OK, so we have this kousa dogwood tree that needs help. It needs to be fertilized and we have determined that 2 lbs of fertilizer per 1" of trunk diameter. This means with a 4" trunk we need 8 lbs of fertilizer. Here comes the tricky part.

We need to use a fertilizer mix of 16-4-8. We can't find 16-4-8, but we were able to locate a 2.75 lb bag of 12-0-0 (nitrogen), a 7.25 lb bag of 0-3-0 (phosphorus) and a 4 lb bag of 0-0-60 (potash).

So how do we use what we found to get a mix of 8 lbs of 16-4-8?

 

How did you determine the fertilizer content of 16-4-8? And how about the amount?

 

Just a guess would be 3.8# Nitrogen, 3.8# Phosphorous and about .3+# of Potash will give you 7.9#, so add pinch more of the blend to get to about 8#. Since you are gardening and not building a piano, you do not have to be too precise.

Everything based on weight.

Dick

 

Soil test results recommended 16-4-8 and based on the subject of the fertilization being a tree (and not something more common like a lawn) we were provided the instructions of feeding it 2 lbs per 1" of trunk diameter.

 

LOL, thanks Dick. I can calculate the ratios and all that (16-4-8 is 4-1-2) but what was throwing me off was the ratio of each individual bag we purchased. I dunno, it's been awhile since doing real math and I know a kousa dogwood isn't a piano, but I also want to make sure I don't kill the thing...though the way it is looking right now, it may be an improvement.

 

The weight of the bag the fertilizer happens to be in does not have anything to do with dosage for each tree. You just weight out the amounts needed for each tree. That way, the size of the bag has noting to do with the calculation problem.

Dick

 

I know you are aware, but your fertilizer is applied at the drip line, and not next to the trunk. Wifey just passed around behind me and was eavesdropping. She is the gardener.

 

First, it's important to know if the directions or advice you received is for the actual amount of those nutrients or for that amount of 16-4-8 fertilizer. The numbers on the package are percentages. 10-0-0 has 10% nitrogen and 90% fillers. So this is where it becomes important to know if you were advised to apply a certain amount of a fertilizer or if you are to apply a certain amount of specific nutrients. You said you needed to apply 2 pounds of 16-4-8 per inch of trunk diameter. That works out to .32 pounds N, .08 pounds and K .16 pounds P per inch of trunk diameter. Whatever you can come up with to meet that should work.

In the end keep in mind that plants grow all over the planet. Soil and nutrients are not the same anywhere so nothing is exact. If you get it sorta close you're doing alright. And, the plant was surviving before you came along and tried to help it.

 

Thanks to all for your responses.

This is a tree we planted almost 10 years ago and it has grown a lot over the years. Last year we noticed very small leaves at the top of the tree. This year almost the entire tree has very small leaves and very small flowers. It is supposed to shade the house and is not doing that this year. So that is when we started getting the soil sampled and tested and figuring out what is wrong.

It definitely needs nutrients. It was doing fine for the first 7 or so years but we think that as it got larger and larger, its need for nutrients grew as well and it is running out. We just want to help it out. We don't think it will thrive much longer if we don't intervene and your responses are a huge help. We're going to mix up a first batch based on the the .32-.08-.16 lbs per inch as suggested and see if that helps. It's not going to be an overnight thing so we will have to see.

Does anyone have any advice as to how often we should fertilize this tree? I'm very accustomed to taking care of and fertilizing our lawn, but trees are new to us.

Thanks again!

 

Most trees on the planet survive and thrive with no help from us and no fertilizing so I would not be overly concerned. If you're fertilizing your lawn you are already fertilizing the tree.

How were you planning to fertilize the tree? That much fertilizer in one area especially going into the heat of summer is not good for the lawn. Generally early spring and late fall is when it's recommended to fertilize trees.

As for how often to fertilize I would spread it out especially if you want to fertilize now. Maybe split it into thirds. Save 1/3 for fall, 1/3 for next spring then spread the other 1/3 out over the summer. This would would make life easier for your lawn and provide the nutrients to the tree timed more to when it needs them.

 

The tree is not located too close to the lawn so I am not sure it is getting much of the nutrients from when I fertilize the lawn. I guess the question I would ask is if the very small leaves covering 95% of the tree to the point where it practically looks like it does in the dead of winter is not a nutrient issue, what else could it be?

 

Have you examined the tree for pests or disease? I'm seeing a lot of Asian Ambrosia Beetle damage this year and it can make a tree look generally malnourished. It's not the only pest but they do like dogwood and many other ornamentals.

 

What do we look for to determine if we have such a creature?

 

Look closely at the tree. The Asian Ambrosia Beetle can leave little tubes sticking from the trunk and branches that can look like short toothpicks and they crumble when you touch them. Even if you don't have the "little toothpicks" just give the tree a good look over. Look carefully at the bottom sides of the leaves for insects. Look for little holes bored in the trunk and branches.

 

Yeah, we definitely do not have that little pest.