By Robin Y Rivet, for Let’s Talk Plants! June 2022.
Can You Bake a Cherry Pie?
Miracles do happen. Twenty years ago, it was unlikely you could harvest enough cherries from any San Diego tree to pop a handful into your mouth, never mind prepare a homemade pie; not unless you secretly grew an evergreen sub-tropical cherry species.
Plant genetics are mighty complex, but in 2002, the Zaiger family patented a new species of sweet cherry, originally called Regal Lee, which morphed into what we now call the Royal Lee. It was expected to have outstanding potential for our region, as existing cherry cultivars needed at least 500-800 chill hours to break dormancy, but that was unreliable in most San Diego climate zones. Soon after Royal Lee, another Zaiger patent arrived for Minnie Royal. This was useful, as having two different low-chill species were needed for backyard cross-pollination.
Soon the pair were touted as amazingly low-chill cherry trees needing less than ~300-400 chill hours, which is amazing considering one of their parents was Bing. Bing is very high-chill cherry, useful in our county, only if you live in Julian type winters, so no matter if it’s sold at a box store, don’t buy a Bing. But bold Southern Californians bought up in a frenzy these two new lower chill releases. We did.
They have now been around long enough to put many roots down in San Diego’s soils. As these two species were increasingly “field tested” anecdotally in backyards across our region, it became apparent to many gardeners that Minnie Royal and Royal Lee did not always bloom at the same time in springtime, resulting in off years for reliable cherry harvests. However, it also was clear that some gardeners were having success in very low chill coastal spots, perhaps providing as little as 200-300 chill hrs. The required chill hours have been dropped to 200-300 today. Unfortunately, with the vagaries of weather, Royal Lee often sets lighter crops - as it tends to bloom later.
Another issue with these first cherry releases were the rootstocks. Initially propagated on standard Mazzard rootstock, ours wanted to be 40 feet, but who wants to pick cherries up so high? Sadly, tree biology has a mind of its own, so in lowering the crown sufficiently to keep the tree much shorter, the amount of wound tissue eventually triggered canker diseases, and eventually an early demise for our Minnie Royal. Without a happy pollinator, the Royal Lee soon followed suit. Ironically, long after we purchased the first releases of these low-chill cherries, a super-dwarfing rootstock called Z-dwarf was successfully grafted and sold to customers. Oddly, it vanished as an available option for low chill cherries a few years later, almost as quickly as it arrived. I’d guess, but do not know if it’s been deemed unstable, as Maxma®14 seems to be the smallest dwarfing rootstock currently available in our region.
What has changed, is the Zaiger release of a brand new self-fruitful, low-chill cherry called Royal Crimson. It claims the same delicious qualities of its predecessors, but it can be grown solo, and also can act as a pollinator for either Royal Lee or Minnie Royal trees. We bought two, but they’re still young.
In the meantime, I’ll be working on learning to make pie crust…