Aspen Alternatives for the Front Range

By Amy Lentz, Weld County Extension Horticulture Agent

It's tree planting season which means there are choices to be made in yards all across the state. But which tree should you choose?

Today's tree-in-question - the aspen. So many of us want one in our yard to give us that 'Colorado' feeling. From the beautiful white bark to the perfectly shaped and uniform green leaves, or maybe it's the fall color or rustling sound that you just have to have! Before you go out and buy an aspen to plant in your home landscape, I urge you to reconsider if you live along the Front Range or Eastern Plains. These native trees are only native to the higher elevations of Colorado, the mountains and foothills.

Aspens have a few needs that just can't be met down at lower elevations. For one, the soil is much different than that of the higher elevations - it's higher in clay content, more alkaline and drier. The temperatures get much hotter in the summer at lower elevations than what the aspens prefer which can lead to stress. Once an aspen tree is stressed, it can invite other insect and disease problems like oyster shell scale, Marssonina leaf spot or cytospora canker. See PlantTalk Colorado - Aspen Trees (#1701) for more information.

Finally, aspens want to reproduce via suckers and create groves and many home landscapes are just not big enough to accommodate a grove of aspen trees. If you plant an aspen in a small yard, you've probably just planted an aspen for all of your neighbors, too!

Photo: Amy Lentz - Aspen trees in Rocky Mountain National Park. 

So, instead of choosing an aspen tree for your Front Range yard, here are a few interesting alternatives. They won't be exactly the same, but they have similar qualities with much less caution required. 

1. Serviceberry

Serviceberry trees are great for smaller landscapes. They can be purchased in multi-stem form, giving them that 'grove' look without the suckering. They also offer a few things that aspens don't - spring flowers, summer edible fruits and nice fall color. The 'Standing Ovation' cultivar is a taller form, giving it more of that aspen look, whereas the 'Autumn Brilliance' has an intense orange-red fall color.

Photo: PlantTalk Colorado 1213 - Serviceberry

2. Tatarian Maple

Tatarian maple is another tree that can be bought as single or multi-stemmed. The 'Hot Wings' type has guaranteed bright-red summer seed pods creating the appearance of flowering. This tree is better suited to the harsher conditions and low-water or xeric settings once established.

Photo: Adams County Extension Tour the Xeric Garden @ Riverdale Regional Park

3. Redbud

If you like the smooth bark of the aspen, the redbud has a similar appearance in its younger bark but with a more grayish tone. The leaves are larger, but also have that similar heart shape. The redbud also offers a nice display of early spring lavender blooms in most years. Plant this tree in a more protected location from wind and intense sunlight.

Photo: Amy Lentz, taken outside the Boulder County Clerk & Recorder Offices in a very protected northeast facing corner

4. Oakleaf Mountain Ash

If you want something 'mountainy', the oakleaf mountain ash has 'mountain' in it's name! It has low to moderate water needs and has a uniquely shaped leaf, pretty flowers, red berries and nice orange-red fall color. It's not a true ash, so it is not under threat by the Emerald Ash Borer. In fact, it is not known to have any serious insect or disease issues. 

Photo: City of Sheridan, WY - Arboretum

5. Columnar and Fastigiate Trees

So many to choose from! These types of trees are more narrow than wide, making them good for tighter spaces where you might commonly want to plant aspen trees. There are a lot of deciduous trees listed on our CSU Fact Sheet. A couple to consider might be the 'Princeton Sentry' ginkgo or the 'Prairie Sentinel' hackberry. 

Photo: Wikimedia Commons - 'Princeton Sentry' ginkgo

Which Trees to Transplant in the Fall in Colorado

By: Emily Jack-Scott (Garfield County Colorado Master Gardener)

As a rule of thumb the best times to transplant most trees and woody shrubs is in early spring (as soon as the soil can be worked), or in fall (after leaves drop) – the key factor being that the tree or shrub is in dormancy. In some parts of the country, fall planting is actually preferable since most trees are channeling energy into root growth in autumn, as opposed into shoot and leaf growth in spring. However in Colorado, fall can be less ideal since the ground can be very dry in winter and roots of transplanted trees can suffer additional damage. If you do choose to transplant a tree or shrub this fall, there are several considerations that can improve your odds for success.

Firstly, aim to complete the transplant by the end of October. Transplanting any later in fall or winter will leave little opportunity to help water in the new planting before the ground freezes. New transplants are particularly susceptible to winter drought injury due to the dry winter soils in Colorado. This can be curtailed in part by winter watering, which is critical for newly transplanted trees and preferable for all established trees and shrubs in Colorado (refer to Fact Sheet 7.211 Fall and Winter Watering for more information). Winter drought can also be helped by properly mulching a newly transplanted tree (refer to Fact Sheet 7.214 Mulches for Home Grounds).

The species of the tree also factors into transplanting success. This is in part due to the difference in root structure between different species – with some species having shallower, more fibrous root systems that are better adapted to transplanting, especially in fall. Some types of trees really should only be planted in spring including oaks, fruit trees, poplars, willows, redbuds, and birches. Other species can be more successfully transplanted in the fall such as maples, alders, lindens, catalpas, elms, ashes, and honeylocusts. Conifers such as pine and spruce benefit from being transplanted when soils are warmer.

Whether you choose to transplant a tree or woody shrub this Fall or wait until Spring, ultimately the success of your planting depends on following proper tree-planting steps (refer to GardenNotes #633 The Science of Planting Trees). Happy planting!

Additional Resources:

Fall and Winter Watering. https://extension.colostate.edu/topic-areas/yard-garden/fall-and-winter-watering-7-211/

Fall Planting. http://planttalk.colostate.edu/topics/trees-shrubs-vines/1707-fall-planting/

Fall Planting of Trees and Shrubs. https://hortnews.extension.iastate.edu/1997/8-22-1997/fallplant.html

Planting and transplanting trees and shrubs. https://www.mortonarb.org/trees-plants/tree-and-plant-advice/horticulture-care/planting-and-transplanting-trees-and-shrubs

When is the best time to transplant trees? http://blog.davey.com/2017/11/when-is-the-best-time-to-transplant-trees-pine-oak-maple-and-fruit/