Hi Steve, I think before you prune your tree,you may try some research on what cultivar your tree really is. I think it might not be the cultivar 'Witches' Broom' and may be another. Can you see the graft union? Has it been grafted on a high standard or do you see a graft union close to the ground?
Heres a photo of a 'Witches' Broom' i have grown for years.

Al

When you Google this Ginkgo sizes and shapes are all over the place.

I suspect this name covers more than one dwarf clone, This one looks as if it will be moderate in growth rate.

Yours could be a species grower and it could get big basing that on the robust growth look it has. Check for a graft union. If there it could be anything and incorrectly labeled.

I think the true one grows in a globe shape to about 10 to 12 inches in diameter and 3 ft. high when grown on a standard.
The one shown in the photo, left center, I believe to be a correct representative of Ginkgo biloba 'Witch's Broom'

This one 10 years old. {{gwi:639426}}

Dave

lets start .. by discussing WHY???? ... you want to maintain HEIGHT????

its a tree ... none of us suggest TOPPING trees ...

all the info you need.. on a fully established tree.. is right there in your pic .... look at last years growth ... w/o a scale.. it looks like 8 to 12 inches ... it will ... w/o doubt.. grow at that rate for the next 100 years.. unless you kill it ...

topping it.. will expose.. repeatedly ... new wounds ... and lead to eventual decline... over the next decade or two for sure... lol ...

you are not in snow load ... so personally.. i dont care about two leaders with that weird crotch between them ...

i would probably clean up the low hanging branches that I THINK IS see down low ... expose the 'Y' .. and revel in it ..

trying to reduce to one leader is not really imperative... and probably too late to be done ... i would prefer 2 ... to a 30 degree angle in the trunk ...

a WBroom .... is a plant with a reduced growth rate as compared to the mom it was taken from ... such is the basis for ALL named varieties of any type of plant.. but especially in the conifer world ... IMHO ... when its name was lost... IF IT EVER HAD ONE .... it becomes NEAR impossible to name it.. we can have a lot of fun speculating.. and guessing ... but personally... i would never feel secure in ever stating with any certainty ... that i KNOW the name ...

one thing.. as i type endlessly .. lol ... that strikes me ... is that i have a few .. non-WB types... and i cant even get them to grow.. IN MICHIGAN .... at the rate yours is growing at .... which makes me wonder.. if the cause of your Y ... in the trunk.. wasnt a failure of a graft ... and you have the plain old understock gingko tree ...

you have a nice tree there.. if you can enjoy it for what it is... rather than forcing your own aesthetic on it .... so i am right back to how i started .... WHY??? ... do you want to top it???

all that said... it is yours... if you want to topiary it into some certain shape or form.. knock yourself out ... its a prerogative of ownership ...

good luck

ken

ps: i may be mocked for the analogy ... but in the hosta world.. i like to say.. that a $100 hosta without a name tag ... is nothing more than a $5 hosta ... as they all look alike.. when you really get down to brass tacks ...

Here is a link that might be useful: growth rates in conifers .. of which a WB usually indicates a lower annual growth rate.. than the norm ... yours is definitely NOT a mini nor a dwarf ....

Thanks, all, for the input.

Al - The graft union is just below the lowest branch, about 4' high. Is there any way to research the cultivar, absent accurate information from the seller?

Dave - see above re the graft. It maintained the "witch's broom" form for quite a while, with ball-shaped growth appearing to radiate from a single point. It was only this fall that I noticed the substantial increase in diameter of the leaders, along with a much thicker trunk.

Ken - Points well taken, but I was sold this tree as a witch's broom, dwarf variety that would not exceed 10'. It's in the wrong spot for a larger tree - it's too close to the house. How can I tell if the graft failed? All of the branches appear to originate from above the swollen area I've assumed is the graft union

Hi Steve,

16, 17, 19 and 25 inches. Those are the lengths of last year's (2013) growth on one of my 'Mariken' ginkgo grafts. I made the grafts in 2010. They just sat there and put out the anticipated 3-4" of growth for the first few years.

I just went out in a below zero blizzard to take the measurements and to confirm the graft union. The graft union on the pic you posted is really obvious if one enlarges it.

I've noticed over the years, while grafting about 50 different gingko cultivars, that few of them read the books or the websites that tell them how and when to grow.

I've observed a similar pattern of growth between 'Mariken' and 'WB' (Witch's Broom). It may well be that the cultivar that you have is not just a random witch's broom but the one specifically named 'WB'/'Witch's Broom'.

That being said, I think that you can expect an irregular growth rate in the future.

As Ken says, it IS your tree. If you want to hold it back so it fits the allowed space, then you'll need to prune it so that it can grow into the allowed space over the coming years. Pruning back the longer shoots will stimulate more side branches which will thicken the "ball", if that is what you are after. You'll then get a specimen that looks more like those in Al's or Dave's photos.

An alternative, if you have the space elsewhere, is to transplant it in early spring or late autumn when it is not in leaf.

If there is someone out there who is in their 30's or 40's who wants a challenge, there is a distinct need for someone who is willing to grow and document such growth patterns in ginkgo cultivars. They are a beautiful and unique set of conifers (not to argue taxonomic trends) which lack the documentation that many other plant groups have achieved over the decades.

Charley Hunter

let me try again ... due to MY FAILURE to communicate ...

with a non-recently transplanted tree/confer ... your annual growth rate.... is right there in your pic ... you need no further information ....

the only reason it might be less... would be severe drought .. something environmental ...

if you do not like .. or appreciate how it is growing.. you need to become proactive on pruning ...

and i would NOT define that as simply giving it a haircut ... what we might call 'topping it' ... we can help with that ... and can recommend some good pruning shears and tree saws .. they really make a difference in tree surgery ...

but what its name is.. is basically an interesting side fact ... but irrelevant to the process ... though you might be able to find out from the seller.. who his wholesaler is.. and they might be able to tell you what they grew .. and sent for retail ... etc ... a little sherlock holmes ... [even a list of names to narrow down the search, is better than nothing]

two things for sure ... prune off anything below the graft ... but never prune off the graft ...

as an example of pruning theory ... in your pic.. at 3 o'clock ... there is a potential third leader ... nothing wrong with that.. UNLESS ... it is growing toward the house... if so ... it probably should go down at the right trunk ... looking at the shadows of the other trees... it is on the north side.. and it will elongate to get to sunlight ... and MIGHT.. someday ... outgrow the others .. not only toward the house.. but making a lopsided tree ... or not.. who knows ... just giving you a flavor of pruning ideology ...

pruning trees.. is really no big deal ... its hard to kill them with properly made cuts.. and they always grow back .. and if you screw it up.. they usually sort themselves out.. but all of that.. can take years ...

but if you are one of those peeps who dont want to mess with it.. and dont enjoy the challenge of inflicting your will on a tree .. then be done with it ... life's too short if its pissing you off ... lol ...

good luck

ken

It's gonna get too big for where it's at?
Move it .....and then relax.
Mike