TikTok's Bizarre Advice For Hydrangeas Comes Straight From The Bathroom. But Does It Work?

TikTok is full of clever gardening ideas, whether it's using a power drill for planting bulbs to plant more in less time or transforming plastic bags into ties to give your floppy plants extra support. However, while some hacks are ingenious, others are a little questionable. One such eyebrow-raising TikTok tip is to use urine to make your hydrangeas blue. The reasoning behind this is related to the pH levels of the soil. For hydrangeas to be blue, they need to live in acidic soil with a pH between 5 and 5.5. This acidic sweet spot allows aluminum to be available for the plant to absorb, turning its petals blue. Once the pH creeps up to 6, aluminum is no longer available, resulting in pink blooms. 

Since urine is acidic, the reasoning behind this TikTok hack is it will lower the pH enough to change your hydrangea bush's color. To find out if this idea has any legs, we tapped the expertise of House Digest's Garden Editor and in-house Master Gardener Tiffany Selvey. According to Selvey in an exclusive interview with House Digest, you won't be able to get stellar results because urine isn't acidic enough to get the soil to where it needs to be. Here is a closer look at the science.

If you're looking for a fast way to change your hydrangeas blue, urine won't be your ticket to cooler shades. "In theory, this makes sense, but it's unlikely that urine is acidic enough to significantly change the pH levels in soil. To grow blue hydrangeas, [the] soil needs a pH of around 5.4," Selvey exclusively tells House Digest. "According to Healthline, the average acidity of urine is 6.0 — that's more alkaline that is needed to have an impact on the color of a hydrangea bloom." Plus, she notes, when you consider the amount of urine you will need to make the dirt patch acidic enough and that irrigation and rainfall will dilute it, necessitating frequent reapplication, you are unlikely to see the intended results. 

However, if you want to go ahead and try this hack anyway, Selvey warns to only add the byproduct to the ground and never on the plant itself. "While urine might not be acidic enough to change the entire pH of soil, leaves and stem tissue are much more sensitive to acid, and you could damage them," she notes. "So, if this is something you've decided to do ... aim for the ground." Otherwise, the gardening shortcut might cause more damage than good. 

If not urine, what can you use to make your hydrangeas blue? Luckily, there are plenty of proven methods to get that bright blue color in your garden. "The tried and true methods of adjusting soil pH are using a sulfate-based product to increase acidity and lime to decrease it," Selvey exclusively tells House Digest. "Many of these products are organic and safe to use around family and pets. Of course, always read the label before using for safety precautions." Elemental sulfur and aluminum sulfate are the most common additives to reduce pH.

Aluminum sulfate is faster-acting, so it will get you those blue blooms faster, but sulfur tends to be more affordable, making it a better choice for those gardening and experimenting on a budget. For example, you can get a 5-pound bag of Southern Ag Aluminum Sulfate for $19.99. Alternatively, you can get a 5-pound bag of sulfur, such as Earth Science's Fast Acting Sulfur with Nutri-Bond, for $12.