Often referred to as a fruit, rhubarb is actually botanically classified as a vegetable crop. A member of the buckwheat family (Polygonaceae), it is a perennial with a woody, fibrous root system and long greenish-red leaf stems that resemble celery. Rhubarb plants have been used in both medicinal and culinary applications over the centuries and today most people know it as the ‘pie-plant’ for the fruit-like role it plays in pastries and desserts.
Rhubarb is native to Central Asia. As far back as 5,000 years ago, the powdered root was used by the Chinese for medicinal purposes. Its use spread throughout Europe and by the late 1700s, the stems began to be utilized for their culinary applications. Today, rhubarb is commonly grown across Canada where it is well suited to our temperate climate and doesn’t mind the long harsh winters.
Although rhubarb can be found in backyards and abandoned lots across the country, the majority of the stalks that make their way into the grocery and food processing industries are grown in fields or hothouses. The colour of the rhubarb stalk depends on the variety and growing conditions, not its level of ripeness. Colours vary from light green to deep purplish-red.
Field rhubarb – Field rhubarb often has thicker stalks and darker green leaves because it is exposed to sunshine. The interior of the stalk is a lighter green colour and fibrous. It is available May – June and sometimes into July.
Forced rhubarb – Sometimes known as winter rhubarb, these plants are tricked into growing inside darkened, temperature-controlled sheds and warehouse-type facilities called hothouses for harvest during winter months. This rhubarb has thinner, redder stalks that are pink all the way through with finer fibre strands and paler green-yellow leaves. Hothouse rhubarb is available as early as January through to June.
How to Buy:
When buying rhubarb, make sure you’re only paying for the stems. Rhubarb leaves are inedible because they contain a high concentration of oxalic acid which, in large doses, is poisonous to humans and animals.
Select stalks that are firm and shiny. If you have the choice, select the younger, redder stalks of the plant that are thinner and less fibrous because they are more tender and sweet.
Avoid stalks that are limp, wrinkled, blemished or have split ends.
If harvesting your own rhubarb, wait until the stalks are at least 30 cm high and select the thinner, more delicate ones over the thicker stalks as they’ll be more fibrous and therefore tougher. Grasp the stalk near the base and twist to pull out, which will allow a new stalk to regrow in its place. Note that the colour of the stalks indicates the variety, not necessarily the level of ripeness, so don’t assume you have to wait for the new stalks to turn red before they are ready. Discard leaves immediately (contrary to common belief they can be composted).
How to Store:
After removing the leaves, wash the stalks and pat them dry. Remove any blemishes from the surface of the stalks with a sharp knife. Don’t cut the stalks until you are ready to use them so they don’t dry out.
Uncut stalks can be stored in the fridge for up to 7 days.
Rhubarb freezes well. After washing, cut stalks in ¼ inch or ½ inch slices (adequate for most dessert recipes) and place them on a parchment-lined baking sheet. Be careful to not overcrowd the pan. Freeze for at least 4 hours and then transfer frozen fruit to an airtight container or bag. Properly packaged rhubarb will keep in the freezer for up to 1 year.
Frozen rhubarb can be used in smoothies, crisps and muffins without thawing.
How to Prepare:
There is generally no need to peel rhubarb, but sometimes the stems of wild or field-grown rhubarb are quite fibrous, making them difficult to work with. You can remove the fibrous outer layer with a small sharp knife. Cut a small slit at one end of the stalk and peel the skin back to remove all the stringy fibres with it.
You should never cook rhubarb in aluminum, iron, or copper pans, as the acidity will react with these metals and discolour them. Choose pans made of enamelled cast iron, anodized aluminum, nonstick coated aluminum or glass.
Rhubarb stalks can be eaten fresh (dipped in sugar) if you enjoy the tart crunch. It can also be used to make canned preserves, jams and jellies, sauces, pies, crumbles, muffins, loaves and juice, just to name a few. There is more and more culinary experimenting taking place for savoury applications as well.
Rhubarb is well known for its high-quality celery-like fibre, but it also contains several micronutrients, including Vitamins A and C, thiamin, riboflavin, niacin, potassium and phosphorus. With its high water content, a 250 mL (1 cup) serving of raw rhubarb contains only 20 kilocalories.
How Rhubarb is Grown:
A perennial plant, rhubarb thrives in the varying climatic conditions across Canada but historically, commercial production has been concentrated in British Columbia, Ontario and Nova Scotia. Strong growth and quality stalks result from a short, cool growing season followed by a long, cold winter.
Farmers buy seedling plants from nurseries and then split sections of the fibrous root off mature plants and reseed them in new fields. This is the most efficient way to propagate, although rhubarb can be planted from seed. The root sections are planted in evenly spaced rows that will allow for the plants to spread and reach outwards as they mature (3 to 5 feet). Some farmers then mulch and seal the row with a plastic covering to inhibit weed growth and trap heat and moisture. In this case, irrigation is necessary to make sure the roots have access to adequate moisture.
Rhubarb is hardy and mostly self-sufficient in our northern climate, but farmers monitor their crops for weeds, diseases and insects that might damage the leaves or stems. They also remove flower stems as soon as they appear to redirect the plant’s energy away from flower production back into the stems. Flower stalks can reach 4 feet high.
A young rhubarb plant isn’t harvested the first year or two to let the plant establish itself. The following 8-10 years of growth are the most productive.
Growing plants in the dark, often with a little warmth, is called forcing. It is a simple way to trick nature into early growth. Rhubarb farmers dig up older, nutrient-rich rhubarb roots from their outdoor fields in the fall and plant them in heated barns with irrigation hoses to ensure they stay hydrated. Forcing rhubarb creates stems that cannot photosynthesize and produce chlorophyll so they spread out reaching for the sun and put all their energy into producing long, smooth deep red stems that are more tender and sweeter than their outdoor counterparts. Harvest starts about 4 weeks after growing begins and can extend to 6 – 8 weeks.
In both growing scenarios, the stems are pulled from the plant when they reach the appropriate length, about 30 – 40 cm. Each plant can be picked multiple times as the stalks come into maturity at different times during the harvest season. Once they’re hand-picked they are packaged into boxes or wrapped in bunches for direct-to-consumer sales. The harvested rhubarb is stored in a high humidity cooler at 0 degrees celsius and can retain its quality in these conditions for 2 to 4 weeks.
Canadian Crop is Available: April – July
Grown in: British Columbia, Ontario, Nova Scotia