Debbie Musser, who gardens in La Habra, emailed as follows: “We’re having to get a probably 75-year-old ash tree taken down soon. It got a fungus this year, but more critically, it’s apparently had an infestation of termites and other critters (ants? bees?) over the past many, many years. There are now three large tunnels (two of which intersect) in the crotch of this big tree, which has shaded our yard and back of our house for many years. At some point we will replace it and be looking for something drought-tolerant, relatively quick-growing, and not too messy (no jacaranda or pepper tree) — something that will eventually provide shade for a patio but not get so tall that the utility company must send tree trimmers to hack it way back every two years. An olive tree has been suggested, but we sure don’t want to be cleaning up olives every year, and we hear that the sterile ones can become “unsterile” over time. Someone suggested a palo verde. We have a lot of crape myrtles in the area, but not much canopy. Any suggestions?”
For your specific requirements, the consensus arboreal selection among California gardeners and landscapers is the Marina strawberry tree (Arbutus ‘Marina’). Marina’s increasing popularity derives from its rosy pink flowers, lush foliage, and cinnamon red bark, as well as a relatively rapid growth rate to a mature height and canopy spread of 25-40 feet. Still, you can’t have everything, and there is some complaint about the necessity to clean up exfoliating bark and marble-sized fruit. The pebbly fruit, edible but bland, is quite ornamental, turning from green to yellow to orange to bright red with a bumpy skin. Marina’s name comes from a boxed specimen that grew in a nursery in San Francisco’s Marina District. The ancestry of every Marina tree can be traced back to cuttings taken from that tree.
You are correct in noting that supposedly sterile olive trees sometimes revert to producing fruit. However, the Swan Hill variety is truly sterile, so fruit drop will not be a problem with it. While olive pollen is highly allergenic, Swan Hill releases less than 1% of the pollen wafted through the air by typical olive trees. Swan Hill’s mature height and spread is between 25 and 30 feet.
The fact that you reside in La Habra got me thinking about avocado trees and Rudolf Hass, who, in the neighboring community of La Habra Heights, planted and grew the avocado variety that bears his name. Hass had someone graft the Fuerte variety to a large planting of avocado seedlings, but the graft on one seedling didn’t take. Hass wanted to uproot the seedling but was persuaded by the same individual responsible for the failed graft to leave the seedling alone since it looked especially robust.
For your purposes, however, a Fuerte tree, somewhat smaller than a Hass, would be appropriate as it matures to a height of 25-35 feet with a spread of 20-40 feet. While a Fuerte tree will produce some fruit without a pollinator, if you wanted to increase its yield, you could plant a semi-dwarf Gwen avocado nearby. Gwen is ideal as a companion pollinator tree since it is a heavy producer itself but will not take up much space, with a height and spread of 10-15 feet. Keep in mind that, if you like oranges, Valencia and navel orange trees — standard size, not semi-dwarfs — grow to a height of 25 feet with equal spread.
All of the above trees are evergreen, but if you wanted to consider deciduous species, there are two inviting possibilities to consider. After all, you may want more sun on your patio during fall and winter when temperatures cool, and trees that shed their leaves allow the sun to shine through and warm the area. At the top of this list would be saucer magnolia (Magnolia x soulangeana), whose mature height and spread are 20-30 feet.
No matter your mood, your soul will brighten at the sight of a saucer magnolia in full bloom; its flowers are fresher, cleaner, and more refined than those of any other tree. Its floral display is enhanced by the fact that flowering takes place when the gray-barked tree is still leafless as winter ends. In this state, at the moment when flowers open, you see what look like hundreds of brilliantly burning lamps on an arboreal candelabrum. These barely opened blooms have been compared to tulips, goblets, and water lilies. Soon, when the petals lay down, the flowers take on the look of shallow saucers, as wide as 10 inches across.
For fall beauty, nothing surpasses a persimmon tree. Its broad, leathery leaves turn brilliant shades of yellow, orange, and red as temperatures cool. At the same time, the fruit ripens from green to orange. Often remaining on the branches after much of the foliage has fallen, persimmons stand out vividly against the tree’s bare limbs. A combination of persistently hanging fiery fruit and foliage gives the persimmon an especially distinctive seasonal glow. Although trees mature to a demure height of 15-20 feet with equal spread, they may eventually reach twice this size.
You mention a palo verde tree, and its thornless variety (Parkinsonia ‘Desert Museum’) is recommended for your precise situation. It is a sterile variety, and so you will not need to worry about the messy seed pods that fall from conventional palo verde species. However, there is a massive drop of yellow flowers in late spring and summer, so you will need to be prepared for sweeping your patio on a daily basis during this time. It is as drought-tolerant as any desert tree and, given water on an occasional basis, remains evergreen. Should it experience extreme drought, it will shed its leaves during summer to conserve moisture. Vibrant green bark on trunk and branches (“palo verde” means “green stick” or “green pole”) enhances its appeal.
If you would like to share a gardening experience, please send it to joshua@perfectplants.com. Your questions and comments, as well as gardening conundrums and successes, are always welcome.
California native of the week: Catalina cherry tree (Prunus ilicifolia subsp. lyonii) is an amazingly attractive and underutilized species, being both drought- and cold-tolerant (surviving 10 degrees after its third year in the ground), and suitable for an evergreen hedge. Some classify it as a large shrub due to its girth of 10-15 feet and a height of only 25 feet, although, under ideal growing conditions or being trained appropriately, it could reach twice that height. It has glistening, heart-shaped leaves and assumes a domed form as it matures. If you like having birds around, this is the tree for you since its fruit is irresistible to avian creatures of every type. Fuzzy, cream-colored caterpillar flower clusters put on a dazzling display each spring. Since it can be trained into a medium-sized tree, I was going to recommend it for patio shade until I learned that its fruit stains hardscape surfaces.