Chapter 117 Pinus sp.
117.1 Pines
A Japanese white pine in the National Arboretum collection. Link to original image.
All of the species listed below have shorter needles that would make them better suited for bonsai. The first three species are the ones used most often in Japan for bonsai. The two species from Eurasia and nine species from North America are either already used frequently for bonsai, or are worth investigating for bonsai in the future.
| Species | Common Name | Size, No. Needles | Native Range | Notes |
|---|---|---|---|---|
| Pinus densiflora | Japanese red pine | 2, 3-5 inches | Japan, Korea, China, SE Russia | lean mix |
| Pinus parviflora | Japanese white pine | 5, 2-2.5 inches | Korea and Japan | lean mix |
| Pinus thunbergii | Japanese black pine | 2, 3-4 inches | Japan and South Korea | lean mix |
| Pinus mugo | Mountain pine | 2, 1–3 inches | High elevations of southwestern, central and southeast Europe | lean mix |
| Pinus sylvestris | Scots pine | 2, 1-2 inches | Western Europe to Eastern Siberia, south to the Caucasus Mountains and north into the Arctic Circle | lean mix |
| Pinus clausa | Sand pine | 2, 2-4 inches | Central Florida | lean mix |
| Pinus contorta | Lodgepole pine | 2, 1-2 inches | Western North America, near the ocean, dry montane forests, subalpine zone. | Look for cultivar ‘Spaan’s dwarf’ |
| Pinus echinata | Shortleaf pine | 2-3, 2.5-4 inches | Southeast US from Virginia to Texas | lean mix |
| Pinus edulis | Pinyon pine | 2, 1-2 inches | southwest US | lean mix |
| Pinus glabra | Spruce pine | 2, 2-3 inches | Coastal regions, Gulf Coast states | general mix |
| Pinus pungens | Table mountain pine | 2-3, 2-3 inches | higher elevations of Appalachian mountains, PA to SC | lean mix |
| Pinus rigida | Pitch pine | 3, 2.5-4 inches | eastern US, NC to Maine | lean mix |
| Pinus strobus cv. ‘Densa’ | Dwarf Eastern white pine | 5, 3-5 inches | Eastern North America, Maine to NC | Look for cultivars ‘Densa’ and ‘Nana’ |
| Pinus virginiana | Scrub or Virginia pine | 3, 2-3 inches | eastern US, NJ to Georgia | general mix |
117.2 Soil: General Deciduous / Rich Conifer Mix
Ratio: 3 parts bark, 1 part grit
Add-ins: dolomitic limestone (~5 lbs/yd), Tree-Tone (15 lbs/yd)
pH: ~6.5 (slightly below neutral)
Moisture: Average
117.3 Soil: Lean Conifer Mix
Ratio: 2 parts bark, 1 part grit
Add-ins: dolomitic limestone (~5 lbs/yd); Tree-Tone (15 lbs/yd)
pH: ~6.5 (slightly below neutral)
Moisture: Fast draining
117.4 Light
Routine: Full sun
117.5 Cultivation Notes
117.5.1 Potting & Root Pruning
Pines are repotted in late spring. Lift the tree from the pot; if there are numerous white root tips, the tree is ready. If white root tips are not present, it is too early or the tree is not healthy enough for root pruning.
117.5.1.1 Top & Branch Management
Heavy pruning: pine branches form growing tips called candles. Left undisturbed, the candle extends to form the leader for the trunk and branches. Side branches emerge in a radial spoke pattern from the base of each candle. Needles emerge along the length of the candle, and stand out perpendicular to the stem.
This natural structure is shaped using a modified clip-and-grow method. When the candles first emerge, remove 3/4 of the candle by breaking it off (do not cut it.) This triggers the basal branching buds to elongate instead. When the basal side branches are several inches long, one branch is selected to be the side or back branch, and another to be the new leader. The other side branches are removed. The process is repeated each year to produce a zig-zag main trunk that has side and back branches at each bend.
Each individual branch is developed in the same way, with two adjustments. First the candle is allowed to extend until the needles begin to stand up, then it is broken off. This produces full length branches quickly. Second, the branches that are retained are arranged differently. There should be one branch pointing forward, and one pointing backward; the candle remnant becomes the leader for the branch. Once the branches have 2-3 side branches, the leader and side branches are allowed to extend without pruning for 2-3 years to thicken them if needed. Then they are cut back hard to their final lengths.
Fine pruning: to maintain current structure, pinch immature candles by 1/2 to 2/3. Branch prune in early autumn as sap falls. In alternating years, cut the branch tips in the fall to reduce congestion.
Leaf pruning: DO NOT leaf prune pines. Branches without sufficient green mass die. Pinch out individual bundles of needles during the growing period to maintain the silhouette. In fall, shake or brush out dead needles by hand to allow more light to penetrate, and activate dormant buds.
117.5.2 Feeding
Avoid over-feeding pines. Most species are adapted to be early colonizers or to live in marginal soils. Excessive feeding produces excessive or spindly growth.
Pines do better being fed every 3-4 weeks from the time the first spring growth appears to early winter (end of December here).
According to University of Minnesota, pines prefer a complete fertilizer with nitrogen content slightly higher than phosphorus and potassium levels; 10-8-6 is generally recommended. Applying the standard practice of feeding bonsai at 1/2 normal levels, the target is around a 5-4-3 NPK ratio.
Organic options:
- Espoma PlantTone (NOT TreeTone) is a 5-3-3 mix, which very close to the target. It is an organic that must be incorporated into soil and broken down by microbes.
- A 1:1 mix of Espoma HollyTone (4-3-4) and cottonseed meal (6-2-1) or TreeTone (6-3-2) would be an organic option that also provides a slightly more acidic soil.
Finding an appropriate soluble fertilizer is more difficult. The only options I could find that are generally available:
- HyR BRIX 4-3-3 All-Purpose Liquid.
- Jack’s Classic 20-20-20 All Purpose Food, diluted 1:4.
- Dyna-Gro Bonsai-Pro Liquid Plant Food, 7-9-5
None of the other commonly available inorganic liquid fertilizers have the right balance recommended for pines. For example, Scott’s MirAcid is 30-10-10, so would need to be diluted 1:3 or 1:4 to be appropriate, and still would have insufficient potassium and phosphorus.
Several bonsai outlets sell fertilizers that are along the lines of 5-7-4 or something similar, but none have a pine-specific option. Alternating between a bonsai-specific and diluted general acidic fertilizer might be a solution.
117.5.3 Pests & Problems
Pines can be attacked by pine sawflies (actually a wasp relative) whose caterpillars chew off the needles, and pine beetles that burrow in the cambium and girdle the tree, girdles and kills the tree. They also are susceptible to several different blights that I described in the topic on diseases.
117.5.4 Winter Storage
Store in mulch outdoors, and protect from hard freezes and wind. Keep trees relatively dry, with minimal water. No other special precautions are needed.
117.6 Propagation Notes
Japanese black pines are grown from seed. Red pines can be seed-grown but are slow to develop. White pines keep their smooth un-fissured bark, so rarely develop an appropriately craggy trunk. So rather than growing them from seed, most white pines are grafts. The main trunk is a black pine, but the foliage is provided by a high-grafted white pine scion. The graft union tends to be obvious, so must be hidden by foliage pads.
A Japanese black pine. Note how the black pine has longer needles and more deeply fissured bark than the white pine in the photo at the top o the page. Link to original image.
117.7 Artistic & Styling Notes
117.8 Additional Information
117.8.1 Natural History
Pines are found across the entire Northern hemisphere, and in some regions reach into the tropics to nearly the equator. Currently there are more than 150 accepted species of pines, not including hybrids. They are long lived and typically reach ages of 100–1,000 years, some even more.
The needles are bundled in clusters called fascicles. There can be 1-7 needles per fascicle, but 2-5 is most common. Each fascicle emerges from under small brown scales. If a shoot is damaged or clipped off, the needle fascicles just below the damage will form one or more new buds to replace the growing tip.
The new spring shoots or “candles” have short needle buds that lay flat along the length of the candle. As the candles lengthen the needles green up and turn outward. Managing extension and maturation of the candles is the main way of controlling branch development.
Most pines grow well in sandy acid soils with good drainage. Several species are adapted to extreme conditions of cold due to high elevation, while other species are particularly well adapted to growth in hot, dry semidesert climates. A few species are fire-adapted, meaning they require a low-temperature fire to release or germinate their seed, or to push them out of their seedling growth form.
117.8.2 In Cultivation
Many pine species currently in cultivation have dozens of cultivars, including dwarf forms.