First off, don’t buy root bound plants. It’s just a bad business, trouble and tears. In general, you should always try to buy the youngest plants you can find. They are healthier than plants which have spent more time in a pot, and will quickly grow to match the size of older, more expensive–and more likely than not–root bound plants.
How do you know if the plant is root bound? Look at the bottom of the pot and see if roots are poking out the bottom. This is a bad sign. Don’t be afraid to gently ease the plant out of the pot to check its condition. If you see more roots than soil, this is a bad thing. If you’re buying fruiting or flowering seedlings, look for the ones which have not yet flowered, even though the ones which have flowered are cuter and may look like they have more promise. They’d don’t. They’re flowering or fruiting out of desperation to spread their seed before they expire in their pot prisons.
But sometimes we end up with a root bound plant. This week, in a fit of madness which doesn’t make a lot of sense in retrospect, Erik and I broke our own rules, doing two things we never do: We 1) bought a couple of plants at The Home Despot and 2) we bought these plants in gallon-sized pots. The plants had already put up flowers. And yes, of course they were root bound. Extraordinarily so. They were living in dense pots made of their own roots.
As I tried to resuscitate and plant these babies, I realized that I should post this technique on the blog, in case it might be helpful to others. Forgive the photos. Erik wasn’t around to help me take them, and the battery on the camera was flashing red, but I needed to get those plants in the ground as quickly as possible. I only had time for a couple of bad shots.
How to Save Root Bound Plants
First off, I’ve found that root bound plants are often dehydrated plants, because the pots are mostly full of roots, making the soil hard and water repellent. If this is so, it helps to give the plants a good soaking before you un-pot them by placing them in a bucket of water for a few minutes.
Method A) Mildly root bound plants can be helped along by gently massaging the root ball with your hands just before planting to loosen the roots and open the ball if it has become hard-packed. If there are any big, long roots circling the root ball, trim those short. You can do a similar thing with a hose to open up the soil and loosen the root ball.
Method B) If your plant is extremely root bound, as mine were today, you’ll find you can’t simply work the roots apart with your fingers because they’ve formed a sort of impervious mat or pseudo-pot of themselves. In this case, you have to be ruthless. Get yourself a sharp knife and make long vertical cuts down the sides of the root ball–how many depends on the size of plant, and what you think is best, but I find I usually make 3 to 5 cuts. These cuts do violence to the roots, but will allow new root growth at the cut sites, giving the plant a chance to spread its roots out in your garden’s soil, instead of trying to live within its own, self-made prison.
In these extremes cases, there is also usually a thick mat of tangled roots at the bottom of the root ball, pressed into the exact shape of the pot bottom. I tear this layer off. Then I put my thumbs up the middle of the root ball and stretch it open just a little if necessary, gently, to make sure the center is soft and not rock hard or densely tangled.
Get your plants in the ground as soon as you can after these operations. If possible, work in the shade, or in the early morning or evening, so the plants don’t spend much time with their tortured root balls exposed to the midday sun. Water well, and maybe top dress the new plantings with a handful of worm castings, or water with worm casting tea, or some other kind of plant pick-me up, to apologize to them for all of the rough handling.
It is very important to watch your plants closely after transplanting. They are like critical care patients until they begin to grow new roots. Until that time, you’ll likely have to water them more frequently than a normal plant, because their root structure is all messed up. If the sun is strong, provide them with some shade. Also consider mulching to slow down water loss. Baby them as much as you can.
[ETA: One of our readers reminds me that another way to up your chances of success is to trim back the foliage of the plant. Fewer leaves means it will need less water, and can spend more energy growing new roots.]
No plant wants to be handled this way but with luck and care, the plant might do well afterward. The only alternative is planting it root bound, and no root bound plant can thrive. As in its pot, it will be hard to water, and it will live a short, sad life, always sickly and constrained, if it makes it at all.
As a caveat, I know of a few types of plant which can’t abide any fooling with their roots at all, like bougainvillea, for one, but if you buy a root bound plant, or allow one of your own seedlings to get that way, you really don’t have much of choice, or much to lose, so give it a try.