Mighty oaks make a profound statement in the landscape

on December 27, 2008 at 4:53 AM, updated December 27, 2008 at 5:02 AM
Choose an oak that best suits the location and role it will play in the landscape.

The oak has become more a part of our culture than most other trees. For Americans, oaks represent strength and durability. "From little acorns mighty oaks do grow" is a proverb we've long used to indicate that small beginnings can lead to great things.

The Romans called oaks Quercus, and that has become the Latin name of the genus that all oak species belong to. A number of Quercus species are native to Louisiana, and we use a variety of them in our landscapes. As a group, oaks are among the larger and longer-lived trees. Their size, however, means that care must be taken when selecting oaks for the landscape.

Oaks are not among the fastest-growing shade trees, but some species grow more rapidly than others. A slower rate of growth has its benefits, however, as it contributes to the strength of the wood and long life of these trees. The water oak, for instance, grows quite rapidly for an oak, but has relatively brittle wood and a short life expectancy.

Gardeners considering an oak as a shade tree need to consider the available species carefully, and choose the one that best suits the location and role it will play in the landscape. Now is a great time to plant oaks (and other shade trees). Here are some of the choices.

Water oaks

Perhaps the most common species in the New Orleans area (at least pre-Katrina), the water oak (Quercus nigra) self-seeds freely, and many local ones grew from seedlings that homeowners simply ignored.

The fastest growing of our native oaks, the water oak also is the shortest-lived. Most grow to be massively large (60 to 80 feet tall and a 40-foot-wide spread) in just 50 to 60 years. At maturity, they tend to develop decay in their trunks and fall apart.

Although they make very nice shade trees early in their lives, these habits of decay and breaking or blowing over in high winds make the water oak among the less desirable species to plant.

Live oaks

The live oak (Quercus virginiana) is virtually everyone's favorite -- for many people, it is their favorite tree altogether. There are good reasons for its popularity. With its lustrous, dark, semi-evergreen leaves and graceful spreading branches, the live oak is outstandingly beautiful. It also is one of our most hurricane-resistant native trees.

The live oak is a tough, strong, decay-resistant species that has an exceptionally long life expectancy as a result. Live oaks can live for hundreds of years, and grow to be massively large.

To stand in the presence of an ancient live oak is to be humbled and awed by its size, endurance and beauty. We are fortunate indeed to live in one of the few places in the world where these amazing trees grow to perfection. I do love live oaks.

Given this, you might be surprised to hear that I'm constantly telling people not to plant them. Did I mention that live oaks are huge? At 60 feet, the height is fairly modest for an oak. The issue is their spread of 75 to 100 feet, making them far too large for the typical urban lot. Planted in the wrong location, a live oak can overwhelm a yard and landscape, and neighboring yards as well, casting dense, heavy shade.

In addition, a mature live oak's massive surface root system can destroy sidewalks, curbs, driveways and patios if planted too close to them. And their natural low, spreading growth habit (live oak branches typically sweep down to the ground as the trees age) is unsuitable for the typical urban landscape or street planting. As a result, live oaks have to be pruned over time to force them into unnatural upright shapes. Even then, it is common to see large, low branches scarred where vehicles have hit them, or massive wounds where these branches had to be pruned to clear traffic lanes.

So, my advice is to love the live oak for the magnificent tree it is, but to be careful when considering it for your landscape.

Nuttall and Shumard oaks

Two native oak species I'm recommending a lot these days are the Nuttall oak (Quercus nuttallii) and Shumard oak (Quercus shumardii). These two species both have moderate growth rates -- faster than live oak, but slower than water oak. They live longer (more than 100 years) and are not as prone to trunk rot as the water oaks.

The Nuttall oak is particularly well suited to the south shore, while the Shumard oak is native to the more upland soils of the north shore. When planting on the south shore, avoid planting the Shumard oak in low, damp areas.

Both of these oaks have upright, oval growth habits, and will reach 50 to 60 feet tall and 30 to 40 feet wide, suitable for urban landscapes. They lose their large, deeply lobbed leaves from late November through early December.

Both will achieve some fall color. The Nuttall oak turns a dull yellowish-orange, while the Shumard oak turns a more attractive burgundy red.

Willow oaks

The native willow oak (Quercus phellos) is very similar in size, shape and growth rate to the Nuttall and Shumard varieties. It is an excellent tree for the entire New Orleans area and, like the other two, deserves to be more widely planted.

The name comes from the tree's very narrow, willow-shaped leaves. And here is my favorite characteristic: Not only does its leaf give the willow oak a unique texture and appearance, but it makes the tree one of the neatest ones around. The narrow leaves seem to just disappear when they drop in the fall. As far as deciduous trees go, this one is less likely to burden you with leaf raking in the fall.

Other oak species

There are additional species of oaks from which to choose. Information on them is available online or in reference books, such as "Southern Plants," by Odenwald and Turner.

Notable species include the Southern red oak (Quercus falcata), cherrybark oak (Quercus falcata var. pagodifolia), Japanese evergreen oak (Quercus glauca; at 20 by 15 feet, a smaller evergreen species), cow oak (Quercus michauxii, also called basket or swamp chestnut oak) and overcup oak (Quercus lyrata).


I have lots of trees in my yard, mainly sweetgums. I have been mulching my fallen leaves into my lawn with my lawn mower -- three times this season so far. Can I overdo this mulching? I still have leaves and will probably need one more pass of my mower. I also have many leaves in my flower gardens. After all the leaves have fallen, I would like to add a light layer of garden soil before adding pine straw mulch. Is this OK?

I do think it is possible to put too many finely chopped leaves into your grass. This could lead to thatch build-up, a layer of dead organic material between the green blades and the soil. Lawns with too much thatch tend to be prone to insect and disease problems and drought. If possible, try to bag the leaves once or twice during the season, and dump them in flower and shrub beds for mulch. Or, if you mow without a bag, try to direct the leaves flying out of the side chute into beds where they will serve as mulch. If you want to add soil to the beds, it would be best to remove the leaves, add the soil, replace the leaves and then add the pine straw. If the soil is not critically necessary, then just put pine straw over the leaves.

I received a croton/crouton (not sure how to spell it) plant as a gift and want to give it the proper care. It is about 2 feet tall and about 12 inches across. Is this an inside plant, or can it be planted outside? How often should it be watered?

The croton is a tropical shrub grown for its colorful leaves. Gardeners often add them in the fall to displays of mums and pumpkins, where their colorful leaves in shades of red, orange, yellow, chocolate and dark green brighten the composition. You can leave yours outside over the winter, but you must bring it indoors on nights when freezing temperatures occur. Crotons are not hardy and will be damaged by freezes. Or, keep the plant inside in front of a bright sunny window. Water when the soil begins to feel dry. If you want to try growing it in the ground, plant it outside in April or May, once it is warm. Next winter, you will again have to protect it from freezes.

I've been seeing a lot of moths fluttering around my house this fall. Do you know what kind of caterpillar eggs they are laying? Somehow, I think they are bad news. I've tried spraying the still ones with liquid Sevin, but don't think it's killing them.
Ann Lagarde

They are likely buck moths, which show up this time of year. The females lay eggs on twigs of live oaks; the caterpillars will hatch next spring and feed on the leaves. If they are buck moths, your fears are well founded, since this is a stinging type of caterpillar. There is nothing practical that can be done to control the flying adults, so effort is focused on the caterpillar stage. If you have live oaks in your yard, watch them carefully in March and early April for masses of the black, spiny buck-moth caterpillars. If you see large numbers of the insects, you should have your tree sprayed.
