How to Grow A Tomato Plant Indoors with LED Bulbs
We set out on an experiment with the objective: grow tomatoes indoors as simply as possible.
Without investing in massive lights, equipment, and countless tools, we decided to stick to the basics to see if we could bring a dwarf variety tomato plant seed (Vilma) to a mature plant with ripe fruits. And we did just that. In 88 days. While constantly documenting and putting together the photos into a three and a half minute time-lapse.
Background & Equipment
We know that tomato plants are classified as “high-light” plants and that they thrive with high PPFD (light intensity). We see these plants do very well when they receive PPFD levels up to around 600 µmol/m2/s. We also know that the bigger pot size a plant gets, the more space it has to grow massive root systems.
But what happens if we only have a basic setup with a small light source and a tiny (4 dl/13 oz) pot? Can we still bring the plant to maturity, and will it carry fruits? This was our challenge.
Here’s the equipment that we used and links, if you want to try on your own:
We bought ours from a Swedish shop but similar seems can be found here:
1x Container, eg food or fruit (4 dl/13 Oz)
Lamp: 5.7W 2700k 345lm LED E27 Bulb with 36 degree focusing lenses
We used this lamp: https://www.amazon.co.uk/dp/B00MB5Y12U
But for America based growers, the following lamp seems on paper to be a fair alternative, although we haven’t used it ourselves:
Lamp holder: IKEA Tertial lamp
But any lamp holder that matches the bulb’s E27/E26 base would work.
Hydroponic or general nutrients
Easy to use pre-mixed for beginners: https://www.amazon.com/dp/B000RNCKQ2
Mix & match yourself for experienced growers: https://www.amazon.com/dp/B017H73708
Yara nutrient mix for advanced and large scale growers.
From our previous PPFD tests with household bulbs, we knew that this 5.7W LED bulb performs well and can produce a high PPFD at a distance of between 10-14”/25-35cm.
However, these bulbs have a rather small light footprint, which means they don’t cover a large area. Would it still be enough?
A 2700K spectrum is rarely used for a full grow cycle, if at all. There’s an old misconception that plants want 6500K as they have developed in sunlight. Plants will grow in almost any light, just with different shapes and results.
Even with 2700K. We chose this Kelvin for simplicity, as the majority of all off-the-shelves household bulbs are produced with this color spectrum. It is also a nice hue to have lit in the open space for 24 hours each day.
As we wanted to record the entire grow, we realized a few days in that we’ll need to give the plant light 24 hours of the day, every day, to get decent photos. The plant would likely have preferred at least a couple of hours of darkness where it could rest and muster strength, but for our convenience, we pushed it 24/7 with light.
So, with seemingly poor starting conditions, can we still make it work? Is the tomato plant strong enough to thrive even when it’s given far from ideal circumstances to grow?
The tomato seed was germinated on top of wet paper towels enclosed in a box for two days then transplanted 5mm deep into a dampened coco medium inside a 4 dl/13 Oz container. The plant grew healthy and really started to look like a plant after four weeks.
The plant was watered with the same mix of nutrients and concentration throughout the whole grow.
The NPK was 2-1-3, the EC was 1.3 mS/cm, and the PH was 6.0.
Measuring the nutrient solution this carefully is not necessary to succeed and especially not if growing in soil. We share these numbers to be precise but plants will grow fine with less strict nutrient planning.
The tomato plant was watered every time the medium started to look dry on the top or when the plant started drooping from dehydration. The pot had drilled holes in the bottom and was watered heavily every other watering to prevent salt build-ups and to wet the medium thoroughly. Another 10mm of nutrient solution was also added to the outer container as a small reservoir, to be able to water less frequently.
It was initially given a PPFD intensity of 150 µmol/m2/s (around 45 cm/18" between lamp and plant) for the first three weeks.
Intensity was increased to 225 in its fourth and fifth weeks.
Intensity was increased to 250 in its sixth week.
At week seven, PPFD was set at 300 µmol/m2/s (around 30 cm/12" between lamp and plant) and the lamp fixture was also raised to its top position. After this, the plant gradually grew closer to the lamp, and grew too close at day 60.
An attempt was made to get the affected branch out of the hotspot with a bamboo skewer and a zip tie, but to no avail. The only solution from this point was to start rotating the light source around the plant to not completely burn the top foliage.
Our tomato plant started producing its first flowers around day 38. The flowers matured for 10 days before they opened, on day 48. They were hand-pollinated at day 50, and they dropped at day 53 when fruits also started to form. A leaf covered this process, unfortunately, but the fruits became visible at day 56.
The first fruit was harvested day 88.
The plant had grown so large that it fell over when left unattended day 77.
Half the plant was trimmed after this to combat the imbalance.
Again, here's the video with the full time-lapse:
The experiment was a success. We were able to grow our own tomatoes from seeds. The entire process took 88 days and although the yield was limited, we got nice, red, and tasty fruits.
With more light or a better lamp, larger pot, more consistent, and strict watering schedule I’m sure we would have significantly improved our yield. More light almost always equals a greater yield. Same thing goes for pot size. Letting the plant rest, have a couple of dark hours, could also possibly have improved its health and finally the yield.
Still, tomatoes are very resilient and can endure tough conditions. They have a natural will to live and to grow, as demonstrated in our test. Even with a simple setup, it’s fully possible to grow tomatoes indoors at home.