We’ve all been there, one or more of our plants isn’t doing well and you think, maybe it’s not getting enough light?

Is inadequate lighting really an issue? how do you tell if it’s affecting your plants? and if it is, what can you do about it? Let’s find out!

To Do: Add some pictures of well lit plants vs plants grow under inadequate lighting.

Symptoms

Stretching:

The easiest way to tell if your plant is not getting enough light is to look out for “stretching”; this is the term used to describe a plant that is unusually tall, with long gaps without leaves along the stem. This is also known as getting leggy, or having extended internodes. By contrast, a well lit plant will be short and stocky with short internodes and many leaves per inch/cm of plant stem.

In a garden or field, stretching is useful as getting tall helps a plant to compete with its neighbours and hopefully get above them and out of their shadows. In an indoor situation it’s less useful, gaining an extra few inches or centimeters is unlikely to result in more light and stretching is not a good strategy, but I’ve tried telling that to my plants and they just won’t listen!

Some plant varieties are more prone to leginess than other, for example I’ve always struggled to grow coriander/cilantro as I find my seedlings immediately get leggy as soon as they germinate. Perhaps I need to try germinating it in a propagator with lights.

Leaning:

Stretching causes the stem to be thin and weak which results in the next symptom: leaning. The plant will naturally bend towards what little light in available, that coupled with the thin stem will often cause it to fall over. A certain amount of bending towards the light is expected, but if the plant becomes so tall that it can’t support its own weight then it becomes problem. A well lit plant, especially one where the light is coming mostly from above, won’t have a significant lean and will be short and stocky enough to support the plant’s weight.

The stretching and leaning happens because a certain amount of light (especially blue light) is needed to inhibit cell growth and elongation. Without enough light, and particularly on the shaded side of the plant, the cells elongate and the stem stretches. If this happens more on one side than the other then the plant bends, hopefully pointing it in the direction of the light source and getting it more light.

Small Leaves:

If a plant is in the dark, there’s no point pouring energy into leave production. Instead the few leaves it does produce will be small and they will be spaced apart (see internode elongation above). Plants require light to create useful energy for growth, in low light conditions there’s not much energy to go around, so the energy is better off spent on getting close to the light than producing leaves that won’t get much light.

Yellow Leaves:

Plants get the green colour of their leaves from a chemical called chlorophyll. This chemical plays a vital role in turning light into useable energy in a process called photosynthesis. However, plants need to spend energy to produce chlorophyll. Under low light conditions, in a similar energy saving tactic to the small leaves above, the plant will conserve energy by not producing as much chlorophyll. This is visible to us as a yellowing of the leaves. By contrast, a plant grown under good lighting conditions will have a rich deep green colouration as it will be packed with chlorophyll.

If you’ve ever eaten forced rhubarb or asparagus then you might have noticed these foods are a different colour to their “normal” counterparts. Forcing is the process of growing a plant in the dark, and this challenging process is done to fruits and vegetables with special characteristics. Forced rhubarb is sweeter than normal rhubarb and is characterised by its pink (not green) stem. If you pay attention you might spot the tiny yellow leaves – a far cry from the usually huge green leaves of unforced Rhubarb. Asparagus spears are usually green, but when forced they are white rather than green.

To Do: Add a picture of forced Rhubarb.

Yellowing of leaves can be caused by other factors, such as mineral deficiencies, so shouldn’t be used as an indication for

Slow Growth:

As mentioned above, plants need energy to grow and they get that energy from light. Under low light conditions the plant will not be able to grow as quickly so will grow more slowly or may even appear to stop growing altogether.

If you’ve noticed some or all of these symptoms in your plant, then you should consider giving it access to more light to see if the plant’s health improves.

Fixes (How to give your plants more light)

Sunlight:

Often the easiest option is to give it more sunlight. If it’s warm and sunny consider putting your plants outside. If they are outside already consider moving them to a sunnier spot. If you can’t more them outside, consider moving them to a windowsill or to a windowsill that gets more direct sunlight.

These are great options if you have them, but it’s if it’s winter and you live far from the equator then there might not be many hours of sunlight to go round. If you live an a urban environment then you may not have access to outdoor space, even windows might be at a premium.

Existing Artificial Light:

Thankfully, artificial lighting can just as effective and is often easier. If you’re going to have lights on anyway then it can also be free. Take a look around your room and consider whether there’s an existing spot that gets more light. Perhaps you have a side light or a desk light that you could move your plant to be underneath. You could consider putting your lamps on a timer so they come on automatically in the evening. Even moving a plant from a dark corner to a brighter spot can make all the difference, especially for low light plants.

Switch to Low Light Plants:

Some plants need high light levels (basil, I’m looking at you!) and won’t grow well for me indoors over winter unless I give them some dedicated grow lights. One option you should consider is growing a different type of plant, I find Pothos has no problems growing next to a table lamp year round. I have plenty of rooted Pothos cuttings that I occasionally sell on eBay. Let me know in the comments if you’re interested.

To Do: Add an article on low light plants.

Grow in Summer:

The next is to consider growing at a different time of year – the growing season can be short, but it can be intense and fun to grow with the seasons as nature intended, enjoying the fruits of your label in autumn/fall with everyone else.

Dedicated Grow Lights:

If you’re determined to grow basil over winter then another option is dedicated grow lights. These can range from function to beautiful and can be expensive or made yourself cheaply and fairly easily. That said, there is an ongoing cost to running grow lights (see my grow running cost light calculator to get an idea). Personally, I light to integrate my growing lights with my home decor. By building beautiful lights that light both the plants and the room in a high quality glow, I get the benefit of healthy plants, lit beautifully while adding layered lighting that lifts the room. These lights can take a struggling houseplant in a dark corner and turnin it into a beautiful centrepiece for the room. Money well spent if you ask me.

To Do: Write up and link to the build of my chilli lamp/stand and add a picture here.

Not everyone will be hand crafting their own lights, so if you want to buy one then I’d say use whatever light you prefer. The amount of light is more important than it’s exact colour. I used to use the pink/purple (red/blue) glow lights as I felt they were more efficient, until I realised that for me, they took the joy out of growing as I couldn’t admire my plants. Instead I came to realise that white LEDs are as efficient (they have has far more research and development poured into them than grow lights) as more importantly for me, they can be beautiful. Cooler (bluer) shades of white light is probably better, but there’s not much in it, and I prefer to have warmer (redder) lights in my home so I personal built grow lights using warm white (2700k-3000k) LEDs.

Running costs:

A powerful 25W grow light (enough for about 6 plants) costs me around £3.60/year to run for four hours a day, six months a year. I keep this on a windowsill and those four hours gives extra light at the end of the day to extend the hours of daylight. This is with currently expensive 18p/kWh electricity tariff.

A smaller, 4W single plant grow light might cost me £1.8/year to run for 8 hours a day, six months a year. This assumes it’s not near a window so needs longer hours of light. The cost will depend on your electricity tarif, try plugging your numbers into the grow light calculator to see how much it would cost you.

To Do: add a write up for a single plant 4W grow light and link to it here.

Conclusion:

Hopefully you’ve learnt how to spot the stretching, leaning, small/yellowed leaves and stunted grow of a plant with inadequate lighting and you can easily tell if your plant is getting enough light. I hope you’re also got some ideas of how to fix the issue if it’s affecting you and your plants. Whatever fixes your choose, I hope they work well for you and let you keep on growing.

To Do: add a picture of some deep green stocky basil plants loving life under a grow light.