Refining Pines

This article derives from a presentations Bjorn Bjorholm and Jonas Dupuich did for our club in Autumn of 2021. They gave us a lot of information - so this is a long article on several related topics.

The section on fertilizer is also applicable to deciduous trees you defoliate.

Before We Start

You need to know some basic information about pines before reading this article. So, please familiarize yourself with the first two sections of Black Pine Basics. - Identifying Pines and How Pines Grow.

Phases of Development

Most teachers talk about trees being in two phases of development - Development and Refinement.

Development phase refers to the time when you are focusing on growing the trunk and main branches to the size you want. During this phase you are feeding it a lot and usually have it in an oversized pot or even in the ground. If in a pot you are using mostly pumice as the growing medium because that allows lots of oxygen to get to the roots and support fast growth. Fertilizer with higher amounts of nitrogen is also used during this phase.

Refinement phase is when you have slowed down growth so that new growth will focus on creating lots of smaller branches with shorter internodes and smaller leaves or needles. During this phase you will use a smaller pot with a different soil mix - a bit of pumice but lots of akadama. This soil will drain less quickly and less oxygen will get to the roots so the growth will be slower and finer. Fertilizer used will have lower amounts of nitrogen.

Bjorn prefers to break the Development phase into two phases: Early-Development and Late-Development.

Early-Development is as above but Late-Development refers to when we’re starting to work on secondary branching and ramification. This requires a change in how fertilizer is used. This will be part of the fertilizer discussion later in this article.

How to Induce Back Budding

The main focus of the meeting was how to induce pine trees to produce buds not at the tips but somewhere closer to the trunk. But first a quick description of the three different types of buds on a pine tree.

Different Types of Buds

You also need to recognize different types of buds found on a pine tree. There are three different types.

Terminal Bud - at the end of the new candles that have emerged this year. New terminal buds can form as early as April in our area but can be as late as summer depending upon the weather. If de-candled this year then new terminal buds will form about a month or so later.

Terminal Bud

Adventitious Buds - This type of bud forms on the surface of the branch away from the tip. We can induce these to form in the late summer to early-autumn via some techniques discussed below. These buds can appear almost anywhere on the branch, but usually are on smooth wood that developed in the past couple of years. They don’t appear on portions of the branch where flaky bark has formed.

Adventitious Buds and Needles

Adventitious Bud

These are more likely to develop on branches that receive a lot of sunlight and that’s one of the reasons we remove old needles – more sunlight reaching inside the tree will stimulate these buds to appear. Sometimes they will turn into new growth next year but if so the growth will be very small - a few short needles. They won’t produce elongating candles until the third year.

Tiny needles emerging during first year

Needle Bud - This type of bud develops inside the gray sheath, or fascicle, that surrounds the base of the needles. The bud might appear inside last year’s needles or two year old needles depending upon the tree species. These buds are pretty rare and we don’t know of a way to stimulate more to develop.

Needle Bud - Needles emerging from Fascicle or Sheath

Needle Bud - Needles emerging from Fascicle or Sheath at base of needles

Timing of New Bud Appearance

Adventitious buds and needle buds, if they form, will be at the end of summer. Trees have the ability to sense the temperature and several different wavelengths of light striking the tree. The trees use this information to change their behavior.

As the daylight hours increase the trees break new buds and elongate existing growth. As the daylight hours decrease the tree sets new buds before going dormant.

The amount of light a tree receives varies by where the tree is growing and that changes the timing of bud appearance. In our area new buds on pine trees should appear early-to-mid August while further south buds might not appear until late August or early September because their days are slightly longer. Variations in the weather can affect this timing. For example, if spring is especially overcast and rainy then the start of spring growth may be delayed.

Dual-Flush Pines in Late-Summer / Early-Autumn

Dual-Flush pines (Black, Red) are treated differently than Single-Flush pines (White, Scotts). This next section applies to Dual-Flush only.

During early-refinement phase when you want the tree to continue thickening you should allow the main terminal bud to grow - don’t de-candle. Candles on side branches may be de-candled. Once the trunk and main branches are as large as you want them to be (late-development phase) you should de-candle all candles. Continue to de-candle everything during refinement phase.

If a dual-flush pine is strong enough to be de-candled then this procedure is done sometime in summer. After 2-to-4 weeks a second flush of growth (new buds) will appear. We’ve been teaching that at this point to remove excess buds and only keep two. However, Bjorn recommends letting all the new candles grow for the rest of the summer and to remove all but two just as the new growth “hardens” (needles become stiff and pointed to the touch). Advantage to this approach is that by spreading the tree’s nutrients to grow many branches each should be shorter than if there was only two branches.

Here is the recommended procedure for removing extra candles.

Inspect the tree and identify the average size of new candles across the entire tree.
As you look at each set of new candles identify two that are close to that average size then remove the others. If the new candles are all smaller than the average size keep the two that are closest to the average.
If the new candles are all larger, keep two that are smallest. You can cut longer candles back so that they are “average” size. If you do this make sure your scissors are very sharp and mist the tree for a couple of days afterwards so that the cuts are less likely to become brown.
We want the two candles that we keep to be on opposite sides of the branch. It would be nice if these form a horizontal plane, but if not we can twist the branch with wire.

This is a good time to remove all two year old needles that are beginning to turn brown. Also, if there are a lot of last year’s needles remove all but 5 to 8 pairs of needles. Leave the needles spread all around the base of the new needles. Also remove any needles from previous years that may still be on the tree. If you don’t remove two year old needles they will tend to fall off by themselves in December / January.

Three years of needles on branch

Removing unneeded needles does two things. It allows more sunlight to get into the tree. It also stresses the tree and one reaction is to produce additional adventitious buds to form so the tree can replace the lost needles. New buds will appear in the next couple of months - before the tree goes dormant for the winter.

By plucking the needles, as opposed to cutting them off at the sheath, you are creating small amounts of damage on the trunk. This seems to encourage more buds. You may see some sap bleeding. If the bleeding seems excessive you can wait a week or two or simply cut the needles off leaving a couple of millimeters of stub. The stub will fall off by itself in a couple of weeks.

If you find a situation where the new candles are too long and nothing you can replace them with, you can “break” the candle back. This is a technique you use on single flush pines to shorten candles. Basically use scissors to cut the candle back to the length you want. This will produce new terminal buds but they won’t grow until next year.

If you have long needles on your tree, perhaps on a candle you didn’t cut earlier in the year, you can cut them back so that they are more in scale with the new candles. To minimize the tips of the needles from browning make sure your scissors are sharp - and mist the needles for a couple of days.

You should also cut off excess candles at this time. Single flush pines often produce 3 or more terminal buds. Some varieties of dwarf varieties may have crazy numbers of new buds. Remove all but two - and keep two that are the same length. You can do this any time before spring. But if you wait until spring all those extra candles will cause a knob of growth at that part of the branch - and you don’t want that.

Single-Flush Pines in Late-Summer / Early-Autumn

These trees aren’t de-candled. Also they don’t hold needles from two previous years, only needles produced this year and last year. Last year’s needles will be starting to yellow. They will naturally fall off this winter, but to induce back budding we want to remove them now. Leave all of this year’s needles.

This year’s needles are at the top of the branch below and last year’s needles are further down the branch.

Before plucking needles

After plucking needles

Wire Immediately After Stripping Needles

If you wire immediately after removing old needles needles it will be before new adventitious buds form so you don't have to worry about knocking them off. Bonus, as you wire you will be flexing the branches and creating micro-tears in the bark. These also can stimulate the tree to form adventitious buds. But this isn't a recommendation to be excessively rough with your tree!

Fertilizer

We will be applying fertilizer after this year’s growth has hardened off. The fertilizer will help pump up new buds that will emerge over the next few months so that they will be strong and ready to grow next spring. When we apply this fertilizer varies. If your tree is a single-flush pine then that will have hardened off by mid-summer, but dual-flush pines that were decandled will still be growing until late summer or early fall. So wait longer on those trees. We want to apply a relatively high nitrogen fertilizer, such as Gro-Power - a 12-8-8 fertilizer.

Problems to Watch Out For

When adventitious buds form and then drop off it may be due to a couple of issues. The new buds may be shaded out or the growth on the end of the tree is so strong that the tree decides it doesn’t need to continue growing the buds. The solution to both situations is to remove more needles when you thin. You may even remove some branches to get more sunlight into the tree.

How To Decandle in Summer

When asked about the technique of cutting a long stub on top branches, a short stub on lower branches and a medium stub in between Bjorn said he uses that technique, but only on trees where the candles are of similar size. Trees that are early in their development often have a lot of variation in the size of new candles. For these he recommends the following approach.

Leave weak candles alone.
Cut medium candles all the way back to the base.
Two weeks later cut the longer candles back to the base.

This process allows less vigorous growth to get a couple of weeks head start on the stronger growth.

For trees that are more closely in balance he recommends cutting candles all at once, with different size stubs - as we’ve been teaching.

Using Fertilizer to Encourage Back-Budding

Bjorn also talked a lot about fertilizer. I’ve tried to capture it all below and will be updating the Fertilizer Basics article soon.

Bjorn began by discussing Macro Nutrients. This term refers to the three number printed on the package you buy - like 15-8-8. You’ll often see these listed on the label as N-P-K. N refers to the amount of Nitrogen available in the fertilizer. P refers to the amount of Phosphorus and K refers to the amount of Potassium. Each plays a key role in plant development.

Varying the amount of nitrogen has a big impact on your tree. More nitrogen drives more growth. When you’re in Development stage when you want to fatten up trunks you’ll use fertilizer with a higher amount of nitrogen. That will also mean larger leaves and internodes, but in this stage that’s not a bad thing.

N-Nitrogen is responsible for green color and new growth. It is needed for cell division and the manufacture of protein.
P-Phosphorus is associated with good root growth and flowering. It also aids resistance to disease and pests.
K-Potassium is associated with healthy cell activity.

Micronutrients are minerals (copper, iron, molybdenum, zinc, etc.) that aren’t needed in large quantities but are important to the health of the tree. Chlorosis (yellowing between veins of a lead) is caused by shortages of different micronutrients. What’s happening is the leaf doesn’t have enough of a vial mineral and so can’t produce enough chlorophyl to fill out the leaf. That means it’s not producing as much sugar as it could and so the tree will suffer. Using a fertilizer that includes micronutrients is usually sufficient but occasionally you’ll need to add more. See our Fertilizer Basics article for more details.

Fertilize Differently

Bjorn recommends using Osmocote Plus for trees in Early-Development phase. He says it's really good for promoting lots of fast growth and this is what we’ve been recommending to users in our Fertilizer Basics article. The amount of fertilizer varies based on the size of the pot. For shohin he recommends using 1.5 to 1 teaspoon. For medium sized trees use 1.5 to 2 teaspoons. For larger trees he uses 1 to 1.5 tablespoons.

The high nitrogen can burn new roots so use about half the recommended amount when spring growth is first appearing. You can increase the amount later in the year. Osmocote pellets generally last a couple of months before they need to be replaced. You can stop replacing the Osmocote in October. There will be enough left in the pellets to support the tree as it enters its dormant period.

As you move into Late-Development you want to cut back the amount of nitrogen so that they leaves and internodes start to become smaller. And once you enter Refinement phase you want even less nitrogen. Bjorn prefers to use Gro-Power. It’s a medium-high nitrogen organic fertilizer with a lot of micronutrients and humic acid which helps plants absorb nutrients easier and improves microbial activity in the soil. The amount Bjorn uses varies by species.

For dual-flush pines (Japanese Black Pine, Japanese Red Pine, Pitch Pine) he wants the first flush of growth to be lush and green because it is going to be removed (decandled) in Summer. He recommends applying fertilizer in early spring. When it is time to decandle remove the fertilizer from the tree and don’t fertilize again until the second flush of growth has hardened off - late-August to early-September. Then add fertilizer to support the buds - as described above.

For single-flush pines (Japanese White, Scotts, Ponderosa) he recommends withholding fertilizer in the early spring because we don't want large needles or internodes. If you wait until the first flush of growth hardens off, usually early-to-mid-July, before applying fertilizer this year’s growth will be more compact. Continue replacing fertilizer as needed until the tree goes dormant.

For other conifers (junipers, cypress, spruce) Bjorn applies fertilizer just as new growth emerges.

For broadleaf species (e.g. maples) Bjorn recommends withholding fertilizer until the first set of leaves have hardened off. Then he looks at each tree to decide if he is going to defoliate it or not. For trees that he doesn’t defoliate he will apply fertilizer then. This is generally sometime in May for us. For trees that he will defoliate he continues withholding fertilizer until the new leaves have hardened off. This is generally sometime in July for us.

Once in Refinement phase he follows the same rules as during Late-Development phase, but uses an organic fertilizer that has an even lower amount of Nitrogen, something below 10%, just to slow down growth a bit more.

Timing Considerations

Generally we apply fertilizer in the spring and continue to replace used up fertilizer until late-summer. But once the trees go dormant there’s no reason to apply more fertilizer. Bjorn said that for most temperate climate trees go dormant once the average daily temperature has been 45 degrees for two weeks. For us that’s from December to February.

The focus of the talk was on improving back-budding in late-summer to early-autumn. To improve the changes of these new buds to grow into new branches we want to use fertilizer with 10-15% nitrogen. Apply this once the growth has hardened and before new buds start to appear.

Most root growth occurs in the autumn before the tree goes dormant, although some growth occurs during our warmer winters. Roots always grow rapidly after repotting. Because building roots requires phosphorus the fertilizer we use should always have about 10% as the middle number.

We often use 0-10-10 fertilizer in the autumn, but Bjorn suggested also using it in the spring after repotting trees. During repotting fine roots that absorb water and nutrients are mostly lost and have to regrow after repotting. This takes about 2 weeks so any fertilizer you apply during the first two weeks isn’t going to be absorbed by the plants so leave it off for a couple of weeks. But after those two weeks the tree will need additional phosphorus to support new root growth. At that time you don’t really need more growth on the top so very low or no nitrogen would be appropriate. A few weeks later you can add Osmocote or Gro-Power if that makes sense according to what is written above.

To help understand what all those words mean, here are two timing diagrams. The first one refers to any tree - except dual-flush pines you will de-candle or deciduous trees you defoliate this year.

When to apply fertilizer

For Dual-Flush pine trees that you de-candle or deciduous trees that you will defoliate here’s when you apply fertilizer. (Winter is unchanged from previous diagram)

Revised schedule for Dual-Flush Pines or Defoliated Deciduous trees