Key Takeaways
- Water crystals are polymer-based crystals that absorb and slowly release water, acting like tiny sponges in the soil. They’re especially useful in containers, raised beds, and sandy soils where water drains quickly.
- Water crystals benefit plants like tomatoes, ferns, and petunias that need consistent moisture, but they can harm succulents, cacti, and herbs like lavender that prefer dry conditions.
- While water crystals are an effective soil aid, they shouldn’t replace good plant care.
Keeping plants properly hydrated can be a challenge for even the most diligent of plant parents. One solution to this problem is integrating water crystals into your plant’s soil—but do they really work, or are they an overhyped waste of money? Here’s what gardening pros have to say.
- Amy Enfield, PhD, senior horticulturist at Scotts Miracle-Gro
What Are Water Crystals?
According to Amy Enfield, PhD, horticulturist, water-storing crystals are polymers that are designed to hold large amounts of water. Think of each crystal like a tiny sponge. “They are sometimes referred to as hydrogels and are normally made of polyacrylamide,” Enfield says. “Before they’ve absorbed water, they are small, white granules that resemble sugar crystals.”
Water crystals serve as temporary storage for extra water to increase the water-holding capacity of container soil, reduce the need for watering, and help plants withstand periods of drought. “They can even increase soil aeration from their repetitive expansion and contraction,” Enfield says.
Where Should You Use Water Crystals?
Water crystals are commonly used in indoor and outdoor container plantings, including hanging baskets and window boxes, Enfield says. “They can also be added to the soil in raised bed and in-ground gardens,” she explains. “The crystals are mixed into the soil at a specific label rate. When the potting mix is watered, the crystals swell into gel-like beads, absorbing and binding water molecules. As the surrounding soil dries, the water in the crystals is gradually released back into the soil, making it available for plant roots.”
Do Water Crystals Really Work?
Water crystals work and can be very good at helping your soil hold onto moisture longer and reducing the need for frequent watering. “For example, I had a coworker who swore by them to help keep his container-grown tomato plant alive and hydrated during the hot, dry Phoenix summers,” Enfield says.
However, their overall effectiveness can vary depending on certain factors. “They work best in well-draining soils, which is why they are good in containers,” Enfield says. “That also means they work better in garden beds with sandy, fast-draining soil (versus heavier clay soils that drain more slowly and naturally hold water longer).”
What Plants Are Water Crystals Best For?
Enfield notes that water-storing crystals should be used with container-grown plants that prefer consistently moist soil, are sensitive to drought stress, or have a high water demand—think ferns, impatiens, hydrangeas, petunias, and vegetables, including tomatoes and peppers.
However, Enfield warns against using them for drought-tolerant or desert-adapted plants like succulents and cacti, as well as herbs that are native to the Mediterranean, such as lavender and rosemary. “These plants thrive in fast-draining soil and are more prone to root rot and other moisture-related issues if their roots are constantly damp,” she says.
Water crystals also don’t last forever, Enfield adds. They will need to be replaced every few years, and you’ll still need to take proper care of your plant. “While they’re not a magic solution—and do not substitute for good watering practices—they can be helpful when used correctly,” Enfield adds.
How to Use Water Crystals
While Enfield recommends reading the instructions on the package, it’s crucial to thoroughly mix them into the soil. “The crystals need to be worked into the soil where the roots are growing to be effective,” she says. “For new plantings, this means incorporating the crystals before planting. For existing plants, it means creating holes around the plant and adding crystals near the plant’s root zone.”
