Why Is My Rhubarb Not Turning Red?

As a rhubarb grower, you likely expect to harvest beautiful red stalks. So it can be disappointing when your rhubarb plants produce green stalks instead of the iconic red ones.

Don’t worry – there are some simple reasons why your rhubarb isn’t turning red. With a few easy fixes, you can get your plants producing gorgeous red stalks again in no time.

It’s Just the Variety

The most common reason for green rhubarb stalks is simply the variety you’re growing. While the red stalks may be what we think of for rhubarb, there are actually a number of popular green varieties too.

Some all-green varieties include Riverside Giant, Canada Green, and Sutton’s Green There are also speckled varieties that produce stalks with a mix of green and red, like Victoria, Cherry Red, and German Wine

So first off, check what specific variety you’re growing. If it’s one of the green types, then there’s nothing wrong at all – the rhubarb is supposed to be green! This is just the natural coloration for that variety.

Location and Sunlight

Rhubarb needs full sunlight to produce the deepest red stalks Plants grown in partial shade may end up with lighter pink or green stalks,

If your rhubarb patch receives less than 6 hours of direct sun per day, try moving the plants to the sunniest part of your yard The more sunlight the better for getting that rich red color

Southern exposures are ideal, especially against a light-colored wall or fence that will reflect additional sunlight onto the plants.

Age of the Stalks

Younger rhubarb stalks often start out light green or pink, only turning red as they mature. So if you’re harvesting the rhubarb early, the stalks likely haven’t reached their full color potential yet.

Try leaving some stalks on the plants longer to see if they redden up. Most varieties reach peak red color once the stalks are around 18 inches long.

For green varieties like Riverside Giant, the stalks will likely always stay green, even when mature. But for red and pink types, patience as they grow may reward you with redder stalks.

Soil Acidity

Rhubarb prefers slightly acidic soil, around pH 6-6.5. When grown in very acidic or alkaline conditions, it may not produce the deepest red stalks.

Test your garden’s pH to see if it’s in the optimal range. Local extension offices often provide low-cost soil testing. You can also purchase DIY test kits.

To lower pH in alkaline soils, amend with compost, coffee grounds, pine needles or elemental sulfur. For acidic soils, add lime or wood ash to raise pH. Recheck annually.

Nutrient Deficiencies

While nutrients don’t directly affect stalk color, deficiencies can result in generally pale or smaller plants. This means the stalks may be lighter than their full potential.

Rhubarb needs consistent nitrogen over its lifetime to thrive. Insufficient nitrogen leads to small weak plants with light green leaves and stalks.

Phosphorus supports root growth and bud formation. A lack causes slow growth and dull colored leaves.

Potassium promotes strong stems and resistance to disease. Deficiency causes mottled leaves and stunted plants.

Before fertilizing, test your soil to identify any shortages. Supplement as needed based on soil test results.

Location History

If you’ve recently moved an established rhubarb plant, it sometimes takes a year or two to bounce back and produce those nice red stalks again.

Transplant shock from moving can temporarily affect the plant’s vigor and coloration. But with time to recover and establish in its new home, it should be back to normal.

Likewise, dividing large plants can temporarily impact stalk color. Give divided plants a season or two to get growing strongly again.

Previous Harvest Practices

How the plant was maintained by previous owners can also impact color for a while after you inherit or purchase it.

Removing all stalks each season and not allowing some to fully mature can result in weaker plants with greener stalks.

Not cutting back foliage before winter can leave plants buried under debris, causing issues. Trim leaves back after frost and discard debris near plants.

Top dress annually with compost or manure to maintain soil nutrition. Your plant should recover with consistent care going forward.

Fixing Acidic Soil

If your rhubarb is green due to very acidic soil, take steps to gradually raise the pH:

• Add dolomitic lime or powdered eggshells, and work into soil. Retest and add more if needed.

• Mulch yearly with unfinished compost or grass clippings rather than acidic materials like pine needles or oak leaves.

• Consider a new location away from shrubs or trees than can acidify soil, like evergreens.

• Improve drainage to prevent acidifying soil moisture buildup. Rhubarb hates wet feet!

• Don’t overdo nitrogen fertilizers which can reduce soil pH over time.

Achieving Proper Sunlight

Maximize sunlight in existing rhubarb patches:

• Trim back and remove any encroaching tree branches or shrubs.

• Consider removable reflective mulch early in season to boost light when plants are small. Remove once they fill in.

• Position taller companion plants like corn or tomatoes to the north of rhubarb so they don’t shade it.

• If plants are heavily shaded, transplant to a sunnier location for best color and growth.

Providing Adequate Nutrition

Use organic fertilizers as needed to correct any soil deficiencies:

• Test soil and add nitrogen-rich amendments like compost, manure, or feather meal if needed.

• Work in phosphate-containing bone meal in fall for strong roots and growth.

• Mulch with grass clippings or use potassium-rich wood ash if soil is lacking.

• Address other deficiencies like magnesium or iron based on soil test results.

Caring for Transplants

Get newly moved or divided rhubarb off to the best start:

• Transplant in early spring once ground can be worked or in fall after plants go dormant.

• Water transplants regularly for the first season to prevent transplant shock.

• Use a diluted biostimulant like seaweed extract monthly to reduce stress.

• Avoid harvesting any stalks the first year after transplanting to allow recovery.

Patience for Young Plants

Be patient with young or newly established rhubarb:

• Don’t harvest at all the first year, and only lightly in the second year.

• Allow some stalks to mature each year to encourage vigor and red coloration.

• Top dress with compost or manure annually to support growth.

• Young crowns may only produce green stalks at first, improving as roots establish.

Key Takeaways

• The variety, age of stalks, sunlight, and soil conditions are the biggest factors affecting rhubarb color.

• Green varieties will never produce red stalks. Allow pink and red types to fully mature for deepest color.

• Maximize sunlight exposure and maintain acidic soil around pH 6-6.5.

• Correct any nutrient deficiencies, especially nitrogen, for healthiest plants.

• When in doubt, get your soil tested and amend accordingly!

Be patient, and with a little TLC you should once again be rewarded with a bountiful harvest of crimson red rhubarb stalks to enjoy. Let that beautiful color enhance pies, jam, baked goods and anything else you love to make with rhubarb!