Trees in parks and gardens 2010

[johnw]

Stephen  - I am happy to hear the Broussonetia turned out to be hardier than expected. 
johnw

It turns out that it's even hardier than I had imagined as I've just discovered a couple of shoots high up in the plant which is abouit 1.5m high!! Yesss...

Stephen - Can you grow Robinia pseudoacacia?  Someone from Norway told me they had no luck with it at all.   They become very big trees here so that was a shock.

johnw

[Lori S.]

Acer negundo 'Kelly's Gold'. Members in the USA will probably be amazed that I would give A. negundo garden space as I believe it is a weed species with you but they never seed about here.

It's quite nice to visit riverine hardwood forests of Acer negundo - Manitoba maple is the common name - where they occur on the Canadian prairies.  Re. being "weedy", the rap against them, also in these parts, tends to be that they are attractive to aphids which feed on the plant juices and excrete honeydew... which falls on anything beneath the tree, and then is host to a black mold.

Not surprising as while Acer negundo is generally tough as nails its range goes into California and this is where Flamingo was discovered. 
johnw

An even better indication of the hardiness of the species is that it is native to the Canadian prairies! 

[johnw]

An even better indication of the hardiness of the species is that it is native to the Canadian prairies! 
[/quote]

Lori

But its hardiness is variable.  The Acer is an impossible weed in Ontario but rather restrained here but fully hardy.  Cornus florida which ranges from northenr New England into the mountains of Mexico. We cannot flower nor get the selections from Texas to live but a few years here - ie 'Cherokee Chief' etc..  The books say CC is hardy in Zone 5b yet they lump all the floridas in one basket.  The northernmost ones are reliable on the coast here - Z6a/b.

johnw

[Lvandelft]

Luit, how tall will the Tilia cultivar eventually reach?  It's rather fetching.

Mark, they told me 6 m. in 20 years. It's sold here as full standard tree too.
But I do like the more natural form! After 3 years it's just about 100 cms., so I believe it will reach the 6 m. earlier?

[cohan]

Luit, how tall will the Tilia cultivar eventually reach?  It's rather fetching.

Mark, they told me 6 m. in 20 years. It's sold here as full standard tree too.
But I do like the more natural form! After 3 years it's just about 100 cms., so I believe it will reach the 6 m. earlier?

the miniature is interesting!
we have a T cordata growing here very nicely, and i've been trying to find out how tall it should get, as i don't really want a giant shade tree where its growing..i read european mentions of a large tree indeed, but a saskatchewan reference (i don't remember the exact details now) to a much smaller tree... i'd rather not start hacking at it if i don't have to, since it has such a nice shape...
it was trialled in alberta along with various others, and was marginally hardy at some sites, but is doing well here, no signs of damage..

[Stephenb]

Stephen - Can you grow Robinia pseudoacacia?  Someone from Norway told me they had no luck with it at all.   They become very big trees here so that was a shock.

johnw

John: I haven't tried it, but it has a reputation of not being easy and I doubt very much it would make it in my climate. Shouldn't really compare our climate zones with North American, so I won't, but I'm in Norwegian zone H4-5 (min. -25C) whereas the best zone is H1. Robinia pseudoacacia is supposed to be OK for zones H1-H2. However, Robinia x ambigua 'Decaisneana' has proven hardy in this area. A friend who lives near to the airport in Trondheim (near me) has a good sized tree and I've been offered a root cutting, but it's a bit too invasive for my liking! Here's a couple of pictures from his garden:

 

[Ragged Robin]

Robinia are wonderful for foliage and I love the flower panicles too.... R. pseudoacacia is  a particular favourite because of the acid yellow glow which looks wonderful against any sky but particularly a blue one    The only trouble is it grows to 80 feet high I believe    

[Stephenb]

Thought you might like Robinia Robin, for some reason or another

Has Robinia naturalised in your area (I know you have...)?

[TheOnionMan]

Robinia pseudoacacia has an interesting history here in the USA, originally with relatively restricted distribution, it has spread to nearly every part of USA and is considered a noxious weed species in some States, as it is in my State of Massachusetts where sale of the plant is prohibited.  Its invasiveness is not restricted to North America, but is also listed as invasive in some European areas, such as in Poland.

When the trees are in bloom, one realizes just how widespread it is, it is EVERYWHERE.  Here are some links that purveyors of Robinia might find interesting:

Wikipedia
http://en.wikipedia.org/wiki/Robinia_pseudoacacia

More useful is this USDA Plant Profile
http://plants.usda.gov/java/profile?symbol=ROPS

Global Invasive Species Database
http://www.issg.org/database/species/ecology.asp?si=572

One that I have admired in the past, is the smaller shrubby R. hispida.  This one is particularly common near coastal areas here, liking the sandy soil found in these areas, but the species can grow anywhere and is widespread.  It has a similar story as R. pseudoacacia in terms of distribution, R. hispida was initially native to several southeastern US States but has spread and can be found throughout much of the country now, and including southeastern Canada.  This species is highly variable, in some forms the very large showy "blousy" clusters of rich pink bloom covering low (1-2 meter) thickets of stems, in other forms, the floral display is not nearly as good.  Out of bloom, I do not find the irregular messy thickets particularly attractive.  The species, like many Robinia species, suckers strongly, and many people who have tried cultivating this species, complain of its terrible invasiveness.

Robinia hispida
http://www.google.com/#hl=en&q=robinia+hispida&aq=f&aqi=g3g-m1&aql=&oq=&gs_rfai=&fp=19d13023017841d
http://en.wikipedia.org/wiki/Bristly_locust
http://www.missouriplants.com/Pinkalt/Robinia_hispida_page.html

[johnw]

Mark - I love the bark on the Robinia which to me resembles wet cement that someone has pulled a pointed trowel from top to bottom.  I see a few seedlings around local trees - mainly in our drier sandier counties - but never see the masses as with hispida nor the incredible suckering habit of the latter.

johnw

[TheOnionMan]

Mark - I love the bark on the Robinia which to me resembles wet cement that someone has pulled a pointed trowel from top to bottom.  I see a few seedlings around local trees - mainly in our drier sandier counties - but never see the masses as with hispida nor the incredible suckering habit of the latter.

johnw

John, there is much to like about Robinia, they are rather fetching in bloom, and as you mention, the bark, but their global track-record speaks of other concerns or dangers regarding invasiveness in general that needs consideration.  With R. pseudoacacia, it has more to do with spread by seeding, much the way Paulownia tomentosa has become an invasive weed tree in parts of the mid-Atlantic States that I'm familiar with... witnessing its glorious invasion (glorious on account of the beautiful purple-blue flowers) first hand driving along hundreds of mile of highway where the roadside habitat has been usurped by aggressive alien flora.  One can be mindful of differing climates that can mitigate the invasiveness, for example; Paulownia reaches its northern hardiness range in New England, and the trees are rare, and would be most unlikely to ever become invasive in this climate, but not far away further south, it's another story.

With R. hispida, all that I have ever seen of this species (and I've seen and admired it a lot), is that it invariably grows into wide-spreading thickets, certainly some looking more menacing and aggressive (gorgeous in flower though) than in other locations.

[johnw]

Mark - I guess it's a case of one man's weed. I doubt I'll see the day that Paulownia seedling will make it the next year here. Still lovely to see them along the freeways in NY and NJ.

I was just in St. John's and their weed tree is Laburnum alpinum, it's everywhere.  There is a steep cliff near one of the downtown interchanges that must have a thousand tree cascading down.  A perfectly sight until the leaves turn black in late autumn.

johnw

[Roma]

On Thursday night, before a very interesting lecture by Charles Notcutt on Trees & Landscapes of the Americas, covering parts of Chile, Colorado and Washington State, I spent almost an hour in the Cruickshank Botanic Garden in Aberdeen. 
While my main interest is alpines I like most plants.  Here are a number of trees and shrubs which caught my eye.

A very colourful corner of the Terrace with Wisteria, Ribes speciosum, Crinodendron hookerianum and Embothrium coccineum (the wall behind is about 8 foot high)
Closeup of Ribes speciosum
Crinodendron hookerianum and
Embothrium coccineum in another part of the garden
Laburnum with Enkianthus campanulatus

[Roma]

A few more

Azara lanceolata
Magnolia wilsonii
and for Lesley Juniperus recurvus coxii

[Roma]

Another shrub and a small tree
Chiliotrichum diffusum
A cristate form of Cryptomeria japonica