The Cost of Sex

Source material: 2017, April-July

          In the course of my biology education, the cost of sex and reproduction to an organism has repeatedly come up across specialties—and plant sex is certainly no different. For mammals, females usually carry most of the energetic burden due to long gestation and lactation periods relative to other animals. However, sometimes males in the animal kingdom also pay a cost to pass on their genes. For example, a male walrus in "rut" undergoes a reproductively active period of a few months, where the walrus directs massive amounts of energy to its sole focus of reproducing and vocalizing for potential mates. During this period, male walruses can lose their coat of brown fur, have increased disease susceptibility, and their eyes start to turn red and bulge out as an odd indicator of systemic bodily neglect. There is also the famous example of a praying mantis male literally sacrificing itself to offer nutrients to the mom and in turn, increases the fitness of his offspring. The aptly named black widow spider undergoes a similar ritual.

          With such examples in mind, it should come at no surprise that all those flowers in last month's blog post, Spring at Elandan Gardens, have a cost to those trees too. The trees' hard-earned sugars and nutrients were spent in exchange for beauty, pollen generation, pollinator attraction, wind pollination (for less showy trees with cones, most maples, etc.), and seed maturation. For a healthy tree, these expenses are not a problem, but we may still have reason to intervene and choose whether to allow our bonsai to reproduce or not. I will demonstrate some examples of how one might acknowledge the energetic cost of plant reproduction and control it as a tool to speed development, increase health, or maintain the balance of vigor of your bonsai.

Sections:

1. For Trunk Development
2. For Recovery
3. For Disease Resistance
4. Final Thoughts and Tips

One of Dan's Azaleas covered with flowers and reproductive energy.

          The basic premise behind my suggestion to control your bonsai's reproduction is that this control can be done harmlessly (I already know there are some who contest this claim). But for those who are willing and able to carefully nip unwanted cones and flowers in the bud, I hypothesize it can be done to the benefit of your trees for a variety of purposes.

1. For Trunk Development

          As a first example for my case, below is a Japanese black pine (Pinus thunbergii) pre-bonsai that Dan has grown from seed in the ground for over 20 years (I'll save the trunk shot of that tree for a future post). The purple objects pictured are a few dozen pollen cones (aka staminate cones or microstrobili) on a single candle of this ground-grown pine. These pollen cones produce hundreds of thousands of pollen grains and disperse them into the wind with hopes that random chance will deliver their genes to a seed cone (aka ovulate cones or megastrobili). As you can imagine, that is hugely wasteful to the plant, but necessary evolutionarily because pines are only pollinated by the wind - they have no animal intermediary to rely on. For our purposes in bonsai, I suspect this evolutionary strategy results in significant amounts of the photosynthetic product that ends up floating in the air as wasted energy. That wasted energy is what slows down the efforts of trunk-building for those of us who develop our own stock.

Field-grown Japanese black pine with numerous pollen cones.

           The next two pictures show another potential waste of energy for your trees in the ground - the more widely known cones which actually bear the seeds (hence "seed cones"). Seed cones on a Japanese black pine require two years to mature. This spring, I took a photo of a new ovulate cone just alongside one which started last year. Unless you have a desire to collect the seeds of the tree, I recommend snuffing out the potential cone in their first year before too much energy is invested. Below you can see the volume of wood that is added to the cone over the first year that could instead be accelerating the growth of your pre-bonsai. After the first year, such a substantial amount of energy has been invested into the cone that I prefer to leave them on and collect them for seeds in the fall.

0-year seed cone vs 1-year seed cone of Japanese black pine.

Five new seed cones on a single Japanese black pine candle,
also currently growing vigorously in the ground for trunk-development.

2. For Recovery

          Another instance in which this control is useful is for trees recovering from major events in their life history, such as an aggressive styling bend or recent collection. Most often, trees will help us in this endeavor by not reproducing if they are not growing vigorously and if they are not already healthy, but I have heard of some instances where trees attempt to maximize their reproduction in response to poor health; perhaps the tree is betting its circumstances are so dire the individual would not be able to survive long-term. I am honestly not sure if preventing that reproductive energy expenditure would help the tree in the latter case recover or not, as that scenario is one I have only heard of from other bonsai enthusiasts and have yet to witness myself.

3. Disease Resistance

          In one particular case, I have been most strongly motivated to ensure the removal of every cone I could find. Dan's multiple ponderosa pine (Pinus ponderosa) yamadori (wild collected trees) are all multi-century old specimens from the Rocky Mountains and many of them have faced difficulties in Seattle over the years despite being initially healthy upon collection. One of the major challenges to growing ponderosa pines in the northwest is there is a host of problematic diseases that enjoy preying on these pines and have killed far too many of Dan's best ponderosas (unfortunately including the tree he first gained fame for in the bonsai community by carving deadwood with a chainsaw). Ponderosa's annoyingly elevated disease susceptibility here results from a combination of factors - a climate they are not accustomed to (wet, mild winters as opposed to their dry, frigid homelands to the east), a parasite native to the ponderosa's natural range which no longer has predators once the tree is brought here (that was the case for the unappealing, but non-lethal, black fungus in the needles below), a persistent foreign invader which has wiped out millions of trees since it emerged (mountain pine beetle), and the ponderosa's ability to act as a new host to native pathogens (the case for a boring insect larva which has earned my ire most of all and will be the subject of my next post). My hypothesis and hope for this sometimes troubled species is that removal of the energy-sapping cones will force more energy to be directed to other vital functions such as the production of defense compounds from diseases we know the plants to be at risk for here.

The black fungus affects old needles on some of Dan's ponderosa pines.

A collected ponderosa Niwaki (landscape tree styled as a bonsai) covered with cones.

Ponderosa seed cones close-up. Like black pines, these also require two years to mature.

Removal without damage is simple and achievable!

With caution, you can ensure you do not cut or damage needles in the process.

4. Final Thoughts and Tips

Cone Removal Tip:

          From early winter to early spring, the pollen cones and young seed cones can easily be removed by rubbing some dexterous fingers gently on the cone away from the center of the candle (applies to both types of cones) or by careful use of pruning shears. I have heard it said in the past that these techniques were not advised for use on Japanese black pines out of fear of damaging the new candle growth; however, I have found that as long as one is only gently holding the branch (not holding on to needles), that I can remove the offensive parts without damaging any needles noticeably.

Balance of Vigor:

          I mentioned I suspected (a lot of suspecting going on today here...) this technique could also be employed to balance the strength of a tree. What I meant by that suggestion is that one could theoretically allow a strong branch that does not need to thicken or develop further to flower fully and completely let it expend energy producing mature seeds, while other areas that are weaker or less developed could be prevented from flowering at all in an effort to allow that branch to catch up in thickness or in strength. I am not sure how often this situation may come up, but I am excited to think of the possibilities with this as an added tool in mind for my bonsai adventures.

Benefits of Allowing Reproduction:

          Despite devoting an entire article to reasons not to allow your bonsai to reproduce, in reality, it will likely never make or break your tree. I primarily hope practicing bonsai with the plant's reproduction in mind could make for small, but helpful, changes in the health and efficiency of my trees. That said, there could be an unexpected and dramatic benefit to allowing reproduction to go through in some instances.

The magical hinoki cypress which backbuds (so far only twice on the whole tree). Picture from October of 2016, discovery made while pruning it in spring, 2017.

         Recently, while thinning a hinoki cypress (Chamaecyparis obtusa), another student of Dan's discovered two separate spots on the tree that made cones (which was already rare for hinoki cypresses in bonsai culture). Even rarer though, at each site of a cone, there was evidence of the tree back-budding onto old wood. Hinoki cypress is purported to be a species that does not back-bud at all, so these two instances of coincidence stood out as potentially something of interest for further investigation. We hypothesized the hormones produced by or involved with the hinoki seed cones played a catalytic role in the back-budding on an otherwise stubborn species.

An Example Where It's Easier to Ignore The Subject: 

          Lastly, as I mentioned, it does not always matter in a big way whether or not you go to the trouble of performing this task. Here is one example that would be a complete waste of time.

Japanese red pine (Pinus densiflora) in refinement with small seed cone on the tip of a candle. These shoots will be removed to build ramification anyways - no need to remove the seed cone.

Japanese red pine from above after de-candling (new shoot removal).

          If you made it this far, thank you for reading my blog. As always, I hope you will share any feedback you have on this topic in my comments, and I hope some of you will find this perspective thought-provoking.