How to Grow Strawberries Indoors
Growing strawberries indoors can yield great results, but it has some challenges.
If you really like this aromatic and healthy fruit and have some indoor area to spare, give them a chance, they might surprise you.
Updated: March 23, 2023.
Before starting to grow strawberries indoors, there are a few things to consider:
Growing Location, Light, and Temperature
Indoor location for growing strawberries can be everywhere - an ordinary windowsill, on a flower shelf with other decorative plants (strawberries are both good tasting and very decorative plants), on the wall using some vertical growing system, small greenhouse, etc.
Strawberries grow best at room temperatures between 20 and 25°C (between 68 and 77°F), but they will tolerate both colder and warmer temperatures. After all, their vegetation period starts early in Spring and continues to the late Autumn.
This, of course, highly depends on geographical location and somewhat on the strawberry variety.
Strawberries will also tolerate some draft, but sudden drops in temperatures can harm the plant and lower the fruit yield.
Strawberries are plants that grow in direct sunlight, even during summer. The strength of direct sunlight is between 32.000 - 130.000 lux, even 180.000 during summer, depending on location and season.
Strawberries can grow in the shade but much better in direct sunlight. So, if you are not growing strawberries on a windowsill on the southern window, consider having some artificial lighting that can provide enough light for growing plants.
Growing strawberries indoors under lights is relatively very easy - get a strong and robust metal shelf with 4 or 5 tiers and place containers with strawberries on both sides of the shelf.
Place grow lights of suitable strength under each shelf to increase the light for the lower shelves and to simplify watering, position drip tubing along the shelves.
Note: electricity and water don't go well together, so be sure to either use high-quality components, or water manually.
When berries are outside, there are no problems with pollination. However, indoor strawberries must be hand pollinated. This is not complicated, and it doesn't require much time.
Strawberry flowers are ready for pollination when petals are fully opened, the pistil (female part) is yellow-greenish, and the stamen (male parts) is brownish. We say '-ish' since this varies a little bit from variety to variety, especially from berry to berry - various berries can be grown indoors, not only strawberries.
For hand pollination small, relatively soft makeup brush is recommended - gently brush the pollen from the stamen to the pistil and do this from flower to flower. Be sure to cover the entire pistil, or you can end up with partially pollinated strawberries.
Also, after finishing with the last strawberry flower, feel free to start all over once more - this way, one is certain that there are no missed flowers and that whole pistils are pollinated.
Note: there are hand pollinators on the market that operate using small batteries. Personally, I have never used one, and therefore, I can't recommend any of them.
Pollination can be done on a daily basis - when the strawberry flower is pollinated, white petals will soon start to die, leaving green sepals (green leaves surrounding the flower, below petals) around the soon-to-be strawberry.
If You have a small greenhouse, feel free to open the window or two and let bees and other pollinating insects do their job.
Strawberry Types and Varieties
Day neutral strawberries are recommended type for growing indoors, especially Alpine strawberries.
Ever-bearing varieties can be used, too, but they don't bear fruits all year long.
Day-neutral strawberries can bear fruit all year long, just keep temperatures during summer below 40°C (104°F) and during winter above 15°C (59°F), especially if you grow strawberries on the windowsill.
Note on Alpine strawberries: there are several names for this type of strawberries, but these strawberries look like wild strawberries, taste like wild ones, generally grow no runners, and if conditions are met, they bear small and very aromatic fruits all year long.
Having 20-25 small Alpine strawberries doesn't require much space, provides enough flowers for almost daily pollination, and bears fruits on a daily basis - their fruits are very small, but single Alpine strawberry fruit leaves enough flavor and fragrance in the mouth that it is simply a shame to compare them with commercially grown strawberries.
Growing System and Watering
Depending on the strawberry size, a strawberry plant requires 0.5 to 2l (dm3) of soil. Alpine strawberries can be grown rather densely, but they also need some space.
On average, if you provide 1-1.5l of growing soil per plant, strawberries are going to be happy.
Strawberries can be grown hydroponically, and such systems don't require much maintenance after they are set up.
Also, such systems are often vertical growing systems, and they provide the best yields per used area.
But, setting them up can be time-consuming and costly, and hand pollination is a must. Such systems also include artificial lighting for plants in the form of LED lights or small fluorescent tubes, and as such, they often don't require to be positioned near the window or glass doors.
Turning lights on and off and water circulation is controlled using electronics. High-tech systems obviously cost some decent money :)
If you are interested in growing strawberries at home, start with vertical container having 4-6 positions per row, with a height of up to a meter (3-3.5 feet).
Position such container near the glass door and use 2 (two) fluorescent tubes, or equivalent LED grow lights for artificial lighting of the vertical strawberry planter.
Tubes/LEDs should be positioned vertically, some 40cm (16 inches) away from the vertical container, some 60-90° away from each other. If possible, use a light meter to check light strength in various positions and turn lights on and off automatically or manually. Automatic timers are rather cheap these days, so consider automatic turning on and off.
If you plan on growing strawberries on a windowsill, you can use rectangular containers or round pots. Rectangular containers provide more growing area per length of a windowsill, but round pots are easier to manipulate and rotate on a regular basis.
Personally, I prefer growing more plants in the area that I have, but round pots are much better in this case - all of this is IMHO, of course.
Growing Soil and Fertilizers for Strawberries
Strawberries prefer slightly acidic soil with a pH level between 6.0 to 6.5. Also, a pH level between 5.5 to 7.0 is acceptable, but slightly acidic soil is preferred.
The pH level of the soil can be tested using small test kits - take a small amount of your soil, mix it with the chemicals provided, and compare the color with the chart provided with a kit.
Strawberries require balanced nutrient levels - nitrogen for leaves, potassium, and phosphorous for flowering and bearing fruits. Not to mention many other required microelements ...
Growing soil should be enriched using compost, humus, aged (or dried - in the form of pellets) cow or horse manure, and NPK fertilizers optimized for strawberries.
This is an oversimplification, of course, but if you add, for example, too much nitrogen, you will get plants with plenty of large leaves but only a few flowers and fruits that are prone to diseases.
Many home and even commercial growers grow strawberries directly in the potting soil bags, periodically adding required fertilizers - this is a very simple setup; just be sure to make enough drainage holes and try not to overwater the plants.
NPK fertilizers with a gradual release of nutrients (up to 4-6 months) are highly recommended in combination with organic fertilizers - they are added 2-3 times per year, saving time and effort.
When growing strawberries in a small area, it is perhaps best to buy sterile soil optimized for strawberries and NPK fertilizers with a gradual release of nutrients.
Harvest - finally :) When growing strawberries at home, indoors, ripe strawberries can be picked up on a daily basis and consumed right away.
Strawberries taste the best when they get their characteristic red color - take your time and pick the fruit a day later, especially if you are testing a new variety.
Strawberry Pests and Diseases
Strawberries grown indoors are protected from mice and birds, but sometimes pets can be rather damaging - parrots and similar birds are often let outside of birdcages, and if left unattended, they can make a mess not only by eating ripe fruits, but they can damage the plants and dig the soil out.
Insects and diseases can and should be treated with (preferably) organic agents.
However, in some cases, the usage of fungicides and similar chemicals is required. In that case, carefully read the instructions, and whatever you do, do according to the instructions.
After plants are treated, be sure to wait the required period of time, before picking the strawberries for consumption.
Strawberries are easy to grow - they require some care and some time, but very soon, they will pay you back with a rich and tasty harvest.
Don't hesitate to test various types and varieties because you never know what is the perfect strawberry for you until you find one ...
Even then, some surprises are maybe just around the corner :)