Coming across something you don’t recognize in potting soil can be concerning. How many times might you have found yellow balls on the potting soil you just bought? What are they? Something to worry about?
The small yellow/orange balls in the soil are likely to be slow-release fertilizer under pellet form. They are common in the majority of potting mix and added to increase the soil nutrient content. However, although more rarely, those yellow balls can also be insect eggs.
In either case, this can sometimes be something to be worried about. Read on to discover what exactly you are looking at, whether or not you need to worry.
The yellow, sometimes orange balls you have discovered in the soil, or growing medium around your plants are likely to be slow-release/ controlled-release fertilizer. I found them in the majority of potting mix commercially available. Indeed, this is the most common form to add fertilizer.
Fertilizer balls are small degradable spheres of polymer resins and vegetable oil filled with a liquid fertilizer or fertilizer salts to feed plants. More appropriately, these small balls are called ‘prills.’ One common type of fertilizer prills is made by Osmocote, though there are other brands on the market. Such brands can also be found in blue, or (more rarely) in other colors.
What is inside Osmocote fertilizer balls?
Osmocote prills are filled with Ammonium Nitrate, Calcium Phosphate, Ammonium Phosphates, Calcium Fluoride, and Potassium Sulphate. Do not worry, nothing to be worried about. These are just the chemical names of the significant nutrients element for most plants (also known as nitrogen, potassium, and phosphorus). There are different formulations with differing amounts of these active ingredients to serve the nutritional needs of plants. Some formulations also include other micronutrients (such as iron, manganese) for plant growth.
Fertilizer prills are added to potting mix and used for grown nursery plants. They can slowly provide everything plants need to grow well and strong over time.
Fortunately, these fertilizer balls will not usually pose any risk to your plants. In fact, they will help their growth by slowly releasing nitrogen, phosphorus, potassium, and other nutrients over time. Too much synthetic fertilizer, however, can ‘burn’ plants. And there may be no way of knowing whether the product used was an organic one.
The good news is that those balls of fertilizer are not classified as a hazardous material. Osmocote and similar pellet fertilizers pose only a minor risk to human and animal health.
Ingestion of only large amounts of product can cause severe internal gastrointestinal irritations for people or pets. Direct contact with uncoated fertilizer may cause irritation to skin or eyes. And though the coating makes this unlikely, breathing in the contents of the prills can irritate the nose, throat, and lungs.
Ingesting the product can lead to gastrointestinal irritation, muscular weakness, and blue-tinged skin (cyanosis), especially in infants.
Finding a few yellow balls in with your potted plants is unlikely to be a problem. And not something that should cause you massive concern, even if you have children or pets. But do take care when handling them.
The yellow/orange fertilizer balls into the soil will take around 2 years to totally degrade. However, the speed by which the outer shell (the hard part) and the inner content (either liquid or in crystal) degrade varies significantly.
The inner part (the nutrients) is always the first to disappear. These nutrients tend to pass through the outer shell (the releasing process) with a speed that depends on temperature and soil conditions. This is generally a slow process (that’s why they are called “slow-release fertilizer”). The higher the temperature of the growing medium, the more quickly nutrients (inside the yellow balls) will be released. At 60F (15C), for example, they will be released over 4-5 months. At room temperature (around 70F or 21C, inside your home), fertilizer will be depleted within 3-4 months.
The outer coating of the prills takes far longer to break down. EU controlled-release fertilizer policy states that the polymers of such products should biodegrade – mostly into CO2, biomass, and water. At least 90% of the organic carbon should have converted into CO2 no more than two years after the end of the claimed functionality period.
So no remnant of the fertilizer should still be visible in the potting soil after 2 years beyond the end of the claimed period of functionality. If you have not bought new potting soil or container plants within that time frame, or added fertilizer yourself, it is likely that the yellow balls are something else.
Yellow or different colored fertilizer prills should not be confused with small white balls. Small white balls, like small pieces of styrofoam in your potting soil, are most likely to be perlite. Perlite is used to add aeration/ drainage for potting mixes. It is a volcanic glass that has been expanded through heating at 1600 F.
If you find beige-ish pieces, then you might be looking instead at vermiculite. This is also used for soil aeration/ drainage. These are hydrated laminar minerals, also heated to extreme temperatures. They are totally inert and won’t pose a problem to you as a gardener.
To know more about the difference between perlite and vermiculite, you can check the article below.
Usually, insect eggs are slightly smaller than fertilizer balls and will lack the distinctive hard outer coating. Insects eggs are rather squishy, similar to goo at the touch. They might often have an elongated shape rather than spherical.
Moreover, insect eggs are concentrated in one spot compared to fertilizer balls that are uniformly spread across the soil.
Hence, with a stick or any other tools, just move them around. They look hard and dry, and all of the same size? Then relax, they are just fertilizer pills. With a stick, you are to break them with a little pressure? Well, you need to read further than.
Slug/ Snail Eggs
Slug and snail eggs are generally more like fertilizer balls except for some species, such as the giant snail and all the larger snails. But depending on where you live, you may find eggs around the same size as fertilizer prills. Different species of slug and snail have very different eggs. So it is a good idea to familiarize yourself with those that are found in your area. Generally speaking, slug eggs are paler than fertilizer balls. Often they are also more transparent.
Worms’ eggs can be very similar to fertilizer balls in size and color. But if you look carefully, worm eggs are usually not perfectly spherical, but rather slightly elongated. If you look very closely, you’ll see a ‘tail’ on them or some kind of hair (you might need to use a magnifying glass if you are curious or a phone with a good zoom)
Ants can also become guests of your potting mix or indoor herbs if you are not careful (usually they are attracted by other pests). Ants eggs, although might change in the function of the species, they are usually bean-shaped and white/pale yellow in color. More often than not, you can find such eggs digging into the soil.
If you are dealing with ants eggs, you will realize it very soon. Indeed, ants tend to multiply quite quickly, so if you disturb their eggs, you will see many ants coming. Again, like all the other insect ants, eggs are all gathered in the same spot.
Vine Weevil, Ladybugs and Others
If you see balls that are more orange than yellow, they might be vine weevil eggs. Black vine weevil eggs are a deeper orange in color. These three are those closest in appearance to fertilizer prills.
Also, ladybugs produce eggs that might be confused at first to fertilizer balls. These are useful insects for gardens, although hardly ever they settle indoors. Their eggs are orange and more elongated than spherical. Usually, ladybugs are the least of your problems. In this case, I would just go with the manual removal.
Spiders, although rarer, can decide to lay eggs on your potted herb. However, they are easy to recognize due to their silky appearance. They are often on the net (perhaps between plant leaves), or you might find a spider carrying them around.
What to do if you find eggs into your soil
If you suspect that you have found eggs in a potting mix or in the growing medium in your containers, remove these by hand to ensure that they don’t hatch and cause problems for your plants. If the eggs belong to worms (a beneficial creature), consider if you can take eggs outside to let them thrive in the outdoors soil environment. I would suggest as a precaution, to wear gloves.
Another solution, although more extreme, is to get rid of the soil altogether of your potted plant. Why? Because insects are small, and even removing all the eggs might not be a reason strong enough to leave (or to not start a new nest). This is, by far, my favorite approach. If you go this route, also check how to prune your plant roots if you need to.
- What are yellow balls in soil? Most of the time, they are fertilizer balls, although they might be eggs.
- Eggs are slimy, soft, and often all gathered in one place.
- Are the yellow balls dangerous to me, my kids, or pets? If fertilizer, not a huge risk – but care is advised
- If they’re eggs, what might they belong to? Slugs or snails, worms, ants, ladybugs are the most likely culprit.
Are fertilizer balls suitable for plants? Yes, in general, the fertilizer balls are slow-release fertilizer that provides the three essential macronutrients that the majority of herbs and plants require.
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