Pennsylvania’s cold winters make early spring the only reliable time to plant rhubarb for a full season. Knowing the best time to plant rhubarb in Pennsylvania is the first step to a harvest that lasts for years. Rhubarb is a hardy perennial that thrives in the Keystone State’s climate, but timing is everything if you want strong crowns and tender stalks.
Planting too early risks frost damage to new growth, while planting too late means the roots won’t establish before summer heat. The sweet spot is when the soil is workable and the danger of deep frost has passed. This guide walks you through exactly when and how to plant rhubarb in Pennsylvania, from the eastern counties to the western ridges.
Best Time To Plant Rhubarb In Pennsylvania
The ideal window for planting rhubarb in Pennsylvania is from mid-March to mid-April. This timing aligns with the state’s last frost dates, which vary by region. In the southeastern part, like Philadelphia and Lancaster, you can start as early as mid-March. In the northern tier, such as Bradford or Susquehanna counties, wait until early to mid-April.
Rhubarb crowns need cool soil temperatures between 40°F and 50°F to root properly. If you plant when the ground is still frozen or waterlogged, the crowns may rot. If you wait too long, the plants struggle to establish before the heat of June.
Check your local frost dates using the Pennsylvania State Extension’s maps. A general rule: plant two to four weeks before the last expected spring frost. This gives the roots time to settle without the shoots getting hit by a hard freeze.
Why Spring Planting Works Best In Pennsylvania
Rhubarb is a cool-season crop that goes dormant in summer heat. Spring planting lets the crowns develop a strong root system before the weather turns warm. The plant then uses that energy to produce stalks the following year.
Fall planting is risky in Pennsylvania because the ground freezes early in many areas. If you plant in October, the crowns may not have enough time to root before the soil temperature drops below 40°F. Spring is the safe bet for a long-lived patch.
Regional Variations Across Pennsylvania
Pennsylvania spans USDA hardiness zones 5a to 7b. This affects your planting calendar.
- Zone 5a (northwest and north-central): Plant in early to mid-April. Soil warms slowly here.
- Zone 6a (central and parts of the northeast): Plant from late March to early April.
- Zone 6b (south-central and some valleys): Mid-March to early April works well.
- Zone 7a and 7b (southeast and Philadelphia area): Plant from mid-March to late March. You can sometimes push to early March if the soil is dry.
Check your specific zone using the USDA map. Then adjust your planting date by about one week earlier for each warmer zone.
Preparing Your Soil For Rhubarb
Rhubarb needs well-drained soil with a pH between 6.0 and 6.8. Pennsylvania’s clay-heavy soils can be a challenge. If your soil stays wet after rain, consider building a raised bed.
Test your soil pH at least six weeks before planting. You can get a kit from a garden center or send a sample to Penn State’s soil lab. If the pH is below 6.0, add lime according to the test results.
Steps To Prepare The Planting Bed
- Choose a spot with full sun. Rhubarb needs at least six hours of direct sunlight daily.
- Remove all weeds, especially perennial ones like quackgrass. Rhubarb hates competition.
- Dig the soil to a depth of 12 inches. Break up any large clumps.
- Mix in 2 to 4 inches of well-rotted compost or aged manure. This adds organic matter and nutrients.
- Add a balanced fertilizer like 10-10-10 at a rate of 1 pound per 100 square feet. Work it into the top 6 inches of soil.
If you have heavy clay, add sand or perlite to improve drainage. Rhubarb roots rot easily in waterlogged soil.
Choosing The Right Rhubarb Variety
Not all rhubarb varieties perform the same in Pennsylvania. Some are more cold-hardy, while others produce earlier stalks. Pick a variety that matches your region and taste.
Top Varieties For Pennsylvania
- Victoria: A classic green-stalked variety. It’s reliable and produces well in cooler climates. Stalks are tender but less red.
- Canada Red: Deep red stalks with a sweet flavor. It’s hardy to zone 4, so it handles Pennsylvania winters well.
- Crimson Red: Bright red stalks that are sweet and tender. Good for zone 5 and 6.
- Valentine: A newer variety with excellent cold tolerance. Stalks are red and hold their color when cooked.
- Glaskins Perpetual: A green-stalked variety that produces over a long season. It’s less prone to bolting in heat.
Avoid seed-grown rhubarb if you want consistent quality. Buy crowns from a reputable nursery. Crowns are one-year-old root divisions that establish faster.
How To Plant Rhubarb Crowns
Planting rhubarb correctly sets the stage for a decade or more of harvests. Follow these steps for the best results.
Step-By-Step Planting Guide
- Dig a hole that is 12 inches wide and 12 inches deep. Space holes 3 to 4 feet apart. Rows should be 4 to 5 feet apart.
- Place the crown in the hole with the buds facing upward. The top of the crown should be 1 to 2 inches below the soil surface.
- Backfill the hole with the soil you removed. Gently firm it around the roots.
- Water thoroughly after planting. This settles the soil and removes air pockets.
- Add a 2-inch layer of mulch around the crown. Use straw, shredded leaves, or wood chips. This keeps the soil cool and moist.
Do not cover the buds with more than 2 inches of soil. If planted too deep, the crown may rot. If too shallow, it may dry out or heave during freeze-thaw cycles.
Container Planting Option
If you have limited space or poor soil, grow rhubarb in a large container. Use a pot that is at least 18 inches deep and 24 inches wide. Fill it with a mix of potting soil and compost. Plant the crown at the same depth as in the ground.
Container-grown rhubarb needs more frequent watering. Check the soil every few days during dry spells. Move the pot to a sheltered spot in winter to protect the roots from extreme cold.
Caring For Newly Planted Rhubarb
After planting, rhubarb needs consistent care through its first growing season. The first year is about root development, not stalk production.
Watering
Keep the soil evenly moist but not soggy. Water once a week if there is no rain. In dry spells, water twice a week. Use a soaker hose or drip irrigation to avoid wetting the leaves, which can cause fungal diseases.
Fertilizing
Apply a balanced fertilizer in early spring when new growth appears. Use 10-10-10 at a rate of 1/2 cup per plant. Scatter it around the crown, not directly on it. Water after applying.
In midsummer, side-dress with compost or a nitrogen-rich fertilizer. This supports leaf growth, which feeds the roots.
Weed Control
Weeds steal nutrients and water from young rhubarb. Hand-pull weeds regularly. Mulch helps suppress them. Avoid using herbicides near rhubarb, as the plant is sensitive to chemicals.
First Year Harvest Rules
Do not harvest any stalks in the first year. The plant needs all its leaves to build a strong root system. If you see flower stalks, cut them off immediately. Flowering diverts energy from root growth.
In the second year, you can harvest a few stalks. Take no more than one-third of the stalks from each plant. In the third year and beyond, you can harvest fully.
Common Problems And Solutions
Rhubarb is generally low-maintenance, but a few issues can arise in Pennsylvania gardens.
Pests
- Rhubarb curculio: A small beetle that punctures stalks and crowns. Remove and destroy affected stalks. Keep the area weed-free.
- Aphids: These suck sap from leaves. Spray with a strong stream of water or use insecticidal soap.
- Slugs and snails: They chew holes in leaves. Set out beer traps or use diatomaceous earth around the plants.
Diseases
- Crown rot: Caused by wet soil. Improve drainage and avoid overwatering. Remove infected plants.
- Leaf spot: Fungal spots on leaves. Remove affected leaves and avoid overhead watering.
- Powdery mildew: White coating on leaves. Improve air circulation and apply a fungicide if needed.
Bolting (Flowering)
Rhubarb bolts when stressed by heat or drought. Cut flower stalks as soon as they appear. This redirects energy back to the roots. In hot summers, provide shade cloth to reduce stress.
Harvesting Rhubarb In Pennsylvania
Harvest time comes in the second year after planting. In Pennsylvania, the main harvest season runs from May through June. Stalks are ready when they are 12 to 18 inches long and firm.
How To Harvest
- Grasp the stalk near the base.
- Pull it gently to one side. It should snap off cleanly.
- Do not cut the stalk with a knife. Cutting leaves a stub that can rot.
- Remove all leaves from the stalk. Leaves are toxic due to oxalic acid.
Harvest only stalks that are thick and firm. Thin, spindly stalks indicate the plant is still young or stressed. Leave them to grow.
When To Stop Harvesting
Stop harvesting by early July in most of Pennsylvania. This gives the plant time to rebuild its energy reserves for winter. If you harvest too late, the plant may not survive the cold.
In cooler regions like the Poconos, you can harvest into mid-July. In warmer areas, stop by late June.
Winter Care For Rhubarb In Pennsylvania
Rhubarb is hardy, but Pennsylvania winters can be harsh. A little protection helps ensure a strong start in spring.
Mulching For Winter
After the first hard frost, cut back the dead leaves to 2 inches above the crown. Apply a 4- to 6-inch layer of mulch over the crown. Use straw, shredded leaves, or pine needles. This insulates the roots from freeze-thaw cycles.
Remove the mulch in early spring when the soil starts to warm. Do not leave it on too long, or the crown may rot.
Dividing Rhubarb Crowns
Every 5 to 7 years, rhubarb crowns become overcrowded. Divide them in early spring while the plants are still dormant. Dig up the crown and cut it into sections with a sharp knife. Each section should have at least one bud and a good root system.
Replant the divisions immediately at the same depth. This rejuvenates the patch and gives you more plants.
Frequently Asked Questions
Can I plant rhubarb in the fall in Pennsylvania?
Fall planting is risky because the ground freezes early in many parts of Pennsylvania. The crowns may not root before winter. Spring planting is much more reliable.
How long does rhubarb take to grow from crowns?
From planting, you can expect a small harvest in the second year. Full harvests start in the third year. Crowns establish faster than seeds.
What is the best month to plant rhubarb in Pennsylvania?
April is the best month for most of Pennsylvania. In the southeast, late March works. In the north, early to mid-April is ideal.
Can rhubarb grow in partial shade in Pennsylvania?
Rhubarb prefers full sun. In partial shade, it produces fewer stalks and may become leggy. Aim for at least six hours of direct sun daily.
Do I need to fertilize rhubarb every year?
Yes. Apply a balanced fertilizer in early spring and compost in midsummer. This keeps the soil fertile and the plants productive.
Final Tips For Success
Planting rhubarb at the right time is the most important factor for a thriving patch in Pennsylvania. Early spring gives the crowns a head start before summer heat arrives.
Choose a sunny spot with well-drained soil. Prepare the bed thoroughly before planting. Water and mulch consistently during the first year.
Be patient with your first harvest. Waiting until the second or third year pays off with larger, sweeter stalks. With proper care, your rhubarb patch can produce for 10 to 15 years.
If you live in a colder zone like 5a, consider adding extra winter mulch. In warmer zones like 7b, watch for bolting in hot weather and provide shade if needed.
Rhubarb is a forgiving plant once established. Stick to the spring planting window, and you will have a reliable source of tart stalks for pies, sauces, and jams. Enjoy the process of growing this old-fashioned perennial in your Pennsylvania garden.