Dahlias need just as much nitrogen as the other nutrients. In fact dahlia fanatics give them much more nitrogen. Most dahlias are 4 feet tall. In order to reach such a height they need water, sunlight and fertilizer. If you have been fertilizing your garden area for several years with a typical garden fertilizer like 10-10-10, the potassium and phosphorus will build up on your soil and you need less of those elements. But Nitrogen does not build up in the soil. In that case, you may need something like a 20-5-5 that is really a lawn fertilizer. So, or the first couple of years in your garden, use a balanced fertilizer like 10-10-10 and later, you can gravitate toward the higher nitrogen products. The reason that people say not to use lots of nitrogen is that if you have too much in the soil when you are digging your tubers, the tubers have a tendency to rot more easily. Therefore, do not fertilize after August 1st or so and the nitrogen in the soil will be used up by the time you dig in the Fall.

Thanks teddahlia

Sorry for my stupidity but...
the dahlia site says to use a nitrogen level in which the nitrogen # is at least 1/2 the phos. and pot. so now i'm kind of confused. I understand (or trying to anyway) the logic of 20-5-5. Actually, no, i don't relly understand. Sorry...can you try to explain it again.

Phosphorus and to some extent Potassium build up in your soil when you fertilize and will stay in the soil for years. Nitrogen washes out every year. Fertilizer has three numbers: the first(N)represents the percentage of Nitrogen in the product. The second number represents the percent of (P) Phosphorus and the third the percentage of (K) Potassium. A balanced fertilizer would have the the same number for each. Examples: 5-5-5 or 10-10-10 or 20-20-20. The article you read recommended a product like 5-10-10 or 10-20-20. I said if you have fertilized heavily in the past use something like a 20-5-5 instead. You are wasting the extra money that the 5-10-10 costs if 20-5-5 works. That is the cheap lawn fertilizer. If you have not fertilized that area very much and have not built up the levels of Phosphorus and Potassium, use the 5-10-10. Or, if you use any of the fertilizers mentioned above, your dahlias will grow fine. How about just give them a little bit of fertilizer in June and in July and whatever you use will work. A plant takes up what it needs and leaves the rest in the ground. A farmer who fertilizes many acres has to be concerned about over fertilizing as it wastes money and pollutes the environment. If you used the 5-10-10 or 1--20-20 for five years or so, you will have built up levels of Phosphorus that will cause a decline in plant growth. You will also have decreased the Ph of the soil and may have made it so acid that the plants are affected.

Hi teddahlia
OK...one more time around. I have not used a lot of fertilizer in the past. I've generally just let things go. I did/do use compost early in the season. The Dahlia tip site says to use just manure not compost. So are you saying that because I have not used a lot of fertilizer I should get a 5-10-10 type. This will, i think, provide the plant with enough Nitrogen for it to develop and give the plant the P and K that it needs as I have not been providing it each year.
Is that right?
(humbly) Dale

Yikes! Every garden is different. I have read the same things about the soil. I talked with a woman that has a beautiful garden of every kids of plant imaginable so I asked her how she fertilized all her different plants. She told me she uses Plant Tone on everything! I am going to use 5-10-10 month before I put in the tubers and when they are up about a foot, give them a boost of water soluable with a higher N reading and than let them go for about a month and see what they need. This is after I test the soil.

Thanks so much teddahlia!! I have learned a lot and while I still don't feel totally confident I do feel enabled to make choices...the right choices i hope.

I hope other people will benefit from your wisdom
Thanks again!

Dale