempting to leave a grow light on all day, every day, believing that non-stop sunlight will result in continuous growth. However, this is untrue. According to several studies, plants need both light and dark time–– it seems as though they rest in the night, similar to us!
Too much light will exhaust tomato plants and can result in irreparable damage. In other words, tomatoes need about 8 hours of darkness a day.
This may then have you wondering how long to leave a grow light on a tomato plant. Typically, it’s recommended that tomatoes receive about 8 hours of natural light daily or closer to 16 hours of artificial light. Most hydroponics system, for instance, run their lights for 16 hours a day.
If you’re using a combination of natural light and LED grow lights, you’ll need to do your own fine-tuning to find out just how much light your plant can receive.
Step 5: Water Your Tomato Plants
When growing outside, water your tomato plants at least once a day due to the heat and sunshine. With indoor tomato plants, a good trick is to stick your pointer finger in the soil. If your upper knuckle is dry, you should water your plant. Try to keep your pot consistently moist but not soaked. Too much or too little watering can cause tomato splitting or blossom end rot.
Step 6: Fertilize Your Tomato Plants
Tomatoes like to be fed frequently with small, consistent amounts of fertilizers. An excellent place to start is with a weekly feeding of Miracle-Gro Tomatoes (You can also do a diluted dose of liquid kelp or fish emulsion – but for simplicity, I like to go with Miracle-Gro). A variety of factors can cause you to need more or less fertilizer. If they’re producing more leaves and less fruit, you may have too much fertilizer – or your fertilizer is too high in nitrogen. Similarly, if the leaves start to yellow or your flowers and fruits aren’t developing, you may need more.
Step 7: Hand Pollinate Your Tomato Plants
Tomato plants have all the anatomy to pollinate themselves. So you could grow a single tomato plant in your home, rather than having a pair or more. That said, especially when growing indoors, you’ll need to help pollination to maximize your yields. There are a few ways you can do this. You can rub a small paintbrush, a cotton swab, or even a low-powered electric toothbrush around each of the flowers. Or you can simply tap or gently shake the stems each day.
An easy and more hands-off way to help with pollination is by putting an oscillating fan near your tomato plants. You shouldn’t have the air directly on the plant, but the oscillating action can help the plant move and pollinate itself in the faux breeze. It will also improve the air circulation, helping protect your tomato plant (and other houseplants) from pathogens.
Step 8: Touch Your Plants
You may have heard that you should sing to your plants, but a gentle touch could be more effective. When growing indoors, plants don’t get the same amount of stimulus they would outside. There’s no rain, wind, pesky bugs, etc. And this cushy life could give your tomato plants a weak constitution. As your plants grow, gently run your hands over the leaves and stems regularly. This can help with plant hardiness and potentially improve yields.
Step 9: Pruning & Other Tomato Maintenance
The primary reason to prune your tomato plants is to redirect energy to your leaves toward producing fruit. Tomato foliage is great, but you can’t eat it. Pruning and removing suckers (which are new shoots) will also improve the airflow. Pruning is essential when working with indeterminate varieties.
For a complete guide on pruning your tomato plants, start with these resources from the University of New Hampshire.
Step 10: How to Harvest Your Tomatoes
It’s pretty simple to judge when your tomatoes are ready for harvest. When growing indoors, it will take about 60-70 days to reach maturity. The bottom of the fruit will begin to ripen first. From there, monitor the color of the tomato and test the firmness. If this is your first time harvesting, go to the grocery store and buy some tomatoes. You can test the firmness of these and then compare them to the ones growing in your home.
To harvest the tomato fruit, grasp it in one hand while the other hand holds the stem. You can break the stalk right above the calyx, the green and pointed leaf-like structure on top of the fruit.
Step 11: General Tomato Plant Questions, Care, And Maintenance
Once you’ve taken care of the germination and the light, you’ll need to focus on regular care and maintenance. While merely keeping a tomato plant alive may not take much care, maximizing its yield potential will require consistent work and attention. Use these tips to maximize your results.
Can You Grow Tomatoes From Store Bought Tomatoes?
Many people wish they could simply take a store-bought fruit or vegetable, bury it in the ground, and have a beautiful, colorful tree filled with their favorite foods. However, fruits and veggies from your local grocery store, tomatoes included, are typically grown so that they can’t reproduce from themselves. In most cases, they don’t even grow from seeds anymore. So, unfortunately, the tomato seeds left over from your salad are mostly useless. That said, you may be able to use the seeds from heirloom tomatoes or those grown as a small, local crop. Like potatoes, cherry tomatoes can be cut in half and sprouted to yield a budding plant. Nonetheless, we recommend the tried and true method of using the humble seed!
Can Cherry Tomatoes Be Grown Indoors?
While cherry tomatoes might be easier to grow from the store-bought fruit, they are still easier to grow from seed. Similar to other tomato varieties, you can grow cherry tomatoes indoors. Cherry tomatoes work incredibly well in a hydroponic system. Here are a few of our favorites:
How Long Does A Tomato Take To Grow?
The time it takes to grow a tomato plant indoors can vary based on several factors. That variance is even more significant when growing tomatoes outdoors, so consider that a benefit of indoor gardening. When grown outdoors, the season in which you plant a crop will change the time it takes to succeed. For example, the early season takes about 70 days, the midseason about 50-60 days, and those grown late season can take more than 80 days.
However, when grown indoors, tomato plants usually follow the mild, mid-season trends, so you can expect a tomato plant to be ready for harvest anywhere from 50 to 60 days after planting.
Keep in mind, though, that this estimate does not account for how good of a gardener you are! Poor growing conditions can stunt growth, and different varieties will vary a bit. As mentioned above, determinate plants will yield one batch of fruit, whereas indeterminate tomatoes will be available for harvest over a more extended time.
Should I Cut Dead Leaves Off My Tomato Plant?
Cutting dead leaves off your tomato plant can be a helpful piece of the pruning and maintenance process. Some dead leaves may start to decay in a way that can disease the rest of the plant, so removing them when you see them is best practice. Pruning will help your tomatoes fruiting always.
Too many leaves, especially dead ones, can also block sunlight from the fruit on a bushier variety of tomato plants. And even though the leaves are no longer alive, a dead leaf takes up precious real estate on your homegrown tomato plant. If you make way for more tomatoes, chances are, more will come! Any bit of energy you can redirect toward your flourishing plant is well worth it.
The 🍅 is growing well. The instructions told me to cut off to leave only three main branches living but I didn’t want to kill perfectly happy seedlings. 🥺
— Alex Wang, MD (@drwangmd) July 23, 2020
Can You Keep A Tomato Plant Alive All Year?
At this point, you might be wondering, “How long can you keep a tomato plant alive?” Ideally, the plant would stay alive all year long, continually bearing fruit without needing to replant. Unfortunately, it’s not that simple. The bush-like plants will typically give enough fruit for one harvest and then die out but can potentially regrow in the following season.
The more vine-like tomato plants are more likely to stay alive all year, though bearing significantly less fruit in the winter. Houseplants, in general, won’t grow as much as their outdoor counterparts, but just because the yield has fallen off doesn’t mean the plant is no longer alive or can’t bear fruit in the future.
Getting Started With Indoor Tomato Plants
While certainly not as easy as growing outside, it is possible to grow your tomatoes inside. If you live in a city or location with short summers or longer winters (looking at you, Chicago!), then indoor tomatoes may be your best option. They’re a good project, and there’s nothing better than biting into a fresh tomato on a cold winter’s day.