To Repot Now or Not to Repot Now -

- that is a difficult question! (With, again, apologies to Ol' Bill Shakespeare.)

The reason the question is difficult is because our weather here in northern Indiana continues to be, as I put it previously, weird! We've continued to see unusual swings in temperature, from shirtsleeve weather to well below freezing and back to balmy, all in a matter of a few days! Before the middle of March had arrived, one of my yews had already started to set this year's crop of arils. Here, that's about a month early!

All else being equal, I would love the chance to start repotting a month early and gain that much on the growing season! But what makes the question difficult is that this year, all is not equal. We have the early warmup, but we also continue to have the wild swings in temperature. Together they create the dilemma.

For any who may not be familiar with the nature of the dilemma - and especially readers in tropical parts of the world -  here it is.

When temperate-zone plants emerge from their winter dormancy, growth goes into high gear, both above and below ground. New leaves emerge, twigs elongate, new wood is laid down; and the roots, at the same time, are spreading out, developing new feeder roots, adding girth to primary roots, and so on. This rapid growth continues for roughly six weeks (exact length of the growth flush varies by species,) and then tapers off. Growth continues slowly for the rest of the season, but most of the plant's resources after the first six to eight weeks are directed toward maturation of tissues and then into storage of sugars for the following spring's growth flush. (Some species have a second, some even a third, growth flush later in the season; but the spring growth push is always the biggest and most important.)

Obviously, the ideal time to repot one's trees is right at the start of the spring growth flush (signaled by the swelling of the leaf and needle buds.) At that point, the roots are starting rapid growth, and the tree will recover from root-pruning most quickly and with the least trauma.

Unseasonable cold throws a wild card into the game. New roots are sensitive to cold, newly pruned roots even more so. Cold slows down root growth, and thereby slows down recovery for a freshly repotted tree. Worse, too much cold, or cold that's too severe, can injure or even kill new root tissues.

The other horn of the dilemma is the fact that the repotting window is limited. Miss the window, and the tree's root system will struggle to recover. If the tree is a conifer, and especially if it's a member of the Pinaceae, if the window is missed the root system usually won't recover at all. This is a lesson I have personally learned the hard way; I've killed more pines by wrongly-timed repotting than by another mistake.

And this year's window has opened early. Bonsai practitioners who wait too long for temperatures to stop imitating a roller coaster risk missing the repotting window altogether. Waiting another year is then often the safest option, but has its downside: a tree that is not repotted when it needs it will start to become rootbound (or more rootbound,) and will miss out on the overall rejuvenating effect of root pruning.

On the other hand, bonsai growers who proceed with repotting now risk having their trees' roots injured by a siege of atypically cold temperatures, and the trees' progress set back as a result. If root pruning has been extensive, a tree could even be killed by a sufficiently deep cold snap.

After weighing the risks on both sides, I've decided to go ahead and repot those trees that are due for it, as fast as I can make the time. (Making time is complicated by the fact that my family and I are moving into a new house, which is also a reason I haven't posted anything on this blog for a few months.)

I'm taking a few extra precautions.

• First, I'm keeping root disturbance to a minimum, even on species like trident maple that normally shrug off massive root-pruning. That means less root rejuvenation, but it also means that when temperature plunges occur, the root system has not been temporarily weakened by pruning any more than is absolutely necessary.
• Second, in a cold spell it's even more important to protect newly-repotted trees from the drying effect of wind. Newly pruned roots can't take up as much water to re-hydrate the leaves and twigs in the first place, and that's more true when they're cold. Extra demand for water because of desiccation of the tree above ground is the last thing they need!
• Third, I've been doing "The Shuffle" as needed. Saturday afternoon I made sure the repotted trees were in the mudroom in anticipation of that nite's expected low of 24 Fahrenheit (almost -5 Celsius.) The next day after church I took them back outside to enjoy a day or two of milder weather. Tonite those trees are back in the mudroom for a few days. I expect to keep up the in-and-out for several more weeks, at least.

Here are pictures of two of the trees I've worked on so far.

This 'Densiformis' yew is the tree I won in a raffle at the MABA 2015 convention last year. (See the end of this post.) On April 16 I plan to take it to a Styling and Refinement workshop with Vance Hanna of the Four Seasons Bonsai Club of greater Detroit, so I didn't do a full repotting of this tree. I shifted just enough soil to let me correct the planting angle, did no root-pruning, and have been babying it ever since!

Taxus x media 'Densiformis,' after work was finished March 13. Provisional front.

Foliage buds about to burst. April 5, 2016.

I've become a bit fascinated recently with the bunjin style (a.k.a. literati.) I bought this Korean hornbeam from Meehan's Miniatures last August with an eventual bunjin in mind.

Carpinus coreana before repotting; March 11, 2016.

Repotted and with new front selected. The wound indicated by the arrow
will become a small uro. Picture taken April 5, 2016.

New leaves emerging on Carpinus coreana. April 5, 2016.

For all my friends in the temperate zones of the Northern hemisphere: best wishes with your repotting, whenever you're able to do it!

:-)  :-)  :-)

More Aerial Roots!

     I said in my last post that if a tropical-bonsai grower wants an aerial root in a given place, he or she usually has to hope the tree will throw one at that point. I was happily surprised a few weeks ago when one of my willow-leaf figs (Ficus salicaria) decided to do almost exactly that.

And then a week or so later, I discovered that my veldt fig (Ficus burtt-davyi) had followed the willow-leaf's example!

This mame F. burtt-davyi is one of my favorite bonsai. Pot by Sara Rayner.

 The orange arrow points to the root that got a response of "Yes! Where I want one!" (Or words to that effect.) I've been hoping for an aerial there for several years. I want an aerial root on this tree for the tropical look, but just one because of the tree's size. And I want it where it's readily seen, but won't compete visually with the hollow trunk. This root's placement is perfect!

I was ready to use another, older aerial (blue arrow) if necessary. I would have grafted that root to the back of the lowest branch, at the branch base, approximately where the new root is emerging. Once the graft took, I would have removed the upper section, between the graft point and the root's initiation point in the canopy. Now I won't have to do that.

Here's a closer look.

The paper-clip hook (green arrow) is there to keep an older root from crossing the end of the new aerial.

Forgive this tree's mildly disheveled look: I'm getting it cleaned up for repotting in the near future.

Meanwhile, the willow-leaf fig about which I wrote in my last post has produced the beginnings of a couple more aerials!

Besides shade and high humidity, plenty of fertilizer seems to be a requirement for initiating new aerial roots.

The blue arrow points to an emerging initiation point. Below it you can see the root I wrote about in my last post, now matured enough to have the straw removed. (You remove a straw from a new aerial the same way you defuse a bomb - very carefully.)

Some aerial roots fail, and sometimes without apparent reason. The yellow arrow above points to another aerial that got started, but was already in trouble when the picture was taken. Five days later, it has withered completely.

Since I don't want this new one to fail, I cut a new length of drinking straw to protect and guide it. This tree's size and intended design allow for more than one aerial in that area.

The point where each aerial enters the soil can be adjusted at future repottings. Once an aerial root lignifies,
it can be wired and positioned like a branch.

On the opposite side of this tree's trunk (red arrow below,) another root-initiation point has appeared. (We need a a less cumbersome term for such point. Any ideas?) I'd like to see this one develop successfully as well, so am going to give it a drinking-straw cover too.

If, like me, you endured acne as a teenager, you'll understand when I say I'm reminded of a pimple!

When I saw this picture, I thought perhaps yet another root initiation point was showing up, out on a major branch (green arrow.) But no joy there: the "bump" turned out to be nothing more than a scrap of loose bark.

I should mention that there is another way to get an aerial root at just the point you want it: graft in a seedling or rooted cutting. That takes longer, but provided the graft takes well and without much swelling, it works. I plan to use that method on a Ficus microcarpa this summer, and I'll post pictures when I do. 

Meanwhile, the tropical  trees will be in the Crate for at least two more months. Who knows how many more aerial roots may appear before spring? ☺

:-)  :-)  :-)

Aerial Roots, Drinking Straws and Snails

     The winter conditions that my tropical trees have in the Crate are of course different from summer conditions outdoors. The two biggest differences are that the light is less intense, tho still adequate for growth; and I keep the humidity a good deal higher. Both those factors encourage aerial roots.

If there is a consistently reliable way to induce a tree to throw an aerial root at a particular point, I don't know what it is. As a rule, the tree initiates a new aerial root somewhere that seems good to it, and the grower has to be ready to encourage and protect the ones that happen to appear where the human wants them!

For any who may not know, one common way to protect a new aerial while it extends down to the soil is to place a piece of drinking straw where the root can follow it down. This maintains high humidity right around the root and serves as a warning to the grower: "Caution! Don't bump!" Since aerial roots are very fragile until they anchor and start to lignify, such reminders are very useful.

A couple of weeks ago one of my willow-leaf figs (Ficus salicaria) initiated a new aerial root very close to a point where I'd been hoping for one. I positioned a piece of drinking straw to protect and guide it, and after a few days noticed that the growing root (which has now reached the soil surface) is visible thru the plastic. I decided to take a few pictures tonite.

The aerial root shows as a somewhat indistinct dark line.

You'll notice a light-blue arrow to the right of the straw. That points to a snail; more on it in a moment.

A closer view of root, straw and snail. You can see the root's initiation point just above
the top of the straw.

This is the fifth snail of this species that I've found around the roots of this willow-leaf within the last two weeks. Snails also find the high humidity and less-intense light in the Crate congenial. But since they feed on living plant tissue as well as dead, I remove them.

This species' shells are about the same diameter as the drinking straw from McDonald's;
less than 1/4-inch (around 6 mm.)

While I disposed of another (sixth) snail I noticed, this one poked out its head and started for home. I don't know how it knew which direction to go. Perhaps it could smell the tree; perhaps it sensed the humidity in the substrate; perhaps it detected the shadows among the roots. I'm afraid it didn't get very far.

It actually looks rather elegant, all in black. But not elegant enough.

:-)  :-)  :-)

"Oh, the weather outside is" - WEIRD!

(With apologies to Messrs. Cahn and Styne.)

   On Christmas Eve, the daytime temperature here in Warsaw set a new record high of 61° F (16° C.) On Christmas Day, the temperature got up to 55° F. The normal high this time of year in this part of the USA is 33° F, just above freezing.

Temperatures have been above average all autumn. I couldn't find certain confirmation, but I think both October and November were the warmest on record here, and December may well turn out to set a record average, too. Our first frost didn't arrive until the first half of November, a month later than usual. So far we've had exactly one - count it, one - snowfall that required me to get out the snow shovel. (It did give me a chance for a nice picture.)

Japanese maples branches flocked with snow, beside the church we attend.

There is at least one obvious and major reason for the unusual weather. There is a well-established correlation between the presence of a strong El Niño phenomenon in the eastern Pacific and milder-than-average winters across much of the USA. The present El Niño is unusually strong in many regards, which goes a long way to explain why, in spite of the calendar, we've been running around in shirtsleeves more often than jackets!

(I consider the jury to still be out on the question of atypical global warming. I'm waiting for more conclusive evidence, one way or the other.)

The unusual warmth has of course affected my trees. Buds on several of my hardy trees started to swell in early December, as if spring had arrived, and swelled enough that I became concerned! The danger, for any who don't know, was that the trees would start to actually push new growth - and then the weather would return to normal and the tender new growth be killed by freezing temperatures. If that happens, a tree has expended some of its stored reserves for nothing.

Buds swelling on a hybrid yew (Taxus x media 'Densiformis',) December 13, 2015.

I'm thankful that concern hasn't turned into reality. Most likely, I think, because of the shorter days as the winter solstice approached, the buds have stopped swelling and the trees appear to have gone into dormancy. I was glad to see the needles on my yamadori ponderosa turn to their normal winter shade.

This lighter green is normal for ponderosa needles in winter.

Normally, my tropical trees are settled in the Crate by mid-to-late October. This year, I moved them into their winter quarters on November 28th. (With some incredulous shaking of my head at the late date.) I had been doing the "tropical two-step" with them for a couple of weeks by then, moving them indoors overnite when the lows fell into the upper 30's F, then back outside during the day. With daytime temperatures often in the 50's F, I wanted to give them the advantages of natural sunlight for as long as I could. But by the 28th, enough was enough.

And sometime in the next couple of weeks my half-hardy trees will be moved into the mudroom, and the hardy trees will go under their rack in the side yard.

The long-term forecasts call for above-average temperatures for the rest of the winter. In view of that, I've considered leaving my hardy trees out and just making sure they were protected from hungry and inquisitive critters. But a recent blog post by Michael Hagedorn on winter chilling requirements led me to change my mind.

The gist of what Hagedorn says is this (unless I missed something.)

1. Plants that are native to the earth's temperate and cold zones need a certain amount of winter chilling, measured in hours at temperatures between 33° and 50° F (.5° and 10° C.) Winter-chill requirements vary by species.
2. If a plant doesn't get the hours of chilling that it needs, its growth the next season will be affected; some species won't break dormancy until their chill requirements are met.
3. Temperatures below freezing don't count on the plant's internal chill clock. (I have no idea why that might be.)

Once my hardy trees are  under the rack, they won't be as much affected by temporary temperature spikes that would interrupt their chilling requirements. So when spring does come, they'll be more likely to break dormancy on something approaching a normal schedule, and then grow well next season. The fabric that covers the rack will also serve to break the wind, and will hold in the fumes of the mothballs I use to discourage chipmunks, squirrels, and other cute-but-destructive little scoundrels.

To see Michael Hagedorn's post on hardiness and winter chilling for yourself, please click here. The post is thoughtful and well-written, and I recommend it.

:-)  :-)  :-)