Some dahlia questions

9 years ago

I love dahlias! Last year some inexpensive dahlias provided me with an unbelievable amount of flowers after the second year of planting. This year I replanted those shallowly (just covering them basically) and also got some "name" dahlias from Swan Island. They were much smaller, as expected, than what I had over-wintered. The directions said to plant them six inches so I did. My dahlias from last year are almost all growing, some flowering and some not. One of my new Swan Island dahlias is not growing at all and one seems stuck at one inch. Only one of the new ones have flowered but the others are at least growing although most are pretty short. So....my questions are:

1) How deep should I plant the dahlias? Just under the surface or six inches?
2) When can I and should I separate the tubers when I take them out? I did not do so last year since I didn't quite know what to do, but I am glad to if it is a good idea or to share some.
3) Should I fertilize with Miracle Grow or something else if the plants are a decent size?
4) Usually I just put the tubers in buckets and put them in the back of my garage where it is cool but not freezing. I also do this with cannas and glads. Is it better to put the tubers in peat moss or vermiculite (or something else)?

Thanks in advance for your help.

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Comments (4)

morpheuspa (6B/7A, E. PA)
9 years ago
1) Yes. :-)

I vary a bit. The dahlia that got planted late this year went at the surface to get them moving as fast as possible. The earlier dahlia went at about three inches to make them easier to dig up in fall.

My early decorative dahlia ended up around an inch or so deep, but they're very small plants when mature--twelve inches.

The larger the dahlia, the deeper you should (generally) plant it.

2) If you look online, there's a whole method for separating tubers. I tend not to do this, simply cutting them in half and keeping half the stem on one part and half on the other. I'm lazy.

3) Yes. I use a combination of monthly Milorganite and weekly half-strength Miracle Gro across the entire garden. While dahlia don't strictly need much fertilization, like any other plant they benefit from it. The plants and the flowers both get larger and have better color if well-fed.

Being very well fed, my dahlia (and everything else) usually exceed listed heights, flower power, and color.

4) I put mine in paper bags in the cellar, which averages in the fifties, leaving the clumped dirt on the tubers if I'm not splitting that year.

Technically, cooler (but not freezing) storage in peat moss or vermiculite is best and does help keep them damp. In real life, that's just not going to happen.

So far, losses have been zero, but maybe I'm just lucky.
burry
Original Author
9 years ago
Thanks so much for your help!
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portia
9 years ago
morpheus, does splitting the tuber clump with half and half guarantee 'eyes' on both sides? I am a bit intimidated by splitting this fall/next spring.

burry, I ordered some nicer tubers this year too and my growth rate is hit or miss it seems also--a few of my SI ones are doing well and others never did anything.

I gave fish emulsion at first for nitrogen, and now MG bloom booster and about 1/2 of my plants are starting to bud now. I do like fertilizing though, gives me something to do while I wait. ;)
morpheuspa (6B/7A, E. PA)
9 years ago
>>morpheus, does splitting the tuber clump with half and half guarantee 'eyes' on both sides? I am a bit intimidated by splitting this fall/next spring.

In my experience so far, yes--if you split the stem in half, giving half the tubers one piece of stem, and half another.

You can split them more if the dahlia wants to do that, keeping bits of stem on each set of tubers. One of mine last year spontaneously fell apart into three. Two are in my garden, one is in my mother's,

(Shhh, I don't always split. I actually like a multi-stemmed, wider, denser dahlia. It's a little more susceptible to powdery mildew, but I can control for that if I have to. Plus I have limited garden space for dahlia as they're used as accent plants).

>>I gave fish emulsion at first for nitrogen, and now MG bloom booster and about 1/2 of my plants are starting to bud now. I do like fertilizing though, gives me something to do while I wait. ;)

Cool! Mind the phosphorus levels over time, it takes a while for them to go toxic and toxic levels are very, very high. But over the course of years, it can get there. Mine's riding very high at the moment, so I'm limiting phosphorus sources for the next...well, decade or so!

The occasional garden soil test is a good idea. Mine this year pointed out a modest calcium shortage (with the accompanying pH problem), and a low boron level.