Wetting agents are surfactants (soaps or extracts) added to water to reduce its surface tension. When poured into pots, they help water spread evenly through the potting mix, preventing water from simply channeling down the sides of the pot or beading up on the surface.
Jerry Coleby-Williams from Gardening Australia suggests making your own wetting agent from agar agar which is a seaweed product. Buy powdered kelp from a health food shop and slowly incorporate boiling water until you have a thick paste. Add 250ml of this paste to 4.5 litres of water and water this onto beds.*
Unlike fertiliser, which can become toxic in large quantities, soil wetting agents are usually harmless. But once the soil has recovered, repeatedly applying them is a waste of time and money.
Wetting agents reduce water's surface tension, helping it soak evenly into dry or hydrophobic soil. They're ideal for lawns with dry patches, runoff issues, or uneven water absorption.
Following the label rate is critical. While non-ionic surfactants rarely cause issues, excessively high rates can occasionally lead to membrane permeability changes or phytotoxicity, especially under certain environmental conditions. Importantly, applying more product does not increase longevity or performance.
Yucca plants are great at sequestering and using water. Yucca is high in natural wetting agents called saponins. Saponins are steroidal-based natural chemicals that actually make water wetter, breaking the polarity of the water molecule.
Application of wetting agent should be carried out 2-3 times per watering season. A sound strategy is to get your 1st application down early in the watering season (late Oct) long before the Winter moisture is gone from your soil profile.
Dish soap and home remedies:
Simple dish soap in a bucket of water is actually a simple wetting agent. The web is replete with hundreds of DIY versions. Keep it simple – ½ cup of Ivory dish soap per 5-gallon bucket and one 12 oz.
You can make your own soil wetting agent using the food grade thickener, agar agar (algin), derived from seaweed. Buy powdered kelp from a health food store. Slowly add boiling water to agar agar and stir to make a paste about the same consistency as wallpaper paste.
The wetting agent should be applied to the lawn prior to rain or watering. You can apply to the whole lawn which may include some greener areas or just to the dry areas. If applying to dry patches, treat an area slightly larger than the patch itself.
Wetting agents, also known as surfactants, are chemical substances that reduce the surface tension of a liquid, enabling it to spread more uniformly across solid surfaces. By lowering this tension, they allow the liquid to better interact with and even penetrate; materials it would otherwise bead up on.
They are not the same. Whilst they are surfactants, they have wildly varying properties. Buy a soil wetting agent. It's not much more in price.
Factors to Consider When Selecting Wetting Agents
An organic wetting agent (surfactant) lowers water's surface tension, allowing it to spread and penetrate evenly into soil or cling to plant leaves without beading or running off. These natural compounds ensure your plants get the maximum benefit from water, liquid fertilizers, and foliar sprays.
There are three types of wetting: spreading, where a liquid spontaneously displaces air on a surface; adhesional, where liquid droplets adhere to a surface; and immersional, where work is required to immerse a solid in a liquid.
In most domestic homeowner situations, the easiest and most accessible surfactant to use is dishwashing liquid. As mentioned earlier, soap contains the surfactant Sodium stearate. Liquid dishwashing liquid can be added to a tank mix of the herbicide or pesticide being applied and mixed with water.
Aloe Vera has saponins, which make it an effective wetting agent in root drenches and surfactant, or carrier in foliage applications.
Yes, 20 minutes is often enough if you have standard spray heads. However, the exact time depends entirely on your system's output. Most lawns need about 1 inch of water per week, requiring a deep, infrequent watering schedule.
When should I apply wetting agents? The best time to apply a soil improver with a wetting agent is at the start of winter, in early summer and as recommended by the manufacturer. Always water in wetting agents until they foam. This means they are activated and doing their job.
These can wilt after just a day or two without water, especially in a hot, sunny spot and especially when recently planted. And although new summer annual flowers and veggies can go three or four days without rain or watering, they also can begin to suffer beyond that.
"Poor man's fertilizer" is a traditional gardening term for snow.
One primary reason not to use Miracle-Gro is that its synthetic, water-soluble fertilizers rely heavily on salts. Over time, these salt accumulations can build up in the soil, potentially burning plant roots, altering soil chemistry, and killing beneficial, natural microbes that keep your soil a living ecosystem.
Can I use dishwashing liquid instead of a wetting agent? No — detergents harm plants and soil microbes.