QUESTION: I want to install grasscrete in my driveway. We need permeable paving to recharge our aquifers so my moopuna will have water to drink.

How hard is it to do?

— Mandy, Nuuanu

ANSWER: Grasscrete, where grass is grown in cells interspersed between concrete, is not as easy as it looks and isn’t cheap to install, but it is an akamai and aina-friendly investment in our underground water aquifers.

Too much concrete everywhere causes our precious wai (water) to run off into storm drains. We should install permeable surfaces like grass and plants, grasscrete and permeable concrete rather than concrete and asphalt.

At the University of Hawaii at Manoa, we installed permeable concrete and various forms of grasscrete at the Information Technology Center, 2520 Correa Road. You can check it out to get some ideas for your garden and driveway.

Grass grows better in summer, even here in Hawaii. Installations, aeration or other treatment are best done in the summer months with longer days for deep root establishment. May and June are good months to start.

That said, here is a basic step-by-step for installing grasscrete:

1. Grass grows best in full sun with well-drained soil. So trim your trees.

2. Prep the soil by rototilling as deep as you can (at least 4 to 8 inches).

3. Add in a 1-to-1 mixture of soil and No. 3 blue rock gravel and wet it down.

4. Lay in the grasscrete tiles, Geoblock or plastic grids and make them level with your current driveway or yard.

5. Fill in the pukas with the 1-to-1 soil mix.

6. Lay in turf grass sod. Zoysia “El Toro” grass is highly recommended.

7. Water gently and thoroughly.

8. Fill in soil to make the grasscrete level with surrounding areas.

9. Roll the new turf using a turf roller to get the roots in intimate contact with the soil and gravel mix.

10. Water daily until grass is established, then water every other day. Do not drive or park on it for as long as possible (two to three months is ideal to fully establish well-rooted turf grass).

11. Keep cars off the grasscrete as much as possible. A parked car blocks the sunlight that grass needs to grow and stay healthy.

12. Top-dress the area with either silica sand or high-quality compost to fill in any low spots once the ground settles to make it level.

13. Carefully mow the grass with a sharp-bladed lawn mower to help it spread and get established.

Heidi Bornhorst is a sustainable landscape consultant specializing in native, xeric and edible gardens. Reach her at heidibornhorst@gmail.com.