Fertilizing Acid-loving Trees


Active Member
I posted on the old QDM site that I used Miracle Grow orchid foot to feed oak/chestnut trees because I bought it as a closeout for 59 cents a box at Kroger. Others have recently posted their preference for MG - Orchid food. The purpose of this thread is to offer some different options that you might want to consider from either a cost or effectiveness perspective.
But 1st.... reference to an excellent article that explains why acid loving trees (oaks/chestnut/dogwood) need additional elements beyond N,P & K.

Fertilizing Landscape Trees
Horticulture Farm Advisor, University of California Cooperative Extension,
Stanislaus County;
Horticulture Farm Advisor, University of
California Cooperative Extension, Mariposa County
Sixteen fertilizer elements are required for plant growth. Three of the elements—carbon(C), hydrogen (H) and oxygen (O)—are provided by air (through CO) and water(H2O). In the soil, plant roots absorb the remaining 13 elements: nitrogen(N), phosphorous (P), potassium (K), calcium (Ca), sulfur (S), magnesium (Mg), manganese(Mn), zinc (Zn), boron (B), copper (Cu), iron (Fe), molybdenum (Mo), and chlorine (Cl). The first six are termed macronutrients because the plant uses them in large amounts. The last seven are called micronutrients because they are used in much smaller quantities. The 16 elements are considered essential because
• in the absence of any one of these elements, the plant will fail to complete its life cycle
• each element is specific and cannot be replaced or substituted for by another element
• each element has a direct effect on the plant (rather than an indirect effect, such as repelling insects that might prevent the plant from completing its life cycle)
Nutrient deficiencies, especially deficiencies in nitrogen phosphorus, and potassium, are not common in most woody landscape plants, except in palm trees, which often develop nitrogen, potassium, manganese, and magnesium deficiencies.
Woody plants growing in soil-less media in containers can often develop nutrient deficiencies. When nutrient deficiencies do occur, they cause reduced shoot growth and leaf size, leaf chlorosis, and necrosis and dieback of plant parts. (emphasis added /rest of article omitted - but a good read).

For those of you using container systems like "root-makers," the Miracle Grow products seem like a good deal. Orchid food sells for about $4 for 8 oz; however, Miracle Grow Azelea and Rododendron food contains the EXACT same elements and fertilizer - in the same proportions/sources as Orchid food - and it sells for $6 for a 1.5 lb carton. 3 X the food for only 50% more in price. On May 17, I enjoyed a BOGO on Azelea/Rododendren food at Lowes .... I received 3 lbs of food for $6. 3lbs of MG Orchid food would have cost $24 (4 X as much). Peters makes an almost identical product for acid-loving plants; I bought closeouts of Peters Azelea food for $1 a tub with 3 plastic bags containing 3.75 lbs of product. Any of these products will work well for container trees that you have the time to mix/feed every couple of weeks.

For trees planted in final locations, mixing MG - or any other water-soluble plant foot - is time consuming and not very practical. I don't have time to mix/feed 100's of trees every 2-3 weeks. Some folks merely throw a little triple 10/12 or 13 on the tree and move on. This does not provide the other micronutrients that ensure vigorous growth and healthy trees. I use a Stay Green product made for Azalea/Rododendron that is similar to Miracle Grow products in terms of micro-nutrient composition with a few notable exceptions. 1st, it is in solid form (granules) and feeds for up to 3 months (throw it on in March/April and forget it). 2nd, it has 3x as much iron which - for me -is important for acid-loving trees. 3rd, it does not have any copper in it (MG products do have copper); however, I am willing to make the trade off of more iron for the absence of copper, and 4th ... it does not have as much N,P,K ..... so I mix a bag of triple-12 with a bag of Stay Green azelea & rododendron food in equal proportions. I bought all their $10 bags at Lowes 2 years ago for $1@. Hope this thread gives you some ideas about feeding your acid-loving trees. Good luck. Photos to folloiw.
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Thanks for this thread. Citing the article is good for all of us.

I don't know if I stated this often enough - I use Osmocote Plus in my rootmaker 18s. When I up size to a grow bag, I add Osmocote Plus again.

I don't want to hijack your thread.

Wayne ... while I greatly admire and respect your generosity in helping others get started growing chestnut trees, I respectfully disagree with your advice to add Osmocote Plus to seedlings UNLESS a person (especially in mid-U.S. states like Ohio, IL, Ind, MO or KS) has a greenhouse or other means to protect young trees from the elements (freezing weather) during 6-9 months following application of Osmocote+. As you and others may know, most Osmocote products will feed up to 4 months ,and Oscomote Plus will feed up to 6 months because of the resin coating on the fertilizer materials. If a person in central/northern Ind applied Oscomote Plus on March 1, it potentially could feed the tree, and promote new growth, until September 1. That is a full 2 months beyond your suggested early July cutoff date for applying fertilizer (to allow new growth time to harden off). Obviously if one has a plant shed or greenhouse, or other means to protect new seedlings, or lives in the deep south (south FL, TX, southern CA) Oscomote Plus ... while fairly expensive compared to other options ... would work well.
If you visit page 7 of your Chestnut thread, you will read an inquiry from someone using Oscomote (don't know if it was Plus). He writes
9-2-2016 page 7
"Here's a question for the experts: I have ~80 hybrids in 1 gallon RMs that were transferred in May and fertilized then with Osmocote, but not since. Most of the trees showed an initial growth spurt and then stalled at around 24", with the leaves gradually turning dark green and new buds developing as expected. I had some sun damage too, but that's my own stupidity. However, around a dozen trees suddenly started to shoot out new growth in July. The growth is mainly from the main stem or a crotch thereof, with only a couple of trees sending up new shoots from the root system itself. My question is whether this new growth came too late and whether the trees will have time to harden off properly before the winter. I'm choosing my best 36 to plant and I don't want to choose trees that look great now but die back in the cold. I am in Rochester, NY, with the property about ten miles South of Lake Ontario, nominally zone 5/6"

As promised in my original post, here are pictures of some tree fertilizers I have used. Incidentally, for those who prefer water-soluble products like Scotts orchid food or rododendron/azelea food, Schults has an almost identic al product for about 75-80 % LESS per ounce.


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I want to be clear - this is your thread.

I want to be clear - I have been known to make mistakes. I have learned a great deal from my mistakes.

I want you and others to be successful.

Good luck.

Orchid fertilizer is roughly 786.45% better than any other fertilizer for trees in 1 gallon pots.....MUCH better growth and health after I started this practice.
Hmmm. Good to know. I fert my potted seedlings with standard miracle gro every couple weeks. I will change it up.
What would you recommend for some pin oaks showing chlorosis issues? Planted 4 years ago. Think i need to drop the ph of the native soil.