Watering Basil The Right Way! (Indoor And Outdoor!)

Watering basil is often where many fail in growing basil, it was honestly the case for me decades ago as well. The water needs of basil are often overestimated, causing overwatering and root rot. Depending on the temperature and location (indoors or outdoors), among others, basil will require different watering routines. How much water? How often to water? I’ll help you learn how to water basil correctly today!

How often and how much to water basil depends on 1) pot size, 2) soil type, 3) plant age, 4) temperature, and 5) location. These are important for watering both indoor and outdoor basil plants. Generally, basil needs 1–2 inches of water per week. Water it until the soil is moist and/or excess water drains from the hole.

Basil plants, if you do not live in a very cold or moist environment are relatively straightforward to maintain. Do not let bad watering behavior deprive you of healthy and strong basil.

1. Pot Size

Basil plants in larger containers require more water less often than plants in smaller pots. Planter size is inversely related to watering frequency. However, avoid excessively large pots as this can cause rot.

Suppose that you are using a potting mix heavy in compost—you shouldn’t do that but I’ll discuss more about it later. This potting mix has the tendency to absorb a significant amount of water and hold it.

If you are also unlucky enough to have a young basil plant of only a few inches in height kept in an overly large planter, then things can go south quickly.

In this case, you’ve got a large amount of soil that can hold liters of water. Now think, do you think that a small basil plant can absorb liters of water? No. The soil will stay wet for a long time, especially if you watered it generously. As a result, basil roots are constantly in contact with water.

How is that possible? Do basil roots extract water from the surrounding soil? Yes, it does, but at the same time, the water in the surroundings keeps pulling towards the drier area around the plants. The result? The roots are always wet!

This condition, called overwatering, followed by root rot, is the cause number one of dying basil indoors.

As such, when discussing a good size for a basil plant I usually don’t recommend anything more than a 12-inch-wide planter. Unless your basil has grown into a large and well-developed plant over the years.

For more check the full growing basil guide, Growing Basil From Start To Finish (With 2 Gold Tips)!

2. Soil Type

The frequency and amount of water basil plants need may also be determined by checking the type of soil they are growing in. Basil in nutrient-rich potting mix will require less water than gritty loam soil. Clay-rich soil require even less water than either, while sand-rich soils need so much water often.

The soil type you grow your basil plants in—whether directly in ground or in a container—makes a significant difference in how much and frequently basil needs to be watered.

1. Clay and Silt

Basil in clay-rich soil don’t need much water. Nevertheless, it’s not recommended. While clay holds water well, it doesn’t drain easily but gets compact quite readily, making it unfit for growing basil.

Use clay soil taken from the outdoor garden and chances are that you are going to kill your basil after a month or less. Indeed, in many areas around the world (the UK included) outdoor soil can be clay heavy.

As discussed in our soil guide, clay suffocates many plants with “weak roots” (basil included).

Clay is a very “dense” growing medium that behaves like a wall preventing the adequate exchange of gases that the roots breathe. In addition, water will be either stay on top of the soil surface (like a puddle) causing stem rot, or collected in undersurface pockets (rotting the roots).

Basil in clay just cannot be watered as basil in clay will not grow. The same applies to silt and any mixture of the two.

2. Sand

When grown completely in sand or in sand-rich soil, basil would require an excessive amount of watering and attention from the gardener which is neither feasible nor advisable for most.

Growing basil exclusively in sand is another bad idea. You see, sand is a growing medium with drainage capabilities that are too high and quick. In other words, it retains very little water—if it even absorbs any.

Watering a basil plant in the sand is still possible but you might need too much water, way too often. This is not only environmentally friendly. You’ll end up wasting a lot of water. Besides, doing so is very demanding.

Sand has also the problem of not being able to retain nutrients as well, leaving the plant virtually unfertile with little to no nitrogen, potassium, and phosphorus for plants to absorb.

3. Potting Mix

A potting mix with a high content of peat moss or compost or coco coir should be watered way less often than a basil plant with a more gritty potting mix or rock loam soils in some gardens.

Did you use a good potting mix but still had your basil die due to overwatering? Then, start inspecting the ingredients list on the package if you can find any. If not, try to get in contact with the company!

Coco coir, peat moss, and compost are well-known among gardeners and even scientists. These materials are recognized for their ability to increase water retention.

This generally means that, unlike gritty mixes and soils, such growing mediums need to be watered way less often. Remember, they trap and hold way more water per volume.

The results prove that the soil on the plot with the dose of compost of 100 t.ha−1 showed an increase in the humidity. Organic matter, applied at the above-mentioned amount has a positive effect on soil moisture retention

Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis

Also, it’s important to also keep in mind the potting mixes and soils containing high amounts or organic materials like compost so basil plants grown in them require less water. Why? Compost can absorb from 60% to 145% of its weight water!

Despite the fact that basil can be grown in a potting mix without the addition of any gritty material like pumice or perlite, watering can still be a challenge. As always, it’s better to underwater than overwater basil!

3. Plant Age

Young basil plants will benefit from more frequent watering with small amounts of water than occasional watering with so much water, especially when they are in big pots. The opposite is true for mature basil plants as deep watering induces better rooting.

Quite obviously, a small plant will absorb way less water than a fully developed one. However, many forget this detail by providing several liters of water at once to their 2 weeks old basil plants.

More water is not always better, especially for basil. If you provide a massive amount of water at in one sitting, your basil plant will take a long time to absorb it.

This is not a problem if it was not for its roots thin and fragile underdeveloped roots.

Basil plants are easily prone to root rot when their roots are constantly in contact with water. For healthy development, they should have the opportunity to go through a water and dry cycle.

4. Temperature

Higher temperatures generally mean that basil plants require more frequent early morning deep-watering. Whether indoor or outdoor, basil will typically need more water in the hot summer months.

Sure, basil is a herb that loves warmth. Even then, temperatures that are far too high can cause your lovely plant to lose moisture much faster than normal.

Meaning, basil will need much more water on incredibly hot summer months.

In extreme cases, you might even have to water your basil every other day or even daily if, especially with temps soaring way over 86°F or 30°C outdoors.

Learn the about the ideal temps for growing baisl in our article on temperature tolerance!

But for the rest of the year, you can easily get away with watering your basil about 1–3 times every week.

5. Location

When grown indoors, potted basil plants require much less water than those cultivated outdoors—whether partially or completely. In particular, the soil of outdoor basil plants dry up faster.

Truthfully, the amount of water and how often to give it will largely depend on where you grow your basil plants.

Here, I’m talking about both both the macro and micro scale.

Point in case, basil grown in arid and hot areas like Arizona will need a lot more frequent deep-watering than basil growm in humid and cold states such as Monatana.

Furthermore, if you keep your warmth-loving plants indoors, where it’s generally much cooler and moderately humid throughout the year, you don’t have to watering it often. You might even need to wait for more than 1 week before watering it again to prevent overwatering.

This is true for all basil grown in a controlled and enclosed space, be it a grow tent, greenhouse, sun room, or what have you.

On the other hand, basil grown outdoors are exposed to the elements including wind, rain, and sunlight—everything, really. As such, they are likely to everaporate much faster than indoor potted basil plants.

How Often to Water Basil? (2 Scenarios)

An indoor basil plant, as well as outdoor ones, should be watered immediately and thoroughly 1) at the first sign of wilting or 2) when the soil just an inch below the surface starts getting dry.

How often should I water basil? I’m pretty sure you’ve asked yourself this question numerous times already. You know how the pot size, soil type, plant age, and temperature can all affect the need to water basil plants. However, the key question is when and how often to water basil plants!

Moreover, the answer to the question “how often to water basil indoors” is pretty much along the same line as the one for “how often should you water basil outdoors”.

If there is one thing that I would like you to remember from all of this, it’s this: There is no precise amount of water or perfect frequency by which a basil plant should be watered. Many different variables affect a basil plant’s watering needs.

1. Slight Wilting

Once basil leaves start drooping, home gardeners can take it as a sign to water the herb. The plant is indirectly communicating this need through such wilting. Only water is necessary for it to recover.

I define basil as a very expressive plant. Healthy basil loves moist soil (not waterlogged). When it does require water (and none is found) its leaves will start losing more water than they absorb.

In a few hours, the basil will start bending on itself and the leaves will look droopy and without life. No worries, this is normal and your basil is still fine (if you do not wait days before watering).

The basil leaves and stems will come back to life in as little as 2 hours! All the leaves will be “meaty” and stand upright again. This is how incredible basil is!

Should you wait every time for the basil to wilt before watering it? Not at all!

Once you get used to your basil wilting, for example, and you know that every 4 days your basil will start drooping, you don’t need to wait for too long before watering it.

Indoor basil needs more water in summer than in spring. This is because the higher number of daylight hours pushes the plant to produce more leaves and so increasing its water requirements. Hence, the watering schedule should be adapted accordingly to the season (temperature and daylight hours).

2. Dry Soil

Indoor potted basil should not be watered based only on how the topmost layer of its soil or potting mix looks. A superficially dry soil refers to the fact that the top soil may still seem moist despite being still damp does not mean that also the soil around the roots is dry.

This is another mistake in watering—particularly with beginners—basil that I see often.

Indeed, the superficial soil might be dry but where the roots take their water is the “deep soil” and not the superficial one. Also it’s not unusual to have the soil surface dry but the soil beneath it quite moist.

What can you do then? Easy, stick your finger 1 inch within the soil. What are the results?

1. Is the soil sticky to your finger? Does it feel wet? If so then your basil does not need water;
2. Is the soil dry at the touch even 1 inch below? It is crumbling-looking? In this case, your basil needs water. If it is not wilting it will be very soon.

Having said all that, think back to how you tend to your basil plants. How often do you water basil? You may need to change your watering routine based on the factors and scenarios I’ve discussed!

How Much Water Does Basil Need?

Assuming the planter size and potting mix have been chosen correctly, a basil plant needs 1–2 inches of water per week. Keep watering until the first droplets of water comes out from the drainage holes.

If someone tells you that your basil needs exactly one cup per week or 1.5 inches of water, regardless of the size and age of your plant, can even harm your basil.

This is another controversial topic among gardeners despite not being difficult: How much water does basil need?

Basil is an herb that is not meant to grow in rainy places (if not possible for you, ensure proper drainage. This is because basil hates having “wet feet”.

This problem is even more relevant for potted plants where the soil is limited.

Indoor potted basil should be watered even more carefully because the soil might not drain as well as the outdoor one.

To understand why this is the case and how you can easily check that, you need to imagine the soil like a sponge. After a certain point, the soil is “saturated”. This means that it cannot absorb more water. Any further water you add to it will leak out.

When the soil starts dripping from the planter it means that it had enough. Hence, there is no point in adding more water. This is usually too much for a basil plant. As mentioned before Basil hates wet feet.

Create Your Own Routine for Watering Basil!

To create a routine to water basil, it is important to gradually water the soil until the saturation point is found. This is the point where the soil cannot take more water in.

Apply such a technique by:

1. The first time use a measuring cup or something that tells how much water you are using
2. Place an amount of water around a fourth of the soil volume. No need to be precise here
3. Pour the water into the planter
4. Is the water leaking from the planter drainage holes? If so, in the next water try to put a bit less
5. If not, then you are sorted.

The “quarter rule” is because many potting mixes can absorb around a third of their body weight in water. Hence, using for the first time an amount of water that is a quarter of their soil volume, places you on the safe side and you avoid overwatering the plant.

FAQs

Summary of Watering Basil

Young basil planted outdoors with a large pot, gritty potting mix, and higher growing temperatures,. May require freqent watering. Once this fully matures, watering frequency and the amount of clean fresh water a basil plant needs will naturally increase.

In comparison, well-grown mature basil plants cultivated outdoors in compost-rich fertile loamy soil and low to room temperature will need, whether they’re grown indoors right next to a sunny window or exposed right under full sun.

Sources

• “Evaluation of compost influence on soil water retention” by Pavel Zemánek in ResearchGate
• “Characteristics of Composts: Moisture Holding and Water Quality Improvement” by Christine J. Kirchhoff, et al. in The University of Texas at Austin

yourindoorherbs.com is part of the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites like mine to earn advertising fees by promoting good quality Amazon.com products. I may receive a small commission when you buy through links on my website