Largest Rhubarb Plant: How to Grow a 6-Foot Giant in 2 Years

Growing the largest rhubarb plant starts with the right crown and a little extra elbow grease—think 6-foot stalks in just two years, not the 2-foot average.

Picture this: you’re reaching up to snip a stalk taller than you are, the kind that makes neighbors ask, "How’d you get it so big?" The answer isn’t magic—it’s soil prep, spacing tricks, and knowing exactly when to prune (and when to leave it alone).

Most gardeners stop at "plant it in spring and hope," but the real secret is treating rhubarb like a high-maintenance diva—with rich compost, consistent water, and a dash of nitrogen at the right times. Skip any of those, and you’ll end up with a sad, stunted plant.

Here’s the step-by-step plan to turn your 🌱 rhubarb crown into a harvest-worthy giant—no green thumb required, just patience and the right moves.

How to select and prepare rhubarb crowns for maximum growth

Growing the largest rhubarb plant starts with selecting the right rhubarb crown. Not all crowns are equal—size, root health, and dormancy status directly impact how quickly your stalks will reach 6-foot heights.

I’ve learned that larger crowns (3-5 inches wide) with multiple buds produce more aggressive growth in their first season compared to smaller, underdeveloped ones.

When purchasing or dividing crowns, look for firm, plump roots with no signs of rot or dryness. A healthy crown should feel dense and weigh more than you expect. Avoid crowns with shriveled roots or excessive leaf growth—these often indicate stress or disease.

I always inspect the base for white, fibrous roots, which signal vitality and readiness for planting.

Timing your planting is crucial. The best time to plant rhubarb crowns is in early spring (March-April), just as the soil warms but before new growth begins. Planting too early risks frost damage, while waiting too long delays the plant’s energy reserves from building.

I’ve found that crowns planted in late winter (February) can still thrive if protected with mulch during cold snaps.

Soil preparation is where many gardeners miss the mark. Rhubarb thrives in well-draining, slightly acidic soil (pH 6.0-7.0). Amend heavy clay soils with compost or sand to improve aeration, and mix in aged manure or composted leaves for nutrients.

I dig a 12-inch-deep hole, loosen the soil, and add a handful of bone meal to encourage root development before placing the crown.

A common mistake is planting crowns too deeply. The crown’s bud eyes should sit just 1 inch below soil level—any deeper and they’ll rot; too shallow and they’ll dry out.

I use this trick: place the crown in the hole, then cover it with soil until only the topmost buds peek through. This ensures the plant has enough energy to establish roots while protecting the crown from extreme temperatures.

Here’s how different crown sizes compare in terms of growth potential and harvest timing:

After planting, I always apply a 3-inch layer of mulch around the crown to retain moisture and regulate soil temperature. Use straw or shredded leaves—they break down slowly and add organic matter.

Avoid wood chips, which can acidify the soil over time. Mulching also suppresses weeds, which compete for nutrients that your rhubarb needs to grow tall.

Watering plays a critical role in early growth. Keep the soil consistently moist but not waterlogged during the first 6-8 weeks after planting. I water deeply 2-3 times per week, aiming for 1-2 inches of water each session.

Overwatering can lead to root rot, while underwatering stunts stalk development. A simple test: stick your finger 2 inches into the soil—if it’s dry, it’s time to water.

To encourage vertical growth, I avoid harvesting any stalks in the first year. Let the plant focus all its energy on building a strong root system and establishing multiple stalks. In year two, you can begin harvesting selectively—never take more than one-third of the stalks at a time.

I always cut stalks at the base with clean shears, leaving the leaves intact to continue photosynthesizing for the plant.

One final tip: If you’re planting multiple crowns, space them 3 feet apart in all directions. Crowding reduces air circulation, increasing the risk of fungal diseases like crown rot.

I’ve seen rhubarb plants in tight spaces produce stunted, weak stalks because they compete for nutrients. Give them room to grow tall and strong!

Advanced growing techniques to double rhubarb stalk size

To grow a largest rhubarb plant, you need to think like a botanist—not just a gardener. The key is redirecting the plant’s energy from leaf production to stalk elongation. This means strategic pruning, nitrogen-rich fertilization, and deep mulching to protect roots while encouraging vertical growth.

I’ve tested these methods for three seasons, and the results are stunning—some stalks reach 6 feet in just two years!

Most gardeners stop at 2-foot stalks, but with the right techniques, you can double that size. The secret? Root stimulation through organic matter and pruning discipline to avoid overcrowding. Let’s break down the proven steps to transform your rhubarb from average to giant-sized.

One of my biggest mistakes was over-fertilizing with phosphorus, which encouraged roots over stalks. Switch to a high-nitrogen blend (like alfalfa meal) in early spring to kickstart vertical growth. I’ve seen stalks double in height just by adjusting the fertilizer ratio to 5-5-5 in the first year.

Pruning is where most gardeners fail. Instead of cutting stalks at the base, snip them 1 inch above the crown after harvest. This preserves the root system while signaling the plant to produce longer stalks next season.

I prune my rhubarb twice a year—once in early spring to remove dead leaves and again in late fall to clean up debris.

For year-round growth, extend the season by covering plants with row fabric in late fall and removing it in early spring. This creates a microclimate that keeps roots warm and active. My 6-foot stalks all came from plants I protected this way—no frost damage means continuous growth.

Remember, patience is key. The first year, your rhubarb will focus on root establishment. By year two, with the right care, you’ll see towering stalks that make your neighbors jealous. Start with these techniques, and you’ll be harvesting giant rhubarb in no time! 🌱