How do you fertilize hydrangeas?

donnabaskets(Zone 8a, Central MS)October 28, 2008

This year, I was trying to be a "really good" gardener, so, for the first time, I gave all my hydrangeas a handfull of slow release fertilizer. And, for the first time, I got virtually no blooms at all. My Endless Summers which have always bloomed non stop, bloomed once, and not again at all until just recently (I assume the osmocote has worn off by now). My blushing brides didn't bloom at all, except a very few early on. Also, the leaves on many of the plants developed black spots early on, but which have been replaced by nice green leaves since late summer.

I had virtually no blooms on my old fashioned ones either.

I know I have read that hydrangeas like commercial fertilizer, but this experience makes me question that wisdom. What is your experience?

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luis_pr(7b/8a Hurst, TX)

Depends on your soil and how much fertilizer you added. If your most recent soil test says that your soil is in good condition then there is no need to do anything but mulch. In some cases, you can simply supply additional minerals by adding weak fertilizers like coffee grounds, liquid seaweed or liquid fish. But if your soil has enough nitrogen or has too much, adding fertilizers might keep the plant in growth mode instead of bloom mode.

Unfortunately, it is hard to verify what caused the problem with certainty; we can only speculate now. The weather and lack of (or too much) water can also cause problems.

As for which kind of fertilizer to use when you need to use fertilizers, you can use cottonseed meal, manure or a general-purpose slow-release fertilizer in Spring. The amount to use depends on the size of the plant but, say on a new shrub, you can add either 1/2 to 1 cup of cottonseed meal / manure. For a general-purpose slow-release chemical ferilizer, read the label. In either case, you should apply the fertilizer twice every year (May and July) where you live or just once (June) if you live in the northern states.

Here is a link that might be useful: Fertilizing Hydrangeas

    Bookmark   October 29, 2008 at 3:16AM
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ostrich(3a AB)

Oh Donna, I did the same thing the year before and there was hardly any bloom, but lots of nice foliage growth!!! LOL!

Now, I have given up fertilizing my Endless Summer, except for giving it a good layer of mulch with lots of organic matters every year, and it's doing great!

    Bookmark   October 30, 2008 at 5:25PM
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I think we tend to fall under the spell of fertilizer company marketing hype :-) Most of the ads you see on TV or in the magazines would have you believe that unless you use Product X and in sufficient quantities, your plants won't grow and you'll never have any flowers and your garden will generally look like crap. It ain't so!! If you have reasonably fertile garden soil and unless your plants show a definite need, fertilizing trees and shrubs established in the landscape is generally unnecessary.

Reasonably fertile garden soil is pretty easy to achieve - most of us have it without needing to add amendments, etc., unless there has been heaving cropping on the soil previously (intensive farming) or the soil has been damaged by chemicals, etc. Those of us who have amended soils will have even more fertile soil. And fertile soils tend to offer most of the necessary plant nutrients without needing substantial supplementation of fertilizers. But if your plants are showing signs of distress - stunted growth, chlorotic foliage, lack of blooming or fruiting, then by all means apply the type of fertilizer of your choosing but only after a soil test to indicate what is lacking. Too much or the wrong type of fertilizer can do more damage than applying nothing at all.

FWIW, I fertilize nothing in my garden (other than container plantings) and haven't for many years, simply because there is no need to do so. I did take the time to improve the soil initially and continue to do so with liberal applications of compost as mulch. Compost, if used on a regular basis, will continue to supply all necessary plant nutrients and most trace elements as it continues to breakdown and decompose and in quantities sufficient to satisfy all plant needs. And there is no risk of applying too much fertilizer or of burning.

Osmocote is a very expensive product that IMO is best utilized on container plantings (and a commercial form is used on nursery grown container plantings). Anything organic will be a better choice, like the cottonseed meal Luis suggested (also helps to maintain soil acidity) but a compost mulch is really all that is usually ever necessary.

    Bookmark   November 1, 2008 at 11:19AM
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The soil in your area is primarily composed of a layer of rich black clay soil, atop an impenetrable layer of chalk, known historically as the Black Belt. Since ground water cannot percolate up through the chalk layer, the black clay tends to dry out during the summer, but with adequate moisture, the soil is nutrient rich.
Our family farms were located in such an area, which allowed bumper organic crops to be harvested, using notill & lowtill, crop rotational farming practices. Cover crops (annual ryegrass, hairy vetch, crimson clover) were sometimes used to replenish nitrogen and prevent erosion.
An added benefit of ground covers, was the increase in song bird population (food source, cover, nesting sites).
Here, in my exburb location, I have primarily red clay, which is also nutrient rich. As gardengal noted, I never fertilize Hydrangeas, once they are planted in the garden.
My rooted cuttings are fertilized once or twice with 15-30-15, water soluble type, to promote first year blooming. After that, no more commercial fertilizer is ever applied, just an annual application of compost or leaf mold and mulching, to retain moisture, here in the Southeastern High Desert!
FWIW, I have one ES that is located in an area that receives full afternoon sun and produces about 125-150 flowers each year. Never fertilized, red clay soil never ammended and only irrigated a few times, when we have no rainfall during a 40-50 day continuous period, which, lately, occurs much too often!

    Bookmark   November 1, 2008 at 2:14PM
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donnabaskets(Zone 8a, Central MS)

You are all absolutely right, and it's really not news to me. My soil is in positively wonderful condition with plenty of organic material top dressed and mulched in each and every year. It has great drainage due to the backbreaking work we did in prepping it before planting. Gardengal, you're right. I simply fell prey to advertising. Lesson learned. Thanks for the input, folks.

    Bookmark   November 3, 2008 at 7:20PM
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hayseedman(z5/6 Ct.)

Sometimes I will put some fertilizer on some of the annuals that are in the ground, but otherwise, plants in the ground get very little fertilizer.

But I do have a lot of Hydrangeas in pots and I do need to fertilize them.

I'm learning about all this myself, but when I make my potting soil I usually will put in a mixture that contains some leaf mold and will add some Greensand. I don't know how much of this is necessary, but it seems to work.

For the plants that have been in pots for several years I do add fertilizer. I do make a point of not fertilizing during the growing season and I think that has helped to keep fungus away. Maybe that's just my imagination, but I think that if I keep my plants on the lean side, even to the point of the foliage looking a little pale, then I don't get nearly as much fungus like leaf spot and powdery mildew. I wait until late in the summer and then I add most of my fertilizer. I might give some of the most pale plants a little Miracle Gro during the early part of the year. I used to believe that fertilizer in the Spring was the logical way to go, but I've converted myself over to believing that the best time to fertilize is toward the end of the season so that the plant will be able to get itself prepped for the winter and next year's bloom. It's the same idea that causes me to do my lawn fertilizing at the end of the season like you see suggested most of the time.

Works for me.


    Bookmark   November 5, 2008 at 7:55AM
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jazzmom516(Zone 7 LI, NY)

Slow release fertilizer is good for all plants provided the first number is not in the low to high teens. Those nitrogen numbers can cause foliage to come out over the flowers. For flower formation, use a fertilizer with a higher 2nd number(phosphorus) in it. I use the Espoma Plant Tone on all my shrubs and perennials in the springtime.

    Bookmark   December 29, 2008 at 8:45PM
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Hold on......fertilizing of landscape ornamentals should be done only if soil tests deem it appropriate or the plant indicates it is lacking specific nutrients. The statement that "slow release fertilizer is good for all plants" just indicates how thoroughly brainwashed we have become by the big fertilizer manufacturers. Ma Nature doesn't go around fertilizing all her plants other than providing the natural accumulation of organic matter or the soil surface. Other than applying a compost mulch on a fairly regular basis and the occasional top dressing with rabbit manure for heavy feeders like roses or clematis, I never fertilize any plants in my garden. They simply do not require any. Annual crops like veggies or container plants are a totally different situation and do require routine supplements, but not trees, shrubs or perennials established in the ground.

Pay attention to your plants - if they are showing signs of nutrient deficiencies, like off-color or chlorotic foliage, lack of blossoms/fruit or weak growth, then by all means have a soil test done to see what may be lacking. Then and only then should fertilizer be applied according to the test results. Unnecessary or over-fertilizing produces just as many harmful results as it does benefits and excessive use of fertilizers is one of this country's major sources of water pollution.

FWIW, a regular application of organic matter in the form of compost or other quality organic mulch is generally more than sufficient to replace any necessary nutrients that may become depleted in the soil over time.

    Bookmark   December 31, 2008 at 12:08PM
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I moved some new hydrangeas to different soil. These I rooted myself. They are full of buds, however some of the bottom leaves are turning yellow and some of the leaves appear to be burned on the ends, all I can figure is I have over fertilized them. I sprinkled a very small amount of 10-10-10 to the bottom of the soil. Could this be wrong ? Nothing has ever been planted on this soil, so I figure it needed some help. Maybe I am wrong. New buds look perfect and the tops of the plants, help !!

    Bookmark   May 1, 2011 at 3:46PM
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Geri, without seeing the plants to confirm, this DOES sound like fertilizer burn. But it is not so much a question of the amount of fertilizer applied than it is to the method of application. Mixing a synthetic fertilizer (and a 10-10-10 IS typically a fast acting synthetic) into the planting hole risks contact of the fertilizer with delicate plant roots, hence the 'burning'. It would have been better to apply any fertilizer you think necessary to the top of the planting area after planting, working it gently into the soil surface.

The good news is that most synthetics tend to be very water soluble and move through the soil rapidly, so the effect is short-lived. In the future, just adding some organic matter (compost) to the new planting area - not just the planting hole - would be a better plan. And using an organic fertilizer rather than a synthetic would remove the risk of burning, as these are slow acting and require mineralization to become available.

    Bookmark   May 2, 2011 at 12:08PM
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PepprGrowr(Zone 5)

Hey guys, got a similar question but a little more specific. I have some cuttings that I have rooted and are currently growing, though slowly, in small pots (my guess are they are about .5 gallon) and I was wondering if there was a nutrient solution or additive I can throw in so that they will grow faster. I am in zone 5 and do not want to put them into the ground for winter unless there is significant growth to keep them alive.

The cuttings are about 6 - 8 weeks old and are growing in a soil-less Faffard Agro Mix. I have some All Purpose Miracle Grow that I have used this summer but am not overly satisfied with its results and would like to get something better.


    Bookmark   August 19, 2014 at 12:32PM
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morz8(Washington Coast Z8b)

Peppr, I don't think there is a good way you can push growth on cuttings in late August and expect that to be mature enough to handle winter in a Z5. A vigorous and expanding root system would be more important than top growth that you can see, your potting medium could have a lot to do with that. Fafard isn't a line available to me here but it seems most growers find it better than any of the Miracle Grow products which are inconsistent in quality IMO. ProMix is another that gets a lot of praise, it's not available within 300 miles of me either so I can't personally recommend.

Do you have some way of protecting the cuttings over coldest weather, even moving them into an unheated space during the worst of winter - garage, unheated enclosed porch...

    Bookmark   August 21, 2014 at 4:33PM
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