When you're preparing your garden beds for a new season, don't rip your plants out of the ground, roots and all. If you do, you'll be robbing your soil microbes of a good meal and degrading your long-term soil fertility.
Yes you can reuse soil with roots in it. However, try and remove as many as possible. Especially the larger roots left behind. Leaving some smaller ones shouldn't hurt anything.
Leaving the roots in works best in large pots/planters, and not so well in smaller pots. Especially down to cell pot size. Outdoors, in the ground, leaving the roots is better, because the soil microbes will digest the roots quickly, improving the soil.
If any of the old tree's roots are still in the ground, the newly planted young tree may not have enough room to grow. The sawdust left behind from grinding and removing a stump usually drastically changes the structure and nutrient balance of the soil making it difficult for the new tree to grow.
To promote good nutrient absorption, trim the roots and loosen up the root ball before replanting. Use a sharp knife or pruning shears for this job, removing as much as the bottom third of the root ball if necessary. Don't be surprised if what you cut off is a thick tangle of root tissue.
The more you upsize your plant's pots, the bigger the plant will continue to grow. When you can't upsize your plant container any longer, or when you want to maintain the size of your plant the way it is, because your plant is inside a terrarium, or it is a bonsai, root pruning is the answer.
The amount of time it takes for tree roots to decompose will depend on the tree species. But generally, it takes between 5 and 10 years, and hardwoods take longer than softwoods.
Trim the Roots
To prune the roots, start with a pair of scissors, pruning shears, or sharp knife. Cut around and under the plant's root ball, removing both roots and soil. You can be pretty aggressive, cutting away both large and small roots.
The root and shoot tip has actively dividing apical meristematic cells which adds new cells and cause rapid growth. The root will stop growing if the tips of the root are removed.
If done properly, root pruning can improve the plant's growth and overall health. This is especially true with container plants that can become “pot-bound,” with the roots girdling around the inside of the pot. This also means those roots can't take up enough nutrients and water to support the plant.
Dealing with Root Rot
Prepare plants for replanting by cleaning the roots gently under running water and removing all brown, mushy roots with a sharp pair of scissors. Cut the healthy root just above the damaged area. Work quickly to replant within a few hours.
Tree roots are a natural material that will decompose over time. However, depending on the size and health of the tree and the remaining roots, it may take a long time. Some roots take decades before they fully disintegrate and add nutrients back into the soil.
There is no question that living roots build soil! Roots provide structure for the soil to hang on to when destructive forces of wind and water occur. Accomplishing this process occurs through the “great exchange” of nutrients and water from the soil in exchange for carbon (carbohydrates) from the plant.
Remove about one-third or more of the old potting mix surrounding the plant's roots. As it grew, your plant removed some or all of the nutrients in the current mix, so you'll want to give it fresh potting mix or soil. Pour a layer of fresh potting soil into the empty planter and pack it down, removing any air pockets.
Do You Keep Old Soil When Repotting? Removing the soil from the roots depends on a number of factors. It's important to understand that discarding old healthy soil can cause damage to your plant's roots, while leaving moldy soil can cause your plants health to deteriorate.
Instead, the roots are slowly decomposed by soil microbes deep underground. Worms, bacteria, fungi, and other organisms all nibble away, ultimately converting the dead roots back into nutrients available for other living plants.
Trust the Process
"You must grow your roots at least one to two inches, which means you will have to wait anywhere from two to four months to allow your hair to grow an inch or two. (If you can, wait even longer)."
Generally, when you see a few inch-long roots, you can move your cutting from water into soil. Waiting until there are several roots will increase the chance of survival during the transplant. But you don't want the roots to be too long, as they can easily get tangled during the process.
Roots are essential for reaching water and nutrients, for anchorage to the ground, but also for interacting and communicating with microorganisms in the soil. A long root enables the plant to reach deeper, more humid layers of soil, for example during drought.
Plants become root bound (also called 'pot bound') when they outgrow their container and aren't repotted in a larger one. So, their roots grow around and around, which halts growth.
Don't remove more than 1/3 of anchoring roots.
Avoid removing large, or anchoring, roots. Anchoring roots provide a lot of support and branch off into many smaller roots. If you must remove some, don't remove over 1/3 of all anchoring roots.
Soaking Your Bare Root Plant
Before planting, you'll need to soak the roots for at least 2 hours and up to 8 to 12 hours, but no longer than 24 hours maximum. This is an important step because it will allow the roots to re-hydrate and absorb water.
Plants keep dirt from washing away
Roots not only keep plants in place, they secure soil, too. Roots grab onto soil to prevent erosion, and consequently, keep nutrients from flushing out of the system.