3,226 Garden Web Discussions | Dahlias

If they are already blooming; they won't get much bigger than they are now. They might get a bit 'bushier'; but not much taller. As far as pinching; that is usually done before it blooms. Each time you remove a bloom that has finished; you are 'pinching' and it will have the same affect in that it will stimulate more laterals (branches) to form. Some bone meal in the ground would not hurt. Just keep them watered; but not too wet; and put some good compost in the soil.
They may need to be staked; but as I mentioned; they are probably at or near their full size now; so if they don't look like they need to be staked; they are probably a smaller variety.
Enjoy!!

Cadence,
You are in zone 8b.
I am in zone 8, so I will try to give you some pointers.
Dahlias are heavy feeders, which means they need composted manure in the soil while you plant them for additonal food.
Bone meal is also good.
In addition, I feed mine also with Miracle grow once every 10 days.
Is your climate humid?
I have humidity, and towards the end of summer they will develop a white fungus on them, you can try to avoid this by thinning them out some, cut the stems in the middle a bit so they aren't so dense.
ALso, water them more in August, it will be hot.
In the hot summer of the southeast, dahilas enjoy a little afternoon shade, so if at all possible, keep that in mind when you plant them.
Never water them at night, ever. If you do, they will rot and die. Always water in the morning. If you have to wait to water them, wait, til a morning that you can.
In the late fall, you will see the dahlias starting to loose leaves, just cut them down, leave about an inch stem, and mulch real good with at least 2-3 inches of mulch over the dahlia for winter sleep.
In the spring, when you see signs of life, just remove an inch of the mulch and start all over again, adding composted manure to the soil around the dahlia without disturbing roots. I just lay it on top of soil and put mulch back on.
I planted my dahlias about a foot apart.(reasonably small ones).
They will get bigger and fatter every year.
Good Luck to you, and by the way, dahlias are addictive!

I was given some dahlia tubers and some of them have mold on them. How should I take care of this? I would love to be able to plant them asap if possible. Or should I just chuck them? Please e-mail me your responses. marjorie.weikert@yahoo.com

Do you have a picture? It kind of depends on how far the mold has spread and where the mold is as to whether it's got a chance.

The height of dahlias is affected by the latitude of the grower. The farther North you live, the taller the dahlias. At our latitude of 45 degrees, dahlias grow somewhat tall. The tallest in my garden in absolute full sun(shade makes a huge difference), the maximum height is about 8 feet for Kenora Clyde. It has reached 18 feet when grown in partial shade(not in my garden). If you use shadecloth, dahlias that grow normally 6 feet or so will reach 9 feet and sometimes even taller.

Ted, that was a relevation, but it makes a lot of sense. I wondered why that one plant grew so much taller than the other, but it was next to some overgrown Christmas trees and I guess it had to work a little harder to get to the sun. Thanks for the insight! I guess I just assumed that a plant wouldn't do as well if planted in less sun. Now I know it can work differently.

Powdery mildew is very infectious and kills dahlias. In the Fall we sometimes get very bad powdery mildew and without spraying, the plants can turn completely white and all leaves that turn white die in a week or so. If you spray after the leaf turns white, the leaf still usually dies but the new leaves will be normal green.
I once had an infection on some cuttings that were inside my house and sprayed them and thought I had cured them. I planted them outside and the powdery mildew infected those plants again and about 10 feet of row near them(in July no less!). I sprayed with a systemic fungicide and controlled it. I use Strike (Triadimefon).

Thanks for the heads up. I appreciate it.

Great. Thanks.

I use Espoma Tomato Tone on all of my flowering plants. Makes life easier to just get a big bag of that at the beginning of the growing season.

They had eyes on them, however, I let them outside one night and the eye dried up. As suggested by one of the members here, I still went ahead and put them in the soil. Till now there is no sign of any growth.

Anna

I had one where the eyes took 3 weeks to start enough growth that I could see it with a magnifying glass. Now that it's potted, it will probably be a couple more weeks before I see anything above the soil.

The numbering system for inorganic fertilizer has confused people for years. There are three numbers and they represent the amounts(as a percentage) of the three major ingredients of fertilizer: Nitrogen, Phosphorus and Potassium. "Balanced" fertilizer would have the same number for each element 20-20-20 or 10-10-10. Dahlias like a fertilizer with 5-10-10 or 10-20-20 or even 12-24-24. All this means is that it has half the nitrogen as the other two elements. Most gardens stores sell 5-10-10. Farmers buy 10-20-20 at the farm store because it is twice as concentrated and much cheaper than 5-10-10.

Most of us are going organic. Alfalfa used as mulch is a great fertilizer. Mint compost is also excellent. Both have all three of the three major elements and work quite well. Bat guano and blood meal are good fertilizers. Of course all types of aged manures are the classic fertilizers for organic gardeners. Chicken manure works great but needs to be applied in the Fall as it is too "hot" (too much nitrogen all at once) for dahlias. They say that rabbit manure can be used fresh and needs no aging.

I follow Swan Islands advice. Work lots of composted manure into the soil, put in a small handful of bone meal when planting. Thats usually it. Sometimes I'll hit them with an additional fert in September when they are in manic bloom stages, but not always. I get plenty of flowers without pumping them full of MG.

I disagree with the need to dig them up -- what would that do but set them back.

Frost isn't a big deal at all - if the top dies off, more will grow. In essence, it is the equivalent of a hard pinch or cutback at this time.

When I worked at the garden center, the first crop of Dutch dahlias would be cut completely back when too big and floppy, and would regrow and be ready to put out for sale in about 4 weeks.

Personally, I think cutting back or pinching helps them to be a little less tall and floppy. Depends on the kind, of course, some of the tall dinnerplate types won't throw many side shoots no matter what you do.

My Dahlia's made it...the frost was a heavy one, and it amazed me that no damage was done to any of the plants...thank you both for your response...I deeply appreciate it...

Cuttings from Corralitos are done in Oasis foam. They are an excellent product and are easy to grow if you follow their instructions and do not over water the plants. The Oasis foam holds an incredible amount of water and if over watered the roots of the plants rot where the foam wraps around them. If the roots rot, the plants die.
When you receive the cuttings in the mail, let them recover under lights or in the green house for a few days and then re-pot into a larger pot and at that time remove most of the Oasis foam. Your success rate will improve dramatically.

Thanks for the input folks. I couldn't upload a picture but the dahlias seem to have recovered for the most part after drying out, though one or two still have curled leaves.

They didn't include removing the foam in the planting instructions so I didn't. After four weeks my guess would be that trying to remove the foam now would be disastrous for the roots. Well, maybe next year.

Thanks again.