Here’s a planting step that takes almost no effort and is easy to skip: make sure the root ball is soaked through before the plant goes into the ground or a new pot. It belongs on any list of ways to help reduce transplant shock, and it matters most for container plants that have been waiting a while to go in the ground.
Soaking is only half the trick, though. A root-bound plant also needs its circling roots loosened, and the hole or pot it goes into matters too. Here’s how to do all three.
The Tip: Soak the Root Ball Before You Plant
The Royal Horticultural Society puts it first in its steps for planting a shrub: make sure the root ball is completely soaked before planting, and standing it in a bucket of water is an easy option. For trees and shrubs, give containerized plants a good water before taking them out of their pots, and soak bare-root trees or shrubs for about 30 minutes before planting.
A University of Georgia horticulturist, Jim Midcap, gives the same advice for container shrubs. Water the plant two to three straight times before planting and make sure the root ball is thoroughly soaked. If it still feels dry, soak it in a bucket for a while just before planting. His bottom line: don’t plant it if the root ball is dry.
Neither of these sources calls for special water for the soak; a bucket of water is what they describe. Leave the pot in until the root ball is wet all the way through; you’ll feel the difference in weight when you lift it.
Houseplants moving to a bigger pot get a similar first step. Montana State University Extension lists “water the plant enough to moisten the root ball” as step one for repotting a houseplant.
Why a Dry Root Ball Causes So Much Trouble
Nursery potting mix and garden soil don’t behave the same way. Midcap explains that nurseries grow container plants in a mix of bark and sand because it drains so well. The catch is that it also dries out quickly, and once it gets really dry, the bark is hard to wet again. “You may think you’re watering enough,” he says, but the plant really isn’t getting enough moisture to survive.
It can happen right after planting, too. On very warm or windy days, he says, the original bark mixture can dry out thoroughly in 24 to 48 hours, even though the backfill soil around it stays wet. Until the roots grow out into the surrounding soil, the plant still depends on the mix in its root ball for water.
University of Arizona Cooperative Extension makes the same point for trees and shrubs: if the irrigation well (the watering basin around the plant) is wider than the root ball, the original root ball may stay dry even though the surrounding soil is wet. And UF/IFAS Extension says to keep mulch off the top of the root ball, because less rain and irrigation water seeps into it when it’s covered, and the root ball may dry out.
So dry soil around a newly planted root ball is not a safety net. It’s another way for the root ball to end up too dry.
Soaking Won’t Untangle Circling Roots
Water rehydrates a root ball; it doesn’t straighten roots that have been circling the pot for months. The roots of pot-bound plants are unlikely to spread out into new soil or compost without first being physically loosened, and roots spiraling around the bottom and sides need teasing out and possibly a light trim.
Signs a Plant Is Root-Bound
University of Illinois Extension lists these signs that a potted plant needs repotting:
- Roots growing through the drainage holes
- Roots showing on the soil surface
- A soil mass filled with roots
- New leaves smaller than normal
- Wilting between normal waterings
Other signs: a plant that needs water too frequently, a top-heavy plant that wants to tip over, and lower leaves yellowing and falling off. Some plants seem to do well when pot-bound while others do not, so check your plant’s own needs.
How to Loosen Circling Roots
- Gently pull circling roots apart. Pull roots away from one another if they are circling the pot, or cut and/or unwind them.
- Cut into a tight root mass. For an extremely root-bound plant, cutting the roots is necessary: use a sharp, sterile knife or clipper to cut about half an inch deep into the roots on all sides and the bottom, then tease the roots apart with your fingers.
- Shave a shrub’s root ball. For shrubs going into the ground, cut off roots that circle the trunk and shave off the outside of the root ball. Research shows this increases root growth away from the root ball.
Repotting a Root-Bound Plant: Bigger Pot, Same Pot or Divide
You have three choices.
- A slightly bigger pot. The new pot should be no more than one third larger than the current one; another rule of thumb is about one third wider and deeper.
- The same pot, with root pruning. Many plants can stay healthy for years in the same size container if the roots are pruned. A light trim of up to 15% of the root system every few years can be enough. When repotting a pot-bound plant back into the same container with fresh compost, prune off up to a quarter of the outermost roots.
- Divide it. Herbaceous perennials can be divided at repotting time and the divisions replanted in the same container. More on dividing and transplanting perennials.
To repot, put a layer of soil in the bottom of the new pot (usually an inch or two), center the root ball, fill the sides to about an inch from the top, tap the pot to settle the soil, then water thoroughly and let it drain. Keep the plant at the same depth it grew in the old pot. Add water until some comes out of the drainage holes, so you know it has soaked right through. Our guide to repotting a houseplant has more.
Afterward, give it a few days in indirect light to reduce transplant shock, and no fertilizer for at least two weeks while the roots regrow. Some yellowing or leaf drop after repotting is normal.
Planting in the Ground: Wide, Not Deep
Once the root ball is soaked and the roots are loosened, give the plant a hole it can grow out of.
- Dig wide and shallow. Dig to the same depth as the root ball but three times as wide. Deeply planted shrubs can become stressed and grow poorly.
- Set it on firm soil. Loose soil under the root ball should be tamped with your foot so the plant does not sink after planting, and the top of the root ball can sit about an inch above the surrounding soil.
- Refill with the soil you dug out. Loosely fill the space with the soil that came out of the hole, unamended. (Mixing some organic matter into the removed soil is also suggested when it is very sandy or heavy clay, so the sources differ on that point.)
- Water as you fill. Slowly add water when the hole is about half filled, to soak the root ball and settle the backfill, then finish filling. Firm the soil with your heel and water well.
If you set a plant on a soft mound of loose soil in the bottom of the hole, it can sink as that soil settles. That’s why you firm it first.
Keep the Root Ball Moist While It Settles In
Water shrubs right after planting and keep up regular irrigation until they are established. For container shrubs, Midcap recommends watering two to three times a week for the first four to six weeks, but warns that overwatering in clay soils can kill plants just as surely as not watering at all. In clay soil, he also says to leave the top of the potting mix exposed, since covering it with clay can seal it so moisture can’t get in.
Just brought a plant home? Before you reach for a bigger pot, read when to repot plants after buying.
Do you soak your plants before they go in the ground? Tell us how it worked in the comments!
Frequently Asked Questions
Should you soak a plant’s roots before planting?
Yes, especially if the root ball is dry. Make sure the root ball is completely soaked before planting a shrub; standing it in a bucket of water is an easy option. Water a container plant two to three times before planting, and don’t plant it while the root ball is dry.
How long should I soak a root ball before planting?
Long enough to wet it all the way through. Soak bare-root trees and shrubs for about 30 minutes before planting. For a dry container plant, soak it in a bucket for a while just before planting, after watering it two to three times.
Does soaking fix a root-bound plant?
No. Soaking rewets the root ball, but pot-bound roots are unlikely to spread into new soil unless they are physically loosened. Tease circling roots apart, and for a tight mass, cut about half an inch deep into the roots on all sides and the bottom, then tease them apart.
How big should a planting hole be?
About three times as wide as the root ball and no deeper. Dig to the same depth as the root ball but three times as wide; deeply planted shrubs can become stressed and grow poorly. Firm loose soil under the root ball so the plant does not sink.
Can I repot a root-bound plant into the same pot?
Yes. Many plants stay healthy for years in the same size container if the roots are pruned, and a light trim of up to 15% of the root system every few years can be enough. For a pot-bound plant going back into the same pot, prune off up to a quarter of the outermost roots and add fresh compost. See our repotting guide.