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Watering Big Trees

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Need help with how to water big trees?

Many folks ask how to water big trees. So that means gardeners are wondering if they should water mature trees. Further, you may be wondering how much water those old trees actually need. And we’ve got some answers to help you figure out best practices about watering big, mature trees!

Drought does stress out mature trees!

Big, mature trees can really be negatively impacted by lack of water. And lack of water might be caused by drought, insect issues, climate change, or other factors. But whatever the cause, if your big, old tree needs water, getting it to them the right way can help them survive.

Watering a big old tree - Thuja plicata

Slow, deep, repetitive watering under the cedars may help them through the summer. Just try not to soak the trunk of the tree while you’re at it.

Old native trees may also need watering!

For years horticulturists and arborists in the Pacific Northwest have been coming to terms with the idea that we’re going to eventually lose many of our native trees. And this loss is likely due to climate change and related issues. In truth, these issues mean these trees may need more water than they’re getting from rainfall.

Sadly, one of the first species we expect to go is our beautiful western red cedar or Thuja plicata. And other natives will probably follow this beauty’s lead.

How construction development may cause a big old tree to need watering:

Recently, we hired New Leaf Arboriculture to help us with some of our biggest tree concerns. And one old tree we were worried about is an enormous, multi-leader western red cedar.

This gorgeous tree has lived through quite a bit of change, particularly in the last few decades. At some point in its long history, a road was paved within feet of it. Later, as recently, as the 1980s it was one among many trees in an undeveloped forested wetland. And kids had nailed a tree house to it during the 1960s and 1970s.

Then, in the 1980s, much of land was cleared around it. And eventually a large building was constructed adjacent to it. Then, because runoff had become an issue from the paved road, much of the water that it (and its remaining neighbors) relied upon was rerouted into a county ditch.

Moreover, the ground above its uptake roots was carpeted with landscape fabric and water-diverting beauty bark.

It’s no wonder this tree was struggling! Rainwater and soil moisture it was relying on was no longer available to this big tree. So, it had begun to suffer. And that means watering this big mature tree by a gardener was it’s last, best hope!

Big mature tree in need of watering

Sparse green growth on the tops of these cedars indicates stress.

Eric and Vance of New Leaf cleaned up much of the dead inside of this beauty and added safety cabling just in case it starts failing in wind or because of its many stresses. And, they reminded me:

Get some water on this tree!

After our arborists assessed this tree, they insisted we start watering this tree. But the question of how to water a mature tree was still there. And the question of how much water to give the tree was also in front of us.

How deeply do mature tree roots need to be watered?

Tree feeder roots only go several inches into the earth. But it takes a while to get a good amount of moisture into already dry soil. And if those roots are burdened by fabric and wicking bark, it’s an even bigger challenge.

So if you can, get rid of that bark layer and the fabric before you start watering.
Beauty bark can cause mature tree water runoff
However, by watering slowly and deeply and repetitively over the course of several days and weeks, mature trees can get watered.

Best watering tools & methods:

Figuring out what kind of tool to use to water your big trees might be challenging. So consider these options for watering big trees:

  • Soaker hoses can be helpful, but you may want to hand saturate the soil before you rely on them. That’s because soaker hoses may drip so slowly it takes forever to get really tough, dry soil wet the first time. But, if you have semi-moist soil in place before using the soaker hoses, they may help keep up the moisture levels over time if you run them consistently and often.
  • Apply mulch over soaker hoses. Putting mulch over the soaker hoses can help keep the moisture from the hoses from running off. And it will slowly release downward to your thirsty big tree roots.
  • Sprinklers are okay, but not the best. That’s because a lot of the water from overhead sprinklers simply evaporates in the air before it gets to the soil surface to water your mature tree roots.
  • Don’t spray the tree trunk when you water big trees. Same rules apply for smaller trees too. That’s because too much moisture building up at the point where the tree enters the earth can lead to rot.

Could it be that your mature tree does NOT need watering?

Big mature trees often do not need to be watered. In fact, over time, they grow adaptations that should help them through normal dry cycles. And sometimes the yellowing you see on an older tree isn’t a problem. Instead, it may be natural behavior.

So how can you tell if your tree needs watering or if the dying parts are a problem?

Top things to consider before investing in all that water:

  • What part of the tree is yellowing and dying back? If the tips are dying, you may need to water.
  • If the interior of the tree is yellowing, it may not need watering. That’s because trees (including evergreens) naturally shed some older leaves. And these tend to be away from the tips of tree branches.
  • Are you seeing dieback or are you seeing something else? Sometimes tree cones add yellow color to a tree. And sometimes the new growth on a tree can be a brighter or “off” color from the typical deep green. If this is what’s happening, you may not need to water.
  • Are you seeing a whole lot of cones forming?  Heavy cone set can indicate that the tree is really stressed out. Cones = seeds, and a tree putting out a lot of seeds may be trying to replicate itself that way as a last ditch survival effort. So if you’re seeing a lot of cones, you may want to water your big, mature tree!
heavy cone set may indicate a big tree needs water

Heavy cone set like this on a Thuja plicata can indicate the tree is extra stressed out.

Final notes on watering mature trees…

If the tops of your trees are sparse: watering your old tree may help.

Moreover, if your big trees have heavy cone set, hurry up and get some water into those roots.

As well, if your big trees are more yellow or brown than green, start saturating that root zone.

Finally, if in doubt, bring in an arborist for help evaluating your situation. They should be able to help you set a course of action toward preserving your precious trees (and costly investment) before it’s too late.

In conclusion, if your soil is dry: water your big trees.

10 comments on “Watering Big Trees

  1. Lindsay John Babineau on

    What a great article. It spoke exactly to the situation that we are dealing with. We’re dragging out our hoses now.

  2. Adam on

    I have a big cluster of very tall WRC trees in the front lawn of my home in White Rock, British Columbia. I have intuitively been watering these every summer. This past weekend with the exaggerated heat wave that just hit the west coast, I had the hose on these WRC and a beautiful 70-foot tall either ponderosa or white pine, I don’t know. I let it drip slowly at the canopy line around the trees. I fear that I may be over watering now as I read your article. You say August-September is the time to water the trees. Should I not be watering my WRC in June? Can I possibly be over watering? The ground is still fairly dry a few days after I water. I think I am softening up the soil and getting deep moisture to settle down in there. The cedar tree is easily 80 feet tall, maybe closer to 90 feet. I am new to the house, and taking care of this tree since I moved here in 2019. The previous owners piled up soil around the base and treated it roughly. Any advice you can offer besides that already shared in your great article is much appreciated. Thank you.

  3. Garden Mentors on

    Adam, It’s great you’ve been giving your trees supplemental water, especially in a heatwave. Big, mature trees may not reveal the stress they undergo today for many years. Keep up the good work.

  4. Jessica Lawrence on

    Thanks for this article! I live in Oakland, CA and have a 70′ WRC that has recovered from dieback thanks to regular deep watering over last 2 years! I wonder if I’m watering in the best way, though, as more than half of its drip line is under paved road/driveways/sidewalk, and the rest is under a lawn with mist sprinkers. I’ve been watering by leaving the mist sprinklers on for 15 minutes, 2 days in a row about once per month. The grass gets very green. Since I started watering like this, the trunk has sunk into the ground by perhaps a foot and the tree has begun to lean. Should I stop mist watering and do below-grass watering with an irrigation wand, which is much less convenient, and hard to know if I’m doing it well?

  5. Violet on

    I have mature apple and plum trees that are approx 30ft tall. Would a soaker hose placed around the drip line be the best way to water them? If so, how often and how long each time? I also have a yard butler spike if that wound be a better way to water. It’s so hot and dry with the drought. Thanks

  6. Garden Mentors on

    Violet,
    Thanks for writing in. Site unseen it’s not possible for us to evaluate a complicated situation like this. However, soaker hoses don’t tend to do the best job. And it if the soil profile is already very dry, you may need to do many deep, targeted and tested soaks to rebuild the moisture in the soil. How long and how often this needs to happen may require someone to evaluate your specific situation on site. Hopefully, you’re able to locate an arborist or gardening consultant in your area to help you with this. If nothing else, you might try doing several slow, deep soaks during the coolest time of day. After watering each time, let the soil rest for a little while, then dig in and to feel if the soil is moist in the root zone. If not, repeat until it is. Then continue watering on a regular schedule that will maintain moisture at level the trees require. (Big, mature trees don’t always require supplemental watering. But in drought, it sure can help.) Good luck!

  7. Barry Curran on

    If I can only get access to a half of a WRC perimeter, will the watering of that half still benefit the entire tree?

  8. Garden Mentors on

    Barry, Thanks for writing in. We’ll assume a WRC is a Western Red Cedar. If you’re referring to something else, please let us know. While it’s ideal to water the entire root zone of a tree, any water you can get on those roots should benefit the tree!

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