Creating a Bonsai Pinetum

A pinetum is an arboretum, or collection of trees, dedicated to conifers. There is a fabulous pinetum at RHS Wisley in the UK (my ‘About Me’ pic was taken there), and the UK National Pinetum at Bedgebury Forest has a collection of 12,000 specimen trees.

Whilst very few of us have the space to create a full-sized pinetum, the wonderful thing about bonsai is that you can create your own miniature version. There are only six conifer families, and within those, 68 genera, some of which would be impossible or at least extremely difficult to procure. So you could have a very respectable and representative bonsai pinetum with around 50 trees. A mame-sized bonsai pinetum might even fit on a single table!

Only a small number of conifer species are common bonsai subjects, so embarking on this project would require some creativity – there won’t be online tutorials or examples for many of these species. Some may be completely hopeless for bonsai (most of the Araucariaceae family for example), others may require conditions that you just can’t provide, but along the way I’m sure you would find a few that make excellent bonsai and give you something unique and different for your collection.

If you want to jump straight to the shopping list here it is, otherwise read on to find out about the trees in the list and where they fit in the different conifer families. For beginners to taxonomy, you start with a family, then a genus (or genera if there is more than one genus), then a species. So for example for Scot’s Pine Pinus sylvestris, Pinaceae is the family, Pinus is the genus, Sylvestris is the species.

Family 1: Araucariaceae

You have a few different options for your representative tree/s from Araucariaceae as it has three genera (agathia, araucaria & wollemia) which cover a range of different forms. The most well-known in Europe would be the monkey puzzle tree (Araucaria araucana) but you could also include a Wollemi pine (Wollemia nobilis) which are available to buy, albeit at a cost. Neither of these are the easiest of bonsai subjects as they have a very regimented architecture with whorled branches, however they do have the advantage of being frost hardy. Wollemia nobilis also does backbud, and grows as a multi-stem.

An alternative could be an Agathis, also known as a Kauri tree. The New Zealand Agathis australis is the third largest known conifer after the giant and coast redwoodsref, depending on where it has been grown it may or may not be frost hardy. The New Zealand Bonsai Association has a Kauri forest on their native species web page.

If you live in the southern hemisphere, many of these options will be easier to find and will be happy outside.

Family 2: Cupressaceae

The Cupressaceae conifer family is a lot easier to cover in your pinetum as it contains 25 genera (listed below) and 152 species.ref You can read about the leaves of many Cupressaceae species in my post on conifer scale leaves. It would be appropriate to include several members of this large family, as many are known as bonsai subjects anyway. An easy selection of five from different genera could include a Hinoki cypress (Chamaecyparis obtusa), a Dawn Redwood (Metasequoia glyptostroboides), a Japanese Cedar/Sugi (Cryptomeria japonica), a Sabina Juniper (Juniperus sabina), and a Thuja (also called arborvitae or cedars, although they are not true cedars).

Expanding to ten specimens across ten genera would allow the addition of five other reasonably easy to procure and grow species: Giant Redwood (Sequoiadendron giganteum), Coast Redwood ( Sequoia sempervirens), Swamp Cypress (Taxodium distichum), Italian/Mediterranean Cypress (Cupressus sempervirens) and an Oriental Arborvitae (Platycladus orientalis).

If you’re a purist and want to include more genera from Cupressaceae, some excellent options would be the Chinese Coffin Tree (Taiwania cryptomerioides), Tasmanian Cedar/Pencil Pine or King Billy Pine (Athrotaxis cuppresoides/Athrotaxis selaginoides), one of the Australian Callitris species such as Rottnest Island Pine or Oyster Bay Pine (Callitris preisii, Callitris rhomboidea), Chinese Fir (Cunninghamnia lanceolata) , Chilean Cedar (Austrocedrus chilensis), Incense Cedar (Calocedrus decurrens) and the Chinese Swamp Cypress (Glyptostrobus pensilis). You may need to grow these from seed, depending on where you live.

To fully represent Cupressaceae you’d also need to add the remaining eight genera, Diselma, Fitzroya, Libocedrus, Microbiota, Papuacedrus, Tetraclinis, Thujopsis and Widdringtonia. Many of these are specific to small or remote locations and/or endangered, but you may come across them while travelling, or while visiting full-sized pinetums or botanic gardens.

Family 3: Pinaceae

This family is a stalwart of the bonsai hobby, containing a massive (for conifers) 11 genera and 232 different species, including the eponymous pines, which account for more than half of these. You can read about the leaves of most Pinaceae in my post on conifer needle leaves. For your first pinetum Pinaceae, consider the UK native Scot’s Pine (Pinus sylvestris), Japanese black pine (Pinus thunbergii) or Japanese white pine (Pinus parviflora) – and perhaps a Pinus strobus which is a separate subgenus within Pinus.

For something unique, you could also include the only single-needled pine, Single-leaf piñon or Pinus monophylla. It’s actually a pine which has fused needles (five of them) which appear as one, and this results in its needles being very fat.

A top 5 selection from Pinaceae would also include species from the fir (Abies), true cedar (Cedrus), spruce (Picea) and larch (Larix) genera, all of which have species which are relatively easy to source and grow, at least in Europe (and most are extremely frost hardy). Let’s make it top 6 to include another well-known genus, the hemlock (Tsuga).

The 7th and 8th Pinaceae specimens could be a beautiful Golden larch (Pseudolarix amabilis the only species in its genus), and the classic Pacific north-west representative the Douglas fir (Pseudotsuga menziesii). The Douglas fir is not actually a fir, it’s a ‘false hemlock’, one of seven species of Pseudotsuga.

Most of these trees are well-known, can be procured either as plants or seeds, and could be relatively easily added to your collection. But the Pinaceae family also includes some extremely rare genera. Cathaya has only one species, Cathaya argyrophylla, or Cathay silver fir, which has a similar history to the famous Dawn redwood – thought to be a fossil but then ‘discovered’ in a small living stand in China in 1946.ref Cathaya was also discovered in China in 1938, but the discovery was not recognised as a new species until the 1950s.ref It is endangered with less than 1000 mature individuals in its native habitat.ref

Bristlecone hemlock or Nothotsuga is also a genus with only one species (Nothotsuga longibracteata) which comes from China, where it is near-threatened and “populations are highly fragmented, with some consisting of just a few scattered individuals”.ref Unfortunately Cathaya and Nothotsuga are probably out of reach for your pinetum unless you have access to seeds via a botanic garden, or live in China.

The 11th and final genus in Pinaceae is also relatively unknown outside of its native region of China, Taiwan & Vietnam – Keteleeria or ‘Yunnan youshan’ has three species, of which Keteleeria evelyniana can be found as seed. So with Keteleeria evelyniana you can still have an unusual Pinaceae in your collection without having to raid your nearest full-sized pinetum.

Family 4: Podocarpaceae

Podocarpaceae is another large family within the conifers, with 172 species across 20 genera – so it is larger than Cupressaceae in terms of size but less well known in Europe and North America.ref This may be because podocarps are mainly found in tropical and subtropical mountain habitatsref, which has resulted in their leaves being quite different to other conifers (read more in my post on conifer flat leaves). It also results in trees from Podocarpaceae being a little harder to obtain in Europe.

There are three main groups within Podocarpaceae which could be represented in your pinetum – these are known as the ‘prumnopityoid clade’, the ‘dacrydioid clade’ and the ‘podocarpoid clade’.

The first group includes Phyllocladus – the so-called celery pines which come from Australasia. A somewhat hardy species includes Phyllocladus alpinus which I note can be purchased in the UK from Bluebell Nurseries, and seeds for other species such as Phyllocladus aspleniifolius are also available online. Depending on where you live these will need protection from hard frosts. Phylloclade species don’t have true leaves, aside from very small, almost invisible ones when they are seedlings. Instead they have ‘phylloclades’ which are photosynthetic flattened stemsref. So, of course you must have one of these interesting plants in your collection!

Also in the first group is the Prumnopitys genus from Polynesia and South America. Prumnopitys andina is known as the Chilean plum yew, and was the International Dendrology Society’s Tree of the Year in 2017. They produced a comprehensive report about this tree which you can read online, and which lists locations where they have been planted outside of Chile. It appears to be seasonally available in a small number of plant nurseries in the UK. I would have included a photo but no decent creative commons images were available, so I’ll add one when I get the chance to find a Chilean plum yew for myself.

The second group (the dacrydioid clade) includes the Dacrycarpus genus, of which Dacrycarpus dacrydioides is a species known and loved in New Zealand as ‘Kahikatea’ from the Maori. It’s the tallest tree in New Zealand, and apparently has a hardy form which can be bought from this provider in the UK. Below is one as a bonsai from the New Zealand bonsai association:

Also in this image is another member of the dacrydioid clade – which happens to be (according to Farjon) the smallest known conifer in the world. Microcachrys tetragona, or the Strawberry Pine, is from Tasmania. Bonsai enthusiast Diana Jones explains in the Newsletter of the Australian Plants as Bonsai Study Group: “Growing on the top of Mt. Wellington is a large tree, about 10m in diameter, called Microcachrys tetragona or creeping strawberry pine. Few people notice it because it is only about 5cm high, being negatively geotropic. This causes a few problems when making it into an attractive bonsai, because in a pot, it just flops.” Nevertheless I think her specimen has a certain charm, and she is definitely one tree ahead of me in the bonsai pinetum stakes.

And one can’t leave this group without mentioning Dacrydium cupressinum, also from New Zealand and called variously red pine, red spruce or ‘Rimu’. My favourite podcaster has covered this species on his blog In Defense of Plants where he says the fleshy cones of this tree are an essential part of the diet of the endangered kākāpō bird. Availability of the ‘fruit’ (not really since it’s a conifer – it’s a female cone) triggers breeding for the kākāpō so it’s seen as critical to their survival.ref The tree itself is a wonderful tree with long dangly stems so I’d love to have one even without a kākāpō.

But if you cannot find Kahikatea, Tasmanian creeping strawberry pine or a kākāpō-infested Rimu, the third group in Podocarpaceae (the Podocarpoid clade) is going to be much easier to represent in your pinetum, because it contains the oft-seen bonsai species the Buddhist pine, or Podocarpus macrophyllus (also called Kusamaki in Japanese). If you are going to have at least one specimen Podocarp, this is likely to be the easiest one to obtain. I have a couple in my London garden (in the ground) but after the last brutal winter I think they would prefer to be indoors, and they are sold as indoor bonsai in the UK.

There are various other Podocarpus species available at nurseries such as Podocarpus salignus or willow-leaved podocarp – it’s probably a good idea to do a local search to see which species are available in your area.

Family 5: Sciadopityaceae

Sciadopityaceae has only one genus (Sciadopitys) and within that only one species, the Japanese umbrella pine or Sciadopitys verticillata. This tree is an endemic Japanese evergreen conifer, with relatively slow growth rates, used in gardens and construction in Japan.ref1,ref2

Unfortunately since this is the only representative of one of the six conifer families, you really do need one in your collection if you are to truly represent all the conifers. This tree isn’t very easy to propagate, and is also quite expensive to buy (at least in the UK), not only that, it doesn’t appear very commonly as a bonsai. I haven’t had any luck growing it from seed (and they were expensive) so I think your best best is keeping an eye on nurseries and waiting until you see one at a reasonable price.

Sciadopitys_verticillata at Pinetum Blijdestein, The Netherlands

Family 8: Taxaceae

Finally we come to the yews, the Taxaceae family which has six genera and 28 species. Many will be familiar with its most prominent genus, Taxus, containing the Common yew Taxus baccata. According to the gymnosperm database, most members of Taxus look pretty much the same, so to save yourself money and time, I’d suggest simply finding the yew that is easily available in your area. For me Taxus baccata are a dime a dozen, you also see Japanese Yew Taxus cuspidata used in bonsai.

I believe you should also have a Japanese plum yew in your collection. Cephalotaxus is a genus with 11 species, which used to be considered its own family, but DNA testing revealed it really belonged in Taxaceae.ref This tree has yew-like leaves and small plum-like fleshy cones which start green and then move through red and dark purple colourationref. It’s not commonly seen as a bonsai but it’s not difficult to propagate and I have seen them available at plant nurseries in the UK. One would assume adopting a similar styling approach to yew would work with this tree.

The remaining genera in Taxaceae are a lot rarer and more difficult to include in any non-tropical pinetum. The New Caledonia Yew Austrataxus spicata is the only southern hemisphere Taxaceae, and thrives in the very unusual habitat of the island, based on ultramafic rock containing chrome and nickel and not much else in the way of nutrients.ref

The Catkin Yew Amentotaxus is a threatened genus with six species found in China, India, Laos, Vietnam and Taiwan.ref One nursery in the UK sells Amentotaxus argotaenia var. argotaenia as a pot-grown specimen to be taken indoors during winter (but when I checked they were out of stock).

The White Berry Yew, Pseudotaxus chienii, is the only species in the Pseudotaxus genus, and is also native to China.ref It has white arils instead of the red arils of Taxus baccata. Cited as rare, it is nevertheless available from some suppliers.

The final genus of Taxaceae and of this pinetum article, is a really interesting one called Torreya which I think deserves a place representing this family alongside the more familiar trees mentioned above.

Torreya nucifera was the International Dendrology Society’s Tree of the Year (2019) and has a full report write-up available online here. This tree is known as the Nutmeg Yew, or in Japanese ‘kaja’ and ‘kaya’ and oil from its seeds (not nuts!) have been used for tempura cooking oil. As a widely cultivated tree, there is availability of Torreya from plant nurseries (eg. here) although the article I linked to says they do not like cool summers so a protected position or a pot may be needed.

Another option from Torreya if you can find one, and have the budget, is the alarmingly named Stinking Cedar or Torreya taxifolia. This is a rare species native to Florida USA, now protected in the Torreya State Park in Florida. One can be acquired for £50 per 2L pot in the UK here.

The end (of this post, but the start of your conifer collection?)

So there you have it, a set of suggestions for creating your own mini-pinetum using bonsai trees across the six conifer families. If you decide to take on the challenge, I’d love to see your efforts – tag me on Facebook (Bonsai-Science) or twitter (@BonsaiScience). Here’s another link to the shopping list, to get you started.

Thanks to the University of Oxford Department of Plant Sciences Conifer Database and the fantastic Gymnosperm database for source material for this article.