Monterey pine (Pinus radiata) is a species of pine tree native to Mexico and the central coast of California. Though the tree is used in various ways (including as pulpwood) and is cultivated worldwide for lumber, it's actually considered rare and endangered in its preferred habitats. Its quick growth rate and arrow-straight trunk make it a very popular landscape tree in the same regions with suitable conditions. The 3- to 6-inch-long dark green needles are clustered in groups of three, and the dark brown seed cones are 3 to 6 inches long, oval in shape. Monterey pine has a very deep taproot that makes it ideal for growing in dry locations.
Monterey pine is normally planted as small nursery container-grown specimen—or simple seedling—in early spring or fall. It is one of the fastest-growing of all pines, adding 3 to 6 feet per year. In ideal conditions, the tree can reach 80 feet within 20 years. There are instances of older trees approaching 200 feet in height.
|Common Name||Monterey pine, insignis pine, radiata pine|
|Botanical Name||Pinus radiata|
|Plant Type||Evergreen tree|
|Mature size||45–190 ft. tall, 15–30 ft. wide|
|Sun Exposure||Full, partial|
|Soil Type||Sandy, fast-draining|
|Soil pH||Acidic to neutral (5.5–6.5)|
|Flower Color||Yellow, brown, cream (non-showy)|
|Hardiness Zones||7–10 (USDA)|
|Native Areas||Western North America (CA to Mexico)|
Monterey Pine Care
Monterey pine trees are easy to care for and fast-growing, making them useful as a landscape tree in many locations. In its young form, a Monterey pine tree has a nice pyramid shape, but as it grows taller, the canopy tends to flatten out. The wind may also transform the branches into various shapes, especially in coastal areas or on windy locations.
The tree is best planted in fertile but sandy soil, in a spot that gets full sun to partial shade, spaced 40 or 50 feet from buildings and other large trees. Monterey pine grows into a very large tree surprisingly fast, so give it plenty of space. Unlike many landscape trees, Monterey pine is best planted as a relatively small potted plant, or even a new seedling. These trees have long tap roots can can become root bound in containers, and larger nursery specimens have a tendency to languish after planting. A 1-foot-tall seedling, on the other hand, may quickly outgrow a 6-foot container-grown tree
Provided the tree can avoid various bark beetles and fungal cankers, it is fairly easy to maintain, usually surviving on ambient rainfall and rarely needing pruning. Be aware that Monterey pine will readily self-seed and be on the lookout for invasive volunteers sprouting up in nearby areas.
Monterey pine trees can grow in a range of full sun to partial shade locations. The native range of Monterey pine includes regions that are sunny most days of the year. If planting a Monterey pine tree as a specimen in your landscape, try to choose a spot that gets at least six to eight hours of sunlight daily. Because the tree grows so fast, it will quickly grow beyond a partial shade location as it reaches upward.
To reach their majestic height, Monterey pine trees need to be planted in fairly nutrient-rich soil with good drainage. The tree also grows best in soil that has a fair amount of sandstone nearby, hence its success growing in coastal areas, like dunes or bluffs. The soil surrounding the tree must be very deep in order to allow plenty of space for the roots; if the roots hit a rock, the tree can become unstable over time.
Regular watering is key to helping a young Monterey pine tree get established. Once the tree is established (after two to three months), it will be moderately drought tolerant and will need to be watered only during extended periods of dryness. If you notice that your tree is dropping an excessive number of needles, that's a good indicator that the tree is in need of some water.
Temperature and Humidity
This pine is considered suitable for USDA zones 7 to 10. While Monterey pine trees can tolerate temperatures as low as 20 degrees Fahrenheit, they should get only brief exposure to that type of weather and will not flourish in areas that dip consistently below freezing. The trees are also humidity lovers and are happiest and healthiest when growing on coastal bluffs and soaking in the salty sea air.
Fertilizer can cause these fast-growing trees to overgrow, so they should not be fed at all.
Types of Monterey Pine
There are no named cultivars of Pinus radiata, but there are three naturally occurring varieties:
- P. radiata var. radiata is the typical form that is normally sold as a landscape tree. It is also the type cultivated worldwide for commercial lumber.
- P. radiata var. binata is a native tree found on Guadalupe Island, Mexico.
- P. radiata var. cedrosensis is found on Cedros Island, Mexico.
Regular pruning is not necessary for this tree, but it can be done to remove damaged or diseased branches or to remove low-hanging branches to raise the canopy. If a tree has excessively long branches, they can be cut back by about one-third their total length to reduce stress on the tree and prevent wind damage. And branches that touch or approach the house or other buildings should be cut back, as these resinous trees pose a distinct danger during wildfires.
October to January is the best time to prune, as this is the dormant period for the beetles that can cause open wounds through which fungal diseases can enter.
Propagating Monterey Pine
Monterey pine is almost always propagated by germinating seeds and planting the tiny seedlings when they are just a few inches tall. Here's how to do it:
- In winter when the they are dry and ripe, harvest some cones—or simply pick them up from the ground. Extract the seeds that are found at the base of the scales by banging two cones together over a box or sheet of newspaper. If the seeds are ripe, they generally easily come loose and fall from the cones.
- Store the seeds at a temperature of about 35 to 40 degrees Fahrenheit for about six weeks. The cold stratification period will improve the germination rate.
- Fill some tall, narrow planting pots with a sandy but fertile potting mix, such as a 50-50 mixture of commercial potting mix and sand. In the commercial trade, special pine seedling cells, up to 1 foot tall, are often used to propagate pine seeds, but this isn't essential.
- Plant the seeds in the containers, just barely covering them with soil. Set the pots outdoors, keep moist, and wait for them to sprout.
- When the seedlings are 2 to 4 inches tall, transplant them into the desired landscape location—a sunny or partial shade location with deep, sandy but fertile soil. Do not wait too long to plant, as the seedling's taproot will quickly become root bound in the pot. Keep the planted seedling watered until it is well established, which generally takes only four or five months.
Although it is a less common method, Monterey pine can also be reproduced from semi-hardwood cuttings taken in late fall. Plant the cuttings in containers filled with sandy potting mix, keep moist through frequent misting, until the cuttings develop roots. This can take as long as 22 weeks. Cuttings taken from young trees are most likely to succeed.
Potting and Repotting Monterey Pine
Monterey is too large a tree and too fast-growing to be practical for container culture.
Monterey pine needs no protection against winter cold, but tiny seedlings may become a food source for deer, rabbits, and other creatures unless you protect them with cages made of hardware cloth for the first year or two. After this, they are safe from serious animal damage.
In areas where bark beetles and resulting fungal diseases are common, spraying the tree with horticultural oil in late winter can help control overwintering pests.
Common Pests and Plant Diseases
Monterey pines are free of most serous life-threatening pest problems, though they can experience minor damage from many insects, including needle miners, midges, weevils, scale, mites, and nematodes. A truly life-threatening problem is created by various bark beetles that can penetrate into the tree, thereby facilitating infection by serious fungal organisms. Prevent bark beetles by pruning only during times when the beetles are dormant, or by applying recommended pesticides (consult local tree experts for advice). An overwintering spray of horticultural oil is often an effective method.
There are a few harsh diseases to which these trees are especially susceptible. One of the biggest issues for pine trees of all types (including the Monterey pine), is pitch canker, a fungal disease that causes swollen lesions to appear on the tree's trunk, branches, and roots. The lesions can prevent the tree from getting water, causing the needles to turn red, dry up, and eventually die off. At one time, it was feared that the Fusarium circinatum fungus might destroy all Monterey pines in the native range, but the species has developed some acquired resistance and is no longer so seriously threatened. An affected tree that is carefully tended may survive the disease, and a systemic soak with fungicide, applied by a professional, can sometimes save an infected tree.
Other common diseases for the Monterey pine tree include root rot, needle blight, and tip blight. While not much can be done if an enormous tree becomes seriously infected, you can remove any diseased plants and keep the base of any specimen trees clear of debris or rotting foliage in order to prevent spread.
How to Get Monterey Pine to Bloom
The creamy whitish brown flowers that appear in winter are very small and nondescript, so there is no reason to encourage Monterey pine to bloom.
Common Problems With Monterey Pine
The most common issues with Monterey pine include fungal disease (see above), but there are some other common complaints:
Tree Is Too Large
In ideal locations, the growth rate of a Monterey pine can be prodigious. There are cases of this tree achieving as much as six feet per year, and if the location was not carefully considered at planting time, it may overwhelm the landscape. But these trees do accept rather hard pruning; you can cut back branches by one-third of their total length every few years, if necessary. But it's also possible that you will need to have the tree removed if the size becomes unmanageable.
Tips of Needles Turn Brown
There can be several causes for this symptom, including insect damage or reaction to pesticides. But more commonly, Monterey pine may experience damaged needles in response to environmental pollution. This is not a tree well-suited to inner-city urban areas or neighborhoods near freeways.
Tree Blew Down in a Storm
This very often occurs if a Monterey pine has been planted in shallow soil, so that the long taproot that normally anchors the tree has been dead-ended by shallow underlying bedrock. If you replant a new Monterey pine, try to verify that the soil is unimpeded to a depth of 5 feet or more. In areas where the soil structure has an underlying hardpan layer, a special "ripping" operation may be needed to break up the hardpan and allow space for a Monterey pine's taproot to take hold.
How is this tree used in the landscape?
Monterey pine is a good choice wherever a large, fast-growing specimen is needed, provided the site has enough room for it to grow. With its high, broad canopy, this pine is sometimes used as a residential shade tree, or as a specimen tree in breezy areas, where it gradually assumes an attractive, wind-swept growth habit. It is best suited for large properties, positioned well away from the home or other structures.
Does Monterey pine pose a fire hazard?
Like all pines, Monterey pine is a resinous tree that will quickly catch fire and burn fiercely. Therefore, it's important to keep this in mind if you live in a region where wildfire is a common threat. The good news is that Monterey pine seeds are activated by fire, and fallen seeds will quickly establish themselves as volunteers should fire kill the parent tree.
How long does Monterey pine live?
Monterey pines frequently live as long as 90 years unless they fall prey to bark beetles and the resulting fungal diseases that can occur.
Does this tree have wildlife value?
For various birds, rodents, and mammals, this tree provides edible needles, twigs, bark, and seeds. The insects it attracts can also lure birds and small animals who feed on them. In native areas, Monterey pine is considered a valuable member of the ecosystem, and may even be protected as a threatened species. Monterey pine is also a well-known habitat for migrating monarch butterflies in California.
Is Monterey pine edible?
Like the pond pine tree (Pinus serotina), the Monterey pine tree is serotinous, meaning the nuts need a heat source to be released. Once free from the tree, the seed nuts can be collected and ground into flour or eaten raw. The nuts were a vital food source for early Western settler; in very harsh winters, the inner bark of the tree could also serve as emergency food, and the tree's needles could be brewed into a tea that was rich in vitamin C. Pine resin (discharge from the tree) was also used well into the 20th century for various medicinal purposes, including treating burns and open wounds.