Colorado’s high altitude means rhubarb grows slowly, so wait until stalks are at least 10 inches long before harvesting. The best time to harvest rhubarb in Colorado is typically from late May through early July, depending on your specific elevation and microclimate. Understanding this timing ensures you get tender, flavorful stalks without damaging the plant’s long-term health.
Rhubarb is a hardy perennial that thrives in Colorado’s cool spring weather. But our unique growing conditions require a bit more patience than other regions. Let’s break down exactly when and how to harvest your rhubarb for the best results.
Best Time To Harvest Rhubarb In Colorado
The ideal window for harvesting rhubarb in Colorado runs from late spring to early summer. For most Front Range gardeners, this means mid-May through late June. At higher elevations, like in the mountains above 8,000 feet, you might not see harvestable stalks until early June.
Here are the key factors that determine your exact harvest timing:
- Elevation: Higher elevations mean cooler soil, which slows growth
- Plant age: Don’t harvest at all during the first year after planting
- Stalk size: Wait until stalks are at least 10 inches long
- Stalk thickness: Look for stalks that are about the width of your thumb
- Color: Red varieties should show deep red color, but green varieties are fine too
How Elevation Affects Harvest Timing
Colorado’s elevation ranges from about 3,000 feet on the Eastern Plains to over 14,000 feet in the mountains. Your rhubarb’s growth rate changes dramatically with elevation.
At lower elevations (3,000-5,000 feet), you can start checking stalks in early May. At mid-elevations (5,000-7,000 feet), wait until mid-May. Above 7,000 feet, early June is more realistic.
Soil temperature is the real driver. Rhubarb needs soil temperatures consistently above 40°F to grow actively. In Colorado, this happens later at higher elevations.
Signs Your Rhubarb Is Ready
Don’t rely solely on the calendar. Look for these physical signs:
- Stalks are at least 10 inches long from base to leaf
- Stalks feel firm, not rubbery or limp
- Leaves are fully unfurled and healthy green
- The plant has at least 5-6 mature stalks
- Stalks snap cleanly when bent, rather than bending or tearing
When To Stop Harvesting Rhubarb In Colorado
Knowing when to stop is just as important as knowing when to start. In Colorado, you should stop harvesting by mid-July at the latest. This gives the plant enough time to rebuild its energy reserves for winter dormancy.
Here’s why stopping early matters:
- Rhubarb needs its leaves to photosynthesize and store energy
- Continued harvesting into late summer weakens the crown
- Weak plants are more likely to die over Colorado’s harsh winters
- Late-season stalks become tough, stringy, and less flavorful
Signs It’s Time To Stop
Watch for these indicators that harvest season is over:
- Stalks become thinner and more spindly
- New growth slows down noticeably
- Stalks start to flower (bolt) in response to heat
- Leaves begin to yellow or develop brown edges
- You’ve harvested for 6-8 weeks straight
If your rhubarb sends up a flower stalk, remove it immediately. Flowering diverts energy from root and stalk production. But don’t harvest any more stalks after you see flowering—the plant is telling you it’s done for the season.
How To Properly Harvest Rhubarb
Harvesting rhubarb correctly prevents damage to the crown and ensures future harvests. Follow these steps:
- Select only thick, mature stalks—leave thin ones to grow
- Grasp the stalk near the base, close to the soil line
- Pull gently while twisting slightly to one side
- The stalk should snap free from the crown cleanly
- Never cut stalks with a knife—this leaves stubs that can rot
- Remove all leaves from harvested stalks immediately
Important: Rhubarb leaves are toxic due to oxalic acid. Never eat them or feed them to livestock. Compost them or discard them in the trash.
How Much To Harvest At One Time
Never take more than one-third of the stalks from a single plant at once. This leaves enough foliage for photosynthesis. Wait at least 2-3 weeks between harvests from the same plant.
For a mature, well-established plant (3+ years old), you can harvest 4-6 stalks per week during peak season. Younger plants should give less—maybe 2-3 stalks per week.
Preparing Your Rhubarb For Colorado’s Climate
Colorado’s dry climate and intense sun can stress rhubarb plants. Proper care before and after harvest makes a big difference.
Watering For Best Growth
Rhubarb needs consistent moisture, especially during the harvest period. Colorado’s low humidity means soil dries out fast. Water deeply once or twice a week, depending on rainfall.
- Give plants 1-2 inches of water per week during growth
- Water at the base, not overhead, to prevent leaf diseases
- Mulch around plants with 2-3 inches of organic matter
- Mulch helps retain moisture and keeps soil cool
Fertilizing After Harvest
After you stop harvesting in July, give your rhubarb a boost. Apply a balanced fertilizer or well-rotted compost around the crown. This helps the plant store energy for next year.
Avoid high-nitrogen fertilizers late in the season. They encourage leafy growth that won’t harden off before winter. Use a low-nitrogen option like 5-10-10 instead.
Common Rhubarb Problems In Colorado
Colorado gardeners face some unique challenges with rhubarb. Here’s what to watch for:
Bolting (Flowering)
Rhubarb bolts when stressed by heat, drought, or sudden temperature changes. Colorado’s spring weather is notorious for swings from 80°F to freezing in one week. Bolting reduces stalk quality and signals the end of harvest season.
To minimize bolting:
- Plant in partial shade if possible
- Water consistently during dry spells
- Mulch to keep soil cool
- Remove flower stalks as soon as they appear
Frost Damage
Late spring frosts are common in Colorado. Rhubarb is cold-hardy, but new growth can be damaged by hard freezes below 25°F. If frost is forecast, cover plants with a frost cloth or old sheet overnight.
Frost-damaged stalks will look water-soaked and limp. Remove them promptly to prevent rot. The plant will usually send up new stalks within a week or two.
Pests
Colorado’s dry climate limits many pests, but a few can bother rhubarb:
- Slugs and snails: Rare in dry areas but common near irrigated lawns
- Rhubarb curculio: A small beetle that punctures stalks
- Aphids: Usually on leaves, not stalks
Most pests don’t require treatment. Hand-pick beetles or wash off aphids with water. Avoid pesticides that could harm beneficial insects.
Storing Your Harvested Rhubarb
Fresh rhubarb doesn’t last long. Use it within a few days for best quality. Here’s how to store it:
- Remove all leaves immediately
- Wash stalks thoroughly and pat dry
- Wrap stalks in a damp paper towel
- Place in a plastic bag in the refrigerator
- Use within 3-5 days
For longer storage, chop stalks into 1-inch pieces and freeze them. Frozen rhubarb keeps for 6-12 months. No blanching is needed—just wash, chop, and freeze in airtight bags.
Rhubarb Varieties That Do Well In Colorado
Not all rhubarb varieties perform equally in our climate. These varieties are known for good performance in Colorado:
- Victoria: Classic green-stalked variety, very productive
- Canada Red: Deep red stalks, sweeter flavor, good for Colorado
- Crimson Red: Bright red, tender stalks, early harvest
- Valentine: Red inside and out, excellent for pies
- Riverside Giant: Large stalks, very cold-hardy
Choose varieties suited to your elevation. Most red varieties need more heat to develop color, so they may stay greenish at high elevations. That’s fine—green rhubarb tastes just as good.
Planting Rhubarb For Future Harvests
If you’re planting new rhubarb, plan for long-term success. A well-planted rhubarb patch can produce for 10-15 years or more.
When To Plant
In Colorado, plant rhubarb crowns in early spring as soon as the soil can be worked. This is usually March or April, depending on elevation. Fall planting is riskier because young plants may not establish before winter.
Where To Plant
Choose a spot with full sun to partial shade. In Colorado’s intense sun, some afternoon shade is beneficial, especially at lower elevations. Rhubarb needs well-draining soil—heavy clay can cause crown rot.
Space plants 3-4 feet apart. Rhubarb has large root systems and needs room to spread. Crowded plants produce fewer and smaller stalks.
Soil Preparation
Colorado’s soil is often alkaline and low in organic matter. Prepare the planting bed by mixing in 2-3 inches of compost or well-rotted manure. Add a handful of bone meal for phosphorus, which supports root development.
If your soil is heavy clay, consider planting in raised beds. Rhubarb hates wet feet, and clay soils drain slowly in our spring snowmelt.
First Year Care: No Harvesting
This is the most important rule for new rhubarb plants: Do not harvest any stalks during the first year. The plant needs all its energy to establish a strong root system. Harvesting too early weakens the crown and reduces future yields.
In the second year, you can take a few stalks—maybe 2-3 per plant. By the third year, the plant is mature enough for full harvests.
Dividing And Rejuvenating Old Plants
Rhubarb plants can become overcrowded after 5-7 years. Signs include smaller stalks, fewer stalks, and a hollow center in the crown. Dividing rejuvenates the plant.
Divide rhubarb in early spring or fall:
- Dig up the entire crown with a shovel
- Cut the crown into sections, each with at least one bud
- Replant divisions at the same depth they were growing
- Water well and mulch
- Don’t harvest from divided plants for one year
Frequently Asked Questions
Can I harvest rhubarb after it flowers?
Yes, but the stalks will be tougher and less flavorful. Once a plant flowers, it’s usually best to stop harvesting for the season. Remove the flower stalk to encourage the plant to focus on root storage.
What is the best month to harvest rhubarb in Colorado?
For most Colorado gardeners, June is the peak harvest month. Lower elevations may start in late May, while higher elevations may harvest into early July. The exact best month depends on your specific location and weather patterns.
Can I eat rhubarb leaves?
No. Rhubarb leaves contain high levels of oxalic acid, which is toxic to humans and animals. Only eat the stalks. Remove and discard leaves immediately after harvesting.
Why is my rhubarb not growing well in Colorado?
Common reasons include: planting too deep, poor soil drainage, insufficient water, or harvesting too much too soon. Also, Colorado’s alkaline soil may need ammendment with compost or sulfur to lower pH. Rhubarb prefers slightly acidic soil around pH 6.0-6.8.
How do I protect rhubarb over Colorado winter?
Rhubarb is very cold-hardy and usually needs no special protection. After the ground freezes, apply 2-4 inches of mulch (straw or leaves) over the crown. Remove mulch in early spring before new growth appears. In very exposed mountain sites, a layer of evergreen boughs can provide extra insulation.
Final Tips For Colorado Rhubarb Success
Growing rhubarb in Colorado is rewarding if you follow a few key practices. Remember these takeaways:
- Patience is essential—wait for 10-inch stalks before harvesting
- Stop harvesting by mid-July to let plants recover
- Never take more than one-third of stalks at once
- Water deeply and consistently during dry spells
- Mulch to keep soil cool and moist
- Remove flower stalks immediately
- Don’t harvest first-year plants at all
- Divide overcrowded plants every 5-7 years
With proper timing and care, your rhubarb patch will provide years of delicious harvests. Colorado’s cool springs are actually ideal for rhubarb—the plant prefers temperatures between 40-75°F. Our summer heat is the main challenge, so early harvesting is key.
Start checking your rhubarb in late May. Look for thick, firm stalks at least 10 inches long. Pull them cleanly from the base, remove the leaves, and enjoy your harvest. With the right timing, you’ll get the best flavor and texture from your Colorado-grown rhubarb.
Remember that each growing season is different. A cold, wet spring might delay harvest by a week or two. A warm spring could push it earlier. Always let the plant’s condition guide you, not just the calendar. Your rhubarb will tell you when it’s ready.