Often, the term ‘pine cones’ is used by folks to refer to any type of cone – but really there are pine cones, spruce cones, fir cones… and in fact many types of ‘coniferous’ trees that all produce cones.
Coniferous trees don’t produce cones until maturity, which is usually between 5 to 20 years of age. Cones typically mature over 2 years and fall in autumn. Tree stress can result in more or fewer cones, and they can have ‘masting’ behaviour, where cones are produced abundantly in certain years.
Generally I find that there’s a bit of an air of mystery about cones – they can be open or closed, they come in such a variety of shapes and sizes, some seem to stay on the tree for a lot longer, some trees don’t seem to make them straight away, others seem to make ‘bumper crops’ at random, and very few in other years.
I love conifers and love teaching my kids all about the different types of cones and telling them apart. I’d love to share some of my knowledge about cones with you, from what I’ve learned from tree experts and my own reading. I also hope to clear up some of the misconceptions about pine cones!
Are pine cones fruit?
No, nor are they seeds. They are the ‘fruiting bodies’ of coniferous trees. Pine trees contain both male and female pine cones! Pollen released from the cones has to travel by wind to female pine cones in order for fertilization to take place. Seeds are mature by the following year.
Coniferous trees are gymnosperms. It means they don’t flower, and the seeds aren’t surrounded by a soft, fleshy fruit, but instead develop within a cone. The word gymnosperm comes from Ancient Greek, meaning ‘naked seed’.
Seeds – pine nuts – can fall from the pine cones while they’re still attached, or can remain in the cone after it has fallen.
How long do pine cones stay on the tree?
The vast majority of pine species stay on the tree for 2 or 3 years before falling. They can be prematurely dislodged by squirrels, or in strong winds.
Why are there no cones on my tree?
There are three potential reasons for not seeing any pine cones on your tree
a) The tree is still juvenile
Cones are the reproductive structures of coniferous trees, and conifers that are very young don’t make them – it takes time for them to reach maturity.
How long does it take before young conifers make cones? ¹
|Juvenile period (years)
The timescales for this occurring are on average somewhat longer than the time it takes angiosperm trees (trees that produce flowers and fruit) to mature, even though there’s a fair bit of variation there as well. I’ve written a lot about this in other posts: for example, most dogwoods take 10 years, hazelnut trees 7-8 years, and plum trees only 3-6 years.
b) It’s part of natural variation
This is the most likely answer if your tree did produce cones, but this year you’re not seeing any, or there are very few.
It’s not uncommon for coniferous trees such as pine to have years of complete cone crop failure, particularly if the year before there was a bumper year, where you were able to collect cones by the basketful. In 1963, there was almost a complete lack of cones on any coniferous species in Washington and North Oregon, and it happened again to lesser degrees in 1966 and 1967 ².
Similarly, patterns of biennial bearing are seen in many angiosperm trees (those that produce fruit and flowers) – I’ve written about this tendency in trees such as cherry, walnut, and rowan (mountain ash). Biennial bearing refers to a tendency to make an abundance of flowers one year, then an abundance of fruit the next.
Coniferous trees do something similar, but the pattern is usually more irregular. Conifers may underproduce for years, and then overproduce and drop a seemingly excessive amount of cones in one year. This phenomenon is called masting. It’s well recognized in oaks and beech trees as well.
Essentially, if trees produce few cones for a few years, it keeps in check the population of squirrels, birds or other animals that feed on the cones and seeds. Then in one year – a ‘mast year‘ it makes so many that it overwhelms the few surviving seed-eaters with more than they can possibly consume, so some seeds are likely to make it to germination and become new trees. It’s believed to be a way that trees have adapted to ensure the survival of their species.
Masting doesn’t happen at regular intervals, which keeps the tree one step ahead of the seed-eaters, who might have been able to adapt towards a set pattern.
c) The tree is undergoing stress
Growing pine cones requires energy and water, just like growing fruit does. Most fruit trees struggle to make an abundant yield if they’re in drought and one would expect a similar finding in conifers. WIth pine cones, the relationship is more complex with a variety of findings having been reported². In general, while larger crops of pine cones in stressed conditions (such as drought) have been observed, there’s a general relationship between healthy tree growing conditions and cone production ¹.
Pine trees have a variety of needs to grow well including well-drained, regularly irrigated soil and good sun exposure. I’ve written more about conditions that stress pine trees (and how to tell if something’s wrong) here.
Conifer trees that have been recently planted – moved from a container, for example – can exhibit browning or a loss of needles, due to a phenomenon called transplant shock. As with fruit trees, which can produce a poor crop due to transplant shock cone production may be detrimentally affected as well. This can last 2 or 3 years – read more about transplant shock in pines here.
Are pine trees self-fertile?
Pine trees are self-fertile, meaning pollen from male cones can pollinate ovules within the scales of female cones, on the same tree. However, this occurs as minority of the time, as trees adapt to reduce the occurrence of self-fertilization, favoring cross-pollination from other trees.
Indeed most conifers are ‘monoecious’- they have both male and female reproductive parts. In pines, male cones are much smaller and softer, and fall around springtime after they release pollen. The pine cones you know – the woody ones used for decorating and craft – are female cones, within which, when fertilized, seeds develop.
Even though they are strictly self-fertile, pines benefit from fertilization from pollen from other trees, due to the introduction of new genetic material and genetic diversity. Self-pollinated pine trees are more likely to have issues with growth and seed production, and to fall foul of unwanted genetic effects such as the expression of recessive genes ³.
A comparison of male and female pine cones
|Size and shape
|Small and thin
|Larger, more rounded
|Lower in tree
|Higher in tree
What time of year do pine cones fall?
As a general rule, mature pine cones fall to the ground between early autumn and early winter. Most other coniferous trees, such as fir, spruce and cedar, follow a similar pattern.
Male pine cones are also known as pollen cones. They usually fall after releasing their pollen in springtime.
When do pine cones open and close?
Pine cones may open and close numerous times before they fall from the tree. It’s been observed that, while they’re still on the tree, cones may close off their scale at times of stress (such as drought) to reduce the chance of fertilization by pollen at a time that’s less favourable, and then open them again when conditions improve.
Coniferous cones cones also open when they’re ready to disperse seed. Dispersal may occur when the pine cone’s still on the tree, or they may remain within the scales until after its fallen.
Should I remove pine cones from the tree?
If you’re interested in your tree growing rapidly, removing pine cones may be beneficial. Pine cone production uses a lot of energy, and if you remove them while they’re maturing, the tree’s more likely to put this energy into growth instead.
This practice is undertaken by many commercial Christmas tree growers.
- Puritch GS. Cone Production in Conifers: A review of the literature and evaluation of research needs. Pacific Forest Research Centre, Victoria, B.C; 1977.
- Franklin JF. Cone production by upper-slope conifers. Pacific Northwest Forest and Range Experiment Station, US Department of Agriculture; 1968.
- Cole L. Effects of Self-Pollination in the Genus Pinus. Undergraduate Honors Capstone Projects; 1980.