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 (I love them!). However, what if your basil is producing only very small leaves, insufficient even for a tiny pot of pesto? It happened to me as well at the beginning of my journey as a green thumb. Here is what to do!
Based on many years of experience growing basil, the most common causes for basil leaves to stay small and not grow big are: 1) overwatering 2) underwatering, 3) insufficient exposure to sunlight, 4) lack of nutrients or 5) too small container (or not enough soil) 6) disease or pests.
How can you get bigger basil leaves? Check the causes and solutions!
Before moving on, if you struggled growing basil go for an easy variety like the Genovese basil (the one you find in the supermarket!)
Overwatering is by far the most common reason for stunt growth in basil and, as one of the many consequences, small leaves. Excess water into the soil will slowly kill the plant and so prevent its leaf from growing.
Knowing the right amount of water that your basil requires a bit of trial and error over time. Indeed, the right amount of water that basil needs vary on the age of the plant (older plants require more water), the container size (a small pot can get soggy earlier so less water is required), and its material (plastic or clay).
What can you do?
To guess the right amount of water I use the finger test! I water enough to make the soil humid but not soggy 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!
In case you already overwatered the plant, let the soil dry out completely. the surface should become very dry and a bit hard to the touch. If you want to go the extra mile take the plant out of the container ad check the soil. If dumps let it rest.
Advanced trick: if you really want to save overwatered basil, remove the soil from the container and replace it with fresh and dry soil. Then water gently and let the plant sit for a few days to recover.
Dry soil at the touch and wilted and crispy leaves are signs of underwatering. Such conditions, if prolonged will limit the leaf size and also push the plant to flower or, in case of prolonged drought, to die.
Spotting underwater basil is pretty easy. The soil is very dry, the leaves remind me a bit of crisp.
What to do?
Give him some water until the droplets of water leave the drainage hole in case the plant is on a small pot. Depending on the varieties you want to avoid leaving the plant without water for too long, so check the soil. In general, watering basil once a week is more than enough in most cases.
3) Insufficient Light Exposure
Basil requires around 5 to 7 hours of daily sunlight to thrive and develop large leaves. Less than four of sunlight will stunt the plant and slow its growth and leaves size.
The amount of light is correlated with the ability of the herb in producing 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 where during non-summer months the number of hours of direct sunlight is very low your basil will not develop and its leaves will remain small. 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.
Growth lights are definitely a great option to encourage basil growth indoors in case you cannot guarantee at least 4 hours of full sunlight.
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 color of light they produce (yes, plants use different colors 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 lifespan (needed considering that you might need to keep it on for several hours a day).
4) Lack of Nitrogen Fertilizer
Basil does not require fertilizer to grow but it is necessary to boost growth and force the plant to produce larger leaves. Fertilizer higher in nitrogen is recommended.
You grow basil for the leaves, not for the roots, not for the flowers. So, ideally, you want a fertilizer that is slightly higher in nitrogen content. If you are a beginner, avoid fertilizer with a very high NPK value (as you will burn the plant). Focus on low NPK with a slightly higher Nitrogen value (the first letter in the NPK label).
What to do?
If you never applied any fertilizer, and you are sure that light, water and planter are in check, then proceed with fertilizing the plant.
Do you want a quick choice? Here you have it – this is a very good one for basil and herbs in general as it is 1) 4-3-3 so, gentle to the plant and 2) higher in nitrogen to boost leaf growth.
Remember, do not overdo it. I fertilize my basil only every 2 weeks in summer, and once a month out in spring.
Fertilizer might not be needed if you have been careful in using fresh potting soil of decent quality. Check the packaging for how it is made off. If it has compost then just wait, the larger leaf might come. However, if it is cheap soil with mainly sand and peat, then use fertilizer.
5) Small Pot
Basil, like many other herbs, absorbs nutrients and water through the development of a long root system. If the soil volume starts getting too small, then water and nutrients will be depleted quite quickly causing slow growth and so, small leaves.
Check the drainage holes! Are the roots escaping from them? Then they grew so much and they are telling you that they need a new home. Simple. I saw herbs (especially my old rosemary) doubling in size by just a pot upgrade! So, yes, upgrading the pot is an effective way to boost growth.
The basil you find in the supermarket they come in a small pot like the one below. Those are unacceptable if you are serious about growing the plant. In such a small plater basil will barely survive. It is great if you are planning to eat them in a few days or so, but they will not grow much.
What to do?
Move the basil plant to a large container with a size of around 2 gallons, possibly in clay, as suggested in this article.
6) Disease and Pests
Downy mildew, Fusarium wilt, Gray mold, and root rot are among the most common basil diseases that cause a large variety of problems including undeveloped basil and small leaves. Lack of nutrients due to parasitic attacks (aphids among the most common) can also cause small leaves in basil plants.
The variety of diseases a basil plant can have is massive. Check this article focused on black leaves on basil just to have an idea. If you see anything crawling on your basil leaves then those are probably pets sucking its sap called aphids.
What to do?
In all the cases above my personal suggestion is to throw the plat (in case is not big yet) and purchase a new one.
If you really want to do the extra mile and save your basil you need to a) identify the disease (use Google lens) and b) use the appropriate treatment or pest removal (with water, alcohol, neam oil) depending on the type of pests.
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 colors on the leaves) are totally fine for consumption.
However, their taste would not be as good as the leaves of 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 the leaves the taste we all love.
A constantly mild ambient temperature (25C), long hours of sunlight exposition, and adequate watering as discussed above will guarantee the best flavor 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 originates from the famous Italian sauce name “Pesto Alla Genovese”). However, there are more than 100 species of different basil, and a few of those varieties have 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, a bit like a chihuahua (here you have your puppy comparison) cannot grow more than a few centimeters with leaves that barely are longer than 1 cm.
Other types that you might easily encounter in supermarkets or shops depending on where you live and that present smaller leaf sizes than the common Genovese basil are for instance holy basil, spicy globe basil, fino Verde basil, Cuban basil etc.
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