Basil is one of the most famous culinary herbs. No surprise that many, including myself, attempt quite often to grow it at home. It is easy to find in many supermarkets, it propagates quite well in water from just a small stem. However, many gardeners fail in growing such an aromatic herb. Bad soil is the main reason.
The best soil to grow basil needs to be well aerated with medium drainage capabilities. It should have a neutral pH and a medium level of organic matter and nutrients. Basil will not grow in compacted and high water retention soil such as clay, silt neither in nutrients poor ones such as sandy.
My best pick to grow basil is FoxFarm in which I grow basil with no issue due to the good balance between its structure and nutrients balance. In case you grow basil in a planter indoor, then I would suggest adding up to a third of perlite to the growing medium.
If you have an outside garden or just simply a driveway you might be familiar with those weeds that grow between pavement cracks. I have always envied them. They can grow anywhere, in any condition, with little to none water and with almost no soil. However, this is not the case with basil.
Basil is quite a demanding herb compared to others (the so-called hardy). The soil makes a massive difference for its growth and it needs to meet some minimum requirements if you do not want your plant to be drawn, suffocated or under/overfed.
Let’s start with the soil structure. Basil can only thrive in light soil and well-aerated soil.
What does that mean in practice?
Here a checklist to verify that your basil plants soil is adequate:
- Fingerpick at dry soil: With your fingers grab some of the soil from the surface once dry. Does it come out easily or you need to dig in with lots of strength. If the latter the soil is too compacted and it is a sign of lack of aeration. This is especially true in the planter where the soil needs to be extra airy;
- Water Drainage Insufficient: Once water, the water tends to create a paddle that lasts a minute or so? If so, then your soil is not well aerated. Indeed, water should go through relatively quickly from the surface without stagnating too long at the top. This problem can also be caused by peat moss that has totally dried. In this case, just move the soil with a toothpick;
- Water Drainage Excess: If you have your basil in a pot, drop a small amount of water on dry soil. You can see the water coming out from the drainage hole straight away? This is a bad sign of extremely well-drained soil. The water, especially if in small amounts, should not drip through the drainage hole but be totally absorbed by the soil so the basil has the opportunity to “drink” from it.
To have an idea of an extremely well aerated and draining soil think of cacti mix. If you are not familiar with cacti mix then what about sand. These are very extreme cases in which the first two points of the checklist will be passed but not the third one. Indeed, such soil retains little to no water. This is ideal for cacti and plants that can survive with some of the water that quickly passes through them This is not the case for basil or any other culinary herb.
Here is a trick.
If you grow basil in a not very sunny/dry area, or slightly cold (68F and below), then the drainage is even more important as overwatering can be more of a concern. In this case, you need to add perlite to increase the drainage of the FoxFarm soil. You should add a third of perlite to the potting soil above. The brand below is a pretty good one and will make the cut.
This is because the water in indoor planters tends to stay longer into the soil due to generally lower temperature (especially in summer and spring when the basil is supposed to grow) and lack of aeration (that limits evaporation). This will reduce the risk of overwatering, root rot.
Basil, as the majority of herbs and fruit plants really, requires some form of nutrients to be added externally. This is particularly important when you grow them in a planter, where the absence of natural external contribution (insects, old leaves, and natural organic material in general) is not contributing to the soil nutrients level.
Hence, basil soil needs to have some nutrients. Again, what does that mean? There is no hard science or exact formula here. Some scientific publications claim that an equal amount of Nitrogen Potassium and Phosphorus is ideal for basil. For example, a 10:10:10 as NPK level is pretty good for basil.
However, remember that common potting soil does not normally have such a high level of nutrients per unit of volume (these nutrients are dispersed in large volume) and it comes from manure and some other form of organic fertilizer.
Tip: You need to have soil slightly less nutrient-rich than basil needs.
Adding nutrients to the soil through a liquid fertilizer is relatively easy and totally normal for herbs such as basil. On the other hand, removing nutrients from the soil (in case it has too much) is definitely quite hard and definitely not worth it.
The soil I use has an NPK of 0.3-0.45-0.05 that, despite being slightly low in potash, it still does pretty well (the Foxfarm here on Amazon to check more of its features).
Moreover, the soil needs to have the capability to hold nutrients. Indeed, during normal soil fertilization, the nutrients will “hand around” in teh soil so the plant can absorb them at the time needed. However, if the soil loses all the nutrients at the first watering (or rain) then your basil is going to starve. The majority of potting soil has such features due to the presence of compost and peat moss.
However, if you decide (for some strange reason) to use sand to grow basil this will not work as sand holds very little nutrients over time. So, in case you do not provide constant nutrients, your basil will just starve.
As discussed in this article ideally you want a 10-10-10 fertilizer. However, given that this often is not found in the shop anything that is on an equal balance among NPK and lower than 10 is fine (avoid higher if you do not want to burn the plant roots).
For indoor plants, I normally opt for liquid fertilizer (those that you need to add to water or even those already ready to pour into the soil).
It is possible to grow basil in cacti soil. Such mix has a very high drainage and areation, that is beneficial for a basil plant. A basil plant in a cacti mix will require a more frequent watering and fertilizer.
I would recommend adding a third of compost to the cacti mix so as to have a higher water and nutrient retention capability. Of course, you need to fertilize relatively often (I would go twice a month during summer) with an organic fertilizer.
It is not uncommon while going around gardening forums and Facebook groups, to see images of dying basil plants with their owner asking for help. Most often than not the cause is a bad soil choice.
Let’s see what are these mistakes and how you can avoid them.
Providing nutrients to the basil plant is needed for its growth, but only in the amount and time required.
Basil does not need fertilizer when it is a seedling.
Be careful to not over-fertilize your plant. Too many nutrients can (almost literally) burn your basil plant from its roots. This is because of an excess accumulation of nitrogen salt-based compounds in the soil. Indeed, the fertilizer has usually high content of nitrogen that, if not absorbed by the plant (as it is too much), will burn your plant.
Using outside gardening soil in the attempt to save time or/and money from buying potting soil will waste your time and money.
Basil is a very sensitive herb, especially in moist/humid weather, prone to the attack of a large variety of insects.
Outdoor gardening soil carries almost always some type of insects. This can easily multiply in a confined planter and feed on the only organic things living in it (yes, your basil).
Basil breathes through its leaves and especially its roots. This is common to the majority of plants if not all. Hence, using heavy soil like silt or clay (perhaps taken from the outside) will slowly kill your basil plants.
This is because such soil creates a barrier that prevents the movement of gases produced by the plant (through breathing) and new fresh air to come into the plant roots.
Of course, some plants thrive in clay soils, however, those have also different and stronger/thicker roots than basil.
A planter without drainage holes is one of the most common mistakes that can cause the basil to wilt and day (due to overwatering and consequent root rot) independently from how good the soil is.
Indeed, even if the soil has adequate drainage capability but there are no drainage holes the water will start culminating at the bottom of the planter keeping the soil in that region constantly wet and without oxygen.
This becomes a problem for those deepest roots that reach such an area. Indeed, the lack of oxygen will incentivize the growth of those “rotting bacteria” damaging the deepest roots. The diseases will then spread to the others and the plant will very likely die.
Growing basil does not need to be complicated. The soil is one of the major factors that affect the lifespan of your herbs and, in particular of an herb as delicate as basil. What you need to remember when choosing a basil soil is:
- The basil soil needs to have a neutral pH with a medium/low level of nutrients;
- If the basil is meant to be grown indoors, then add a third of perlite to the potting mix (this potting mix and this perlite are pretty good, Amazon);
- Avoid planter without holes or heavy gardening soil
Hope you learned something interested today and happy gardening!
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