Kelley Hanna of The Plant Goddess was asked by homeowners in Pasadena, Calif., to build a retaining wall with the same material as the tree well at the top of the picture. In order to merge the rustic look of the well, the natural look of the yard and the refined look of the new pool area (inset), she installed a green wall with rows of succulents planted between rows of broken concrete, finished it with a smooth cap of formed, poured concrete, and crafted geometric-shaped pavers from colored concrete. This photo was taken one year after the project was completed.

When called upon to create a backyard retaining wall at a home nestled in the hills of Pasadena, Calif., it didn't take Kelley Hanna long to identify some design challenges. First, the client wanted the walls and accompanying steps to be built out of broken concrete, as a large tree well surrounding a giant oak had been.

"But I didn't want just a whole row of broken concrete because they already have a lot of it on their property," says the owner of The Plant Goddess.

The second issue was created by the design of the new pool area, which contrasted with the rustic look of broken concrete.

"It is a completely different vibe," she says. "It's like an Italian villa, with colored concrete and right angles so I had to merge the two styles."

Besides the oak in the tree well, the yard was filled with overgrown natives and large boulders, which led to the homeowners receiving certification from the National Wildlife Federation to be a habitat garden for wildlife. This too was something that Hanna had to consider in her design.

Her solution was to build a type of green wall with layers of plants between the layers of broken concrete, incorporate a few of the boulders in some smaller retaining walls throughout the property, and add some stylish elements to help fuse the different looks.

For the green wall, Hanna relied on tube planters, which are long cylinders in different diameters made of a water permeable fabric.

"The reason I like them," says Hanna, "is because the soil is contained in the tube so when you're dealing with a vertical growing system, you don't have the dirt falling out, which is a constant battle that I have experienced with the other systems."

The succulents growing out of the tube planters include Aeonium Kiwi, Echeveria barbillion, Sedum morganium, Sempervivum sunset, Senecio Vitalis, Graptopetalum Amethystinum. Kichler 18-inch LED lights were installed on the underside of the cap as it was poured. In the ground, Hanna planted red hot chili pepper aloe.

The concrete pavers in front of the wall were formed with boards and constructed with the same poured, colored concrete that was used on the house's pool deck. Dymondia was planted in between them.

To prepare the tube planters, Hanna first watered the tube to moisten the soil inside. Then for each plant, she made a small crosscut in the felt fabric, removed some dirt with a dowel to create a planting hole, placed a small plug or cutting into the hole, and then stabilized it, if needed, with a bit of wet sphagnum moss. After planting an entire tube, Netafim drip tubing was zip tied to the top of it.

After calculating the number of 6-foot-long tubes required, Hanna went to her source, a succulent grower who fabricates them at her nursery in Fallbrook, Calif. Back at the clients' house, broken concrete recycled from a driveway and patio that had been demolished by some of Hanna's colleagues was delivered.

She assembled a sample tube to be used for reference as the wall was being built and then assembled her team of concrete and masonry specialists from Distinctive Construction in San Dimas, Calif.

They poured a 12-inch-deep, 12-inch-wide concrete footing to which the first course of broken concrete was mortared. Hanna reports that the pieces were quite uniform in depth and width, requiring minimal chiseling.

The second course was designed to include tube planters so the reference tube was positioned and then smaller pieces of concrete, some that came that way, some that had to be cut back, were fitted behind it and mortared into place.

The reference tube was replaced with boards to help stabilize the middle two courses as they were installed. The fifth course was set to again accommodate tube planters. Boards were used to again accommodate the next course.

The wall's cap presented Hanna with an opportunity to merge the different styles, so she used forms and poured concrete to create a more polished look. Brackets were set into the underneath ledge of the cap to hold Kichler 18-inch LED lights, which the crew installed and wired.

For drainage, Hanna relied on an NDS EZ Flow gravel-free French drain system that was positioned at the base behind the wall, and weep holes that were left at the base of the front of the wall. The wall was backfilled with three-quarter-inch gravel.

For the tube planters, Hanna favored succulents. She used an X-Acto knife to make small cuts in the tube, then removed a little of the soil and planted plugs and cuttings.

"I think that if you get anything bigger than that, they wouldn't work very well," she says.

To irrigate the plants, she zip tied one-quarter-inch drip tubing to the top of the tube planters and attached them all to one valve. They only require irrigation in the summer and only for a couple of minutes, once a week.

Hanna viewed the ground in between the wall and the pool area as another chance to blend the rustic and the refined. After making forms out of wood, the team poured concrete squares and rectangles, which tied in to the geometric shapes of the pool deck. The same company supplied the concrete for both with the same color mixed in already.

Unlike the pool deck however, spaces were left between the pavers, which were filled with planting mix, outfitted with drip tubing and planted with dymondia.

The entire project took the team of three to four only a week to complete. A year later, when Hanna went to check on its progress, the owner proudly told her about a recent gathering of neighbors who were "standing in the area next to the succulent wall, oohing an aahing."

"The owner was so thrilled," exclaims Hanna. "So I was very pleased."