by Randy Davis 

It's mid-July and the bonsai activities have dwindled for the most part to summer pinching and pad development work. This is the time of year that the observant bonsai enthusiast is paying attention to, among other things, a plant’s ability to reduce the size of its leaves under bonsai cultural practices.  Some plants are better at producing small leaves than others; and, with the smaller size of bonsai becoming more popular these days, plants with naturally small leaves or genera that will respond to pruning and pinching with small leaves should gain your attention. For those of you who love bonsai under 12 inches, a good candidate is the Zelkova genera. A few months back we discussed the world of Elms, and Zelkova is closely related to them.  As a bonsai subject, Zelkova has been used for many years in Asia and is often seen more in Europe than it is here in the United States. There are a number of species of Zelkova. One (Z. sicula) has recently been found on the island of Sicily in Italy which is shrub-like and classified as a rare and endangered species.  For Bonsai the most commonly used species is the Japanese Zelkova (Z. serrata) which has been used extensively in Japan.  For some reason, it has been relegated to small broom style bonsai (most assuredly because of its excellent branch ramification and leaf reduction characteristics). A species that is also worth looking at is the Chinese Zelkova (Z. sinica) which may be treated the same as Japanese Zelkova as it is very difficult to tell the difference between them.  Another species from Western Europe (Z. carpinifolia) is also used but not seen very often.  I have had a few of each of these species here at the nursery for a number of years, and they are finally getting to the size that they can be worked on as young specimens.

Horticulturally, Zelkova can be treated much like its close relative the Elm.  Zelkova are very vigorous growers and, in the ground will grow quite rapidly once established.  Both Z. serrata and Z. carpinifolia are vase-shaped trees in nature and will reach 80-90 feet in time. Despite their normal size when grown in the ground, it is amazing the amount of leaf reduction you can achieve on them under bonsai cultural techniques.

Branches of the Zelkova, with constant pruning for ramification, will also become small and delicate, making them excellent candidates for display in the winter when the branches are bare of leaves.

Zelkova branches can be pruned vigorously at almost any time of the year with the exception of the deep winter months.  Root pruning in the late winter or very early spring before bud swell can be just as vigorous.  I have taken trees in the ground 8 feet high and pruned them down to 18-24 inches without any detrimental effects on them at all.  In fact, you can even take them down more if you space out the pruning with one pruning in the late winter and then again in early-mid spring.  For those of you that attended the Nashville spring show, I pruned a Z. carpinifolia down to just the trunk and a few small branches to show drastic pruning techniques that is often needed on some new training stock.  That tree is pictured on the right 5 weeks after that drastic pruning and is on its way to becoming a nice tree. Zelkova are not subject to many pests and diseases, and it’s one of the trees that is resistant to Dutch elm disease.  Japanese beetle is one of the pests that will eat the leaves of Zelkova and should be watched for in the warm summer months.

You may find it difficult to find Zelkova, although there are now cultivars of the Japanese form (Z. serrata) that are beginning to show up in the commercial nurseries.  Species are always grown from seed, and the cultivars are always grafted onto either Zelkova or Elm root stock.  Unlike its cousin the Elm, Zelkova will not survive from cuttings.  Zelkova cuttings will root but always die over the winter months making them unreliable.  If you can find Zelkova you should take the opportunity to add it to your bonsai collection.  It is great for both the beginner and the seasoned bonsai artist.