Recently, after writing about mangoes, I received an email from Steve Huffman: “It might be worth mentioning that mango sap can cause skin irritation similar to poison ivy. When I was a child, my family moved to Hawaii for several years. I climbed a mango tree in our yard with very painful results.”

This is an important reminder and makes perfect sense since mango is the botanical kin of poison ivy, possessing similarly skin-irritating sap. This sap contains urushiol (yu-RU-she-ol), an oily resin that is highly allergenic, with 85% of the human race sensitive to it. Some people will only itch for a short time after contact, while others may break out in a rash that lasts for more than a month. Urushiol can remain on clothes for years, so make sure to do laundry after exposure to plants that carry the resin. Although dogs and cats are not sensitive to urushiol themselves, they carry it on their fur, so bathe your pets immediately after they take a romp through poison ivy or poison oak. And mango peel is also rich in urushiol, so wash your mangoes before peeling them.

The word “urushiol” comes from the Japanese “urishi,” meaning “lacquer.” Ornamental lacquerware — bowls, trays and boxes — have been valued in Japan for thousands of years. However, there is also a history of people breaking out in a rash after touching these objects due to their shiny finish, a glow made possible by sap from the lacquer tree (Toxicodendron vernicifluum), a poison ivy relative.

If your skin is exposed to poison ivy or poison oak, treatment with manzanita leaves and bark is one recommendation. Boil in water, let the concoction steep for 30 minutes, and then spray or apply with a cloth to the affected area, letting it dry in the open air. Do this several times a day for a few days. Alternatively, you could apply rubbing alcohol or even gin or vodka (rubbed on the skin, not imbibed) to the affected area. Note: Treatments for mitigating urushiol irritation pertain to early application, before a rash develops. Before working with any plant in this family, make sure to wear long sleeves and gloves to prevent skin exposure.

Western poison ivy (Toxicodendron rydbergii) and western poison oak (Toxicodendron diversilobum) are native to California, although poison oak is far more prevalent. The former grows as a vine or ground cover, while the latter can develop into a 10-foot shrub in the sun or grow as a vine in the shade. Both are deciduous, with foliage turning yellow, orange and red before dropping in the fall. Be aware, however, that bare stems of these plants are coated with urushiol; even their dead stems will retain the toxic resin for years. “Leaves of three, let it be” is a mnemonic for remembering the appearance of both plants, since the leaves of both include three leaflets, although the margins of poison ivy are toothed, while those of poison oak are lobed.

These skin-irritating species belong to the cashew or sumac family, with a botanical name of Anacardiaceae, a word that comes from the Greek for “without” (“ana”) and “heart” (“cardia”). It has been suggested that the highly toxic sap and resin from plants in this family suggest the heartlessness of its various species. However, there is another explanation for the family name, derived from the phenomenon of cashew nuts growing, most curiously, outside the fruiting structure known as a cashew apple, which, incidentally, is not toxic. If cashews behaved like typical nuts, they would grow in the “heart” of a fleshy fruit. Instead, the cashew nut, encased by a shell, hangs from the bottom of the cashew apple to which it is attached. While the cashew shell and nut are highly toxic, nuts lose their toxicity after being dried or roasted.

Although there are scattered reports of cashew trees being grown in the San Diego area, I have never seen anyone testify to their cultivation in Los Angeles or its environs. However, you can grow the tree as an indoor plant in a sunny exposure, whether you acquire a live plant or sprout the seeds. Be aware that seeds only germinate while still in their shells, but do so readily. The cashews you see in stores, even those that are raw, will never germinate. You should also be aware that cashews, especially those that are raw, frequently have tiny insect larvae living in them, to be revealed when separating the two halves of a nut. If you do manage to grow a cashew tree, it will take three years before it begins to flower and produce a crop.

Cashews are close to my heart since I have a nephew in Costa Rica who manufactures cashew cheese for his livelihood. Cashew cheese is a soft spread that is simple to make. After soaking the nuts in water overnight in the refrigerator, pulverize them in a food processor, reaching the desired consistency of your spread by adding the previous night’s cashew water little by little, followed each time by a spin of the processor. Add vinegar to lengthen the spread’s refrigerator life. You can also add salt, garlic, lemon juice, cayenne pepper or whatever spices you choose.

The cashew family includes four arboreal species seen in Southern California yards and gardens. One is erroneously dubbed California pepper tree (Schinus molle), which is actually indigenous to Peru. If you ever visit Hidden Hills in the western San Fernando Valley, you will become instantly familiar with this species since it’s the single parkway tree in that community. Its weeping growth habit distinguishes it from other drought-tolerant trees, and it makes an unforgettably elegant, if somewhat melancholic, statement when planted repetitively over long stretches of road, as it is in this locale. Brazilian pepper tree (Schinus terebinthifolius) is its cousin, but with a luxuriously deep green and upright foliar display. The problem with this tree is its adventitious shoots that sprout up from its meandering roots, earning it the reputation as a scourge of well-kept gardens.

Two trees with colorful foliage round out our local cashew family trees. One is Chinese pistachio (Pistacia chinensis), which shows off brilliant, red-orange leaves before they drop in the fall. It has a symmetrical, domed canopy with a mature height of 30-40 feet. The other is smoke tree (Cotinus coggygria), also deciduous, growing to a height of 15 feet. Varieties with maroon to purple foliage are widely planted. Faded flowers resemble billowy puffs of smoke. This is an outstanding small tree that should never need to be pruned, as it keeps its natural, symmetrical shape from year to year.

Three California natives in the cashew family are highly prized for their value as large evergreen shrubs, each of which makes an outstanding informal hedge, ranging from 10 to 30 feet tall. Lemonade berry (Rhus integrifolia) has flat, leathery, sea green foliage and dense clusters of pink and white flowers followed by fruit which should not be eaten whole but can be masticated or sucked for its juice, after which its pulp should be discarded. Soaking the fruit in cold water makes a tart and refreshing summer drink. Sugar bush (Rhus ovata) has similar qualities, but its habitat is inland, whereas lemonade berry’s is more coastal. Laurel sumac (Malosma laurina) exhibits vigorous growth throughout the year. After a wildfire, it is the first plant to recover as it sends up new shoots from the remains of its woody base. New foliage is strikingly red in color before it turns dark green, but stems, leaf edges and leaf veins remain red. Both sugar bush and laurel sumac have upturned leaves resembling taco shells. Laurel sumac is an indicator plant for avocado growing; wherever laurel sumac grows, the climate is favorable for avocados as well.

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After writing about plants with orange flowers, I received the following email from Beth Cann, who gardens in Menifee: “Our favorite plants with orange blooms are our two lion’s tails (Leonotis leonurus). We cut them way back in the fall, but they always come back with a vengeance in the spring.” Cann sent a photo of one of her plants, which appears to have reached its maximum size of 6 feet tall by 6 feet wide. Keep in mind that there is also a dwarf lion’s tail (Leonotis menthifolia) that is 4 feet tall and wide and is highly garden-worthy as well.

Does anyone have a poison ivy story, or a remedy for its irritation? If so, send your experience to Joshua@perfectplants.com. Your questions and comments, gardening predicaments and successes, as well as your experiences with plants you think more people should know about, are always welcome.