Ken Blackford's granite potato mounds

Ken Blackford and I have been Facebook friends for a number of years and I had seen quite a few photos of the rock beds in his San Diego front yard. When Rick Bjorklund suggested we visit Ken prior to the recent Cactus and Succulent Society of America Convention, I immediately said yes. You’ll understand my excitement when you see the photos in this post. Coincidentally, rocks feature prominently in both Rick’s garden (here) and in Ken’s, but to very different effect.

But before I even had a chance to look at the rocks at my feet, my eyes went up to take in these majestic specimens:

Dracaena draco, variegated Euphorbia ammak, Aloidendron ‘Hercules’

These towering succulents are quintessential San Diego.

Dracaena draco, variegated Euphorbia ammak

Ken’s front yard; Furcraea macdougalli on the left

Aloidendron ‘Hercules’

Aloidendron ‘Hercules’ and flowering Leucospermum

Aloe speciosa and Aloe sabaea

Aloe speciosa, Aloidendron ‘Hercules, and Aloe sabaea

In the photo above and below, you get your first glimpse of the rocks.

Aloe sabaea

When Ken bought the house in 1999, the front yard was all lawn. That was the default 25 years ago, and still is in many places today. Ken lived with the lawn for a number of years, but in 2008 something major happened that changed everything: Ken’s mainline sewer collapsed, as did many others in the neighborhood. It turned out that the developer of this 1960s in-fill development (long bankrupt) had used substandard 3" cast iron pipes.

End result: Ken decided to remove the grass after the yard was excavated for sewer replacement. Sky-rocketing San Diego water rates were another incentive to eliminate the lawn. However, because much of it was Bermuda grass, this took much longer than Ken had anticipated – he continued to remove Bermuda grass shoots for another 5-6 years.

Ken knew he wanted mounded beds for improved drainage because his base soil is heavy clay. Much of the material he used to create the mounds was decomposed granite and sand collected on multiple botanizing trips to the mountains and deserts.

The rocks that make Ken’s front yard so unique today were a bit of an afterthought. None of them were on his property, but they do exist in subsoil layers throughout much of the Clairemont neighborhood where he lives. They’re often referred to as “Clairemont potatoes.” It’s easy to see why:

“Clairemont potatoes”

Boophone disticha

Emerging Boophone flower

A mountain of these rounded granite “potatoes” were excavated as part of a construction project at Clairemont High School a few blocks away. Every day, on his way home from work, Ken stopped at the site to fill several buckets with rocks, with approval from the construction foreman.

Initially, starting in 2010, he just dumped the rocks randomly around the aloes, agaves, South African Amaryllid geophytes, and succulents he had planted in the mounds. He was never completely happy with the result, so in 2015, he decided to create his own miniature version of klipkoppies – rock hills found in South Africa (here is a well-known example). This required removing the rocks that had already been placed, sorting them by size, then putting them back, with smaller stones at the base of the mounds and larger ones at the top.

Agave guiengola ‘Crème Brûlée’

Agave victoriae-reginae starting to flower, Agave ‘Kissho Kan’ on the right

Agave victoriae-reginae

Another Agave victoriae-reginae

What you see now aren’t really walls, just rocks set in place on the sloped beds. Tightly laying them together keeps them in place, although gophers can cause disruption.

The plant palette changes with Ken’s interests. Lately, Ken has been focusing more on California natives – and on plants that gophers find distasteful.

Dudleyas are native to the California Floristic Province

Dudleya gnoma from the Channel Islands

Dudleya brittonii from Baja

Dudleya pachyphytum from Baja

South African Amaryllid geophytes (i.e. bulbs, for the rest of us) still have a special place in Ken’s heart. Many of them are easy to grow because San Diego has a climate similar to their native range (dry summers, wet winters). As an extra benefit, they’re toxic to gophers.

One of Ken’s ×Amarygia (Amaryllis belladonna crossed with Brunsvigia josephinae); photo by Ken Blackford

Ken’s interest in South African Amaryllids started in the 1990s when he was living in the East Bay (Northern California) and volunteering as a docent at the Ruth Bancroft Garden. There he met legendary plantsman Wayne Roderick who introduced him to this plant family.

Hundreds of South African Amaryllids are planted in the rock beds

In the last 30+ years, Ken has created a number of hybrids between common Naked Ladies (Amaryllis belladonna) and Brunsvigia and Boophone species. Depending on which species is the seed parent and which the pollen parent, these intergeneric crosses go by the names ×Amarygia (Amaryllis × Brunsvigia), ×Brunsryllis (Brunsvigia × Amaryllis), and ×Boopharyllis (Boophone × Amaryllis). Ken regularly sells bulbs at San Diego area plant sales; most of my Boophone disticha originally came from him.

If you want to find out more, watch this presentation on South African Amaryllid geophytes for California that Ken gave for the San Diego Horticultural Society in October 2021.

Ken’s favorites – South African Amaryllids, dudleyas, agaves, and California natives – live happily side by side in his masterfully built “granite potato” mounds. I love how the rocks go from the smallest pebbles all the way to cobbles weighing many pounds.

Boophone disticha with its signature fan of leaves

Another Agave victoriae-reginae

Mound curving around a utility access panel

Buckwheat and dudleyas

The planting possibilities are endless

I can’t even begin to imagine how many hours of work have gone into these rock mounds, but the result is one of a kind. I’ve visited many gardens, public and private, but I’ve never seen anything quite like it. Creating something that is uniquely yours, that’s the biggest accomplishment any garden could hope to achieve. That’s exactly what Ken has done. And he did it all virtually for free.

© Gerhard Bock, 2025. All rights reserved. To receive all new posts by email, please subscribe here.