Winter damage to ornamental trees in containers

Q. I'm trying to get some help with a couple of trees that I purchased/received last year. All the trees are for zones 4-5 but I noticed that after the winter was over the buds came out but either never bloomed or only very, very slowly. I noticed in some of the trees that half of the tree got "burned" and is dead, the bottom seems to be ok and now I'm getting buds that are growing.

Another one, a Japanese cherry, some of the top buds are dry, brown and dead, the bottom ones are growing poorly and slowly, very slowly.

I got two giant dogwoods that never made it, everything looked ok after the winter, I saw the buds swelling and growing but suddenly it stopped and it started drying out. They got a few leaves but later all of the leaves dried out and died.

I am wondering if this is due to a lack of adaptation of the trees to the Chicago winter or I should have covered the trees to protect them a little bit from the brutal temperature changes during the spring?

A. I would agree that most dogwoods will stand Zone 4 and 5 temps, but Zone 4 for Japanese maple could be a bit ambitious. Bear in mind that shade from the house, being open to the wind, et cetera, produces micro-climates even within a particular Zone. The cold, dry north side of the house may be a Zone 4 while the sunnier south side, protected from the wind could be Zone 5 or 6. Further, a Zone 4 tree in the ground and a Zone 4 in a container are two different animals.

While Japanese maples can be successfully grown in containers, a container on a patio or driveway with no protection against the wind will be more challenged than a tree in the ground. Although wind chill itself has no effect on plant material temperature-wise, wind will dry out a container more quickly and a series of warm spells (especially if increased by heat reflected off a hard surface) and cold snaps can damage the root systems of container plants in short order. Unlike the great architect Mies Van der Rohe's admonition that "less is more," smaller containers will tend to dry out a root ball. Go for larger containers and if possible, move them to a protected area and shield them with burlap, leaves, or some other insulator against the winter's elements.

Now, after considering the temperature Zone let's look at the specimens themselves. They do look very dried out as opposed to being subject to a bacterial or pest problem and some look particularly akin to the sort of winter burn drying common to azaleas and rhododendrons. My humble opinion would be these plants suffered from a lack of moisture either prior to going dormant in the fall, or over the winter. While we have had a somewhat drier than normal spring, the temperatures have been relatively cool and I would suspect the damage done prior to any spring leaf out. Also, the later frosts were still fairly light and unlikely to have done any substantial or lasting damage.

You indicate the trees were "purchased/received" last fall. I'm going to take "received" in the sense of received by shipping and not as a gift. Plants shipped in a dormant state and not either planted or at least healed in quickly can dry out in short order. In a similar manner if the stock you purchased was on a garden center lot, or garden department asphalt area, the plants could have had root damage prior to the purchase. The damage might not have been evident when you looked at them however if they had dried out too often the roots will have suffered. If the plants were container grown and you noticed the roots circled in the pot, it would be an indication that the roots were too large for the size container you bought them in and probably not given adequate moisture during the summer months.

Stress on trees can show up as late as five years after planting. That is, do not think of even the smaller ornamental trees and shrubs as being home free after you have replanted them from the garden center. Think of them as being needy for at least a few years so they can reestablish their roots to match the upper leaf growth. In short, I believe that the plants you have chosen can live and indeed thrive in the Chicago area, given the initial purchase of quality stock, planting in a more advantageous site, or larger containers, and adequate winter protection. Bear in mind that even if your current trees appear to be coming back to health, not only Japanese maples, but also Japanese cherries are normally grafted on a root stock that is a more vigorous grower, but does not have the beautiful foliage of the maple, or the bloom of the cherry. Keep an eye on the ones you have and look to see if the new growth is above or below the root graft. If below, the plant may not be worth growing and in any event, will not be the species you expected.

Good luck with your trees. Please feel free to follow up with the help desk should you wish further clarification, or have additional questions.

• Provided by Master gardeners through the Master Gardener Answer Desk, Friendship Park Conservatory, Des Plaines. Call (847) 298-3502 or email northcookmg@gmail.com.