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Care of Your New 'Catlin Contorted' Tree

What To Do Immediately

Carefully unpack your tree. It is very fragile and may wobble in the pot, so exercise extreme caution. Water the tree and place in a shady location to recover from its journey. In most cases, it will not need immediate repotting and it will be best to keep it in its original container until the first opportunity to repot, usually fall or late winter. At these times you can decide whether to repot. If you are receiving your plant in the fall, wait until late winter to repot.

Watering and Fertilizing

Water your tree normally. That is, water when it needs water. 'Catlin Contorted' grows at a frustratingly slow rate, so it will stay wet longer than most of your other plants. Fertilize normally. If you subscribe to normal soluble chemical fertilizer, then fertilize at recommended full strength every other week.

Watching for Growth

Growth of 'Catlin Contorted' can be agonizingly slow, sometimes only an inch or two in a year, so don't expect big changes. As long as the leaves are deep green and shiny, it is probably in good health. It usually puts out a growth spurt in the spring. Sometimes this can be surprising, and it may even grow an inch or two during this period in some years. Other years it may only grow half an inch. It may or may not have another growth spurt in late summer. This slow growth and its exceedingly tiny leaves and internodes make it an ideal candidate for mame bonsai. Indeed, you will be hard pressed to get it to grow fast enough for any other size bonsai.


Don't let the fragility of this species fool you. It is a light lover and requires very high light requirements. In most cases, it can be grown in full morning sun and afternoon shade with no problem. In very hot and dry climates, it will probably be best grown under about 30 to 40% shadecloth, but early morning sun/ afternoon shade may still be acceptable. It doesn't acclimate to new locations very well, so whenever making a change, do it gradually and slowly. Always start out at lower light levels and move to higher until you get maximum growth without problems.

Indoor Growing  

Forget it. In most cases, unless you are highly experienced in growing temperate climate plants indoors, it will most likely succumb in indoor conditions.  The only exception to this is if you have no proper overwintering location, you may be able to keep it inside for a few months in winter until it can be returned to its outdoor location in spring, but this is not recommended.  

Dormancy and Cold Hardiness

This is a sport of Ulmus parvifolia 'Catlin' and will behave in a similar fashion in regard to winter weather. It is a semi evergreen cultivar that is reluctant to lose its leaves in winter. It may have a slight yellow winter color, but most often the leaves just turn brown and fall off. I have overwintered it in a cold greenhouse (that never freezes) and in the open where it does freeze, but the temperature does not fall below about 25F. It remains evergreen in the cold greenhouse, but it performs better in the open where it is allowed to freeze and lose its leaves. In spring, leafless plants rebound with nice new green leaves and a healthy growth spurt. Cold greenhouse overwintered plants tend to sulk in the spring and don't want to break into new growth.  In cold areas (zones 7 and colder), it is probably best to overwinter with your other plants in a garage or other structure where the  temperatures can be kept between 20 and 40F for most of the winter.  20F in a sheltered structure will be perfectly safe for a properly hardened off plant.

Hardening off should be accomplished normally. That is, allow it to stay outside and experience at least a few mild freezes before and night temperatures in the 20's F before placing it in the overwintering structure. In zones 8 and above, just leave it outside through fall and early winter to harden off naturally. If temperatures threaten to fall below 20F, then some protection is required. I use the irrigation system to apply water to most of my smaller containerized plants on freezing nights in winter. This encases them in ice and keeps the temperature from falling below about 25F, even when the ambient temperature is 15F. This will also prevent freeze drying, which is common for such small containerized plants.

Root Work and Repotting  

I am still working out the fundamentals of root work for this cultivar. It's tendency (and that of 'Catlin' as well) is to produce one or more long thin primary roots and almost no lateral roots. This is a maddening habit for creating bonsai. Often these roots will be a foot long on a plant that is only inches tall. On a plant that is so slow growing, the tendency to just let it grow without root pruning. This is probably a mistake. It is most likely better to root prune and repot every year eventhough the roots will nowhere near fill the pot in a single year. This will allow you to continually trim back the long primary roots and encourage lateral roots instead of just letting the long primaries grow and severely traumatizing the plants with a radical cut back every years. This will also eliminate the problem of soil collapse if you use any organic materials. Since the roots never colonize the pot, the medium stays wetter than normal and the organic amendments will break down in a year or less. Using an all inorganic soil will help with this, but won't solve the problem of long roots, so it will still need yearly root pruning. I have grown it in 100% Profile (Schultz's) and have not seen any better performance than in my bark/perlite mix.

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