Many gardeners have a problem growing rhubarb that turns red. We always assume the trouble is the kind of rhubarb we planted. Mine was inherited. It came with the house. When I asked my mom what was wrong with my bronze rhubarb, she told me that not all of them are deep red. The young stems looked pink, but by the time they’re ready to be cut, they are a bronze-colored green. But Dad said, “You gotta grow the old varieties… the kind that a single stem fills a pie. ” Apparently, everyone (including my grandmother) had that kind in the mists of time.
Okay, so the trick is buying heirloom rhubarb plants. But as I looked for the reddest heirloom rhubarb, I learned that it’s probably not the plant itself that makes it so red, but where it’s planted and how it’s cared for.
With its tart and tasty stalks, rhubarb is a beloved springtime treat Many gardeners grow this cold-hardy perennial for its low maintenance and high rewards But does the “pie plant” prefer acidic soil conditions? I decided to dig into the details on rhubarb’s ideal soil pH and amendments to create the optimal environment.
An Overview of Rhubarb’s Soil Needs
While rhubarb can tolerate a range of soil pH levels, most sources recommend a slightly acidic pH between 6.0-6.8 as optimal. This moderately acidic range provides the right balance for nutrient availability. However, rhubarb grown in very acidic soils with a pH below 60 may exhibit reduced stalk growth and color intensity
Rhubarb does best in well-drained, fertile soil enriched with ample organic matter. The plant’s extensive root system benefits from loose, crumbly earth that allows for good penetration. Heavy clay soils often drain poorly and restrict root development, resulting in poorer growth.
Here’s a quick summary of rhubarb’s key soil requirements:
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Ideal pH range – Slightly acidic, between 6.0-6.8
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Tolerance – Can grow in pH ranging from 5.5 to 7.5
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Drainage – Well-drained soil is essential
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Soil nutrition – Benefits from organic matter and fertile soil
Signs of a Soil pH Imbalance
Monitor your rhubarb plants for signs of nutrient deficiencies that may indicate improper soil pH:
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Stunted growth – With a low pH below 6.0, stalk length and diameter may be reduced. Extreme pH inhibits nutrient availability.
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Leaf chlorosis – Yellowing leaves can indicate an iron deficiency common in very alkaline or very acidic soils. Interveinal chlorosis is typical.
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Brown leaf margins – Excessive alkalinity can cause marginal leaf necrosis. A too-low pH can induce overall leaf browning.
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Poor color – Intensely red stalk varieties may fade to green if soil pH is not ideal. Acidic conditions below 5.5 can turn stalks bronze.
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Lackluster yield – When rhubarb lacks nutrients outside the optimal pH range, harvests are diminished.
Testing your soil’s pH annually helps monitor if amendments are needed to bring levels into rhubarb’s favored range. At the first sign of trouble, take action to correct the pH.
Why Rhubarb Prefers Slightly Acidic Soil
Rhubarb thrives best at a moderately acidic pH for a couple key reasons:
Nutrient availability – Macronutrients like nitrogen, phosphorus, and potassium crucial for plant growth are most accessible in the 6.0 to 6.8 pH range. Micronutrients also remain available but not to excess.
Aluminum toxicity – Under extremely acidic conditions below 5.0, aluminum is freed in soils. This can reach toxic levels and inhibit root function and nutrient uptake. Moderately acidic levels keep aluminum bounded safely.
Water uptake – Rhubarb’s extensive roots absorb moisture best at a slightly acidic pH. Extreme alkalinity causes soil pores to swell, blocking water movement to the roots.
Microbial activity – Beneficial soil bacteria prefer a mildly acidic environment. These microbes fix nitrogen and make other nutrients usable by plants.
** Disease prevention** – Moderately acidic soils help suppress fungal and bacterial diseases like crown rot. Extreme acidity or alkalinity increases disease vulnerability.
Aim to provide rhubarb with its favored pH for optimal nutrient availability without the harmful effects of highly acidic or alkaline soils. Monitor conditions annually and amend as needed.
How to Lower Soil pH for Rhubarb
If a soil test reveals an excessively alkaline pH above 7.0, take steps to lower it gradually into rhubarb’s target range. Useful acidifying amendments include:
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Sulfur – Applying granular elemental sulfur to soil is a traditional remedy to increase acidity. It slowly converts to sulfuric acid. Use 1 lb per 100 sq ft initially.
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Ammonium sulfate – Provides a nitrogen fertilizer bonus. Apply 1-2 lbs per 100 sq ft. Has a rapid effect so monitor pH regularly.
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Aluminum sulfate – Also quick acting. Apply 2 oz per 100 sq ft to start and retest in a few weeks. Can be harmful in high doses.
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Peat moss – Mixing peat into soil during planting naturally helps acidify. Topdress annually around plants.
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Pine needles – An organic mulch that acidifies as it decomposes. Spread 2-3 inches deep around plants.
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Coffee grounds -Sprinkle used grounds around your rhubarb or till into beds. Has a mild acidifying effect.
How to Raise Soil pH for Rhubarb
Conversely, if your soil tests extremely acidic with a pH below 5.5, amendments to raise pH will help rhubarb thrive. Useful options include:
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Wood ash – A traditional liming agent, ash contains calcium carbonate. Apply in light doses of 1-2 lbs per 100 sq ft.
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Lime – Calcitic or dolomitic lime contain calcium carbonate. Till into beds before planting. Use 10 lbs per 100 sq ft.
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Bone meal – Provides a phosphorus fertilizer effect too. Lightly till in 2-4 lbs per 100 sq ft.
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Crushed eggshells – A gentle pH raiser as they break down. Sprinkle around plants.
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Wood chips – Allowed to decay in place, wood chip mulch has an alkalizing effect on soil. Maintain a 2-3 inch layer.
Go slowly when adjusting pH to avoid drastic fluctuations. Retest regularly and amend again if needed to fine tune to the proper levels.
Best Practices for Planting Rhubarb in Ideal Soil
Follow these tips when adding rhubarb to your landscape:
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Prepare planting beds well in advance if pH adjustments are needed. This allows time for amendments to fully integrate.
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Improve native soil by mixing in aged compost or well-rotted manure. This boosts fertility and drainage.
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For purchased plants, create wide, deep holes up to 2 feet across and 14-18 inches deep.
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Place dormant bare-root crowns 1-2 inches below soil level with buds facing up. Pack soil gently but firmly.
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Water newly planted rhubarb well and maintain consistent moisture for fast establishment.
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Mulch around plants with 2-3 inches of organic material like wood chips, straw, or pine needles. This conserves moisture and protects roots.
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Fertilize in early spring with a complete organic fertilizer or compost to support your rhubarb’s growth needs.
Maintaining the Ideal pH Balance Long-Term
Test soil pH yearly and watch for signs of nutrient deficiencies in your rhubarb. Take action at the first indication that pH is shifting out of the optimal 6.0-6.8 range. Try these prevention tips:
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Rotate acidifying and alkalizing amendments to balance the overall pH. Don’t overcompensate in either direction.
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Remove fallen leaves each autumn to prevent excess acid accumulation under plants.
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Incorporate balanced organic fertilizers that won’t drastically alter pH.
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Use wood chip or pine needle mulch that acidifies soil gradually as it decomposes.
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Interplant with flowers like petunias, nasturtiums, and bee balm that prefer neutral to slightly alkaline soil.
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Avoid planting rhubarb in extremes of highly acidic or alkaline soil. Seek a moderate site instead.
With some care in preparing the ideal soil environment and maintaining pH, your rhubarb will thrive for many years of abundant and delicious harvests. The extra effort provides big rewards!
Frequently Asked Questions About Rhubarb Soil Requirements
Below are answers to some common rhubarb soil queries:
Does rhubarb need acid soil?
Rhubarb grows best in slightly acidic soil with a pH of 6.0-6.8. Extremely acidic soils below 5.5 can reduce plant vigor and stalk quality.
What is the best pH for growing rhubarb?
Aim for a moderately acidic pH between 6.0-6.8. This provides optimal nutrient availability without the risks of highly acidic or alkaline soils.
Can rhubarb grow in neutral soil?
Yes, rhubarb will tolerate a soil pH near neutral in the 6.5 to 7.0 range. Growth and yield may decrease if pH strays too far from the ideal range.
Should I add acidifier when planting rhubarb?
Test your native soil first. Only add acidifying amendments if pH is above 7.0. Lower it gradually into rhubarb’s preferred range of 6.0-6.8.
Is wood ash good for rhubarb?
In small amounts, wood ash provides potassium and raises pH beneficially if your soil is very acidic. But use caution, as heavy ash application makes soil excessively alkaline.
Does rhubarb need rich soil?
Rhubarb thrives best in fertile, nutrient-rich soil amended with ample compost, manure, or other organic matter to create the ideal growing conditions.
Conclusion
While flexible enough to tolerate various conditions, rhubarb performs best in moderately acidic soil with a pH of 6.0-6.8. Test soil regularly and amend as needed to maintain the ideal range. With proper pH, fertile soil, and great drainage, your rhubarb will offer abundant, flavorful yields for years to come. Get your soil into prime condition, then enjoy the tart and versatile harvests from the beloved “pie plant.”
Growing rhubarb isn’t difficult.
Once they’re established, these tough perennials do very well even when it rains too much, when it’s dry, and when it’s 40 below zero in the winter. Everyone lets their rhubarb do its own thing after planting. Which is exactly how we arrive at a less than stellar red harvest. You need to do a little maintenance – rhubarb’s own debris alters the stem color.
There is a lot of acid in rhubarb, which is why it tastes sour. Lemons and limes likewise. However, the plant prefers soil with 6. 0-6. 8 pH. And if you’re incorporating acidic organic material into good garden soil, it will reduce the pH. (Which is why you shouldn’t put citrus in the compost pile!).
Some plants are very sensitive to soil pH, like getting blue hydrangeas to give you blue flowers. They may grow just fine when the preferred pH is off, but it messes up the color. And so it is with growing rhubarb.