Rhubarb (Rheum rhabarbarum) is a perennial vegetable hardy enough for Minnesota gardens. It is in the buckwheat family, has a sour flavor and is among the first crops ready for harvest in spring.
Rhubarb is also a “pie-plant,” because you can cook, sweeten and use the chopped stalks as a pie filling, usually with strawberries.
You can also incorporate it into breads and cakes, sweet and use it as a sauce, or cook with sugar, strain and drink it as a refreshing juice.
Few people can eat much rhubarb as a raw vegetable. While juicy and crisp, it is very sour.
Rhubarb is a unique vegetable that has tasty red stalks commonly used in desserts. It is usually ready to harvest from early spring through early summer. But what about harvesting rhubarb in late summer into August – is this recommended?
In this article, we’ll cover everything you need to know about harvesting rhubarb, including whether August harvesting is possible and how to get the best flavor.
Overview of Rhubarb
First, let’s go over some rhubarb basics.
Rhubarb is not technically a vegetable, but is used like one It is actually a perennial plant that dies back in winter then regrows large leaves and red stalks each spring.
The stalks start off green but turn red as they mature. The leaves contain oxalic acid and are poisonous, so always remove them before eating the stalks.
There are two main types:
- Forced rhubarb – Grown early under cover, has sweeter, more tender stalks.
- Main crop – Grown fully outdoors, more tart flavor.
Traditional Rhubarb Harvesting Season
For main crop rhubarb, the traditional harvest season is early spring through early summer. Exact timing depends on climate and variety.
General guidelines are:
-
Don’t harvest newly planted rhubarb at all the first year. Prevents weakening.
-
Start harvesting established plants in spring once stalks reach adequate size, usually April or May.
-
Peak harvest is mid spring through early summer, around May to early June.
-
Stop harvesting by mid to late June so plants can recover and store energy.
So traditionally, rhubarb harvest ends by June or maybe July at the latest. But what if you have some left – can you still pick in August?
Can You Harvest Rhubarb in August?
The good news is rhubarb stalks stay completely safe to eat and retain good flavor through summer and August. There is no truth to the myth that late summer rhubarb becomes toxic or excessively high in oxalic acid.
However, there are some important tips for late summer rhubarb harvesting:
-
Only harvest a few stalks per plant, not the whole plant. Rhubarb needs to recover and store energy.
-
Pick the thickest, largest stalks. Leave smaller, thinner stalks to continue maturing.
-
Don’t harvest rhubarb plants that appear small or weak.
-
Water plants well after late summer harvesting.
-
Add compost or mulch to replenish nutrients.
-
Don’t harvest any rhubarb after August. Allow full rejuvenation before winter dormancy.
So while August rhubarb stalks are perfectly edible, it’s still ideal to finish harvesting by mid-summer.
Reasons to Stop Harvesting in Mid-Summer
Even though August rhubarb is safe, here are good reasons to stop earlier:
-
Frequent harvesting weakens plants over time by using up energy and nutrients.
-
Small, thin stalks need time to bulk up before winter dormancy.
-
Rhubarb needs recovery time before going dormant. Too late harvesting reduces vigor and next year’s yield.
-
Late summer stalks get thicker, tougher and stringier. Spring and early summer stalks are more tender.
-
Overharvesting year after year can kill the plant, which has limited energy to regrow annually.
So for best long-term plant health and maximum yields, it’s best to stop harvesting rhubarb by mid-summer at the latest. But taking a few stalks in August won’t seriously harm the plant if done lightly.
How to Harvest Rhubarb Properly
When harvesting rhubarb, use these tips to minimize damage:
-
Grasp the stalk near the base and gently twist while pulling upwards in one smooth motion. Don’t yank or tear.
-
Use a sharp knife to remove leaves, leaving some stem. Discard poisonous leaves – do not compost.
-
Harvest largest, thickest stalks first. Leave small, thin stalks to continue maturing.
-
Never take more than 2/3 of available stalks. Leave at least 1/3 of stems on the plant.
-
Allow 8-10 weeks between harvests for recovery. Water and fertilize after harvesting.
Storing and Preserving Rhubarb
Rhubarb is versatile in the kitchen. Use it for:
- Pies
- Cobblers
- Crumble toppings
- Jams and jellies
- Sauces
- Juices
- Smoothies
It also freezes extremely well for long-term storage. To freeze:
-
Wash, trim and chop stalks.
-
Spread on a sheet pan and freeze solid.
-
Transfer to freezer bags or containers. Keeps up to 1 year frozen.
Other options are canning chopped rhubarb or making syrup.
Soil pH and fertility
- The best soil for rhubarb is well-drained.
- Loamy soils are better for rhubarb growth than sandy soils. They are more water-retentive and can provide more nutrients to the plant.
- Soil pH is not important. Any garden soil in Minnesota, whether acidic, neutral or basic (“alkaline”), can support a good crop of rhubarb.
- Garden soil tests, because they are usually from parts of the garden with annual plantings, will not provide information about the rhubarb plants needs.
- The rhubarb plant is a “heavy feeder.” The plant must take in large amounts of nutrients from the soil to produce its large stalks and leaves.
- Make it an annual practice to supplement the soil with either a balanced commercial fertilizer or rich compost, or both. Addition of manure or compost can add micronutrients and organic matter to soil.
- Note whether growth is vigorous or weak, and adjust the next springs fertilizer application accordingly.
- Continuous use of high phosphorus fertilizer such as 10-10-10 or 15-30-15, or high rates of manure or manure compost results in phosphorus buildup in the soil.
- Some runoff may occur with phosphate fertilizer. It can then become a major pollution concern in our lakes, rivers and streams.
- High levels of phosphorus support over-production of algae, which causes significant reduction in water quality.
- If your soil tests high in phosphorus, use a low phosphorus (such as 32-3-10, 27-3-3, or 25-3-12) or no phosphorus (such as 30-0-10 or 24-0-15) fertilizer.
Gardeners often acquire rhubarb plants from another gardener who is dividing a large plant. Although there is a possibility of receiving a plant infected with a virus, chances are good that the plant is healthy and vigorous, since it is large enough to need dividing.
You can also purchase plants at garden centers and from mail-order catalogs. Nursery-grown plants will be virus-free.
Catalogs also sell rhubarb seed. The reddest varieties are not available as seed, only as plants.
- Different varieties have varying levels of sourness and fibrousness.
- Varieties also vary in color from almost pure green to almost pure red. Usually the skin is more or less red, while the flesh color varies from pale to darker green.
- Color does not cause any specific flavors. Redder varieties are desirable for pies, because the color of the filling is more attractive than the grayish color of cooked green varieties.
- Plant stature and vigor also vary among varieties. In general, greener varieties are more vigorous and have longer stalks than red varieties.
- Rhubarb leaves are toxic. Do not eat them.
- Only the long, thick leaf petioles, the “stalks,” are edible. The stalks contain high levels of oxalic acid, which can tie up calcium and make it unavailable in the body.
- Eating an occasional dish containing rhubarb does not pose a serious nutritional threat.
- People with gout, kidney disorders and rheumatoid arthritis may want to avoid foods high in oxalic acid and should consult with their physicians about consuming these foods.
Can you harvest rhubarb in August?
FAQ
When should you not pick rhubarb anymore?
You should generally stop harvesting rhubarb by the end of June or early July. After this point, the stalks can become tough, woody, and less flavorful as the plant focuses on storing energy for the next season.
What is the latest date to pick rhubarb?
In the northern hemisphere, rhubarb harvesting generally stops around the end of June or early July. Continuing to harvest rhubarb past this point can weaken the plant, reducing its productivity in the following year.
Can rhubarb get too big to harvest?
Yes, rhubarb can get too big to harvest comfortably, and the stalks can become tough and woody if left on the plant too long. While you can technically harvest rhubarb until the first frost, it’s best to stop harvesting by mid-summer (around June or early July) to allow the plant to store energy for the next season.