From https://garden.org/thread/view/115982/Teach-me-about-ploidy-in-daylilies/ post by hoosierbob on Sun, Jan 18, 2015.
Here is a good explanation of dips vs tets by a member on Gardenweb (Houzz) It was posted a number of years ago but i found it very helpful in my understanding of the difference when I first started out.
“All species of daylilies are diploid. That means they have 22 chromosomes. They get 11 from the mother and 11 from the father plant when they are created. Generally speaking, dips have thinner substance to the flowers and thinner scapes and leaves. When tets were chemically induced, it stopped normal cell division and produced plants with twice the number of chromosomes. This would be fatal in animals, where a slight change often has fatal effects, but it happens in plants and they seem to sort things out. Tets have 44 chromosomes, 22 from each parent. Generally, they have thicker foliage and thicker scapes as well as more substance to the blooms. Early tets seemed to have more issues with scapes ‘blasting’…they were so abnormally thick that they ‘exploded’, but much of that has been overcome in the years since.
Tets have some characteristics that are dependent on more genetic material to carry…teeth and fangs and heavier edges, for example. There are breeders, however that are working to give these characteristics to dips. Dips, have given us ‘blue’ eyes and fantastic patterns (check out Bob Faulkner’s site). Many of the neat patterns and colors of dips can be ‘borrowed’ by tet hybridizers when they use colchicine or another chemical to turn a dip into a tet. These plants have their name preceded with a ‘tetra’ or ‘tet’ prefix. If you look up the daylily, Rose Kennedy, it is a dip, but there is now a tet conversion that makes those genetics available to cross with other tets.
You can create a triploid by crossing a tet with a dip. Usually the tet should be the pollen parent since dip pollen doesn’t seem have the ‘oomph’ to fertilize a tet. The issue is that plant will be a dead end since it is a ‘mule’ with 33 chromosomes, which can’t evenly split between egg and sperm. Usually they are sterile, but plants do have ways to overcome sterility by throwing some fertile eggs and pollen.
The diploid Ed Murray can be bred as a dip or a tet. It seems that it produces some unreduced gametes, which gives some tet pollen and eggs, but this is unusual. Most dips are bred with dips and most tets with tets. Dips do usually produce lots more seed.
I should add that neither dips nor tets are ‘superior’. Dips, having fewer chromosomes, have allowed breeders to create characteristics that haven’t shown up in tets and maybe never will, except for ‘borrowing’ it from the dips. Diploids are often more graceful than tets. As I stated above, tets can give us more petal substance and patterns that dips don’t carry right now. Many gardeners grow both and enjoy both. You only need to worry about the genetics if you are going to hybridize. If you mix up your dips and tets, you’ll be wasting a lot of time on plants that won’t set seed for you. Otherwise, just enjoy the best of both worlds! Hope that helps. Bob
This post was edited by hoosierbob on Sun, Jan 18, 15 at 9:37″