by Todd Rutherford
Whether you’re an experienced or an inexperienced gardener, you’re probably aware of fall planted flowering bulbs. Tulips, daffodils, crocus, alliums, hyacinth and other “fall planted/spring blooming bulbs” have become very iconic harbingers of the advent of spring season. However, there’s a large assortment of flowering bulbs that make a spring-time appearance in garden retail stores, providing their own form of welcoming the passing of winter and the arrival of a new gardening season. The so-called spring planted flower bulbs may be lesser known to the novice gardener, but can be almost as valuable as the fall planted bulbs. These summer blooming plants can be used to place spots of color in-between perennials and shrubs in your landscape. Planted in Spring, these bulbs emerge to provide beautiful flowers throughout summer and fall, with exact flowering times varying per species and cultivar.
In fact, the spring planted bulbs are not all true bulbs. Some may be corms, rhizomes or tubers, which are all different types of storage organs that plants have evolved over time. It is these clever little storage devices that have allowed people to dig them up during plant dormancy, and package them up to be shipped to garden center stores around the world. Some of the spring planted bulbs are perennials, but most are not, at least in the USDA hardiness zone that Denver finds itself in.
Crocosmia corms.
Out of the many types of spring planted ornamental bulbous plants available in your local garden center, I cover three common types here in this post.
Perhaps the best known spring planted bulb is the gladiolus, which hails from South Africa. Botanists consider the gladioli to actually be corms, not true bulbs. Corms are underground plant stems that function as storage organs, whereas true bulbs are underground storage organs made up of layers of fleshy modified leaves. Most gladioli are hardy only to zone 8, which makes them annuals in Colorado. But there are some gladioli that are hardy to zone 5, if well mulched in winter. Gladioli come in many colors and sport bright blooms on upright stems with strap-like leaves.
Like the “glads”, dahlias are another very popular summer bloom that is not hardy in Colorado. Dahlias are placed in the spring planted bulb category because they form tuberous roots which are dried and then sold. The pre-cultivar dahlias are native to Mexico. There tubers were used as a food crop by the Aztecs. The trick to buying dahlias in dry form is that they must have a stem attached to the tubers, because only the stems produce buds, which then produce stems and flowers. There is a huge variety of dahlia cultivars to be found in garden centers. In springtime, the dahlia tubers are sold in bags along with the other spring planted bulbs. But in summer it is common to see the dahlias sold as potted plants. Buying them as tubers is cheaper than as potted plants. Because the dahlias are hardy only to zone 8, if you want them to return to your yard next summer you must save the tubers (with a bit of the stems attached) in a cool but not freezing space, to be replanted in a successive season. Or simply just buy new ones each spring. Dahlias are popular because the blooms come in a multitude of shapes, colors and sizes. If you’ve never seen a 12 inch wide “dinner plate” dahlia flower in bloom, you are missing out on a fascinating sight.
Canna Lilies are another spring planted “bulb” that bring an air of the tropics to your landscape. These flowering plants are often used in annual pots, providing tall, colorful focal points in the center surrounded by lower annuals. Cannas are native to Latin America and are grown as annuals in Denver’s hardiness zone of 5. But if you find the right micro-climate, they may over-winter just fine. I know of one house in Denver, where cannas are planted at the base of a south facing wall on a house, and have become perennial in this residential landscape due to this warm micro-climate spot. Cannas are not true bulbs, but are “rhizomatous.” A rhizome is an underground horizontal stem that can send out shoots and roots from nodes. A ginger “root” is an example of a rhizome that you’ll find in a produce section. Cannas are closely related to ginger and also bananas! Another familiar rhizomatous plant are irises, which have above ground rhizomes. Although canna lilies are often available as potted plants throughout summer, if you purchase them as rhizomes in spring, you get the plants for a fraction of the cost of potted ones. As mentioned previously, cannas develop tropical-like flowers and leaves, giving your patio an island vibe.
Canna rhizomes.
Head on down to your local garden center this spring gardening season and pick up some spring planted bulbs to brighten your landscape this summer!
This is the official blog of Outdoor Design Group, Colorado Landscape Architects. For more information about our business and our services, click here.
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by Todd Rutherford
When it comes to trees in designed landscapes in Colorado, landscape architects and designers don’t have very many species to choose from. With that being said, it might seem heretical to propose that the list of trees to pick from be restricted even further. Specifically, I advocate that large evergreen trees NOT be planted in dense urban areas that experience cold winters, unless they are sufficiently distant from walks and streets located north of such evergreens.
The shadows that large evergreen trees cast can help foster ice patches on walks and roads, compromising the safety and welfare of those who utilize these areas to travel about our towns and cities. If we are going to encourage biking and walking to ease automobile congestion and alleviate environmental impacts, having the safest travel routes we can achieve is a noble goal.
It may be surprising to those who don’t work in the landscape, architecture or planning fields, but many municipalities require that a certain number or percentage of the trees on a landscape plan be evergreen trees. Sometimes these arbitrary requirements restrict designers and architects to squeeze these large winter-shading ice patch-makers into a site where it might be best to avoid them. However, I should mention that some municipalities that I’ve worked with do acknowledge the problem of winter shading from evergreen trees, and they do have instructions in their landscape codes to locate proposed large evergreens away from walks and roads that would be shaded by those evergreens.
I first became aware of the problem of evergreen shadow ice patches as an urban bike commuter in the Denver area. It is frustrating at best, and rather dangerous at worst to encounter a patch of ice on a street during winter time. I have found that often times when biking in the Denver area in winter, the majority of streets can be clear of ice, except for those areas shaded by evergreens that are located just south of walks and streets. But it is not just bikers that would benefit from restricting evergreen trees in urban areas. Walkers and runners would also have an improved level of travel safety due to less icing of their pathways.
An ice patch on a Denver street, from the shadow of a large evergreen tree.
Because the foliage canopy of pine, spruce and fir trees does not drop during winter, melting of snow and ice via solar gain is limited. Deciduous trees, which drop their leaves and allow more sunlight to reach walks and streets, are a better choice in place of evergreens. I acknowledge that evergreen trees are often used for landscape screening. But I question whether this screening is worth it when considering their impact to roads and walks during winter.
Another impact from lost solar gain due to evergreen tree shading is on homes and other buildings. A building that sits in the winter shadow of a large evergreen tree will miss out on solar warmth during a sunny Colorado winter day.
I do realize that in dense urban areas, it’s not just trees that can shade our streets and sidewalks. People need shelter and workspaces, and some of those structures could end up shading streets and cause ice patches. But residents don’t need evergreen trees on their urban lot. I advocate for trees to create shade in summer, visual interest in all seasons, and wildlife habitat. But the choice of tree in tight urban quarters needs to be considered carefully.
Despite the tongue in cheek title of this blog post, evergreen trees can be a wonderful addition to the landscape. I am not actually asking for evergreen trees to be banned from urban areas of Colorado. However it does seem best that in dense urban areas that experience cold winter weather, we should consider restricting evergreen trees to parks and large lots, away from streets and sidewalks where their winter shade will not cause icy travel dangers for walkers, bikers and even cars.
This is the official blog of Outdoor Design Group, Colorado Landscape Architects. For more information about our business and our services, click here.
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by Todd Rutherford
Calamagrostis brachytricha, Korean Feather Reed Grass
Calamagrostis brachytricha, aka Korean Feather Reed Grass, is a clump-forming ornamental grass with green leaves and fluffy flower plumes. It is not as well known as its infamous cousin Calmagrostis acutiflora ‘Karl Foerster’, commonly known as Karl Foerster Feather Reed Grass. But Korean Feather Reed Grass really should get more attention, as it is an indispensable option to add wispy texture to planting schemes in part shade conditions.
PLANT STATS
Scientific Name: Calamagrostis brachytricha
Common Name: Korean Feather Reed Grass
Plant Type: Ornamental Grass
Mature Height: 3-4’
Mature Spread: 2-3’
Cold Hardiness Zone: USDA zones 4 – 9 (up to 6,500 ft)
Water Requirement: Medium. Slightly drought tolerant once established, but prefers adequate moisture. Requires regular amounts of water if it is planted in more sun.
Exposure: Part Sun/Shade
Soil: Tolerant of a wide range of soils.
Flower Color & Bloom Time: The feather like flower spikes have a pink tinge when they initially emerge in late summer, and then fade to straw yellow in fall. Compared to Karl Foerster grass, the flowers of Korean Feather seem to be much more misty and gauzy when they first appear which gives the plants a wonderfully diaphanous appearance.
Winter Interest: Gold foliage and flowers.
Disadvantages: May reseed under certain conditions.
Availability and Sizes: This plant seems to be regularly available at retail nurseries around the front range. It is typically sold in 1 gallon or 4″ pots.
Best Features: A large, showy, flowering ornamental grass that can take shady conditions.
Maintenance Tip: Like other ornamental grasses, trim plants down to about 4-6” above the surrounding soil in late winter or early spring, before new growth begins to emerge.
This is the official blog of Outdoor Design Group, Colorado Landscape Architects. For more information about our business and our services, click here.
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by Matt Corrion
The landscape design includes patio space and a gas fire pit that allows easy enjoyment of the mountain views
Are you considering purchasing a new home? When you tour the lot, examine the adjacent views and how the site may be landscaped and used for outdoor living space. With a little foresight and a good design, the yard can be made into an inviting extension of your home for your family and guests alike.
For this project, located on the west side of Arvada, Colorado, we worked with the homeowners to take advantage of amazing mountain views, while adding value and convenience to their property. A sloped lot was redesigned to provide a flat lawn area and a secondary seating area with a custom gas fire pit. Pavers were used to soften the existing covered concrete patio, and a built-in outdoor kitchen and bar seating were added. Soft lighting provides security and ambiance in the evening, while the Rocky Mountains provide the backdrop for stunning sunsets.
The view from the back of the lot toward the house and outdoor kitchen
View of firepit with tiered lawn behind
The view from the leveled-off lawn are to the outdoor kitchen
The existing sloped backyard
Most builders will include a basic front yard landscape in the home price, but will leave the back yard as bare ground for you to improve however you wish. The design must be approved by the homeowners association. The proposed landscape will need to ensure proper drainage and shouldn’t have any negative impacts on your neighbors lots, or adjacent open space.
The front yard can always be redesigned as well. The front yard irrigation mainline and valves should already be in place, so the design can be modified pretty easily. This homeowner asked us to redesign the front yard simultaneously, and they plan to redo the front yard in a second phase. For the time being, they have completed their landscape, eliminating the bare dirt and allowing them to fully enjoy their new home and yard.
Pavers were installed over the concrete patio that came with the home
Enjoying a beer and the mountain views
This is the official blog of Outdoor Design Group, Colorado Landscape Architects. For more information about our business and our services, click here.
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by Todd Rutherford
As we move further into the fall season, many gardeners have turned their attention to cleaning up and preparing to put their gardens to bed for winter. Gardeners should also take this time to plan ahead for spring blooming bulbs which are currently available in your local garden center. Now is the perfect time to add these must-have jewels to your landscape. For most areas in Colorado, you should plant these bulbs sometime between the middle of September to the end of October. I have planted bulbs as late as November during a mild fall and winter. As long as the ground is not frozen, you can plant bulbs. However, by planting in early fall you give the bulbs time to establish some roots before the soil freezes, ensuring the best success. Lucky for us, the growing conditions in much of Colorado are perfect for spring blooming bulbs. The climate and ecological conditions of many of the bulb’s native ranges are quite similar to our high plains region.
Crocus popping up through veronica and sedums.
The diversity of size, shape and color of spring blooming bulbs is fascinating. Some of the best bulbs to plant in our area are (listed in order of bloom time) :
Early Spring Bloomers: crocus, Siberian squill, snowdrops, dwarf iris, and species tulips
Mid-Spring Bloomers: hyacinths, daffodils, grape muscari, fritillaria and tulips
Late Spring Bloomers: alliums, irises and fox-tail lillies
Alliums with Cholla cactus.
Fall planted bulbs do best in soils that are well drained. If the soil is too wet, the bulbs may rot. The rule of thumb is to plant the bulbs at a depth 3 to 4 times the length of the bulbs. If you buy bulbs in a package, a visual guide to bulb planting depth is usually printed on the package.
Consider adding “bulb food” to the holes you’ve dug before you drop in the bulbs. Phosphorus fertilizer will give your bulbs a boost, and help them become established. Traditionally a product called “bone meal” was recommended for providing phosphorus to bulbs. But research done at Colorado State University has shown that product doesn’t work well in our typically alkaline soil chemistry. Consider a conventional (a.k.a. “non-organic”) fertilizer called “triple super phosphate”. However, using phosphorus from conventional fertilizers has been linked to environmental damage such as toxic algae blooms in lakes and rivers. Use the conventional phosphorus sparingly and carefully. If you’ve not already done so, amending your soil with compost is also a good idea to improve soil texture for your bulbs.
Close up of foxtail lillies.
Most spring blooming bulbs do best in full sun to part sun locations as opposed to deep shade. But if the site is south facing in full sun, that area’s soil may warm up too much in late winter, causing the bulbs to flower early and those blooms would be susceptible to frost damage during cold snaps. It is a good idea to mulch the soil where you’ve planted the bulbs. Mulch will keep the soil from drying out, and help moderate soil temperature so it doesn’t warm up too quickly.
Design-wise, you can tuck just a few bulbs into niches between established perennials and ornamental grasses in your garden, or you could add large groupings of one type of bulb to get maximum color punch in your landscape. One effective way to add bulbs to an existing garden is to place them around low-growing plants that will still be dormant when the spring bulbs emerge. That approach is particularly effective with low growing groundcover perennials. Some people will add early spring bulbs such as crocus or snowdrops to a lawn area, knowing that the grass won’t start growing or need a mowing until after the bulbs are done. And if you want to add bulbs year after year, you might want to make a plan or take photos of where the existing bulbs are when they are blooming. That way you can avoid disturbing the established bulbs next time you add more in the fall.
Tulips mingling with veronica and the remnants of last year’s ornamental grass.
For all the bulbs, you should not remove the leaves after the flowers have faded, until the leaves have turned from green to brown. Removing green leaves too early deprives the bulbs the ability to feed themselves in preparation for the next year’s blooms.
If your bulbs are “happy” where you’ve placed them, there’s a chance they will supply you with gorgeous blooms for many years. Adding spring blooming bulbs to your garden is an easy way to get dependable spots of color into your landscape for a springtime show!
This is the official blog of Outdoor Design Group, Colorado Landscape Architects. For more information about our business and our services, click here.
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