HELP! Fertilizer problem?

michey1st_gw Zone 7August 3, 2014

Good Morning!

This is my first year with Dahlias (in fact, i'm a pretty newbie gardener in general). I have 3 dahlias going in some large pots, and 2 of them have started flowering (HOORAY, I feel like a rock star, lol!).

Anyways, trying to be a good Dahlia mommy, I just gave them a shot of fertilizer (I was feeding the orchids so figured I would give the Dahlias a treat as well). Gosh darnit, wouldn't you know that after-the-fact, I did some googling and found that high nitrogen ferts are bad (I used 1 tbsp 30-10-10 in a gallon of water per the box instructions for "other outdoor plants") for Dahlias >.Did I just kill my plants?!? Is there something I can do to salvage the situation? Should I not worry and just don't fertilize again with the stuff? This is the first time i've fertilized the Dahlias, other than the granular osmocote I added to the potting medium.

Relatedly, (and speaking as a new gardener) this whole fertilizer thing is tough to keep straight. Seems like every plant out there has its own special formulation. Is there a magic "one size fits most" that I can use for the bulk of my perennial flowers (in ground and in pots)? I totally get orchids are special (they are my mom's first love and now that she just downsized, I ended up with her left-overs), but what about everything else in the ground?

Help!!!!

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morpheuspa

It won't kill them if you followed the instructions on the feed, so no worries there! You might just get a lot of greenery growth from it for a short period of time. No big deal.

I tend to use Miracle Gro, which is competitive with what you used, at 24-8-16. I grow gorgeous dahlia and gorgeous everything else.

Once a month I do put a small handful of Milorganite in all the pots. At 5-2-0 it's still high nitrogen, but mostly slow release. All my plants flourish using that.

>>Relatedly, (and speaking as a new gardener) this whole fertilizer thing is tough to keep straight. Seems like every plant out there has its own special formulation. Is there a magic "one size fits most" that I can use for the bulk of my perennial flowers (in ground and in pots)?

Orchids--and African Violet--are special, but most plants will do quite well with any reasonably balanced fertilizer. My 24-8-16 and your 30-10-10 are balanced enough to use on almost everything in the flower garden.

Some people swear by a blossom booster formula, usually around 15-30-15. That's also balanced enough to use on almost everything.

Observation is key. If you see a lot of lanky, weak growth on your dahlia, it's time to cut back severely on the fertilizer.

If you're detecting that those "special" rules for every plant aren't all that "special," you're right. The three fertilizers above are pretty different, but they all do a great job most of the time on most plants.

    Bookmark   August 3, 2014 at 3:26PM
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michey1st_gw Zone 7

PHEW, THANK YOU, Morpheuspa -- that puts my mind at rest!

In my fertilizer "arsenal" (lol) I have the 30-10-10, a bloom-boosting 10-52-10 (as yet unopened), Osmocote plus and milorganite (hooray!). I'm going to go sprinkle a little bit of the milo in the pots in a few days per your recommendation.

Since i'm on a fertilizer bender (hee hee!), i'll try the 10-52-10 on some of my in-ground plantings to see if it makes any difference.

Thank you again!!!

Kindest regards,
Michele

    Bookmark   August 3, 2014 at 6:27PM
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morpheuspa

I also confess to mixing things. I'll take a bag of 24-8-16 and mix it with a bag of 15-30-15. That gives me twice as much of what's effectively (39-38-15.5)/2, or 19-19-15. Then I use half of it in the garden and save half for next time.

Really, I'm playing it by ear. If greenery growth looks weaker, I step up the nitrogen. If I'm encouraging flowering, I step up phosphorus and potassium.

Milo and Osmocote are both great on plants. For Milo, I use a nice sized handful per large pot, and a very large pinch in tiny pots. It's pretty much impossible to overdo the Milo.

For Osmocote, just follow the instructions and you're golden.

This is really, really hard to mess up is what I'm saying--overapplication of most synthetic fertilizers can cause problems. Organics you have to go way, way overboard to the point that I've never heard of anybody doing it in pots or in the garden.

And contrary to popular opinion, dahlia do like to eat. I planted a bunch of clearance dahlia very late--June 16th--and they're setting blossom now, about four weeks earlier than most people would estimate.

Why? I feed well.

    Bookmark   August 3, 2014 at 7:41PM
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SequoiaMatt99

Ironically, dahlia master Steve Meggos suggested a 30 10 10 so it's not a problem. However, use this type of fertilizer at the beginning of the year to jump start the foliage, and switch to something like 6 54 6 for the bloom booster later in the year (yikes that's a lot of phosphorous!)
I've been using organic tomato fertilizer and getting pretty good results- the plants apparently have similar needs.

    Bookmark   August 3, 2014 at 9:35PM
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morpheuspa

It does depend on your soil. In my case, my phosphorus came back pretty high and consistently tests a bit higher every year, so I tend to use phosphorus sources rarely. Once or twice a season tops. Really, I have the margin for about ten years of blooms with absolutely no additions.

For my mother's garden, more would be required, although her P levels are also pretty good.

For the average garden, adding P for a number of years may or may not be a bad idea. Some depends on locale. Some on the soil particulars. Only your soil testing lab could tell you for sure.

    Bookmark   August 3, 2014 at 10:27PM
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portia(PA 6B, Brandywine)

I actually had to give my dahlias a bit more nitrogen when they started to bud--don't know if it was sapped out or what but also read with very hot weather nitrogen can leach out more quickly-so you may be doing them a favor...who knows. :) Fertilizing is not an exact science!

I use the 10-52-10 as well, so in about 2 weeks I'd probably use some of that too, maybe watered down slightly til you can see 'effects' on what you use. I always water down a bit the first time or two just til I feel more comfortable. I use the 10-52-10 on all my annuals and perennials too.

    Bookmark   August 5, 2014 at 11:05AM
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morpheuspa

>>Fertilizing is not an exact science!

You can say that again. Loudly. In fact, just record it and put it on a repeating loop.

If you follow the lawn care forum, I'm big on integrated management. My guide to organic fertilization of lawns (and gardens) amounts to, "when it looks like it needs it. If you can learn to estimate that in advance, great."

There's no good magic formula that'll work for everybody all the time everywhere. On the up side, there are also very few things out there that will cause major issues for most people, most of the time, in most locations.

This week was Miracle Gro...on top of a huge feeding with Milorganite for the gardens. The lawn got a nice shot of soybean meal.

    Bookmark   August 6, 2014 at 1:35AM
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michey1st_gw Zone 7

Well, the fertilized Dahlia's haven't skipped a beat as yet (knock on a tree-stump). It's nice to know that it's not too easy to kill them with fertilizer kindness, though, so long as I exercise moderation and common sense, which does tend to escape me from time to time.

This weekend, it will be milorganite everywhere-- not just on the Dahlias -- and next weekend will be a bloom booster chaser.

NO WORRIES, I GOT THIS!!!! (for now, lol...)

    Bookmark   August 6, 2014 at 9:14AM
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teddahlia

Everybody seems to be hung up on fertilizer numbers rather than how much fertilizer to give dahlias. They need specific amounts of nitrogen, phosphorus and potassium. If you are applying a fertilizer like 14-14-14(that is a formula for some Osmocote products), each dahlia plant needs 2 to 3 tablespoons of fertilizer. Since it is time release, it can be applied all at once at the beginning of the season and you are done fertilizing. if you use 16-16-16 fertilizer(a common formula) each plant would need about 2.5 to 3 tablespoons of fertilizer applied in three applications, one tablespoon at planting and then another about 30 days later and then then 60 days later. No more fertilizer should be given to dahlias after about August 7th or so. If your soil test says you have adequate amounts of phosphorous and/or potassium, you would use a fertilizer with lower numbers for phosphorous and/or potassium. An example would be a typical lawn fertilizer like 20-5-8. Since the first number(the nitrogen) is 25% or so higher than the 14% or 16% numbers above, you would use less of this or no more than 2.5 tablespoons per plant spread over the season. It is the amount of nitrogen applied to each plant that counts.

    Bookmark   August 6, 2014 at 4:24PM
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morpheuspa

>>It is the amount of nitrogen applied to each plant that counts.

Minus leaching and loss to the air.

Rather than attempt some extremely complex calculations, use of organic feeding is much simpler. Apply. The window spanning the correct amount is so wide it's barely worth considering.

Or, if I can't overdo the lawn with 37 pounds per thousand square feet of nitrogen in one year, it's not worth worrying about over-application. And I couldn't, and wasn't too worried about the lawn as I was transforming the soil. It still flourished. The gardens did as well, but only got 24 pounds per thousand.

Heh. Only. :-) That's four hundred pounds of high nitrogen material per thousand square feet over the course of a season, atop the 1,500 pounds per thousand of mulch I put down that year.

Even with synthetics, I apply half the normal rate at the normal interval and everything does very well (this is on top of the organic feeding). Were I to observe excessive greenery growth and depressed flower growth, I'd cut back.

Really, learning to "plant whisper" is the easiest way of doing things, and consequences of error are pretty minor. Slow growth? Step up the feeding. Too much? Step it down. Synthetically, things reset in a week or two. Organically, the problem doesn't occur anyway--but getting enough to build up may take some years.

    Bookmark   August 6, 2014 at 7:56PM
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CCvacation

Ted, how much does foliar feeding substitute for regular side dressing fertilizer? If one uses Miracle Grow common for tomatoes as foliar feed with the 14-14-14 time release, for example, do you consider that overkill, or supplemental that won't build up in the soil or tubers?

You have spoken before about the tubers not storing as well if fertilized after August, but would foliar feed be considered as bad as side dressing in terms of storage issues?

    Bookmark   August 8, 2014 at 7:21PM
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teddahlia

I read that foliar feed is about 15 times more efficient than granular products. I have no idea how they calculated it. Too much of a good thing is still a bad thing late in the season. If the tubers are full of extra nitrogen they have propensity to rot.

    Bookmark   August 9, 2014 at 11:25PM
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CCvacation

Then I'd better get with it and give the final MG foliar dose this week after the rains stop... Maybe mix up another batch of worm compost tea next week for good measure.

Thank you!

    Bookmark   August 12, 2014 at 1:03AM
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portia(PA 6B, Brandywine)

Ted, can you still fertilize with non nitrogen formulas past August or should all fertilization be stopped?

    Bookmark   August 14, 2014 at 2:27PM
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ken_adrian Adrian MI cold Z5

trying to be a good Dahlia mommy

In my fertilizer "arsenal" (lol) I have the 30-10-10, a bloom-boosting 10-52-10 (as yet unopened), Osmocote plus and milorganite

This weekend, it will be milorganite everywhere-- not just on the Dahlias -- and next weekend will be a bloom booster chaser.

==>>>

hey mommy.. you KNOW they arent children.. right??? .. they dont need to be repeatedly fed.. clothed.. educated.. etc ....

you appear to use more fertilizers than a farmer with crops on 500 acres ... crikey ...

do you really think you need this much fert??

i am glad my well head isnt down stream from your place ...

if you have a decent fertile soil ... frankly.. your plants should NEVER need fert ... and if you change your potting media every season ... [and you better for all the salt build up] ... i cant believe you would need more that one or two fertilizings PER SEASON ...

you are on the verge of killing your plants with too much love ... be weary of such .....

ken

    Bookmark   August 14, 2014 at 2:41PM
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morpheuspa

>>you are on the verge of killing your plants with too much love ... be weary of such .....

Not even close. While using some fertilizers is unwise without a soil test, most are OK and there's no real danger of killing your plants.

Standard in the gardens for me is 18 pounds of Milorganite per month from May to August, plus a half-strength Miracle Gro feeding weekly through mid-September.

Deaths so far...well, the rabbits do nibble a few. But otherwise, zero.

I'm starting to limit phosphorus sources in the garden as my numbers are finally showing where they should be for flowers. Potassium is actually slipping a bit and will probably need specific enhancement next year.

Most micronutrients are in the correct range, except boron, which rides a little low. I'm working on that.

Nitrogen is the kicker, it gets used, absorbed, out-gassed to the air, and leached out. Which is why the heavy hitter is organic, to limit leaching.

Your water would be safe. Just as mine is, and has been every year.

>>if you change your potting media every season ... [and you better for all the salt build up] ... i cant believe you would need more that one or two fertilizings PER SEASON ...

The soil in my pots is now six years old and of better quality than it was when it went in...because I keep pouring organics into it. They sit in the rain, get flushed (by accident, mostly) when they're watered, and sit out all winter. No salt build up.

    Bookmark   August 14, 2014 at 2:52PM
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teddahlia

Ken: Are you a dahlia grower?

    Bookmark   August 16, 2014 at 1:57PM
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