Do I need grow lights? Update – Week 2

Read about the first week of growth in the post Do I Need Grow Lights? Update – Week 1.

It’s been two weeks since I transplanted my Deer Tongue Lettuce seedlings from the Aerogarden Bounty to my makeshift Kratky containers. The seeds were started in the Aerogarden on 17th July, so they are now only 18 days old. I started this experiment to test how the lettuce would grow under the light conditions of different rooms; my laundry, my pantry and my kitchen.

In the post Do I Need Grow Lights?, started just after transplanting my lettuce, I actually measured my light more scientifically. Spoiler alert, it was then that I discovered that my rooms were below the ideal levels for plant growth and that I would in fact need to purchase some grow lights.

Since my grow lights haven’t yet arrived, I decided to just let the lettuce sit in those rooms. Sometimes the amount of light to maintain is much less than the amount of light needed to create fresh growth. Even if the plants don’t get enough light in those rooms to actively grow, they may be acceptable places to store plants (if necessary) for a few days before I can completely harvest them.

Week 2 Kratky Lettuce Compared
From left to right: pantry, laundry, kitchen.

The lettuce didn’t really grow during this last week; the lettuce in the pantry being the exception. Compare this to last week:

Week 1 Kratky Lettuce Compared
Week 1 Kratky Lettuce Compared. Left to right: pantry, laundry and kitchen.

The pantry lettuce definitely grew a bit between week 1 and 2, although not as apparent in the photos. The leaves became wider and greener.

The laundry lettuce stayed mostly the same size. Its leaves did start to droop and curl slightly. This area is now being converted into a more permanent grow area including a couple nice grow lights!

The kitchen lettuce had started to die due to the lack of light. It struggled the most, which reflects our light readings that we got in the post Do I Need A Grow Light? The light was just so minimal in this area that the plant couldn’t even maintain it’s size, let alone grow! This area may be okay to store a plant in for a couple days, especially if the plant is destined to be eaten (why harvest all at once if I can pick the leaves off fresh over a couple days), but I won’t be trying to grow anymore in this area.

Despite hearing success stories online, I was a little skeptical if this method would actually work. But…

Photo of Lettuce Roots Growing
Photo of Lettuce Roots Growing

Seeing is believing! Roots emerged from the bottom of the DIY net cup, and quite proficiently. I was honestly quite surprised by the amount of root growth – only two weeks ago there were no roots at all touching the inside of the DIY net cup!

The End Of An Era

This experiment, the total of two grueling weeks, is now over. I’m moving what’s left of the lettuce to live under my new grow light; it’s now an experiment to see if I can get it to survive and recover.

How Long Should My Grow Lights Be On For Hydroponics?

I need sunlight daily to get Vitamin D, but if I get too much at once I will get sunburnt and potentially cancer! It’s better to get an optimal amount of light (such as when wearing sunscreen) over a couple hours.

Daily Light Integral

Just like us plants have optimal light brightness levels, as we calculated in the post How Bright Should My Hydroponics Light Be? Different stages of plant growth will require more or less light strength and lighting time. A seedling might need very low light strength over a short time (its a baby so it needs to sleep a lot), whereas a fruiting plant will need all the extra energy it can get through higher light strength and longer lighting times.

The best way to tell if your plants are receiving enough light to grow is by measuring the Daily Light Integral, or DLI. The DLI is a measure to of how many moles/m2/day our plants get. Notice how we will be converting from umols, or micromoles, to their higher unit. This is a bit like grams to kilograms, or ounces to pounds.

If you already have the PPFD or umols/s/m2, such as whats advertised when buying lights online, then you can use a simple online calculator to calculate your required number of hours to the DLI. If you don’t know how many umols/s/m2 your room or light is, check out the post How Bright Should My Lights Be?

According to Wikipedia having the correct DLI can help your plant leaves to grow thicker, increase flower and fruit yields, have more and stronger roots, as well as have more leaves and heavier biomass (they produce more leaves and less stems and stalks).

According to Specmeters:

DLI
Lettuce (butterhead)14-16
Tomatoes (seedlings) 6-8
Tomatoes22-30

Examples

I found a really great article from the Department of Horticulture and Crop Science: this PDF covers a huge variety of plants, and the recommended lighting and hours lit for each of the growth stages, and what level nutrient solution is ideal.

Lettuce

# Light HoursLight Intensity
(umols)
Propagation12-20150-250
Vegative12-20250-450
Flowering12-20250-450

Strawberries

# Light HoursLight Intensity
(umols)
Propagation12-20250-450
Vegative12-20 250-450
Flowering<12 250-450
Fruiting12-20 250-450

Tomatoes

# Light HoursLight Intensity
(umols)
Propagation12-20250-450
Vegative12-20450-700
Flowering12-20 450-700
Fruiting12-20 450-700

My kitchen had on average 250 LUX from the window – it’s a dark room considering direct sunlight has 900-2000umols. Using the Environmental Growth Chambers calculator, 250 LUX converts to 4.75 umols/s/m2.

If I was growing tomato seedlings, I would need to divide my result (4.75) by the number of hours to reach the ideal DLI of 8. In this case I would need my plants to receive approximately 1.5 hours of sunlight per day. An adult tomato needs 22-30DLI, so as it grows I would slowly increase the number of hours its exposed to sunlight to 6 hours a day.

But I will be using my grow light on my tomatoes. This light produces 565umol/s/m2. Using the same calculator I can tell that for seedlings I only need to expose them to 4 hours a day of light, whilst adult plants would need ideally 14 hours a day.

Quick Reference Chart

This PDF has a wonderful table of many, many, plants that compares different life stages, the strength of light recommended, and how many hours those plants require at such a stage.

Where To From Here?

Beginners Guide To Hydroponic Lighting has a list of all our posts on lighting, written to help a beginner learn the basics and get started right through to more advanced topics.

How Bright Should My Hydroponics Light Be? is the previous post in this series. It explores how much light certain plants needs to grow. I also show you how to convert to the more common used light measurement value umols or PPF, which many grow lights use. Understanding these values, and how they get them, will help you make an informed purchase.

Beginners Guide To Hydroponic Lighting

Wow! Learning about lights for hydroponics, or just plant growing, gets overwhelming fast. So many terms and numbers to keep track of. Here’s a roundup of posts that help explain lighting, all written for an absolute beginner in mind!

Do I Need Grow Lights?

Not everyone has a PAR meter or Quantum meter; they can be expensive. So how else can you measure the light your room gets? Whilst not very accurate, this can give you an idea of how bright your rooms are; helpful in finding out if you need to invest in a grow lamp!

How Bright Should My Hydroponic Lights Be?

This post explores how much light certain plants needs to grow. I also show you how to convert to the more common used light measurement value umols/m2/s or PPF, which many grow lights use. Understanding these values, and how they get them, will help you make an informed purchase.

How Long Should My Grow Lights Be On For Hydroponics?

So you know how bright your light should be, but how long should it shine? Plants need time to sleep and rest too, just like you. This post explores how to determine how many hours of light your plant needs (it can vary a little depending upon how bright your light is).

Grow light heights? Is it too close or too far away? – coming soon

Lights have different intensities, depending upon how far away you are to them. That little candle might not put off much light or heat from across the room, but up close you can still get burnt! This post will be exploring PAR, PPF and PPFD.

Waveforms and Colors – coming soon

Humans can see white light, and our eyes prefer it. But plants actually prefer different colors, most often reds and blues. This post explores the colors that lamps output – usually referred to in waveforms.

If you want a more advanced list of lighting resources, check out the post SAG’s plant lighting guide linked together.

Where to buy organic seeds in Kuwait

Don’t want to read? Here’s a quick list of links:

After researching a bit, and probably jumping into the water too fast when it comes to buying products like grow lights, I have purchased some seeds to grow in my Krakty hydroponic room setup.

Buying seeds was a specific hassle in Kuwait; the very few and limited stores that sold seeds only sold the very common varieties. Think Beefsteak tomatoes; the probably most common tomato you can find at any supermarket. Since such tomatoes are so easy to buy, I want to grow something more unique.

In fact, we even found a nursery selling seeds with the giant warning label on the back: “Warning. Treated with poison. Do not consume or grow food products from these.” What?!

In the end we found a company called Sustainable Organic Q8 that seems to import from reliable producers.

They delivered within 48 hours. We have been very happy with the brand of seeds that Sustainable Organic Q8 sells; which is Botanical Interest. They contain a lot of seeds in the pack, and they so far have a really high germination rate (for me its 100%).

Update – 24th August 2019: We found another Kuwait website selling seeds called My Organic World, though the website is all in Arabic (use Chrome web browser for auto-translate to browse in English). We bought from them, and they delivered within 24 hours! Unfortunately they sold brands Sperli and Kiepenkerl which consensus online says they can be quite expensive compared to competitors. One of the packs we bought only had 5 seeds in it! Not a reflection of My Organic World, but the seed producers themselves.

Update – 31st August 2019: Another Kuwaiti website selling seeds called PlantNMore. though the website is all in Arabic (use Chrome web browser for auto-translate to browse in English). I haven’t bought from this company yet.

Do you know anywhere else in Kuwait to buy seeds? Please let us know in the comments.

How Bright Should My Hydroponic Lights Be?

In the post Do I Need Grow Lights I measured the amount of light in each of my grow rooms, hoping to figure out which room would produce the best plant growth. At the time I was hoping to not have to invest in a grow light; man was I wrong!

A Short Warning

LUX, or lumens, to determine plant growth is widely inaccurate due to the different types of lights and the wavelengths light types each produce. Plants need certain wavelengths, or colors, to grow. No matter how bright your lights are if they are missing those wavelengths then then the plants will just not grow.

This post will not consider the wavelength or colors of lights. I’m trying to keep it as simple as possible so that anyone can follow along, even without fancy gadgets like quantum meters which can easily cost US$500. Future posts will explain wavelengths in detail. Beginners Guide To Hydroponic Lighting has a list of all the posts on how to measure and set up your lights.

You need the umol’s value or the umol/s/m2: in essence umols are how bright your light is. This value is also known as “photosynthetic photon flux” or PPF. Note that PPFD is a different value, taking into account the distance from the light.

Too low of a light strength on your plants may lead them to not growing, and too high may burn or kill them.

How To Calculate Bright Your Light Is

Most people don’t have fancy tools to measure the amount of light in their homes, such as a PAR meter or a quantum meter. Thankfully, you can get free apps on your phone that measure lumens easily.

You can use the Plantekno website to convert LUX to umol/s/m2. Note: many grow lights will tell you the PPF or umol/s/m2.

Natural sunlight has a PAR value of 900-2000μMol/m2/s when directly overhead, varying with location and season. For a grow light to be effective, it will have PAR values of 500-1500 μMol/m2/s.

In comparison, I measured my kitchen window light at 250LUX or 4.6umol/s/m2. No wonder my plants kept dying! As you’ll see below, its way below the minimum light requirements for lettuce to grow.

But how bright should my light be?

Be aware that not all aspects of how much light plants need are fully researched yet : Lefsrud at McGill University has extended upon NASA research and one thing he noted was common incorrect assumptions. For example, many people consider lettuce to a shade loving plant and tomatoes to enjoy full sun. However when shone with 5000 umol’s, the tomatoes suffered whilst the lettuce showed no signs at all! The exact opposite of what was expected.

Research Gate website had several listed studies that mentioned the number of umol’s used for ideal plant growth:

Minimum umol’s Required
Lettuce100-200
Watermelon250
Tomatoes400-500

According to the company Valoya the amount of umol’s a plant needs will vary depending upon its growth stage: seedling, vegetative, flowering/fruiting. They claim that lettuce needs approximately 80 umols during seedling, 150 for vegetative stage and 200 when it begins to flower.

Valoya’s Comparison of umol’s for Lettuce Growth

I found a really great article from the Department of Horticulture and Crop Science: this PDF covers a huge variety of plants, and the recommended lighting and hours lit for each of the growth stages, and what level nutrient solution is ideal.

Here is a small sampling of some common plants and their needed light intensity (taken from above PDF link):

Lettuce

# Light HoursLight Intensity
(umols)
Propagation12-20150-250
Vegative12-20250-450
Flowering12-20250-450

Strawberries

# Light HoursLight Intensity
(umols)
Propagation12-20250-450
Vegative12-20 250-450
Flowering<12 250-450
Fruiting12-20 250-450

Tomatoes

# Light HoursLight Intensity
(umols)
Propagation12-20250-450
Vegative12-20450-700
Flowering12-20 450-700
Fruiting12-20 450-700

Where To From Here?

Notice how I mentioned the number of light hours needed for plants in the tables above? Different plants need different lengths of light exposure. You can’t just leave your grow light on 24/7! The next post in this series is How Long Should My Hydroponic Lights Be On? It explores Daily Light Integral or DLI, the measurement that takes into account growth light strength x time its on for optimal growth.

Beginners Guide To Hydroponic Lighting has a list of all our posts on lighting, written to help a beginner learn the basics and get started right through to more advanced topics.

Do I Need Grow Lights? is the previous step in this series. Not everyone has a PAR meter or Quantum meter; they can be expensive. So how else can you measure the light your room gets? Whilst not very accurate, this can give you an idea of how bright your rooms are; helpful in finding out if you need to invest in a grow lamp!

How Long Should My Grow Lights Be On For Hydroponics? is the next step in this series. You know how bright your light should be, but how long should it shine? Plants need time to sleep and rest too, just like you. This post explores how to determine how many hours of light your plant needs (it can vary a little depending upon how bright your light is).

Do I Need Grow Lights?

Plants need light to grow, obviously. But what is the ideal amount of light? Honestly this question is quite debatable as growth is effected by the strength of light and how long the plants receive light.

I decided to test how much light each of my primary grow rooms are receiving; these are the rooms that I would like to ideally be growing herbs and vegetables indoors. I wanted to know if I could grow plants from the sunlight coming in, rather than buy a grow light. I measured the light amounts throughout the day, as the sun will shift and rooms that might get more light in the morning might receive very little in the afternoon and vice versa.

Lumens and Foot Candles

Warning in using this method

Measuring by lumens and foot candles are both considered widely inaccurate due to the different types of lights and the wavelengths light types each produce. Whilst we can see the light, plants need specific wavelengths to grow. Unfortunately most people don’t have fancy tools to measure the amount of light in their homes, such as a PAR meter or a quantum meter.

Even a rough idea of how much light your plants is getting is better than having no idea, so don’t get discouraged.

How To Measure

Thankfully, you can get a bunch of free apps on your phone that measure lumens easily and then with a bit of maths we can then convert the lumens value to the correct value, umol. I used an app on iOS called “Light Meter”. I did not buy the full version.

I like working in metric units – I just visualise meters easier than feet. Lumens are a metric unit, whereas foot candles are imperial. If you want to convert between the two:

1 foot-candle is equal to 10.76 lux, and this is derived from 1 lumen/square meter = 1 lumen/10.76 square feet. (One square meter = 10.76 square feet).

Minimum Lumens Needed

It was really hard to find this information, since everyone agrees that lumens are not an ideal way to measure light for plants. Furthermore, when most people talk about lights and plants, they will use the measrument unit umols/m2/s or PPF. The post How Bright Should My Hydroponics Light Be? goes much more into depth about what plants need what level of light.

None-the-less, this post is to help you know if you potentially need a grow light. So at a very quick glance at the tables below you should be able to tell if your plants may survive in their current lighting setup.

According to PlantMaid website,

LUX
Low Light Plants500-2500
Medium Light Plants2500-10,000
Bright Light Plants10,000-20,000
Very Bright Light Plants20,000-50,00

Even LumiGrowth website says that plants ideally need 3230-8610lumens/m2 in order to grow.

Obviously these values will all vary depending upon the size of the plant, its life stage (vegative vs fruiting) and the type of plant. Again, check out How Bright Should My Hydroponics Light Be? as this post has much more detail.

My Own Measurements

Kitchen

The following light measurements were taken in my kitchen. I have two locations where I tend to want to keep plants; in the back corner on counters that are rarely used, and underneath the window.

9am12pm3pm6pmAverage LUX
Near Window75232292258214
In CornerLess than 10Less than 101002033

I was honestly surprised that the back corner of the kitchen got so little light. I knew that the kitchen could get quite dark, but the ambient light didn’t seem that dark during the day. This could explain why many of the plants I put in the back corner would keep dying as they were receiving so little light. I thought I just had the opposite of a green thumb…

I was surprised to see that the Kitchen Window (214) received more light than the Laundry (167) overall, as I thought that this area was darker since there is a building overhang. Given this information I may buy a shelf that I can install near the window.

Pantry

The pantry receives the most natural light out of all my “grow rooms”. The room just seems to be ideally faced (at least in summer) to receive bright light throughout the entire day.

Official Photo of Aerogarden Bounty
Official Photo of Aerogarden Bounty

Its also in this room that we have our Aerogarden Bount models currently set up. I took light measurements with the Aerogarden lights both on and off, as the machines will regulate for their specific plants, but light will overflow to the rest of the room when running. The pantry has multiple shelves where plants can be placed, so I measured whilst standing in the centre of the room at equal distance between all shelves. This room does have a window, so one wall will certainly have much more light than others.

9am12pm3pm6pmAverage Lux
Aerogarden On294315243148250
Aerogarden Off27531517273209

Laundry

Unlike most people, we have an indoor laundry. We get too much dust in Kuwait to realistically hang our clothes outside; so we have a washing machine and fold out line installed in a “small” room. It’s a bit like a mud-room. The laundry will be our primary grow room, at least for larger plants such as tomatoes. Its not as highly accessed as other rooms, so the plants will go undisturbed. And the room tends to be slightly more humid than other rooms.

We already know that this is one of our darkest rooms. The window is very small and doesn’t seem to receive much natural light. We are planning to put a grow light in this room in a few days, but we are testing to see how it performs without.

9am12pm3pm6pmAverage LUX
Laundry150235173109167

What Did We Learn

After measuring the light intensity in all my ideal rooms, I have learnt that none of the rooms have enough light to grow any plants. The brightest area was 250 lux, and unfortunately low light plants will need at least 500 lux. So it seems that for me to grow any plants indoors I will need to invest in a couple of grow lights.

Where To From Here?

Beginners Guide To Hydroponic Lighting has a list of all our posts on lighting, written to help a beginner learn the basics and get started right through to more advanced topics.

The post How Bright Should My Hydroponics Light Be? is the next step in this series. It explores how much light certain plants needs to grow. I also show you how to convert to the more common used light measurement value umols or PPF, which many grow lights use. Understanding these values, and how they get them, will help you make an informed purchase.