Dahlias can be like amaryllises. They are almost too easy to grow. Tuber or seed, all you need to do is add water and, like amaryllises indoors in the winter, there is a good chance your dahlias will produce some of the garden's most impressive summer flowers.

On the other hand, just as amaryllises often fail to produce a flower despite rapid and impressive leaf growth, the same thing can happen to dahlias. You get fast growth, perhaps a flower or two, and that is it. Disappointing, especially after a buildup that the plant is a no-fail, fabulous edition to your collection.

How do you ensure that your dahlias will flower? Well, there is a simple way to bar the possibility of disappointment by understanding a key fact. Like any other plant, dahlias want to reproduce so the species can carry on in the next season. They can do so by forming tubers or by forming seed and often they do both.

Once dahlias begin to form lots of tubers, however, they stop producing flowers. This makes sense since the plant would be wasting energy continuing to produce flowers. What induces the production of tubers? When daylight starts to diminish, and especially when it gets to be less than 12 hours.

The other thing that will inhibit flower formation are temperatures over 80 degrees. This is not usually a problem Southcentral Alaska, but I mention it in case an Outsider is reading this column or you intend on growing dahlias in your greenhouse.

So, get dahlia seeds planted this weekend in order to give them plenty of increasing days with increasing daylight to mature. Flats, six packs or other containers should be filled with a damp, well-draining compost or humus mix. Lay the seeds on top and cover lightly with soil. Then put the container in a plastic bag or cover to hold in the moisture.

As soon as you see growth, uncover and reduce the temperature to 65 degrees. Once a set of true leaves appears, transplant into individual containers and continue to do so whenever roots get close to the walls. Crowded roots induce tuber formation and, as you now know, that is not good for the development of flowers.

A good tip when transplanting any seedling is to only handle the plant by those two first "seed leaves" which appear before "true leaves." Do not touch the roots. Dipping in mycorrhizal fungi is also a good idea at this time.

Dahlias have eight genes that determine appearance instead of just two, so seeds collected from last year's plants will not come true to their "parentage." On the upside, it is entirely possible that you will grow a plant that produces the most magnificent blooms you have ever seen. If you collect and use the plant's tubers in future seasons, they will always come true to form because a dahlia's tubers produce clones of the parent plant.