4 Reasons for Small Basil Leaves and Tips To Avoid It

A small genovese basil plant – Photo from Dermot O’Halloran in Flickr

Basil is not only a beautiful and fragrant plant but a source of endless leaves that you can use for Italian delicacies such as pesto or bruschettas. However, what if your basil is producing only very small leaves, insufficient even for a tiny pot of pesto? If you are in this situation I am here to help. After a bit of research, I can tell you causes and solutions so you do not have to give up on your Italian recipe plans!

Then, what causes your basil leaves to be small? Small leaves in a basil plant are typically caused by a lack of nutrients, insufficient exposure to sunlight, lack of nutrients in the soil, or a small container.

How you can address this problem and bring back your plant to his original state? It is easier and cheaper than you might think…

Four Tips That Will Make Your Basil Leaves Big Again

A typical Genovese Basil (the most common basil in many countries around the world) have leaves that, fully growth can reach, a length of typically 7-8 cm and width of around 4. If a 2-3 months old basil is far from those sizes (like 2-3 cm in length) then give a go to the following tips.

I would apply them one after the other, with an interval of 2 weeks, to have the time to notice any change in your plant and so identify the cause of the problem.

Tip #1 – Provide Light If Nature Does Not Help

Basil originated in the sunny African lands. It needs warm weather and plenty of sunlight for its development. Hence, if you are not providing 6 to 8 hours of direct sunlight, your basil will not be able to produce the nutrients it needs independently from how well you water it or fertilize the soil. 

It is not sufficient to place your basil close to a window.  Indeed, if you live in a country (such as the UK, my case) where during non-summer months the number of hours of direct sunlight is very low. Long poor quality light hours with very cloudy weather do affect negatively the basil as well.

What can you do?

You need to provide the hours of light that your basil is missing by using artificial light. Can you use a random incandescent light you have a home? I do recommend fluorescent light over incandescent light bulbs for several reasons.

Sunlight is essential: be sure that the plant “see” clear sky, not only indirect (reflected) light
Photo by Angela Marie from Flickr

First, they produce significantly less heat so they are less likely to damage your basil and can be placed closer to it (saving you space). Second, the colour of light they produce (yes, plants use different colours for different purposes) stimulates more growth. Finally, although more expensive at first, they consume way less energy and hence, way less pricy in the long run. Finally, they have a way longer life-span (needed considering that you might need to keep it on for several hours a day).

A common fluorescent lamp of 16W (like the one at the top of your kitchen counter) placed 30-40 cm away can be an inexpensive solution that can improve your basil overall health if the lack of sunlight is an issue. You might also want to use those inexpensive plug-in timers (a few bucks in most supermarkets) that will automatically turn on/off your lamp when needed.

Check the article below for suggestions on growing light or you can have a look at one of my best pick in Amazon here, the Roleadro 75W.

Remember that the light hours you artificially produce should match the one of the sun (no light at night and no more than 9 hours a day if you do not want to hamper the basil growth or taste).

Finally, if you are more serious you can go for slightly more expensive illumination systems specifically designed for herbs (they range from 20 to 100+ dollars). Although they do provide better results helping your plant to grow even better and larger I do suggest those if you have a great passion for your herb and have already proven also the remaining tips in this list.

Tip #2 – Be A Water Master

If you are providing enough light to your basil but still the problem persists watering might be the next aspect to look at. Water is again essential for the basil to produce its own food (sugar). 

Knowing the right amount of water that your basil requires several trial and error over time!  Indeed, the right amount of water that your plant needs depends on the age of the plant (older plants require more water), on the container size (a small pot can get soggy earlier so less water is required) and its material (plastic or clay)

To guess the right amount of water I use the finger test! I water enough to make the soil humid but not soggy as by sticking a finger in it. You should water again when the soil, with the finger test, gets dry (if you do not want to get dirty you can use a toothpick). After a few times, you will know when and how much to water without getting dirty again!

I test the soil with just a finger to see if it is moist underneath the surface: be careful to not touch the roots

Tip #3 – Feed Your Basil (Literally)

Basil does not need only an adequate supply of water and light but also a fertile soil with all the nutrients needed for its growth. Hence, if the above tips have not brought your basil back to its splendour the soil might be the next potential responsible. Potassium, nitrogen and phosphorus are three main components that your basil cannot live without and must be present in the soil. In the case of soil deficiencies, your plant simply cannot grow properly.

There are plenty of ready to use small kit that you can buy online (just google “soil nutrient test kit”) or a few dozens of dollars to check the level of nutrients in your soil. However, if you are just starting and you do not want to invest such amount of money you can go straight away with two cheaper and quicker options.

The first one is to get rid of the soil and buy/use “fresh” one (for a few dollars you can have a few kgs). The FoxFarm is by far one of my favorites. You can check its price here in Amazon or read about it more in the article below

Another, more “do it yourself” and more fun solution (the one I like the most) is to reintroduce such nutrients in the soil. In this case, the list of fertilizer you can find in grocery stores is endless. If you want to try something more organic in “do it by your self”-style you can use wood ashes (from your fireplace if during winter) or perhaps more easily to find chicken bones (after having clean them under water and dried them in an oven/microwave you smash them with a hammer and mix in the soil at roots level). 

Tip #4 – Give A Bigger Home To Your Basil

If you also tried the above solutions for all the three previous issue hence, the responsible for such small basil leaves can be a too small container. Indeed, as discussed in one my previous article here, containers play a key and often misunderstood role in the plant development

Indeed, a small container forces the roots of a plant to get squeezed in a small volume of soil that is not physically able to provide all the nutrients that a larger plant, with larger leaves, might need.  

Here I am holding a starter pot that you typically find in basil sold in a supermarket. You can notice how small it is, inadequate for a large plant

The solution hopefully is quite simple: move to a large container with a size of around 2 gallons, possibly in clay, as suggested in this article. If you are in a hurry you can grab this excellent self watering pot on Amazon, quite convenient and easy to set up.

Will Such Small Leaves Taste Good?

The leaves of a not fully developed basil, if not other problems are present (such as bugs or basil disease often easily identify spots of different colour on the leaves) are totally fine for consumption

However, their taste would not be as good as the leaves of a fully grown basil. Indeed, the growing conditions (temperature, light and water level) can affect the capability of the plant to develop specific types of substances in the right proportion to give to the leaves the taste we all love.

A constantly mild ambient temperature (25C), long hours of sunlight exposition, adequate watering as discussed above will guarantee the best flavour leaves.

Is Your Basil Going to Ever Have Big Leaves?

When I talk about basil quite often I implicitly refer to the most common basil plant: the “Genovese” type (yes, the name originate the famous Italian sauce name “Pesto alla Genovese”). However, there are more than 100 species of different basil and a few of those produces only small leaves. 

For instance, another variety that you can find in the supermarket and, at first, might be confused with normal basil just at its very early stage is the so-called “Micro basil”. This type of basil is getting very popular in late years and, a bit like a chihuahua (here you have your puppy comparison) cannot grow more than a few centimetres with leaves that barely are longer than 1 cm.

Other types that you might easily encounter in supermarket or shops depending on where you live and that presents smaller leave size than the common Genovese basil are for instance holy basil, spicy globe basil, fino verde basil, cuban basil etc…If you are in doubt in identifying the type of basil a decent resource is the classic Wikipedia page.

Related Questions

What is the basil with the largest leave size? The lettuce basil, with leaves up to 15cm long

What is the basil with the smallest leaves? The micro basil type, with leaves around 1cm long.

How long is the world’s longest basil leaf? Around 20 cm

Further Readings

21 Tips to grow massive basil

Testing the soil like a pro

Should you fertilizer your herbs (basil included)?

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