Cold Hardy Evergreen Oaks

Southern Live Oak
Southern Live Oak

There are a number of Cold Hardy Evergreen Oaks species that can grow in USDA Climate Zone 7 and even Zone 6. Quercus virginiana is commonly called Live Oak. This tree has a natural range from the southeastern part of Virginia through Southwestern Oklahoma through Texas into Northeastern Mexico.These are very distinctive trees. They are the iconic tree of the Deep South. They have a unique shape that is hard to miss. They can be wider than they are tall. They can reach from 40 to over 60 feet in height and from 50 to 100 feet in width. These heights and spreads are for trees in good conditions in their natural range. Trees grown in colder climates will not usually be as massive. The crown provides a dense shade and the individual leaves are shiny dark green with a length of up to 6 inches and a width of less than half an inch to 2 inches.

Live Oaks retain their leaves almost year round but are not true evergreens. They drop their old leaves in spring immediately before new leaves emerge. On Occasion this tree can be more like a semi-evergreen when grown in colder climates. The leaves will stay green until the the temperature get close to 0 Fahrenheit. The temperature can vary slightly based on tree health, moisture etc. The bark is thick and dark and can be deeply furrowed. These trees prefer sandy soil or sandy loam but they will grow in clay. They prefer a decent amount of water but once well established generally don’t need supplemental water. These are deep rooted trees which helps with the hurricanes they deal with in the coastal plain in their native range. These trees are able to deal with salt spray near the coast as well as dealing with some soil salinity. These are very long lived trees. There are trees that were planted in the 1700’s that are alive and well today.There is such a thing as cold hardy southern live oaks. This is a solid zone 7 plant.There are people who are growing these trees in USDA Zone 6 and even Zone 5.

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There are some related varieties of Live Oak that also should get mentioned. Quercus fusiformis also commonly called Texas live oak it differs from the common Southern Live Oak in that the acorns are bigger and the tree itself is smaller.It can reach from 25 to 40 feet in height. This tree can take dryer conditions and also may be slightly hardier than Southern Live Oaks.

Quercus geminata is commonly called Sand Live Oak. It is native from Southern Virginia through Southern Florida and along the Gulf Coast. It grows in sand dunes and forms scrubby forests. It is a smaller tree than the Southern Live Oak. In most cases it grows to around 50 feet tall but in exceptional cases can grow over 90 feet tall. It has thick bark and shiny leathery leaves that are around 2 inches long. So far I have not been able to find cold hardiness information for this tree but I suspect it is similar to the Southern Live Oak. Due to its nature of growing in sandy dry places it may have some greater cold tolerance as sandy barrens can get much colder than surrounding areas in winter due to radiational cooling.

Quercus minima is commonly called the Dwarf Live Oak or Minimal Oak. It is found in the Southeastern United States. It is a small tree growing no larger than 7 feet tall. It may have some potential for cold hardiness especially being a smaller plant but I have yet to find information regarding that.

Quercus turbinella is commonly called Sonoran Scrub Oak and Grey Oak it is native to the Southwest United States and Baja California. It’s range is as far north as Utah and Colorado. It has spiky leaves and usually stays a shrub under 20 feet though it can sometimes grow larger. Due to its more northern and mountainous range this species may have considerable potential as one of the most Cold Hardy Evergreen Oaks

Quercus chrysolepis this is commonly called the Canyon Live Oak. It is native to the West Coast of the United States from South Central Oregon all down the Pacific Coast of California. There are also populations of the tree in Nevada, Arizona and New Mexico. It also grows in northern Mexico. The leaves are glossy and they can reach from 1- 3 inches in size. It can be a shrub under 20 feet in size to a tree of over 100 feet in some cases making it one of the larger Cold Hardy Evergreen Oaks. This tree is quite hardy and can withstand below zero Fahrenheit temperatures.

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Quercus vacciniifolia this is commonly called the Huckleberry Oak. It is a very small shrub usually under 5 feet in height. The leaves are small and leathery. This tree is native to the mountains of Southern Oregon,California, Nevada and into Northern Mexico.I have not been able to find cold hardiness information yet on this plant but I would guess it may be fairly cold hardy due to it being native to higher elevations.

Quercus hemisphaerica is commonly called Sand Laurel Oak or Laurel Oak is a evergreen to semi-evergreen tree. It can grow fairly large over 100 feet although it is usually smaller around 60 feet or so. This is one of those plants that the colder the conditions the less evergreen it will be. The leaves are around 1 inch to almost five inches in length. It prefers sandy soil. The tree is native to the coastal plain from Delaware to Eastern Texas.

Quercus myrtifolia is commonly called Myrtle Oak is a shrub to small tree that can reach up to 40 feet in height on occasion. it is native from Coastal South Carolina to Florida and along the Gulf Coast to Mississippi. I have not been able to find hardiness information yet regarding this plant.

Quercus myrsinifolia is commonly called Bamboo Leaf or Chinese Evergreen Oak. It is native to South Korea, Japan, China, Laos, Thailand and Vietnam. It can grow up to around 70 feet in height. I have not been able to find cold hardiness information yet for this plant but seeing that it is native to South Korea makes a good case that it may be fairly cold hardy.

Quercus stenophylla is native to South Korea, Japan and Taiwan. I have not been able to find cold hardiness information yet for this plant but seeing that it is native to South Korea makes a good case that it may be fairly cold hardy.

Quercus semiserrata is native northeastern India, Bangladesh, Myanmar, Thailand, small parts of China and Tibet. This is a small tree to usually is under 30 feet tall. I have not been able to find cold hardiness information yet for this plant but it is native to higher elevations and it may be fairly cold hardy.

Quercus oxyodon is native to Tibet, Bhutan, Myanmar and Northern India and Southern China. This tree can grow to around 60 feet in height. I have not been able to find cold hardiness information yet for this plant but it is native to higher elevations and it may be fairly cold hardy.

Quercus glauca is commonly called Ring-Cupped Oak or Japanese blue oak it is native to South Korea, Southern Japan, China,Nepal, Bhutan, Northern India, Afghanistan, Myanmar and Vietnam. This tree can grow to around 60 feet in height.I have not been able to find cold hardiness information yet for this plant but it is native to higher elevations and it may be fairly cold hardy.

Quercus acuta is commonly called the Japanese Evergreen Oak. it is native to South Korea, Japan, Taiwan and China. I have not been able to find cold hardiness information yet for this plant but seeing that it is native to South Korea and Japan makes a good case that it may be fairly cold hardy.

I will keep researching this topic and I hope to get more information about Cold Hardy Evergreen Oaks. Many of the Asian species have promise I believe and I will update the post when I get more information.

Cold Hardy Southern Magnolias

 

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Cold Hardy Southern Magnolia in Philadelphia PA.

There are a number growing number of gardeners who are successfully growing Southern Magnolias outside the southern United States. Their natural range is the deep south of the United States. The states in the natural range of this tree include North Carolina, South Carolina, Georgia, Alabama, Mississippi, Louisiana and Texas. In their native habitat they can become very large trees over time. There are some older trees that are over 120 feet tall. They can grow from 1-2 feet a year in good conditions which is considered a slow growing tree. Their natural shape is somewhat like a pyramid with older trees sometimes growing quite wide. This is a broadleaf evergreen tree with large shiny dark green leaves that can be 5-8 inches long and 2.5 to 5 inches broad. The flowers are very showy and large. They are white and up to 12 inches across and have a very sweet fragrance. Southern Magnolia like a well watered but not boggy location and rich soil on the more acidic side. Partial shade to full sun is ideal.

In my personal travels I have seen Cold Hardy Southern Magnolias in Columbus 6A and Lancaster 6A Ohio as well as several specimens in the Toledo Ohio 6A, 6B area. I have also seen them in Philadelphia 7B and Washington D.C. 7A Some of the specimens in Washington D.C. are very old and massive. From my research trees in the wild or trees grown from seed collected from wild trees appears to be hardy to Zone 7A.

Southern Magnolia leaves and flowers
Southern Magnolia leaves and flowers

There are several cultivars that appear more cold hardy than the wild variety. There are two cultivars I am going to mention. The first Cold Hardy Southern Magnolias cultivar is Brackens Brown Beauty. This tree develops a dense canopy with smaller leaves than the wild variety. This is the variety that I have seen planted in Ohio and is possibly cold hardy to Zone 5B. The other cultivar that I have seen tried in the north is Edith Bogue. This is a vigorous tree with a pyramidal shape. Both of these cultivars are worth trying in colder climates than wild grown trees could tolerate. These can grow to decent size trees over time but don’t expect them to get as large as they would in the deep south.

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