Indian plums, called osoberries by natives of the Pacific Northwest and known by their botanical name Oemleria cerasiformis, are heavily fruiting native shrubs abundant on Vancouver Island and found in smaller numbers as far south as Santa Barbara. The Indian Plum Tree is a common understory tree in oak groves.
Unlike other plums, osoberries have male and female trees. Male trees tend to outnumber female trees, but only the female trees bear fruit. You need both, of course, to get your own harvest of Indian plums.
Osoberries have a distinctive mostly-sweet, somewhat-bitter cherry-like flavor. They are tasty, but most people don’t find them to be addictive. Wild animals do, so it’s important not to take all the fruit off an Indian plum. Birds, squirrels, and bears need them to get through the winter.
History of Indian Plums/Osoberries
Osoberries made the Salish people of what is now British Columbia and Washington State dance for joy. Literally.
Although Native Americans and First Peoples enjoyed Indian plums when they were in season, they preserved a large part of their harvest for winter consumption.
The usual method of preserving osoberries was to build a cedar box, fill it nearly to the top with the fruit, and then to cover the berries in salmon oil.
Modern nutritionists would consider the result to be a kind of wonder food, even if it was a bit fishy for most twenty-first century tastes. The Salish people had an osoberry festival in their winter dancing season, at which they ate most of their osoberries.
If you were to come across an Indian plum tree in the woods, how would you recognize it?
We will get into the botanical specifications in a moment, but the way most people identify osoberry trees and bushes in the wild is as the first blooming tree in the spring.
Indian plum trees in the wild grow multiple trunks. (They can be trained to have a single trunk if you want to raise them as an ornamental.) They bear racemes, clusters of white flowers as early as February in California and March on the east side of Vancouver Island, and as late as April away from the coast in British Columbia. If you have a wild Indian plum growing on your property, you will probably notice because of its early blooms.
You won’t, however, want to make a bouquet of Indian plum blossoms. They are a distinctly acrid smell, often compared to cat urine. It’s best to leave the flowers alone so the female trees can bear fruit.
It’s not difficult to determine the sex of an Indian plum tree. The flowers of male trees will bear pollen on long stamens. The flowers of female trees will receive pollen in deep, oval pistils. Nurseries that sell Indian plums usually don’t determine whether they are male or female. That’s something you will have to do in blooming season.
Osoberries have long, elliptical leaves. When you crush them, they give off a scent similar to cucumber (much more pleasant than the flowers).
In form, Indian plums are loosely branched, erect plants that may grow up to about 15 feet (4 to 5 meters) tall. Their elliptical or oblong leaves alternate along the sides of the branches on which they grow. Leaves are darker on top than on the bottom.
Flowers of the Indian plum have five petals. They are greenish-white or bright white, hang down in clusters, and are about half an inch (1 cm) across.
The fruit appear in drupes, like grapes. The individual fruits are about half an inch (12-13 mm) long. They are yellow or orange when they first form, but they turn to a salmon color and then crimson and finally a plum-like blue-black as they ripen.
Green Indian plum twigs turn reddish-brown over the summer. They become filled with pith, and turn a bright orange in the fall. The bark of an osoberry bush or tree is smooth, dark gray to reddish-brown.
An osoberry in a tree-like habitat has certainly received some gardener’s attention. Left to their own, Indian plums always develop multiple trunks. When their branches are laden down with fruit so they touch the ground, the tips of the branches take root. This produces Indian plum tree clones that grow around the parent plant.
Not everybody agrees on how tasty Indian plum fruit is even when it is right. Birds and other wildlife, however, love them. The Indian plum is a great wildlife plant.
Indian Plum Tree Planting Zones
Indian plums grow in USDA Hardiness Zones 7 and higher, wherever there is rainfall of at least 20 inches (500 mm) a year.
Size and Spacing
Indian plums have a way of spacing themselves. They will make new trees wherever the tips of their branches touch the ground. You will have to remove young trees to keep your Indian plums about 15 feet (5 meters) apart under their overstory trees.
Indian Plum Tree Care
The care for Indian plum trees isn’t too difficult for backyard gardeners – just remember to prune them every year or two and fertilize them around late winter or early spring so they can bloom (and produce fruit!) next summer.
Indian plums need dappled, not full, sunlight. They are an understory tree. They should only be planted beneath mature oaks or conifers.
All you have to do to make sure your osoberries get the nutrients they need is to let them use the leaves that fall from the trees above them. Don’t pick up leaves around osoberries in the fall. Let fungi bring your osoberries nutrients from decaying matter all around them. Don’t walk around osoberries unless necessary. This allows the fungi to grow undisturbed. When you do go out to your Indian plum, try to stick to a trail so you do not disturb the fungi that are bringing them water and nutrients.
You can prune an Indian plum to train it to have just one trunk. Otherwise, pruning is not necessary.
Osoberries are harvested by hand when they turn purple, almost black. They are usually ripe in late spring.
Pests and Diseases
Grown in their native range, Indian plums are not susceptible to most of the diseases that affect commercial plum crops.
Indian plums need winter rain and summer warmth. They do not require supplemental irrigation when grown as understory plants.
Common Uses For Indian Plum Tree Fruit
Even in the twenty-first century, native healers in the Salish Tribe use Indian plum bark as part of a complex mixture to make a tonic for treating diabetes and its complications. Research with closely related plants used in medicine in Japan confirms that they work. Connoisseurs of Indian plum fruit juice them and balance them with sugar and vinegar to disguise their bitter aftertaste. In the Pacific Northwest, you may occasionally encounter osoberry juice used to make apéritifs, cordials, and tonics, and as bitters.
What Does This Fruit Taste Like?
Some people are more sensitive to bitter tastes than others. The difference is genetic. If you are bitter-sensitive, you may find the “bite” of osoberry fruit to be off-putting. If you’re not, you’ll find it more like a refreshing mixture of cherry, cucumber, and cantaloupe flavors.
One of the most common preparations of Indian plums is as a “shrub,” a kind of fruit syrup to be added to other foods.
Nearly all recipes for osoberry shrubs involve equal parts of fruit, vinegar, and sugar. The differences in taste come from the type of sweetener used, white sugar, molasses, brown sugar, honey, , or some combination of them, and the kind of vinegar used, white wine vinegar, Champagne vinegar, red wine vinegar, or apple cider vinegar. The mixture may be flavored with aromatic herbs and spices such as basil, cloves, cinnamon, geranium, fennel frond, lavender, rose petals, lemon verbena, lemon balm, or black, red, or white peppercorns. The vinegar and aromatics added to the shrub cancel out bitter flavors.
Mash everything together in a bowl, and let it sit. Then strain through a tea towel and store in the refrigerator for up to a year. The osoberry syrup makes an interesting addition to marinades, glazes, salad dressings, and toppings for crème brulee, puddings, and ice cream.
Here is a model recipe.
- 2 cups of osoberry with the seeds removed. (2 cups corresponds to 500 ml)
- Optional:: 1/2 cup (75 g) strawberries or blackberries.
- 2-1.2 cups (550 g organic brown cane sugar, loosely packed. Brown sugar adds depth of flavor, as does honey. White sugar also works.
- 2 cups (500 ml) apple cider vinegar
- A few buds of fresh rose petals or fresh lavender for floral notes.
- Aromatics as desired.
- A pinch (2 or 3 g) of black pepper and cardamom.
- Mash berries, herbs, and sugar together in a large glass or ceramic, non-reactive bowl (not aluminium or stainless steel).
- Leave the mixture to “sweat” in a cool place for 24 hours.
- Strain the resulting mixture through a tea towel or cheesecloth. Remove all seeds, pith, peels, and pulp.
- Add the vinegar. Let this mixture sit for a week in a cool place before straining again. Then let that mixture sit for another week before decanting into storage containers.
Even if you live in the Pacific Northwest, you should hold this mixture in your fridge so it does not become alcoholic or vinegary.
Ripe osoberries can be delicious, but the seed inside is large. They are difficult to eat directly off the tree. Most people are happier with osoberry syrup than with fresh osoberries.
Canning / Freezing / Drying
Seeded osoberries are suitable for drying. Use them to balance dried cherry flavors. They can also be frozen — or, if you want an authentic, highly nutritious treat, pitted and covered with salmon oil and stored in the refrigerator. (Most people won’t have a taste for this.)
Learn more about cooking with plums at Minnetonka Orchards.
Health Benefits of Indian Plum Fruit
Indian plum fruit have not been scientifically studied to confirm their nutritional value, but it’s like they are a good source of antioxidants and vitamin C.
Where Do You Buy Indian Plum Trees?
Indian plums trees are available in nurseries all over the coastal Pacific Northwest. You can also check out Nature Hills Nursery for more information.
Where To Buy This Fruit
You will need to wild craft or grow your own Indian plums. But if a friend shares Indian plum syrup with you, you are getting a rare treat.