Those Devilish Details – How To Make Your Trees Better

You may remember this American elm, Ulmus americana, from a couple of months ago.  I lifted it and put it directly into this neat funky Chuck Iker rectangle.  It dutifully threw new shoots, and I wired an initial design.  So far, so good.

 

 

 

 

 

 

 

 

 

Here we are this morning.  Very nice growth, as you can see.  I recently pruned back the leader, as it had grown enough for this year.  But now I have a lot of unruly branches that need attention.  They say the devil’s in the details.  They must have been thinking of bonsai when they came up with that one.

Now, how do you go about tackling the details that will take your tree to the next phase of development?  Here’s a step by step illustration of my thought process and the results.

I almost always begin at the bottom of the tree.  In this case, the number one (lowest left) branch of the tree needs pruning.  You can see in this closeup that a secondary branch has emerged all on its own.  Perfect.  I can cut to this branch, and next year let it run before pruning it again.

 

After pruning.

 

 

 

 

 

 

 

My next stop is the branch above the number one branch.  Why not the number two branch, the one on the right side of the tree?  It’s not as thick as I need it to be (see two photos down).  Pruning it back would not be the right thing to do at this time.  You’ll commonly see this in the growth of your trees.  Branches tend to grow with more strength in the apex.  Branches also tend to grow with different degrees of strength in the same part of the tree.  Part of developing your bonsai is to balance this growth by means of selective pruning.

Branch pruned.

 

 

 

 

 

 

 

 

This is the number two branch, the lowest right-hand branch.  You can see that it’s not as strong/thick as the lowest left branch – in part because there are actually two branches emerging from the same spot.  I needed a back branch, so kept them both.

 

Now let’s move up the tree some more.  This branch near the apex is way too strong (not surprisingly, apical dominance you know).  It needs to be “cooled off.”

 

 

 

 

 

 

Cut back pretty hard.

 

 

 

 

 

Now on to the other side of the tree.  Same problem.

 

 

 

 

 

I unwired it and pruned it back hard.  That’s step one for this branch.

 

 

 

 

 

 

 

Now I used the same wire to rewire the smaller branch I cut to into position.

 

 

 

 

 

Now back to the other side of the tree.  This branch needs to be pruned.

 

 

 

Snip.

 

 

 

 

 

Here’s that back branch I mentioned above.  I don’t want this branch to get too thick, as it might cause undue swelling at the point on the trunk where they emerge.  So I’ll prune it back.

 

 

 

Snip.

 

 

 

 

Back up higher in the tree, this branch is now obviously too heavy.  I’d trimmed the secondary branches that emerged, but more needs to be done.

 

 

 

 

Unwire and prune back.

 

 

 

 

 

 

Now I’ve wired one of the secondary branches out as a new leader.

 

 

 

 

 

And here’s the final result.  This is a nice little American elm bonsai.  The species grows so fast that by the end of the 2018 growing season, I should have a nicely filled out specimen.

Let me know what you think.

 

 

One Of The Big Trees I’m Keeping, An Awesome Bald Cypress

In keeping with the weekend’s theme, I wanted to update you on one of the big trees I’m keeping, an awesome Bald cypress (Taxodium distichum).  The last time I blogged on this one was in July.

July is Bald cypress defoliation season.  If your tree is in good health with a solid root system, you can defoliate every July right at the beginning of the month.  There are a couple of reasons for this: one, you get in some extra training as defoliation allows you to put on some wire (possibly after removing any that’s biting in) and bend some of those branches that insist on being straight; and two, you get a fresh set of foliage that allows you to avoid the ratty looking late summer foliage typical of BC.

Here’s the tree back on July 3rd.  The branches are coming along, and the apex I’m building is likewise getting closer to the size I need it.  I’ve grown out and chopped back the leader a couple of times now.  In another two or three years, I should have the crown completely developed.

And here we are today, just shy of three months later.  Doesn’t this foliage look great?  For those of you who have experience growing Bald cypress, you know what they look like in September if you just leave them to grow through summer.  Not very pretty.

 

 

 

 

 

 

 

 

 

 

Notice how much stronger the growth is in the upper part of the tree.  I have many branches growing straight up.  This is normal behavior for most species grown for bonsai.  They’re usually all cut down to control their height, and they’re all programmed to get as tall as they can as fast as they can.  So it’s only natural for them to send growth skyward.

 

 

 

This is all I’ll do for today, just tidying up the growth by removing the up-growth and trimming to shape.  I’ve removed more from the upper part of the tree than from lower down, in order to keep the energy balanced.

There’s plenty of development left to do on this tree, but it’ll wait till next spring.  In late winter I’ll do a thorough wiring and some aggressive shaping of the branches.  Cypress branches all want to grow straight.  That’s pretty boring, so I’ll have to correct it before they become so stiff I can no longer bend them.

Let me know what you think of my progress so far.

Just This One Last Big Tree … I Think

A couple of weeks ago I measured the height of stupidity at 25 feet, because I collected this massive Sycamore that had to be chopped down from that height.

At the time I observed that getting older means working with fewer really massive trees.  They really are a lot of weight to move around.  Oh, it’s okay to have one on the bench, provided you limit the number of moves you make with it.  But a lot of the problem is getting the tree from the ground (saw and lift, wash and chop roots, pot into growing tub) to the bench.

 

 

 

 

 

 

So the Sycamore lived, as you can see in today’s updated photo.  We’re still four weeks away from the dead-end of growth for 2017, so I anticipate additional foliar growth during that time, most likely a need to do some wiring, and then this tree will be limited to root growth (which I doubt has really gotten much under way yet).  Root growth will continue on into fall, so I’m pretty confident this tree will be ready to rock and roll in 2018.  We’ll know then.

 

 

 

 

As many of you know, Bald cypress (Taxodium distichum) is one of my absolute favorite species for bonsai, and it’s certainly the most popular with my clients.  I never seem to have enough of them.  So I reached out to a local fellow collector to see if he had any extra material sitting around that he was willing to part with.  I picked up a handful of nice specimens today.  This is the biggest one I got.

With a trunk base of 8″ (8″ above the soil surface) and a root spread of 20″, this Bald cypress fits right in the category of trees I’m too old to lug around.  It’s got to weight close to 100 pounds.  At the same time, I know there’s someone out there who has just got to have this tree.  So once we’ve matched tree to BC lover, my wrestling days with this one will come to an end.  Meanwhile, it’s very impressive and has an assigned spot on the bench from which it will not move.

How A Few Trees Will Get A Lot Better In 2018

It’s a safe bet to say we spend most of our time in the pursuit of bonsai looking toward the future.  Why?  Well, with the exception of the perfect or “finished” bonsai on our benches, everything’s a work in progress.  So we look ahead to what we’re going to do today when we wire our trees, or what we may need to do next week when it’s time to pinch, or what we plan to do next growing season.  It’s September, so my thoughts are running to the next growing season.  I’ve just about gotten all I can from this one.

Here’s a Chinese privet, Ligustrum sinense, that I potted earlier this year.  The reason this tree came out of the ground is the very neat shari on the trunk.  This feature will be with the tree essentially forever, since the growth going forward will be slow enough that the healing process won’t overtake it.  So all that leaves is building the rest of the tree.  I wired a new leader and some branches earlier this year.  The growth has been pretty good.  But I’ve still only got a leader with some leaves on it.  It used to be a couple of feet longer, but I went ahead and clipped it for the purpose of this blog.  There’s little growth left this year, so I won’t be missing anything.

How will this tree get a lot better in 2018?  First of all, my leader is going to produce buds in the leaf axils all along it.  From these I’ll be able to select crown branches, and wire and position them.  As they grow, and as the new leader I’ll select grows, its base will continue to thicken and that will make the tapering transition look smoother.  I should make very good progress on this in 2018.  In fact, I’d predict that with judicious pruning and pinching and wiring and shaping, I’ll mostly have a Privet bonsai in hand by the end of next year.

This Bald cypress, Taxodium distichum, has been grown from seed.  It’s just a few years old.  But I was able to make something of it this year – a future windswept flat-top style Cypress bonsai.  Though it’s a very juvenile tree, there’s already a design with just four branches and a leader in the crown.  It actually looks like something.  But you can clearly see the youth here.

How does this tree get better in 2018?  I have a couple of chores that will need to be done.  One is to control the growth of the branches already in place.  I’ll do this by first letting them grow uncontrolled, and then doing a hard pruning and wiring as needed.

The second chore is to work on the crown.  I have a leader for my flat-top idea, but that’s all.  It needs to fill out a lot more, and thicken more (though I have to be careful with this).  I’ll do more in the crown more often than elsewhere.  I can’t afford to let it get away from me.

What about the trunk, meaning the bark and the appearance of age?  That’s going to come in time.  As early as next year I may see the bark starting to take on some age.  Even if this doesn’t happen, it’s only a matter of time.

Here’s an impressive Cedar elm, Ulmus crassifolia.  It was a bit sluggish coming off collection in April, and it took some coaxing to get it to finally kick in some strong growth.  In the case of this tree, however, that turned out to be a blessing in disguise.  Why?  Well, in the case of each of the three trunks of this tree, they suffered some dieback.  While we don’t generally want to see this happen, I actually now have the opportunity to build more taper into each of the trunks.  I won’t do anything more than minimal “directing” work in 2018 as the leaders continue growing, but I will be able to control where they go.  So I’ll have the best of both worlds: a great trunk base (3.5″ across), and in the future terrific taper and trunk movement.

Let me know what you think of these future bonsai.  I’d love to hear from you.

Small Change, Big Impact – And How To Hurry A Tree Along

I’ve been having a great time this year with Cedar elms (Ulmus crassifolia).  I slip-potted this one last month, as part of my bound-and-determined campaign to develop this tree into a bonsai as quickly as I can.  This is something I started doing almost 30 years ago, partly out of impatience and partly out of the desire to make a study of bonsai techniques to test limits.

This specimen has been “Cedar elm strong.”  It came back from collection quickly and has grown with vigor since.  It was four months from lifting to bonsai pot.  Now, the main advantages of this specimen and others like it can be summed up as follows:

  • The species is naturally vigorous
  • The specimen has the appearance of age
  • The specimen has actual age
  • Slip-potting (or, though usually less desirable, direct-potting) can be done without fear of killing the tree
  • The specimen has good taper, with the trunk chop being small enough that the tapering transition can be pulled off in the pot and within two years

Given these features, I know I can cut out one or two years’ worth of development time.  What this means is, if I were to have plodded along with this tree in accordance with conventional wisdom, it would still be in a nursery container putting on growth without my having done a thing to it besides water and feed.  Only next year would I sit down and start the styling process.  It would be another year before the tree went into its bonsai pot, and another couple of years before the tree could reach a “finished” (meaning showable) state.  That’s a total of four years.  I am confident that I can reach the same degree of development in, at most, three years by being aggressive.  So why wouldn’t I do that?

Here’s the tree today.  I’ve had to unwire the leader, as it’s grown really well over the past month.  My goal for today is to carve down the chop point (hurrying the tree along), and do some more work on the leader.

 

 

 

 

 

 

 

 

 

 

Here’s the result of today’s work.  This only took me about 10 minutes.  I’ve done some carving at the chop point, which enhances the taper from the trunk into what is going to ultimately be the crown of the tree.  I’ve also taken the opportunity to cut back the leader to a side branch, which I’ve wired straight up.  This is how you build an apex properly.  I’ll let this leader grow on out for the remainder of the season, with the plan of cutting it back again just before the buds start swelling next spring.  I should have the crown mostly built next year.

Now for the pop quiz.  Are you able to see the small change I made today in this bonsai-to-be that makes a huge difference in its appearance?  If you spotted the change in the planting angle, you got it right.  Compare this photo with the first one above.  When I first potted the tree, the more significant slant seemed like the way to go.  It’s bothered me since, but I didn’t want to fool with the tree again so soon.  The roots needed to firm up.  By today they had, so I was able to manhandle the tree into a more upright stance.  It makes a world of difference, doesn’t it?

 

This Crape Is Superb – How Did I Do On The Initial Styling?

I recently acquired a couple of Crape myrtles, Lagerstoemia indica, from a grower, this one and a Pokomoke I’m planning to keep for myself.  The only thing I’ve done to this specimen since I got it was to take off a large leader in back of the tree (you’ll see where a few photos from now).  Today I decided it was time to do some styling – there were numerous shoots coming from the area of the chop, and if I didn’t wire them now the wood would quickly become too stiff for me to do anything about it.

 

 

 

 

 

In this photo I’ve done three things: trim the the crown lightly to remove or shorten shoots as needed; remove some dead knobs where pruning has been done before; and put some wire on the lowest left branch.  You can see the style of this tree right off the bat.  It’s going to be a classic Crape myrtle shape.  Isn’t the trunk lovely?  Great movement and taper, and of course the nebari and root base is superb.

 

 

 

 

Here’s a shot from the back of the tree.  This shows you pretty clearly that large chop point I made.  There are several shoots emerging from the perimeter of the chop point.  This is what I expected and planned for.  I’ll be able to wire a couple of leaders off this point, continuing the design.

 

 

 

 

 

 

And here’s a closeup of the chop point.  Crape myrtle shoots are unique in that once they begin to swell their shape is square rather than round, and this persists for a short time.

My task is to select and wire two of these shoots, then shape and position them properly so that during next year’s growing season they’ll fill in their part of the crown.

This is a good place for a tip on wiring Crape myrtles.  When you go to remove individual leaves, such as those near the base of a branch, you must carefully pull them off directly away from the base.  If you don’t do this right, a slender string of green bark tissue will peel off down the branch.  This is not necessarily harmful to the tree, but it’s not good technique and frustrate you.  So practice, practice, practice.

Now I’ve selected and wired two of the shoots (I’ve already taken off most of the ones I didn’t need).  These shoots will thicken some before fall of this year, and next year they’ll really take off.

 

 

 

 

 

Another shot of the back of the tree.

 

 

 

 

 

 

 

 

 

 

And the finished styling.  I trimmed the crown to shape for today, meaning the amount that would make the tree’s silhouette look as it will once the detailed work is done in the crown.  Next spring, a harder pruning needs to be done, followed by a complete wiring of the new growth once it’s out.

The base of this tree measures 4″ above the root crown, and it’s about 28″ tall.  The flowers are white.  If you’re looking for a large, stunning Crape myrtle specimen for your collection, this tree is available at our Crape Myrtle Bonsai page.

You Can’t Fix Stupid, But I Found Out You Can Measure It

I posted a couple of blogs earlier this year about the stately Sycamore (aka Plane tree), Platanus occidentalis.  As I said at the time, I’ve never worked with the species before as it just has these huge leaves and doesn’t look all that inclined to produce much in the way of ramification in pot culture.  At the same time, the bark of the mature Sycamore is just gorgeous, stark white under exfoliating greenish-tan.  If you’ve ever seen one, you know exactly what I’m talking about.

Recently, out of the blue, a reader asked if I had any Sycamore bonsai available.  I offered the first one I collected this year.  I had originally planned to just keep the tree and work on it, just so I could see what might be made of it.  But hey, I’m always glad to help out a fellow bonsai enthusiast.

The only problem was, I was now devoid of a nice big Sycamore specimen to work on.  However … a few years ago, a volunteer sprang up near the back of my property.  I decided it would be fun to work on, so I chopped it low one season, with the intention of building taper over the course of a few seasons.  But I never got back to working on it again, and it sorta kinda took off on me and got out of hand.

Here it is now.  What I noticed about it is the nice fork in the trunk.  If you do any collecting, this is one of the handy ways to find a tapering trunk in the wild.  Often they will split at  some point low on the trunk, which will allow you to cut to the smaller one and achieve a nice taper right off the bat.

 

 

 

 

 

 

You can make this chop first in the collecting process, if you so choose.  It’s not an absolute, and you have to be prepared to seal the chop point relatively soon after making this cut.

 

 

 

 

 

 

 

 

 

Several minutes later, I’d dragged the tree to my potting bench, washed it off and chopped back the roots.  Not a bad almost formal upright tree in the making.

 

 

 

 

 

 

 

 

 

 

 

 

In case you haven’t yet picked up on the real size of this tree, here it is potted in its growing tub.  Yes, the trunk is about as wide as the tub is deep.

 

 

 

 

 

 

 

 

 

 

 

 

And that means, while you can’t fix stupid (meaning it’s kinda stupid for an old dude like me to be lifting trees this size) I found out you can measure it.  Here’s the whole tree, once I cut off those two trunks.  Stupid is about 25 feet tall.

I did say earlier this year that I was limiting the number of really big trees I planned to keep for my collection.  They’re just way too heavy to be lugging around.  This tree probably weighs about 40-50 pounds all by itself, and 80 or so in its tub.  I do want to find out if I can make the leaves reduce in size enough, and the branching ramify enough, to make this species a potential bonsai candidate.  One benefit to the size of this tree is I don’t need as much leaf-size reduction to make it look good.  Plus, if I can get to the point where the bark starts exfoliating, it should make quite a show.

How To Do A Successful Slip-Potting

Sooner or later you’ll encounter a situation where you’ll need (or really want) to move a tree from a nursery container to a bonsai container out of season.  This can be done with a very high success rate, provided you bear in mind a few key principles.  In this post I’ll show you how I moved a Bald cypress from its nursery pot to a bonsai pot because … I really wanted to.

First of all, it’s important to distinguish between slip-potting done in an attempt to save a tree’s life, and one done because you know the tree won’t mind and you get closer to your goal faster.  Let’s focus on the latter.

Consider these factors before you undertake the slip-potting:

  • Is the tree well-rooted?  You can tell by the strength of the growth, plus you can poke around in the root zone for clues
  • Is there enough time remaining in the growing season to allow for more root growth in time for fall dormancy (for deciduous species)?
  • Is the root mass of the tree shallow enough so that you don’t have to remove more than a bare minimum of roots?
  • Do you have a pot the tree will fit in without any drastic root-pruning (no root-pruning is  ideal)?

Here’s my subject, a really nice Bald cypress I’m training as a flat-top.  This is one of those trees that I knew just what to do with when I collected it.  I’m sure I heard it say “Flat-top.”

The base of this tree is 3.5″ across, above the root crown, and stands about 35″ tall.  It makes a nice statement.

 

 

 

 

 

 

 

 

 

 

 

You may have noticed that prominent dead snag on the trunk.  Looks like Pinocchio’s nose, doesn’t it?  Gotta do something about that, along with the one above it on the right (the one on the left under that living branch will be removed, once it’s served its purpose as a wire anchor).

 

 

 

 

 

Making a jin is not that complicated a process, once you get the hang of it.  You want to make the dead snag taper down while not making it look artificial, like a sharpened pencil point.

You can either carve these with a carving knife, or do the rough work with your concave cutters.  Here I’m starting on the top side.

 

 

I’ve made an angle on the top of the snag.  Good start.

 

 

 

 

 

 

 

Now I come up underneath with my cutters, and make an angled cut as I did on top.  Notice I’m also shortening this snag, which it needed.

 

 

 

 

 

 

 

Now the jin is ready for a little carving to make it look as natural as possible.

 

 

 

 

 

 

This one is done.  It sure looks a lot different that when I started.

 

 

 

 

 

 

The smaller jin above was already the right length.  It just need a little carving.

 

 

 

 

 

 

 

Now let’s get down to business slip-potting this tree.  Prepare your pot by placing screening over the drain holes, at least one tie-down wire, and spread a shallow layer of soil in the bottom of the pot (mostly in the center).

 

 

 

Gently lift the tree out of its nursery container.  You should see lots of roots, as is the case here.  Nice and healthy.

 

 

 

 

 

 

 

 

 

 

All of the roots get folded into the pot.  Do not remove any long roots such as the one you see in the foreground of the photo above.  Those roots are feeding the tree, and you want them to keep on doing it.

 

 

 

 

 

Tie the tree down, then fill in all of the empty space with well-draining soil mix.  Be careful not to damage any of the roots as you work the soil in around them.  Use a chopstick, but don’t jab it into the soil mass.  Push it in gently, then wiggle it back and forth to get the soil to settle in around the roots.

 

 

 

 

 

Here’s the end-result.  I did some light trimming in the crown so I could see how well the flat-top is progressing.  Nice.

The pot is a terrific oval by Byron Myrick.  The size is just right to enhance the impression of height, and the green accents remind me of the swamp.

As far as after-care goes, you can place trees you’ve slip-potted into a shady spot for a week or so.  My experience has been that a well-rooted tree really doesn’t suffer inordinately from slip-potting.

Let me know what you think.  Have you tried slip-potting?  Did you have good success?

What A Nice Surprise This Ficus Gave Me!

Last year I began to get more interested in some tropical species, among which was Green island ficus, Ficus microcarpa.  This year I’ve been working on stock for the future, along with getting a jump-start on some offerings.  I had bought a few larger specimens of both Green island and Willow leaf ficus, including this Green island I decided to keep for myself.

6/23/17

 

 

 

 

 

 

 

 

 

7/23/17

 

 

 

 

 

 

 

 

 

8/4/17

 

 

 

 

 

 

 

 

9/3/17

As you can see from the progression photos, this little guy has come a long way in just over two months.  They never stop growing, even indoors during winter, so I figured it would fill out pretty quickly.  But there’s more to this one’s story.  At our last local club meeting, on August 15th, the theme was tropical bonsai and I decided to bring it in in large part to show off the Chuck Iker pot (one of the primary reasons I’m keeping the tree).  A day or two before, as I was checking on my trees, I happened to notice this one was actually pushing an aerial root from the left-side branch!  It was only an inch or so long, and jutted straight out from the branch.  I literally have no experience with tropical species that produce aerial roots, so while I was enamored with the baby aerial root I had no expectation that anything would come of it.  I mean, we don’t live in the tropics despite our oppressive summer humidity.  So I truly expected the root to wither away.

Imagine my surprise when I noticed, a few days ago, that this aerial root had actually found its way down into the soil!  I literally did nothing but ignore the tree.  And then a couple of days ago, I noticed yet another aerial root emerging from a back branch – all on its own.

Is this the way to make aerial roots on trees?  Well, it’s obviously not an applied technique as it just happened.  I’ve heard of such techniques as putting drinking straws around the roots to increase the humidity around them.  I don’t know how well this works, to be honest.  So going forward, I guess I may end up learning a thing or two.

I’d love to hear what you think of this nice surprise I got.  Do you grow tropicals?  Do you have any experience with aerial roots on ficus?

How To Be Off And Running For Next Year

That time of year is soon upon us, where our trees are more or less done growing foliage and we need to think about what we have planned for them next year.  Bonsai is in large measure a game of patience, but that doesn’t mean you can’t or shouldn’t plan ahead.  And do certain things this year in preparation for next.

For me recently this has meant working on elms.  As a family, elms for the most part can be worked on according to the following guidelines:

  • winter: lifting, chopping, dramatically root-pruning, wiring established trees;
  • spring: chopping, wiring, root-pruning, potting;
  • summer: wiring, potting, pruning, pinching;
  • fall: unwiring, light trimming, light pinching.

I try to take advantage of the entire growing season, based on where each of my trees is along its development path.  With the elms below, I’m taking advantage of what will be our last round of growth for the 2017 growing season.  By doing this, I’ll get a head-start on next year.

This is one of the Cedar elms (Ulmus crassifolia) I got from my friend’s parents’ property back in April.  Nice trunk, nice taper, nice movement, nice bark.  It had bonsai written all over it.

 

 

 

 

 

 

 

 

 

 

 

After a sluggish start, it took off and hasn’t stopped growing since.  Time to make a move on this unbalanced growth while getting a bonsai-in-the-making on the bench.

 

 

 

 

 

 

 

 

 

 

That’s more like it!  I needed to cool off that growth in the apex, or the lower branches were going to be weak going into 2018.  That’s always risky with winter just ahead.

 

 

 

 

 

 

 

 

 

 

This Byron Myrick rectangle suits the tree very nicely.  I basically slip-potted the tree, meaning I lifted it from its nursery container and with minimal disturbance to the roots set it in this bonsai pot.  I filled in with fresh, well-draining bonsai soil mix and watered it in.  This tree is going to be outstanding come next year.

 

 

 

 

 

 

 

 

You don’t see Japanese gray-bark elm, Zelkova serrata, all that often.  It’s a pity, as the species has a lot going for it.  I got some stock plants for a fellow bonsai nurseryman, including a handful of larger ones.  I chopped the trunk (which had been four feet tall) back to 12″, and as buds popped and grew into shoots started working on it.  Because it had a significant root mass, the regrowth was natural as the tree was attempting to regain everything above ground that I was removing.  This process has continued into and through summer.

 

 

 

 

 

 

 

Compare this photo with the one above, which was taken in early August.  That’s some fast development!

 

 

 

 

 

 

 

Time to find out what Zelkova’s are made of.  I cut off all the roots that wouldn’t fit in this Chuck Iker pot, and in the tree went!  If it comes through okay, I’ll have a leg up going into 2018.

You’ll find, as you work with the various elm species, that some of them can take a lot of work throughout the growing season and won’t keel over from it.  Based on my experience, the only ones I’d avoid doing “out of season” work on are Hackberry and Winged elm.  For any of the others, have at it!