Idaho’s cold winters demand planting rhubarb only after the ground is fully workable. The best time to plant rhubarb in Idaho is early spring, typically from late March to mid-April, once the soil thaws and can be easily turned. This timing gives the crowns a full growing season to establish strong roots before the next winter.
Understanding Idaho’s Climate For Rhubarb
Idaho spans USDA hardiness zones 3 through 7, with most areas falling in zones 4 and 5. Rhubarb is a cold-hardy perennial that actually needs winter chill to produce well. The plant goes dormant in freezing weather and regrows when soil temperatures reach about 40°F.
Your local frost dates matter. In northern Idaho, the last frost can be as late as mid-May. In southern regions, it may come in early April. Rhubarb can handle light frosts, so you don’t need to wait until all frost danger passes.
Key Climate Factors For Idaho Growers
- Winter temperatures: Rhubarb needs at least 500 hours below 40°F for proper dormancy
- Spring thaw: Soil must be workable, not frozen or waterlogged
- Summer heat: Rhubarb prefers cool summers; Idaho’s high desert areas may need partial shade
- Rainfall: Consistent moisture is key, especially during establishment
Best Time To Plant Rhubarb In Idaho
For most Idaho gardeners, the ideal window opens when soil temperature reaches 40°F to 50°F. Check your soil with a thermometer or simply test by digging. If the soil crumbles easily and isn’t muddy, it’s ready.
Regional Timing Guide
Use these general guidelines based on your location:
- Northern Idaho (Coeur d’Alene, Sandpoint): Late April to early May
- Central Idaho (Boise, McCall): Early to mid-April
- Southern Idaho (Twin Falls, Pocatello): Late March to mid-April
- Eastern Idaho (Idaho Falls, Rexburg): Mid-April to early May
If you miss the spring window, you can plant rhubarb in early fall, about six weeks before the first hard frost. Fall planting gives roots time to settle before winter. However, spring planting is more reliable for beginners.
Signs Your Soil Is Ready
- The ground is no longer frozen to a depth of 6 inches
- Soil is moist but not soggy
- A handful of soil forms a loose ball that crumbles when tapped
- Daytime temperatures consistently stay above 40°F
- No standing water in the planting area
Choosing The Right Rhubarb Variety For Idaho
Not all rhubarb varieties perform equally in Idaho’s climate. Stick with cold-hardy types that mature early. Here are top picks:
- Victoria: Classic variety, reliable, good for northern Idaho
- Canada Red: Sweet, red stalks, disease resistant
- Crimson Red: Early harvest, bright color, cold tolerant
- Valentine: Deep red, vigorous grower, handles cold well
- Timperley Early: Very early season, good for short growing areas
Avoid varieties bred for warm climates, as they may not survive Idaho winters. Buy certified disease-free crowns from reputable nurseries.
Preparing Your Planting Site
Rhubarb is a perennial that can produce for 10 years or more. Choose a spot with full sun and well-draining soil. Partial shade works in hot areas like the Treasure Valley.
Soil Preparation Steps
- Test soil pH; rhubarb prefers 6.0 to 6.8
- Remove all weeds and grass from the bed
- Dig the soil to 12 inches deep
- Mix in 2 to 4 inches of aged compost or well-rotted manure
- Add a balanced fertilizer like 10-10-10 at 1 pound per 100 square feet
- Rake the bed smooth and level
If your soil is heavy clay, consider raised beds. Idaho’s clay soils can hold too much moisture, leading to root rot. Raised beds warm faster in spring too.
How To Plant Rhubarb Crowns
Planting rhubarb is straightforward. Follow these steps for success:
- Dig holes 2 to 3 feet apart in rows spaced 3 to 4 feet apart
- Make each hole about 2 inches deep
- Place the crown with the bud facing upward
- Cover with soil so the bud is just below the surface
- Water thoroughly after planting
- Add a 2-inch layer of organic mulch around the plant
Space plants generously. Crowded rhubarb produces thin stalks and is more prone to disease. Give each plant room to spread.
Planting From Seed Vs Crowns
Most gardeners plant crowns for faster harvests. Seeds take longer and may not produce true to variety. If you use seeds, start them indoors 8 to 10 weeks before your planting date. Transplant seedlings after the last frost.
Crowns are more reliable and give you a harvest in the second year. Seeds may take three years before you can pick stalks.
Caring For Newly Planted Rhubarb
After planting, your rhubarb needs consistent care through the first growing season. This is critical for long-term health.
Watering
Keep the soil evenly moist but not waterlogged. Water deeply once a week if rain is scarce. In Idaho’s dry summers, you may need to water twice a week. Drip irrigation works well to avoid wetting the leaves.
Mulching
Apply a 2 to 3 inch layer of straw, wood chips, or shredded leaves around each plant. Mulch keeps soil cool, retains moisture, and suppresses weeds. In northern Idaho, mulch also protects crowns from freeze-thaw cycles.
Fertilizing
Fertilize lightly in early spring with a balanced fertilizer. Avoid high-nitrogen formulas, which can cause excessive leaf growth at the expense of stalks. Side-dress with compost in midsummer.
Weed Control
Weeds compete for water and nutrients. Hand-pull weeds carefully to avoid disturbing rhubarb roots. A thick mulch layer reduces weed pressure.
Harvesting Rhubarb In Idaho
Do not harvest any stalks in the first year. The plant needs all its energy to establish roots. In the second year, you can take a few stalks. By the third year, you can harvest freely.
When To Harvest
Harvest when stalks are 12 to 18 inches long and firm. The best time is in spring and early summer. Stop harvesting by mid-July to let the plant store energy for winter.
How To Harvest
- Grasp the stalk near the base
- Pull gently while twisting slightly
- The stalk should snap off cleanly
- Remove all leaves immediately; they are toxic
- Leave at least half the stalks on each plant
Never cut stalks with a knife, as this can damage the crown and invite disease. Always pull by hand.
Common Problems And Solutions
Rhubarb is generally low-maintenance, but a few issues can arise in Idaho.
Bolting (Going To Seed)
If your rhubarb produces a flower stalk, remove it immediately. Bolting reduces stalk production. It’s common after a cold snap followed by warm weather. Keep plants well-watered to reduce stress.
Leaf Spot
Fungal leaf spot appears as brown or purple spots on leaves. Remove affected leaves and improve air circulation. Avoid overhead watering. In wet Idaho springs, this can be common.
Root Rot
Root rot happens in poorly drained soil. Ensure your planting site drains well. Raised beds help in clay soils. If a plant rots, remove it and don’t plant rhubarb in that spot for several years.
Pests
Rhubarb curculio is a small beetle that can damage stalks. Hand-pick beetles and remove nearby weeds like curly dock. Slugs may also be a problem in damp areas; use iron phosphate bait if needed.
Winter Care For Rhubarb In Idaho
Idaho winters can be harsh, but rhubarb is built for cold. Still, a little protection helps.
Fall Cleanup
After the first hard frost, cut back dead foliage to 2 inches above the crown. Remove all plant debris to prevent disease. Do not compost diseased leaves.
Mulching For Winter
Apply a 4 to 6 inch layer of straw or leaves after the ground freezes. This insulates the crown from temperature swings. In areas with heavy snow, the snow itself provides good insulation.
Spring Removal
Remove winter mulch in early spring when you see new growth. Leave a thin layer to retain moisture. If you remove mulch too late, the crowns may rot.
Dividing And Transplanting Rhubarb
Every 5 to 7 years, rhubarb plants become crowded and produce smaller stalks. Divide them in early spring or fall.
How To Divide Rhubarb
- Dig up the entire crown in early spring when soil is workable
- Use a sharp spade to cut the crown into sections
- Each section should have at least one large bud and healthy roots
- Discard old, woody center portions
- Replant divisions immediately at the same depth
- Water well and mulch
Divided plants may take a year to recover before producing well. Be patient and don’t harvest heavily the first year after division.
Companion Planting With Rhubarb
Rhubarb grows well with certain plants and poorly with others. Here are good companions:
- Strawberries: They share similar soil needs
- Horseradish: Deters pests
- Onions and garlic: Repel aphids and beetles
- Legumes: Fix nitrogen in the soil
Avoid planting rhubarb near potatoes, tomatoes, or cucumbers. These plants compete for nutrients and may spread diseases.
Using Rhubarb In The Kitchen
Rhubarb is tart and versatile. Use it in pies, jams, sauces, and even savory dishes. Remember that only the stalks are edible. Leaves contain oxalic acid and are toxic to humans and pets.
For best flavor, harvest stalks in cool weather. Hot weather makes stalks tough and stringy. Store unwashed stalks in the refrigerator for up to two weeks. You can also freeze rhubarb for later use.
Simple Rhubarb Sauce Recipe
- Wash and chop 4 cups of rhubarb stalks
- Combine with 1/2 cup sugar and 1/4 cup water in a saucepan
- Bring to a boil, then simmer for 10 minutes
- Stir occasionally until stalks break down
- Serve warm or cold over ice cream or yogurt
Adjust sugar to taste. You can add cinnamon or ginger for extra flavor.
Frequently Asked Questions
Can I plant rhubarb in Idaho in the fall?
Yes, but spring planting is more reliable. If you plant in fall, do it at least six weeks before the first hard frost. Mulch heavily to protect the crown.
How long does rhubarb take to grow in Idaho?
From planting a crown, you can expect a small harvest in the second year. Full production starts in the third year. Seeds take longer, often three years to harvest.
What is the best rhubarb variety for northern Idaho?
Victoria and Canada Red are top choices for northern Idaho. They handle cold winters well and produce consistently. Timperley Early works for short growing seasons.
Should I fertilize rhubarb in the first year?
Yes, but lightly. Use a balanced fertilizer at planting and again in midsummer. Avoid high-nitrogen fertilizers that encourage leaf growth over root development.
Can rhubarb grow in shade in Idaho?
Rhubarb prefers full sun but tolerates partial shade, especially in hot areas like Boise. In full shade, stalks will be thin and spindly. Aim for at least 6 hours of sun daily.
Final Tips For Idaho Rhubarb Growers
Planting at the right time sets you up for success. Remember that the best time to plant rhubarb in Idaho is early spring, as soon as the ground is workable. Don’t rush it if the soil is still frozen or too wet.
Choose a sunny spot with good drainage. Prepare the soil well with compost. Space plants generously. Water consistently, especially during dry spells. Mulch to keep roots cool and moist.
Be patient with your rhubarb. It takes a couple of years to reach full production. Once established, a rhubarb patch can produce for a decade or more with minimal care. Enjoy the harvest each spring and share with neighbors.
If you have heavy clay soil, consider raised beds or mounded rows. Idaho’s volcanic soils in some areas drain well, but clay pockets exist. Test your drainage by digging a hole and filling it with water. If it takes more than 24 hours to drain, improve the soil or use raised beds.
Rhubarb is one of the easiest perennials to grow in Idaho. With the right timing and care, you’ll have plenty of stalks for pies, jams, and sauces. Start your patch this spring and enjoy it for years to come.