Fundamentals of Bonsai – Spring

Spring is when the tree wakes up from its dormancy in Winter. The daylight length and temperatures increase and this signals to the tree that it is time to wake up. The tree then begins a cycle that it follows through Spring.

Juniper Chinensis Bonsai Shohin

  • Buds begin to swell

  • Leaves emerge and the tree goes into an energy deficit.

  • The first flush of growth hardens off and tree goes into energy positive

The perfect time to repot is while the buds are swelling. While the timing cannot always be perfectly right before the buds break, the closer to bud break (without repotting AFTER the bud break) the better.

When leaves emerge the tree spends some of the saved up energy from Fall to produce foliage with the possibility to generate more sugars and starches. When this happens the energy “bank” so to speak, goes negative. The new leaves are like an investment. Until those leaves harden off and form a cuticle, they do not photosynthesize. Until this happens this investment is a negative overall.

Pruning too much at the wrong time, defoliating, a hard freeze that kills foliage, pest issues that grow out of control, and even missing a day or two of watering can do a significant amount of damage to your tree’s health. While it doesn’t always end in a dead tree immediately, you need to consider this in the long term. You might have a hard freeze one year, prune a little off at the wrong time each season, defoliate in the Summer, and then after a few years you find your tree dead for what appears to be no specific reason.

Cotoneaster Repot Bonsai

This guy died from a late freeze after the first push of growth. I had recently repotted it and it was weak due to that. It never made it out 😦

A better way to understand this is to think of investing a significant portion of your savings into a stock hoping for a consistent return of maybe 7%. Instead of return, your stock plummets and becomes worthless. To be able to do anything with your money you’re going to need an amount of time to recoup the money you lost. If you continue as if you hadn’t lost all of your money in the investment and then spend with the intention to withdraw your invested money, you’ll be negative because you don’t actually have that money. If you have a tree that loses leaves from a freeze and then pushes out new leaves, the tree will have less energy in the bank. If you proceed by delofiating it to get a smaller push of leaves, you’ll find that it doesn’t have enough energy and will possibly die.

The vigor of the growth, length of internodes, size of leaves, and amount of leaves all depends on what you’ve previously done.

Fertilizing frequency and strength play a large part in Spring growth. If you’ve been fertilizing heavily and at the maximum frequency, you’re bound to have a large amount of energy. This will result in a lot of leaves, larger leaves, and longer internodes. The pot size also has an effect. If you fertilize lightly and infrequently, but you have your tree in a large training pot, you will not see small internodes or small leaves. Restricting the area for the roots to grow creates less vigorous growth.

If you’ve repotted a deciduous tree and pruned a large amount of roots, you’ll only see the amount of leaves that the roots can support. For a photo of this see this blog post about the difference.

Let’s go over what we’ve learned:

  • Daylight length and temperature determine when a tree breaks dormancy

  • Fertilizing strength and frequency (are not the only factors, but major factors) correlate with internode length, leaf size, and leaf quantity.

  • A deciduous tree will only push out growth that it can support with its root system.

  • Fertilizing can be throttled with frequency and strength.

  • Energy for Spring growth is stored by the tree in Fall

  • Repotting is best done before the buds break at the beginning of Spring.

  • New leaves take energy to produce and then produce energy when they harden off.

  • Common bonsai techniques (repotting, pruning, defoliation, watering, etc.) performed at the wrong time or late freezes can damage your tree’s health.

Japanese Maple Leaves