The Dry Garden: Why a swirl of roots in the store pot will turn almost any plant into a lemon

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Planting season in Southern California is rarely busier than midwinter, when nursery lots crammed with Christmas trees give way to displays of fruit trees and roses. If you’re haunting stores to select an apricot tree, a flowering bramble, a hedge or even a specimen tree, plant pathologist Jim Downer has a message for you: ‘Good gardening starts with good plant selection.’

By which he means: If the stock you find is root-bound, walk away.

The advisor for the UC Cooperative Extension in Ventura County further warns that bad plants can look good in nurseries. Constant watering and pruning can conceal a multitude of problems. If you see, say, a Santa Rosa plum tree three times the size of the new bare-root stock, or a big ficus tree in a small pot with a low price, it is probably root-bound. Rather than throw it away, less scrupulous nurseries might leave it around to see if they can sucker you into buying it.

One way to check if a plant has outgrown its pot is to look down at the root ball and feel along the side of the pot to see if circularized roots are creeping up in search of space.

Another method is to ask staff to gently tilt the plant and briefly slide it from its can. A thin film of feeder roots lining the bottom can be acceptable. A coil of thick roots growing in a corkscrew around the side means that the plant is a dud.

Spare time being short and freeways being long, many of you may be tempted, as I was recently, to buy last year’s bare-root trees because of their size. More plums! Faster!

As soon as I got them home and found most of them to be dramatically root-bound, I was reminded of the real bottom line: more problems, sooner.

The good news for those who make this mistake with apples, plums and apricots, Downer says, is that deciduous plants are more forgiving if you have to disentangle badly ingrown roots.

This takes work. The worst root-bound plants can be so tightly attached to their pots, peat or plastic that you might have to cut them off. Once the pot is wrenched off, if the roots have formed a pot-shaped mesh, then pierce it and begin trimming through the skein as needed. If it’s badly tangled, do not be shy about employing hammer and chisel. Work until you have the roots splayed out in the plausibly downward and outgoing fashion of a healthy tree. Discard the old soil, along with any root trimmings.

When digging the planting hole, forget the old adage about making it twice the size of the pot. Make it just big enough for the plant to be seated with roots dispersed. Then set the plant aside briefly while you fill the hole several times with water and allow this water to percolate down. Then, return the tree to its hole, arrange the roots and begin filling in the gaps with soil from your garden.

As the soil begins to settle, lift the tree slightly to allow the dirt to tumble down. The crown, where the roots meet the trunk, should be just above soil level, free from dirt or mulch. Away from the crown, create a slight berm that will prevent water from running off and allow it to percolate when you irrigate. Until they become established, newly planted trees will need enough water to keep the soil moist but not sodden.

Where overgrown and circularized roots in nursery stock become a terminal problem is with evergreens. By all means trim and loosen the outer layers of fine roots that might have formed around camellias, citrus trees or conifers, but do not start removing the potting soil or doing deep trimming of the roots. If the roots are circularized, return the plant to the nursery and demand a refund. To underscore why this is so important, Downer points to Canary Island pines, which can grow to 30 feet before they fall. And when they fall on your house or car or you, he says, it’s often ‘because the tree had a root defect from nursery production.’

Finally, once you’ve returned the evergreen root-bound plant to the nursery or fixed the roots of the deciduous one, Downer urges gardeners to go easy on the pruning of the upper branches. Although conventional wisdom dictates reducing the canopy to compensate for the roots removed, he argues that by cutting away the wood, you are reducing the tree’s ability to produce more root-stimulating hormones.

A beauty of this time of year is that most good nurseries are selling stone-fruit trees and roses as bare-root plants. This means the roots will be in a loose planting medium or sawdust. When checking the trunk and branches, you want to see buds forming and flexible wood with good color. If it’s dry and brittle as kindling, it’s dead.

Yes, it’s a drag to drive to a nursery and not find what you want. But as Downer stresses, nurseries might stop trying to sell us bad stock if we stopped buying it. ‘Saying ‘no’ to junk,’ he says, ‘is not a waste of time.’

-- Emily Green

Green’s column on sustainable gardening appears here every Friday. Follow the scene by joining our Facebook page dedicated to gardening in the West.

Photos, from top: A mature plumbago still had the circularized roots of a nursery pot. As soon as the canopy becomes big enough, trees like this often fall over. Credit: Emily Green. The roots of a bare-root rose bush. Credit: Los Angeles Times

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