Can I fertilize now? And what do we do for chlorosis?

susankaJuly 25, 2011

We have a yard with 2- to 3-year-old trees and shrubs of about the same age. They haven't been fertilized since being planted except for a large tablet of some kind that was put in when they first went in and was supposed to last for a year or so (so we were told). Would you advise me whether I can still fertilize, or is it too late? Thank you very much.

Two of the trees look chlorotic to me -- light green leaves with the veins in dark green. One of them is a maple, the other we were told is a "Golden" something. Before we moved here, living in Fort Collins, we had a maple and aspens that were chlorotic and never could get them healthy despite all our efforts. Is there something in this area (Greenhorn Valley in Colorado at 6100 feet) we can do for these two trees? And thank you for your thoughts on either of these two situations.

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treebarb Z5 Denver


Have you lived at this house since they were planted and have they developed chlorosis in previous years? The rain we had this year was exceptional and may have washed the nutrients in the soil away from the plants.

If it's only happened this year I'd punch holes around the driplines of the affected plants and put something like sequestrene in the holes. It is late in the season but I think trees and shrubs aren't going to be putting out much top growth before fall anyway. (please jump in and correct me if that's wrong).

Having said that, if this proves to be an ongoing issue, I'd think about replacing the species you have. Many maples and oaks don't like our high ph clay soil and I'm not sure the unending battle to keep them alive, much less happy is worth it. You've already had that experience with the maples and aspens in Ft. Collins.

I don't fertilize trees and shrubs at all.

I think it might be worth doing a soil test to see what's going on.


    Bookmark   July 26, 2011 at 8:46AM
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Dan Staley

Maples get chlorosis here. If you don't like the look, replace with a tree adapted to our soil pH. Trees do not need to be fertilized unless there is a soil deficiency that affects all plants.


    Bookmark   July 26, 2011 at 11:42AM
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Thanks,Barb and Dan. We were here last year, and the chlorosis was beginning then.

I had no idea trees and shrubs don't need fertilizing; I'm glad to hear that from you both (at least trees in your case, I know, Dan).

I have perennial beds which I know do need fertilizing, but I've only planted them this year.

Thanks again.


    Bookmark   July 26, 2011 at 3:27PM
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Skybird - z5, Denver, Colorado

I don't fertilize trees and bushes either, Susan. Don't fertilize perennials either! LOL! If I have something--perennial--that's looking especially unhappy, I occasionally go around and give a few individual plants a shot of soluble fertilizer, but, generally speaking for things growing in the ground, if a particular plant is really unhappy, it's probably gonna take more than fertilizer to fix it. (Plants in pots are a different story.) Usually it's something more like being planted in a totally wrong environment--light, water, wind, heat, etc.--or in soil that is just so bad that a really major revision would be required to help much. When I have perennials that aren't doing well, if it's something I really want, I'll move it first, usually along with a lot of soil amendment, to see if that fixes the problem, but for the most part, plants that can't make it on their own are outta here, and then I can happily try something else.

Not really saying you should never fertilize anything, but I think a lot of the fertilizer that's being sold doesn't do much more than help the bank accounts of the folks that are selling it! IMO! If you advertise it, they will buy it! "Tree Spikes" for instance! While tree roots may not be very deep, they spread out far, far beyond the trunk of the tree, and even beyond the drip line, and I dare say that most people who use those things pound a few in here and there a few feet away from the trunk and think they're helping their tree! Dan and TreeBarb know a lot more about trees than I do, but I'm guessing that if your trees are growing in your lawn, and you're feeding your lawn a high nitrogen fertilizer once or twice a year--especially in spring, you're gonna be doing far more good than concentrating a little bit of fertilizer here and there with something like the Spikes. I way agree with Dan and TreeBarb that the best thing to do is to put in something that is known to like our soil and conditions out here. Then you can just relax and enjoy your tree(s)!

I have some sort of Spirea in my front yard that has been yellow--yeah, it's supposed to be green--ever since I moved in here. Got tired of it last year and cut it almost all the way down to the ground--thinking it might die for me--but it's back, still yellow! It'll probably be a few more years, but when I finally get around to it, it's gonna be gone--along with some kind of a Viburnum that is TOTALLY in the wrong place, thanks to some landscaper who was getting paid to put "something in!" It's right at the corner of my very small front porch, and if I let it grow unencumbered it would wind up being 10' tall and easily wide enough to completely block access to my front door. If only removing/replacing established shrubs wasn't such a major project, I'd do it now, but in the meantime I can keep trying to kill them! ;-)

And, I know you were asking about trees, but one more thing about perennials! Many, if not most, xeric perennials will do much better if they are NOT fertilized. Things like yarrow, Agastache, Russian Sage. So if your new perennial beds are all xeric or have xeric plants in them, keep that in mind if you decide to fertilize the perennials. Most xeric plants come from places that have pretty tough growing conditions, and have learned pretty well to adapt to whatever they happen to find where they're growing. Too much water isn't good for many xeric plants too--a problem I sometimes have since I have non-xeric and xeric plants all growing side by side! Wish I had enough room to separate them to make it easy for myself! (And wish the cottonwood trees would get cut down so I'd actually have enough sun to grow the things I want to!)

I'm curious now! How many folks around here REGULARLY feed their perennials?


    Bookmark   July 26, 2011 at 5:41PM
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Dan Staley

BTW, I have a yellow spiraea, 'Limemound' that is very yellow. BH hates it, as it is near some veronica 'Aztec Gold' and that's a lot of yeller.

BH also enjoys fertilizing and I have to keep her away from my beds. We have a bed on the side of the house and she'll fert that once a month if she has time...sigh...


    Bookmark   July 26, 2011 at 6:14PM
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treebarb Z5 Denver

Amen, Skybird!

I try to top dress the rose and veggie beds with compost and horse manure once a year. I don't fertilize anything on a regular basis except the veggies and the roses. I only have one rose, a pink Grootendorst that gets chlorosis. The others might be ok if I didn't fertilize, but I do it anyway.

Susan, you might want to check out CSU extension site. You can find plant recommendations in the yard and garden section that will save you lots of frustration going forward. The school of hard knocks has taught me to pick plants that like it here.

Dan posted a link on the Trees forum a while back to a tree recommendation list for the front range that I have bookmarked on my computer.

Dan, I like your sparkly plant logo!


    Bookmark   July 26, 2011 at 8:23PM
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Wow, this sure sounds good to me! We have a dozen or so trees (evergreens and deciduous), and many shrubs and xeric perennials and grasses on rocks with no lawn, but with ground cover which I hope will eventually cover up most of the rocks. I'll take a photo and post it tonight. All are on drip. We had to put the rocks in because the wind is too strong for any other ground cover, and the foxes were digging up our drip lines every night; the rock seems to stop them. We had hoped for a "forest" look; not sure we're getting that, but at least if I don't have to fertilize these guys that will be a lot less work. We're trying to plant things that will be happy here, but I thought they all needed additional encouragement.

Thanks to all of you for your kind and thoughtful advice. I get what you're saying and it sounds good to me.

    Bookmark   July 27, 2011 at 6:58AM
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Dan Staley

My beds only get what the breakdown product is from the wood chips and whatever is there from the original amendment at the time of bed creation, the plants are all adapted to the West and I don't do plants from catalogues back east - once established I maybe water 3-4x/year, haven't watered this year since April. We considered rocks but that would be too hot here. Clay soil is actually the best for transferring and holding nutrients, only downside is dealing with the texture.


    Bookmark   July 27, 2011 at 3:34PM
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david52 Zone 6

I have a weeping birch that has been in the ground for 10 years now, growing well, but I just noticed some pretty severe chlorosis going on, with the leaves getting splotchy yellow. I don't know what happened, the only difference is I watered the lawn up hill a bit more than usual, trying to establish some clover seed. I suspect that I have a 'wave' of underground water with higher alkalinity working its way down the slope, and hopefully will continue along and outta here.

Re fertilizing - I've been using a clover/grass clipping mulch, and thats almost too much. For green leafy vegetables like chard/kale/spinach, thats all they need. Same clipping mulch does wonders for the trees as well.

    Bookmark   July 27, 2011 at 11:28PM
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Everything here has to get along without any mulch or top dressing of any kind though because we have rocks everywhere.

    Bookmark   July 28, 2011 at 6:28AM
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I don't usually fertilize my tress. Only what they get from the lawn fertilizer I apply. It has additional iron and sulfur also. The only things additional they get usually are some iron.Our soil is iron deficient. Several of the tree nurseries when I've bought trees have suggested applying the iron. Otherwise they get nothing. I mulch around things fairly heavy if possible. In this 4 year drought that has really helped. Jay

    Bookmark   July 28, 2011 at 12:00PM
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