Hybrid Poplar, the instant tree: Populus species

Hybrid poplars usually live 35 years or more and grow to 45-90 feet in height. Once established, on suitable sites and given adequate light, nutrients and moisture, the hybrids can grow 4-6 feet a year early in their life span. Diameter increase on a good site will be 1-2 inches per year. First year performance of hybrids and other trees is very dependent on moisture and sunlight availability. They will tolerate a wide variety of nutrients and soil pH as low as 3.0, but of course may not do as well. They can produce 2-3 cords/acre/year, so four acres should heat most homes. (Cord=4~x4~x8’ pile). On some sites the hybrids simply will not perform well even with the best care.
As an energy source the hybrid poplar was found to be North America’s most productive tree at nearly 60 million BTU’s per acre per year, vs. only 38 million for oak. Hybrids produce about 8,600 BTU’s/lb., slightly more than most of the common firewood.
As with native poplars, wild animals will use hybrids as a cover and feed source.

Wildlife Habitat

Mike Hradel – Cold Stream Farm2030 Freesoil Rd.Freesoil, MI 49411(231) 464-5809
Current fashion is to focus wildlife habitat in blocks or rows. It is easy to plant and maintain and provides a quick visual impact of an apparent increase in wildlife populations. We take exception to this. Keep in mind that the predators will also note this concentration of wildlife. If you want to truly maximize wildlife populations you should disperse your wild life plantings as much as possible. Wildlife tends to be territorial so dispersed plantings will accommodate these territories. To draw wildlife out of natural dispersal invites stress, disease, warfare and predation. Research done in Minnesota on ruffed grouse indicated that overall populations could be increased as much as 20X by proper dispersal of habitat!
Another fact to keep in mind is that diversity of feed is important to wildlife. For reasons not fully understood, wildlife doesn’t always show preference for the same food from year to year or site to site in spite of availability. Also, winter fruit isn’t born by the same species every winter. To maximize fruit, seed and nut crops, do not crowd your plantings.
The importance of habitat quality to wildlife is brought home by the late Gordon Gullion’s research for the University of Minnesota. Although his study focused on ruffed grouse population response to habitat quality, to some degree it applies to other species. To summarize his work, optimum habitat provides maximum bird population. No amount of available food or predator suppression will increase grouse population if the cover is inadequate. Feed availability could even have a negative effect of it draws wildlife out of favorable cover.
When I worked in the paper industry I used to commute by motorbike through 12 miles of Manistee National Forest along two tracks for eight years. Along the way was a wide variety of cover. If you are not already aware grouse typically have ten chicks to a hatch and 3-4 of them will survive the summer. During my commutes I would sometimes flush broods. In areas with sparse cover there would be typically 3 or fewer chicks when they were still smaller than sparrows so I would guess there were few or none left by the end of the summer. In areas with dense cover there would still be 8-10 chicks, likely assuring a fresh generation of young adults at the end of the summer. If you are a hunter or just like to see wildlife, you already know, or you will learn that walking poor cover is a waste of time.
In forested areas timber harvest or preferably clear cuts are the fastest method to regenerate optimum cover. Care should be taken to refrain from cutting winter bearing shrubs. Their exposure to light will greatly increase their fruit crops. In the case of grouse, the cuts are best kept to a few acres and made every few years so that there is a succession of tree ages and stem densities in close proximity that grouse need during their life cycle. It is helpful to plant up natural openings with a variety of winter bearing trees and shrubs to supplement the winter, feed sources that are already in place. Supplemental plantings should be avoided along high traffic roads, where motor vehicles are an important predator. In some years wild life will reject even their favorite food sources for no apparent reason so it is desirable to have a variety of food sources available for them to choose from. Also fruit crop failures can be counted on. We see feed rejection happen on the winter-bearing fruit in our yard and in feedback from our customers. Gordon Gullion observed this one winter during his study, when grouse abandoned male aspen buds that are their customary primary winter feed source. In a purely aspen forest this could severely stress the grouse population.
Another incident that may be of interest was an encounter a friend in Maine had with a young male partridge. When cutting firewood and raking leaves around his yard the bird would show up and tag along with him like they were old pals, while he was working. However whenever he would move toward more open areas the bird would become nervous and desert him, unwilling to abandon overhead cover that is important to them. The bird had another curious behavior. When Warren would dump leaves on his mulch pile it inspired the bird to attack the leaves. You’d think a pat would find better things to do than hang out with a bird hunter so close to bird season.
Supplemental plantings of winter-bearing shrubs in high snow regions can be particularly beneficial when snow depths exceed what the wildlife can dig through for long periods of time. Wild turkey have been introduced in many areas outside their normal winter tolerance but they have been able to prosper anyway due to handouts. The trouble with handouts of course comes if they stop happening. Doug Whitcomb a DNR biologist in the northern lower peninsula of Michigan, (typically a high snow fall area) observed a large flock of turkeys that sustained itself largely on a grove of crabapple.

Hybrid Poplar Planting and Weed Control

To your left: DN34 hybrid poplar partway through their first summer.

Hybrid poplar will not survive in shade. Arid areas or sites that have standing water all summer aren’t usually suitable for hybrids. In the first year control of weeds and grass is necessary if you expect to see maximum performance. This control can be with cultivation or with herbicides. Control during the second and third summer is sometimes beneficial.


Large Plantings: The number of trees to be planted per acre depends upon planned tree diameter at harvest.
Harvest Diameter Tree Spacing Trees/Acre Application
6 inches 5’x 5’ 2000 wildlife
8 6’x6’ 1200 firewood
12 8’ x 8’ 700 pulpwood
15+ 10’ x 10’ 500 lumber
- 4’ - 8’ - windbreak

It is important to realize that if plantations are allowed to crowd in they will stagnate in growth. Where clear cutting is practical, hybrids will resprout from the stumps and replanting won’t be necessary.
We recommend initial planting be limited to minimize the cost of mistakes. Never assume your land will be ideal hybrid ground. Also, this allows some time to see which clones do best on your sites. Include other species in your trial plantings to better evaluate your site. On dry sites it is particularly important to learn how deep you will be forced to plant your trees to get what you feel is an acceptable survival rate. This will influence the length of tree you will need to buy and how many you will have time to plant. If you plan to fertilize, you may want to learn what quanityt is cost effective on your site.

Cultivation Method: The best mechanical control of weeds and grasses can be done by plowing and disking several times through the summer and fall the year before polanting to not to allow weed to regain a foothold. Disk again prior to planting as soon as the ground can be worked in the spring. Plant the poplars and cultivate often enough to keep the weeds shorter than the young trees.
Cultivation should be as close to the trees as possible. Weed control is best as if you were growing corn or other vegetable crops. If you are unable to prepare the site the year prior to planting, then the field can be plowed as early as possible in the spring and disked once or twice before planting. After planting, frequent cultivations should be made to keep the field free of weeds. Unnecessary cultivation should be avoided since it results in increased moisture loss.

No TillMethod: Where grasses such as quack grass are present, the chemical Round-up is very effective in June or early fall, prior to planting, when the grass is actively growing. The manufacturer’s recommendations should be followed. If the trees are to be planted in rows 8- 10 feet apart, strips 4-5 feet wide can be sprayed, and the trees planted in the middle. For row spacings closer than 8 feet, total broadcast of the chemical should be used.

Dacthal, Devrinol, Loroz, or Surfian as a preemergent (follow manufacturer’s directions) should be applied right after planting. For weeds that are resistant to these herbicides, Paraquat can be used, preferably before weeds or grasses are over 5 inches high if the tree is higher than that at planting time. This allows spraying weeds ~th minimum foliage and new growth on trees being burned. Poor weed control can be made up to some degree by using larger planting stock to assure sunlight on the young tree above the weeds. No till conserves moisture and reduces erosion.

Caution: Chemicals can be very injurious to hybrid poplars. Care should be taken not to put on more than is suggested, in particular with preemergent herbicides. In fields that have been planted to crops, no poplars should be planted if Aatrex or heavy doses of Simizine have been used to control vegetation. They are fatal to poplars, especially if they have been used for production for severalyears. An easy way to tell if the soil contains any residual chemicals harmful topoplars is to take soil samples from the depths you plan to plant in various parts of the field, put them in a tray, bring them inside and plant oats. If the oats germinate and look healthy in a couple of weeks, you can plant poplars. if the oats don’t germinate in ten days or look unhealthy, don’t plant poplars. Retest your soil in the early spring of each year until your tests are positive. Rooted stock is more resistant to residual chemicals than cuttings.
If your intended planting site has been treated with Princep or Simizine in the past 6 months so state on the order form so we will select tolerant clones for you.
The use of chemicals with poplars is new and much still has tobe learned. The suggestions given are merely suggestions and should work, but may not. Much depends on weather, soil and temperature.

Small Plantings: For yard tree planting, it is best to scalp a patch of sod, perhaps two feet in diameter, before planting. Infields, weeds can be controlled by using black plastic, heavy cloth, old roofing felt or shingles. if applied properly this can collect and conserve rainfall on dry sites. Mowing has been effectively used for weed and mouse control. if mice or voles move in under your mulch they should be eliminated before winter sets in.

General Planting Suggestions: Try to plant poplars as soon as the frost is out. This will allow good root development before trees start to leaf out, which can maximize growth and survival. When planting on sites that will be wet throughout the summer, don’t plant roots deeper than six inches. On drier sites plant deeper; the drier the deeper, several feet down is not unreasonable. Do not fertilize if there is danger of weeds outgrowing the trees, since hybrids will die without direct sunlight on their leaves. Do not fertilize after July. High nitrogen fertilizers generally give the best response, at about 300 lbs./acre, or a tablespoon/tree. Good weed control minimizes winter rodent damage. Irrigation may be a necessity for the first year in very dry areas, or weather. Lack of moisture is probably the chief cause of tree failure or poor growth during the first growing season. This is more common on sandy planting sites. You can get maximum survival on dry sites during dry spells by giving each tree a gallon of water a week. The moisture supply when planting cuttings is even more important than with rooted stock. In event of severe drought, water the second year also.
Fall Planting: Some people prefer to plant in late fall. Fall planting should be avoided on sites with high mouse or vole populations or on soils with a tendency for frost heaving. There is more tendency for some of the top to die back due to winter drying. In some situations, fall planting may be superior to spring planting. We can’t ship hybrids before November. Do not use planting gels, as they promote frost heaving and winter kill.