Rhubarb is a perennial vegetable that can remain productive for 15 years or more, but its vigor often declines after about eight to ten years due to overcrowding. Division and transplanting are necessary maintenance tasks to rejuvenate older plants, increase yield, and start new patches. In Minnesota, successful transplanting requires careful timing due to the short growing season and harsh winters.
Optimal Timing for Transplanting in Minnesota
The best time to transplant rhubarb aligns with the plant’s natural dormancy period, minimizing stress on the root system. This period offers two distinct windows for gardeners in Minnesota: early spring and late fall. Early spring transplanting should occur as soon as the soil is workable, which is typically before new growth starts or when the leaf stalks are less than eight inches tall.
The alternative, and often preferred, time is late fall, after the first hard frost has caused the foliage to die back. This timing allows the plant to focus its energy on establishing new roots over the winter. Transplanting while the plant is dormant is crucial because it ensures the root system can recover before the next growing season begins. Rhubarb requires a cold period below 40 degrees Fahrenheit to break dormancy and stimulate spring growth, making Minnesota’s climate naturally suited for this process.
Preparing the New Site and Dividing the Crown
Selecting the new location requires attention to the plant’s long-term needs, as rhubarb is a heavy feeder. A site that receives full sun is best, although some afternoon shade is tolerated, and the soil must be well-drained to prevent the crown from rotting. Rhubarb will not thrive in waterlogged conditions, so incorporating organic matter, such as compost or well-rotted manure, is necessary to improve soil fertility and drainage.
Before digging up the plant, cut back the stalks to about two inches above the crown to conserve the plant’s energy for root growth. The entire root clump should be carefully lifted using a spading fork to avoid excessive damage to the roots. The mature root crown is then divided using a sharp spade or knife. Each new division must contain at least one strong bud, or “eye,” and a healthy portion of the root system.
The Physical Transplanting Process
Once the divisions are prepared, they must be replanted quickly to prevent the roots from drying out. Dig a planting hole wide enough to easily accommodate the entire root mass. The most critical step in replanting is controlling the depth of the crown, which is where the new buds will emerge.
The buds should be positioned approximately one to two inches below the soil surface when the hole is backfilled. Planting the crown deeper can lead to rot, while planting too shallowly may expose the buds to damage. After placing the division, the surrounding soil should be gently firmed to eliminate air pockets around the roots. Each new plant should be given at least three feet of space from its neighbors to allow for mature growth.
Essential Post-Transplant Care
Immediately after transplanting, the new divisions require a deep watering to settle the soil and hydrate the roots. Consistent moisture is necessary for the next few weeks until the plant establishes itself. After the initial watering, apply a thick layer of organic mulch, such as straw or shredded leaves, around the plant.
In Minnesota, this mulch layer is important for providing insulation and protecting the crown over the harsh winter. A layer of four to six inches of mulch should be added once the ground freezes to protect the crown from temperature fluctuations. Most importantly, no stalks should be harvested during the first full growing season after transplanting. Allowing the plant to dedicate its energy to developing a robust root system ensures long-term health and a plentiful harvest in subsequent years.