Planting and Mulching Trees and Shrubs [fact sheet]

Selecting healthy plants
Take a step back to examine the plant’s overall structure. Shrubs should have several stems coming from the base of the plant. Most trees, on the other hand, should have only one upright trunk and branches should be evenly spaced along the trunk. A few species such as birch are sometimes grown as clumps and so may have multiple trunks. In general, however, you should avoid purchasing trees with double trunks, dead branches, trunk cracks or wounds, or leaves that show signs of insect damage, disease, or drought. Avoid buying weedy containers or ball-and-burlap (B&B) products so that you don’t introduce more weeds to your own landscape. The presence of weeds, algae, or decomposing burlap on a B&B plant also indicates that it was harvested quite some time ago.

Choose plants with healthy root systems. Healthy root tips are generally light in color; older or diseased roots are dark colored. If the plant is container-grown, carefully remove the pot and take a look at the roots for yourself. A good root ball will stay intact. Avoid pot-bound plants, plants with a thick root mat at the bottom, or with numerous large-diameter roots circling inside the container wall (Fig. 1).

Fig. 1. Woody plants grown in plastic containers often have dense, matted roots.
This plant is“pot-bound” or “root-bound”.

It’s harder to check field-grown, B&B plants (Fig. 2), but you can. The trunk should taper outward where it enters the soil and you should see a few major roots connecting to the base of the trunk at the soil surface (see Diagram 1). If not, probe into the soil ball about three inches away from the trunk with a blunt nail or wire, trying to locate a few large roots within two inches of the surface. If you don’t find any, avoid that plant because it is buried too deep. Many of the tree’s roots are left behind in the nursery when a B&B plant is harvested, but the structural roots present in the soil ball provide enough stored energy for new roots to grow out quickly, under good conditions.

Fig. 2. Field grown trees are harvested and then wrapped in burlap and baskets for sale and handling. Trees like this leave over 80% of their roots in the nursery. The roots outside the burlap regenerated in a mulch layer while being held in a sales yard.

A third type of planting stock is sometimes available: trees grown in porous fabric containers, sometimes called grow-bags (Fig. 3). Roots in these fabric containers are generally dense but fibrous and the larger roots should form swollen nodules at the container edge, rather than circling like in a plastic container (Fig. 4). The nodules store carbohydrates that are used for rapid root growth once transplanted. Trees grown in fabric containers are lighter weight and easier to handle than B&B plants, so they require staking and frequent watering after transplanting. Research at UNH shows that these root systems have structural advantages for trees and may enhance growth and longevity.

Fig. 3. Woody plants grown in porous fabric containers have most of their roots contained within the bag, and the small roots that grow through can be easily shaved off before removing the bag.


Fig. 4. These root systems have had the soil washed off in order to compare the roots structure of birch trees produced in a plastic pot (right) with those from a fabric container (left). Large circling rootsand the bottom root mat should be removed from the plant on the right before transplanting. The plant on the left has better root structure and the swollen root nodules (circled) provide energy stores for new root growth.

Transporting and storing your plants
When moving your plants, handle them by the wire basket or container and not by the trunk or branches. Move small plants in a van or car trunk but don’t leave them exposed to excessive heat in a parked vehicle. Larger shrubs and trees should be laid down in a pickup bed or trailer, secured to prevent rolling, and covered with a tarp during the ride home, to avoid windburn. Load and unload them carefully; avoid dropping or bouncing plants on the ground. Many B&B trees weigh over 250 pounds, so specialized equipment is needed to move and install them.

The best thing for your plants is to transplant them as soon as possible. If you can’t plant right away, water them frequently to prevent the root balls from drying out. Plants in containers will need watering daily in the summer; sometimes even more than once a day. If you find they dry out too quickly, you may want to give them a temporary home in the shade. B&B plants still still need watering every 1-2 days but won’t dry out as quickly as containers.

Digging the hole
First, find the trunk flare (also called the root flare) on your tree or shrub. This is the base of the trunk which tapers out just above the first permanent roots. Small temporary roots may have grown above the root flare if the plant was too deep or covered with soil or mulch – ignore these small roots and find the topmost woody root growing radially out from the trunk; usually it will be at least ¼” in diameter. If there is excess soil or potting medium on top of the permanent roots, carefully remove it to expose the trunk flare. Any temporary small roots above the flare can be cut off with hand pruners.

Measure the height and diameter of the root ball now. The most common mistake people make when planting a new tree or shrub is making the planting hole too deep and narrow. Instead, dig a hole only as deep as the height of the root ball. Make the hole two to three times as wide as the diameter of the root ball; the sides may be sloped as shown in Diagram 1. Digging a wide hole loosens the soil and provides a good environment for new roots to begin growth.

At this point, you should have a healthy plant ready to be planted into a properly-sized hole. Carefully place it in the hole to check the depth. If you’ve made the hole too deep, remove the plant and place some soil back into the hole, firming it with your foot. The soil underneath needs to stay firm so the plant doesn’t settle later on.


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