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Plant Answer Line Question

Keywords: Cryptomeria

My Black Dragon Japanese Cedar has a lot of dead branches. The tree is healthy otherwise. A foot of new growth this year. The nursery told me this was normal. Can you give me an opinion?


Apparently, dieback is often seen on Cryptomeria, as the following information from North Carolina State University Cooperative Extension, no longer available online, suggests:

Cryptomeria can have leaf blight or spot. Branch dieback is common. Dieback has not been associated with a disease but has been touted as the nature of the tree. Pathologists are still researching this. There may be some tip dieback associated with a disease.

There is another discussion of a Cryptomeria with dead branches on University of British Columbia Botanical Garden's forum which mentions rust and needle blight (both fungal diseases) as possible causes.

You may want to bring samples of the affected branches (along with your photo) to a Master Gardener Clinic for diagnosis.

You may find this University of British Columbia Botanical Gardens Forum discussion of interest.

The growth rate of a foot a year makes sense, considering that this is not a large tree. See below what Great Plant Picks, a Seattle-based website, has to say about this tree. An earlier version of the page linked here, from Iseli Nursery, indicates a growth rate of only 3-6 inches a year.

Information from Iseli Nursery: Cryptomeria japonica 'Black Dragon' (Japanese cedar )
Cryptomeria japonica is one of the most variable conifers you can imagine, with plants ranging from very dwarf rounded shrubs, trees with golden or contorted leaves, and wild forest trees to 80 feet high and 20 feet wide. 'Black Dragon' takes the middle road, neither too small nor too big. It has the deep green, needle-like leaves characteristic of this species and grows to about 7 feet high and 8 feet wide in twenty years. This very dark-foliaged conifer is easy to grow and combines well with plants having larger or variegated leaves.
Japanese cedars thrive in full or part sun in well-drained, humus-rich, acidic soil and average moisture. May grow quickly when it first comes home from the nursery, due to the added fertilizer it gets there, but within a year it will settle into its dense, compact habit of growth.
Cryptomeria japonica 'Black Dragon' is an evergreen, coniferous shrub. It grows wider than high, with an overall pyramidal shape. In 20 years it will reach only 7 feet high and about 8 feet wide.
Hardiness: USDA zones 6 to 9

Date 2019-04-27
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Plant Answer Line Question

Keywords: Tree staking, Cryptomeria

I recently planted a 1 gallon, approximately 2-foot Cryptomeria japonica 'Sekkan Sugi' in my yard. I noticed it leans. Is it normal for it to lean? Do I need to stake it so it grows straight? If so, how I would stake it?


According to Oregon State University's Landscape Plants website, Cryptomeria japonica 'Sekkan Sugi' is meant to be upright.

An excerpt: "Seems to be some confusion about this selection(s?), listed as both fast and slow growing. Perhaps some of the confusion can be attributed to insufficient attention in handling similar Japanese cultivar names. Jacobson (1996) lists 'Sekka Sugi' and 'Sekkwia Sugi' as synonyms for the warped and twisted cultivar, 'Cristata'; and that 'Sekkan Sugi' may appear as 'Sekhan Sugi'. van Gelderen and van Hoey Smith (1996, p 216) have a picture of a cultivar listed only as 'Sekkan'."

Based on what Seattle-area Great Plant Picks says about Sekkan Sugi and Cristata, I think that you may want to support your tree carefully, as both cultivars are described as upright.

Here is an article from Iowa State University Forestry Extension on the matter of whether or not to stake a tree:

"If possible, avoid staking and/or guying trees. Small trees, trees less than six feet tall or less than one inch in caliper or diameter, should not need staking to support them. As tree planting stock gets larger, their root system, ball-and-burlap, or pot size may not be sufficient to support them without tipping or transferring top movement down to the root system. With trees that may be able to support themselves, plant them and watch the planting hole for several days after planting. If the tree tips or leans, it needs support; if the plant stem at the soil line is moving excessively, creating a 'crowbar' hole which is a quarter of an inch or larger than the stem of the tree, it probably needs support."

The book The Tree Doctor by Daniel and Erin Prendergast (Firefly Books, 2017) says that staking might be needed if your newly planted tree is in a windy or exposed location. The authors recommend anchoring the tree with at least two stakes at equal distance from the trunk. Drive the stakes into solid, undisturbed ground at least 2 feet deep, and tie the tree with biodegradable material like burlap, rather than wire encased in rubber hose. Leave at least an inch of room between each tie and the tree trunk. The tree should be able to sway in the wind. Remove the stakes and ties after a year. I also wonder if you could carefully dig down and shift the position of the tree in its planting hole to guide it upright. If you are able to do this easily, you can avoid staking.

Date 2019-04-25
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Plant Answer Line Question

Keywords: Cryptomeria, Tree roots

I have a question about Cryptomeria japonica 'Black Dragon.' I would like to know the approximate diameter and depth of the root system at full growth. I am trying to convince the local cemetery to permit me to plant one there.


According to Richard Bitner's Conifers for Gardens (Timber Press, 2007) Cryptomeria japonica 'Black Dragon' typically grows to about 6 feet tall. As a dwarf form of C. japonica, I would expect its roots not to be much of a problem. The (non-dwarf) species can grow to 160 feet, in which case, roots would extend a considerable distance. The local website, Great Plant Picks, features the variety 'Black Dragon' and says it grows to about 7'H x 8'W.

Here is general information on trees and their root systems, from Tree Roots in the Built Environment (Roberts et al., Centre for Ecology & Hydrology, 2006):

About root depth:
"A further misconception about tree roots is that they occur typically in significant quantities at substantial depths (i.e. greater than 3 m.) in the soil profile. [...] from numerous studies involving comprehensive root excavations the indication is that typically as much as 90% of the tree root length occurs in the upper metre of soil." According to this same source, conifers usually have about 70% of their roots in the upper 50 cm. of soil."

About root extent:
"[...] large species differences exist but it is also the case that the horizontal extent of tree roots substantially exceeds the perimeter 'dripline' of the crown. [...] there is a good relationship between crown spread and root radius but the relationship tends to be very species specific. Roots extending furthest from the tree trunk are usually found in the soil surface. [...] the maximum extent ot the tree roots is reached before the canopy has completed expanding, suggesting that the ratio of root spread to crown spread may decrease as trees become older."

This same source also says the root extent is highly dependent on soil environment (richness of soil, access to water and nutrients).

To summarize, what all this means is that the width of your tree's crown will give you only some idea of the extent of the roots, and most of those roots will be shallow.

Date 2019-05-22
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