How do I shepherd my trees through adolescence?

October 13, 2009 8:49 AM

How should I support and trim my two trees so they'll grow up to be big and strong?

They're past the sapling stage (in other words picture C) and when one broke its single support stick (about 6 feet high), I trimmed it and staked both. Now the untrimmed one caught enough wind to pull up a stake and break it's support stick.

The pictures include closeups of leaves & berries as I don't know what kind of trees these are. I'm in San Jose, California and I bought the house a year ago, soon after the trees were planted.

I've trimmed both down to 4 foot diameter cylinders so they'll live until I can get better support installed, but what's the tradeoff between trimming and support? Should I keep the support light and foliage trimmed to "encourage" the trees to thicken their trunks or do I need beefy support? The other trees on my street are also mostly young [Google StreetView] so the wind can be pretty strong.

Lastly, where do arborists get strips of tire?, which some prefer over wire through garden hose for spreading load & preventing bark chafing? The increasingly misnamed Orchard Supply Hardware (now owned by Sears) had sticks and stakes, but no ties of any kind.

posted by morganw to home & garden (10 comments total)

Those aren't berries in the picture, but flower buds. My wife thinks the tree is a Jacaranda, but I can't remember what the flowers look like (even the color) and I have no pictures of the trees flowering.
posted by morganw at 8:56 AM on October 13

Arborist here. Looks like you have Crape Myrtles.

Nurseries grow trees with stakes so they'll be tall and straight. It's not the best thing for the trees. Think of grocery store apples: crappy varieties, selected more for shelf life than for flavor. It's all about the marketing.

First off, take off the nursery stake - the one that's tied directly to the trunk. The trunks won't develop the strength they need to resist wind unless the trunks are stressed slightly by wind and movement. Nursery grown trees have ridiculously long, thin trunks, because they are staked early on.

The guy lines you have are okay. Tighten them up a bit, taught, not tight. What you want is to train the tree to grow straight, and to not blow over and snap in the wind. Unfortunately, because the trees already have thin trunks and are top heavy (again, trained that way in the nursery) they are prone to wind breakage.

Don't use wire ties or wire inside tubing, ever. The problem is that people leave the stakes/ties on too long and wire will damage the bark and eventually girdle the tree. You can buy "Cinch-ties" in a nursery, rubber tubes that are used to tie to 2" diam lodgepole stakes. For guys like you have on your trees, you can rig the ties to the end of the line. You want a broad, soft surface area where you touch the trunk. Cotton ties are good, as they will rot off eventually.

You won't need the stakes or guys very long if the tree develops properly. Two, three years at most. If you have issues with the crown being heavy and blowing in the wind, thin out the interior of the crown by pruning some branches out. You want to get rid of broken, disased, or crossing branches. Cut them almost flush with the trunk. Never leave a stub, and never, ever top a tree, ever. Topping is pruning the central leader.

Another rule is to not prune more than 25%-30% of the foliage off a tree, ever.

Crape Myrtles are fairly bushy as trees. They are really large shrubs, and will want to spread wider than they get tall. Prune off low hanging branches every year or other year to keep the crown above head height, if you mow under them or want to walk under them.

In California, you can prune almost year round. You want to prune Crape Myrtles either in January/February, when they are out of leaf, or just after they flower. It's not critical to live by those rules in San Jose, though.

Check out the International Society of Arboriculture website for pruning and tree care practices.
posted by Xoebe at 9:53 AM on October 13 [1 favorite]

Stake the heck out of them. I use four poles angled away from the tree. Then cloth straps around the trunk and wire between the straps and the poles. So far my force grown mesquites are doing well.

I used 8 foot stakes, and drove them in about 2 feet. Then tied the wires at about 6 foot off the ground. You may not have the luxury in that location. But I'd at least try to get the stakes up off the ground so the wires/strings are closer to level (I may be wrong, but this seems to put less strain on everything and still protects the tree from snapping).
posted by krisak at 9:56 AM on October 13 [2 favorites]

Beefy support will result in weak trees, they need to be able to bend with the wind as they grow. This might have already happened. I get strong winds that bend the tops of my new trees over, and I've never considered staking them.

I have no idea where arborists get strips of tire, but you can probably talk a tire shop into giving you an old tire, as it saves them having to pay for disposal.
posted by yohko at 10:01 AM on October 13 [1 favorite]

That makes sense, Xoebe and yohko - the way I have mine staked down gives it room to bend while progressively reinforcing the tree as it bends father. The 6 feet of pole allow for some decent flex.
posted by krisak at 10:42 AM on October 13 [1 favorite]

Xoebe is spot on about staking- your tree needs to be staked so that it is supported, but can move and build up supportive tissue. Nursery stakes are only for storage and transportation, and should always be removed.

If your tree has good form you should need to prune rarely, if at all. Trimming ends of branches can increase bushiness, and that can make it denser and heavier- harder for the tree to support itself while growing. Crape myrtles are also prone to fungal disease, which can be exacerbated by dense foliage. Unless a young tree has diseased or crossing branches or is obviously imbalanced, I don't prune them at all. Pruning tends to encourage more growth in various spots, which leads to more pruning, which stresses the tree. Early fall pruning of crape myrtles slows down the entrance into dormancy, which also promotes fungal growth and doesn't allow the tree a good rest period. Pruning too late in spring and you lose all the flower buds on the new growth. So avoid it unless necessary, and then do it minimally in early spring before buds swell. Old wives' tales say that pruning crape myrtles encourages bloom, but there is no evidence for this.

If you want to remove lower branches, do it gradually as the tree ages. Never remove more than 20% of the canopy in a year. Generally, crape myrtles have an upright branching structure, and rarely have to have lower branches removed. What is more likely is removing branches that are spaced too closely or crossing.

Good pruning info here. Lagerstromia (crape myrtle) is shown being pruned as a multi trunk tree in the drawings, but you can apply the same ideas to a tree with a single trunk. The article also discusses why it is important to leave lower branches on young trees, only pruning them if needed when they have reached at least 1" in diameter.

Water deeply but infrequently- crape myrtles hate being in wet, undrained soil.

Try calling Capitol Nursery for tree staking materials- they used to have rubber ties when I worked there many years ago. They know all about crape myrtles, too. It's a very popular tree in San Jose.

Those aren't berries in the picture, but flower buds. My wife thinks the tree is a Jacaranda, but I can't remember what the flowers look like (even the color) and I have no pictures of the trees flowering.

Actually, those are the fruiting bodies- the tree has already flowered.
posted by oneirodynia at 11:30 AM on October 13 [1 favorite]

Actually, those are the fruiting bodies- the tree has already flowered.

Of course. Makes perfect sense.

Thanks for the answers everyone.

The least desirable time is immediately after new growth develops in the spring. A great amount of food stored in roots and stems is used in developing new growth. This food should be replaced by new foliage before it is removed; if not, considerable dwarfing of the plant may occur. This is a common problem encountered in pruning.

Oops! Most of what I cut was new growth around the sides & top. It's not Spring, but these trees grow really vigorously and only seem to go dormant for a couple of months in the Winter. The one I had cut back before (early Summer) had plenty of fruit on it.
posted by morganw at 11:56 AM on October 13

We also wrapped the trunks of our sapling for the first two years with a plastic wrap with holes in it. It's a hard plastic that comes coiled. In Toronto (6B, I think), the winter sun will crack the bark of new trees as the rest of the trunk is cold/frozen but the sun side heats up. Don't know if you have this prob or not as crape myrtle is too tender for this climate.
Strong agree with the staking, esp the advice about letting the tree move and removing the stakes after a couple of years. As long as the part attached to the tree doesn't rub the bark, you'll be fine.
posted by x46 at 12:37 PM on October 13

I think you'll be be okay this time around- if you pruned all that new growth off regularly it would be problematic.

You can help with entry into dormancy (it is always very short here in the Bay Area, but crape myrtles still do fine) by allowing fruit set. This cycle has hormonal responses that let the tree know that the resting period is coming (crappy phrasing, but you get the idea). Likewise, trimming trees produces hormones that cause growth, so doing it late in summer through fall (depending on the plant) can delay dormancy. This is very general info- there may be other specific reasons to prune particular trees in late summer; apricot trees here are prone to a disease that spreads during wet periods when pruning cuts are still oozing sap, so they are pruned in late summer sometimes so that those cuts can heal before rain begins.

You can also help by only fertilizing in spring, and avoiding unnecessary watering in early fall. If you've been deeply watering and allowing to go dry for the first few years, your tree will develop a deep root system that is resistant to drought even when we have the late September heatwaves. Unfortunately for us, those late heat waves make us feel we need to water our gardens (sometimes we do), and heat + water can encourage unwanted fall growth.

Like I said though, crape myrtles can do very well in San Jose, so you shouldn't have to agonize over this stuff. Just do any necessary pruning in late winter/early spring, and fertilize lightly just as it begins to get warmer but before it stops raining, late April-ish, usually. Mulch with bark chips to prevent soil compaction in that parking strip, and try to really minimize your lawn watering so the trees aren't constantly getting wet.You may need to change your sprinkler pattern if you have them out there, increasing the tree mulch circle to the tree's dripline is preferred.

Your local independent nursery (not Home Depot! Orchard used to be OK but it really depends on who works there) is a good resource, as are online sources from agricultural extensions or pretty much anything from a .edu address.
posted by oneirodynia at 12:48 PM on October 13

Did you cut the whole things down to four feet? If so, you will be having problems for some time to come.
What Xoebe said about staking was pretty good, but I'd say if you already cut the tops off, you probably don't need to bother staking at all, because there's not much levering the stem any more. Hopefully they have enough energy stored to keep rooting; you'll have to deal with the top later through pruning.
In general, staking should allow a little stem movement to encourage tissue growth without allowing anything to go so far that it gets stuck in it's flex.
posted by Red Loop at 5:53 PM on October 13