Use the links below to jump to these areas of our Tree Care FAQs:

Pests
Roots/Soil/Tree Basin
Hardware
Pruning
Watering
Other

Pests:

Why do the leaves of my tree have brown edges, what can I do?
Brown edges are often simply windburn. This is caused by wind drying out the edges of the leaves. More water can make up for the drying factor of wind. The leaves of deciduous trees will often look "tired" in the fall, as they are getting ready to drop. Just wait and watch. Fresh new leaves should emerge in spring.

The leaves are yellowing and dropping, what does this mean?
For a deciduous tree, this may simply be a natural occurrence. It could also be a sign of nutrient deficiency. Trees low in nitrogen have green new growth and yellowing older growth. Nitrogen is available in most fertilizers.The yellowing (chlorosis) related to iron deficiency looks different; the leaf turns yellow but the veins stay green. Add chelated iron (available at garden stores) to the soil as directed on the package. If you have an Italian buckthorn (Rhamnus alaternus) iron deficiency can be fatal for this species, so take care of it soon. In heavy clay soil, yellow leaves could be a sign of overwatering. Cut back on water to see if this is so. Other evergreen trees sometimes produce a few yellow leaves. As long as there is still green new growth, it shouldn’t be a problem.

There are ants crawling up my tree. What can I do?
Get a sticky product like Tanglefoot at a garden store and put around the base of the trunk as a barrier for ants. Reapply as needed, because live ants will use dead ones as a bridge to get across. Ants are not there to hurt the tree. They are there to "shepherd" other insects like scale and aphids. Controlling those insects should cut down on the ants. See our pest management page for more details.

Roots/Soil/Tree Basin:

How can I make the roots grow straight down?
Roots don’t generally grow straight down. They grow typically in the top 24 " of the soil, where the water and nutrients are. You can encourage them to grow downward by watering with a slow drip, such as a hole in a water bucket. Watering slowly lets the water penetrate the soil more deeply. Move the water source regularly to get all the rootball. Soil type also affects how roots grow. Roots will have an easier time penetrating sandy soil and a harder time with clay. We do plant some species with 18" rootguards, which detour roots downward. They may eventually U turn after some years. Rootguards are not recommended with every tree, as they can make firm rooting more difficult.

What is mulch, why do I need it and where can I get it?
Mulch is undecomposed organic matter such as wood chips or leaf litter that is used on top of the soil. It has many benefits! It keeps moisture from evaporating so fast, holds down weeds, and looks nice. Over time, it decomposes into the soil, which benefits all soil types by adding organic matter. Before adding mulch to sandy soil, fertilize with nitrogen first. That’s because as mulch decomposes, it uses up nitrogen at first. Don’t put mulch into a planting hole, or it will decompose without oxygen and produce sulphur. Yuk! Mulch should be about 3" deep and not piled around the trunk! Too much moisture near the trunk will cause rot. See our mulch page to find sources of mulch.

Help! My sidewalk is cracking! What do I do? Can this be prevented?
The easiest and cheapest thing to do is to find out if you can expand your tree basin, or cutout. Call the Bureau of Urban Forestry to see how much you can expand without a permit, 641-2674. Or consider getting a permeable landscape permit and making a sidewalk garden! Visit Plant SF for more details. Less concrete to maintain this way, less flooding in a storm, and more elbow room for the tree!

If you have to repair concrete, there are three steps: Concrete removal, root pruning and concrete replacement. Have a certified arborist do the root pruning! This is not something just anyone can do. See our arborist referral page for referrals. For a large tree, you may have to repair some concrete every 5 years or so. Too many root prunings are not recommended for a tree; always consult a certified arborist.

To prevent sidewalk conflicts for young trees, water using a slow drip. After a few years, you can use a flat shovel around the edge of the tree basin every 6 months or so to preventatively cut off surface roots. Plants in heavy or rocky soil will have a harder time establishing deep roots.

Should I fertilize the tree?
Fertilizer often does more harm than good. Chemical fertilizers can’t be fully absorbed by the plant, so those chemicals end up in the groundwater. Excess nitrogen makes the soil too acidic and hard to work. Be sure you really need to fertilize. If you have soil with clay and/or silt content, it should not need fertilizer. Regular addition of organic matter like mulch should be enough. Sandy soil is very low in nutrients, so adding organic fertilizer once a month or so can help. Organic fertilizer is slow to release so the plant can take it up. Organic sources of nitrogen include lawn clippings and fish emulsion. Certain species don’t care for fertilizer; many Australian natives don't like phosphorus. Look up your tree in the Sunset Garden Guide for more info.

Can I bury the tree deeper to make it stand up better?
The trunk should not be buried; it will cause rot. This will make the tree less stable, not more.

How can I prevent roots from getting in my utility pipes?
Roots are lazy, but opportunistic. They don’t break into pipes that are sound, but do exploit cracks, holes or weaknesses. Many old sewer pipes are terra cotta, the same material as flower pots. Over time they develop cracks and roots will exploit those. Consider replacing an old terra cotta sewer pipe with more modern materials.

When I take the ties off the tree and shake it, the roots appear to be moving. What does this mean?
The tree is not quite rooted. Different species root at different speeds. 3-5 years after planting is average. In addition, soil type is a factor, and a tree recently hit by a car may become more loosely rooted. It’s worth checking for any circling roots leftover from the time when it was in a pot. Gently excavate about 1" down around the trunk, as far out as you see roots. Look for roots that are circling or knotting, preventing the tree from sending out its structural supporting roots. These problem roots can be cleanly cut, if smaller than a finger, allowing new roots to grow from this location. Make sure to water the tree right after this root pruning and continue watering weekly. Mulching will help ensure the newly forming roots stay moist. Keep the tree lightly tied and supported, it needs to move in wind to get stronger. Trees need "exercise" too!
See our soil and basin care pages for more information.

Hardware:

When can I take the stakes and ties off?
Support hardware is there for two reasons; to establish the roots and to keep the trunk upright. If both of those have happened, there is no need for support hardware. To test, take the ties off the tree and let it sway free. If the trunk still has a lean and is elastic, continue lightly supporting the trunk where needed. Also shake the tree and look at the ground. If the roots appear to be moving, look for circling roots as described in the previous question. Look at the hardware every few months and be sure it is lightly supporting and causing no wounds. Adjust as needed.

The tree is staked but it’s still leaning. What can I do?
Are the stakes broken underground? Shake them to see. If they are wiggly, they are probably broken and need replacing. Is the tree leaning because the trunk is elastic or because it is poorly rooted? An elastic trunk can be retied — as loosely as possible — to the point where the tree is straight again. You may need a longer stake to do this. If the tree is poorly rooted, look for circling roots and prune as described above. Follow up with regular watering to strengthen roots. See our hardware page for more information.

Pruning:

What’s wrong with topping a tree?
Each tree has a genetic plan for how to grow. You’ll see that the trunk and branches start out thick at the bottom, then taper off to be thin at the top. Each species grows in a way that is right for itself. Knowledgable pruners respect the shape of the tree while gently training it to be as safe and non-intrusive as possible.

When the tree is topped, the internal plan is ruined. The tree is forced to survive by sprouting wherever there are dormant buds. These spindly sprouts come out of large cut branches. There is no natural taper. The new sprouts are crowded and weakly attached, and if allowed to develop, become more hazardous than the original branches. In addition, it’s ugly. See our tree topping page for more info.

What about the trees in Golden Gate Park and by the City Hall? Are they topped?
Those sycamores are pruned in a special way called pollarding. This originated from French peasantry, who discovered that they could cut a lot of firewood off certain trees and they would still be alive in the spring. Pollarding is a technique and doesn’t just mean hacking off all the branches of a tree. Only certain species can take this kind of pruning. Consult an arborist if you want to pollard a tree.

When is the best time to prune?
In San Francisco’s mild climate, almost anytime is good for most trees. We prune young trees year round, although we avoid pruning in the rain as certain kinds of diseases are more easily spread then. For deciduous trees, many people prefer to prune them when they are leafless. However, there is a school of thought that suggests pruning them in full leaf to avoid excessive sprouting afterward. In rare cases of cold weather, don’t prune frost-tender plants before frost is expected. Some species have specific requirements: Ceanothus (wild lilac) should not be pruned in the winter. Pines should be pruned during the winter, to avoid pine pitch canker. Consult an arborist if you are not sure.

How often should the tree be pruned?
Most of the trees planted through our program are pruned on this schedule: 18 months after planting and 3 years after planting. We recommend 5 years after as well. Fast growers, which include acacia, elm, locust and peppermint willow (Agonis spp.), are pruned at 12 months instead of 18 months. After the 5 year anniversary, prune on a regular basis as needed, depending on rate of growth, environmental and other factors. Just don’t delay for 10 years then prune a bunch off the tree to make up for it. Think of tree care as dental care, a little effort and expenditure on a regular basis to avoid an expensive and painful procedure later.

A branch broke off! Should I put something on the wound to help it heal?
It used to be standard practice to apply a "wound dressing" on pruning cuts and broken branches to "help" the tree heal. It turns out the tree can heal just fine by itself, given time, and the dressings often trap moisture under them and cause rot, rather than protect from it. So leave the wound alone, take care of the tree in other ways with water and/or mulch, and give it time.

A branch almost broke off! Can I tie it back on?
In general it is not worth it. It’s better to make a clean cut and move on. There may be certain conditions in which it works, but if done poorly, it can cause rot or wound the tree. If you have specific knowledge of grafting, and it’s not posing a hazard, give it a try, but don’t just duct tape a huge broken branch and expect it to grow back. See our pruning page for more info.

Watering:

Can I overwater my tree?
If you have very heavy clay soil or underground water the answer is yes. If you have sandy soil it is much more difficult to overwater. For the first few years after planting, generously water up to 20 gallons a week in sand and 15 gallons in clay. Water year round- 1" of rain is only 5 gallons to the tree. San Francisco gets about 20" of rain per year. Cut down on water if the soil is always wet or smells swampy. Also, after the first year, Jacaranda trees are fine with only 10 gallons of water a week. See our watering page for more details.

I use a hose. How do I know I’ve given the tree enough water?
The hose should be turned on to a slow drip. To measure the flow rate, let it run into a vessel that you know the volume of. For example, a 5 gallon bucket or a 2 gallon watering can. See how long it takes to fill that vessel and do the math for 15 or 20 gallons. Chances are it will be a long time. My test revealed 70-90 minutes. So it might be better to use a vessel with a small hole in the bottom. If you fill up a 5 gallon bucket and let it drain, you know the tree got 5 gallons. We usually give you the bucket that the tree comes in to use as a watering vessel. Line it with a trash bag, poke a hole in the bag at the bottom of the bucket, and let water drain out. These buckets hold about 6 gallons (even though the nursery calls them 15 gallon buckets, they don’t hold 15 gallons of water). Sometimes people steal the buckets so keep an eye on them.

When can I stop watering the tree?
In general, 3 years after planting. See our watering page for more details. For California natives, such as Ceanothus, Coast live oak (Quercus agrifolia), Buckeye (Aesculus californica), water through the first dry season only. If the tree is poorly rooted, you may need to continue watering after the recommended time to strengthen the roots. Remember, 1" of rain is only 5 gallons to the tree!

If I water the tree less than suggested, won’t the roots grow more, and deeper, as they look for water?
Our observations have shown otherwise when it comes to young street trees in San Francisco. Underwatered trees just seem listless and poorly rooted. Young trees just aren’t developed enough to take the stress of underwatering. Even "drought-tolerant" species need water to get established. So raise the kids right! They’ll thank you later! See our watering page for more info.

Other:

How can I get FUF to care for my tree?
We visit trees planted through our program at least 3 times in the first 3 years on a scheduled basis. You can contract us for additional visits up to 5 years after planting. After 5 years, we will continue to be a source of advice and referral for you. Due to our limited resources, we can only visit trees planted through our program but will always serve as a source of advice and referral. Call 415/561-6890 x102 for more details.

How come FUF doesn't take care of large trees?
To work on large trees in a safe and professional manner, we’d need a lot more equipment, staff, training and insurance. We just can’t send a volunteer up a tree with a chainsaw! So we refer you to the professionals for larger jobs. However, with the right funding source, who knows, we could expand our operation…

Can I donate a tree to FUF?
Our needs are very specific. We plant 15 gallon potted street trees. Only certain species will do, in a certain shape and condition. We don’t have the capacity to dig up or move large trees. If you have a 15 gallon potted tree that you think might work, you can call us, but there are many trees we cannot plant. We do take potted Christmas trees only during certain times of year. Call us for more details.

My neighbor has a tree in his yard that is causing me problems and he won’t prune or remove it. What can I do?
There are no city ordinances to deal with trees on private property unless the tree poses an imminent hazard, such as a large dead tree. If you think the tree is hazardous, call the Bureau of Urban Forestry at 641-2677. Otherwise, try to can speak your neighbor and reach a compromise. You do have the right to prune any limbs on your side of the fence as long as you do not ruin the health or economic/aesthetic value of the tree. Community Boards at 415/920-3820 ext 101 helps mediate disputes between neighbors, should it come to that.