The underground portion of the hosta plant is called the crown. It is the point of growth for hostas and all leaves and flower stems originate from buds on the crown. The roots extend out of the bottom of the crown.

Larger hostas have a thickened crown that may become quite large as the plant matures. To obtain a division capable of developing into a new plant, there needs to be enough so that a piece may be removed that contains some of the crown, some roots and either a leaf (during the growing season) or buds (during the dormant part of the year). Many of the larger hostas tend to multiply slowly and may not produce a lot of buds each year.

Smaller hostas may have a thinner, intertwined root system. Often these start with the original division and then grow by  rhizomes out to the sides in all directions. Again, as long as you can separate them so that you end up with a piece of crown, stems or buds and roots, you have a division. Cultivars such as ‘Golden Tiara’ multiply quickly and may be divided almost yearly if you need more plants to spread around your landscape.

Hostas may generally be divided “when the shovel is sharp” but this depends on post-division care. If you keep them adequately watered, they will survive division most any time. However, the cool days of the spring and the fall are the best for assured success.

Be sure to use sharp tool when you make divisions. Ragged cuts tend to stay open longer and may lead to rot problems. Although you will often hear the advice to dip the cut crowns in a fungicide, there are millions of hosta divisions made each year without this step. It would be more important if you have an existing problem with root rot in your garden. Generally, it is not needed.

Some cultivars of hosta are sterile and do not produce viable seeds. However, the vast majority produce perfectly good seeds which you may plant. You should be aware that, unless you go through some special steps, the seeds you harvest from your garden will produce hostas with the basic leaf colors of green, yellow or blue. Even if the parent plants were variegated, you will rarely get a variegated seedling.

Let the seeds mature on the plant and the seed pods should be nice and dry when you harvest them. Inside will be the small, paper-like black hosta seeds. If you want to plant them in the garden or inside under lights, you can plant them anytime after harvest.

If you want to store them until next spring, you can put them in the freezer for the winter. They do not need a stratification (cold, moist treatment) to germinate.

Commercially, some hostas are produced in a high tech process called tissue culture. Very small pieces of plant tissue are taken from the mother plant and are processed in a highly sterile environment. The pieces are placed in test tubes with a special substrate and are continually divided as new cells are formed. Eventually, from a small piece of a plant, thousands of exact duplicates i.e. clones may be created.

This is an expensive process since every step must be kept in a disease free, sterile conditions. If the growing room is contaminated by fungal spores from outside, everything may be lost to mold and rot very quickly.

During this process, sports (spontaneous variations from the original plant) often occur. This can result in a new variety or a plant that must be discarded since it is not the same as the mother plant.

3. At the end of a successful process (i.e. no contamination) you have thousands of small plants exactly like the one from which you took the original piece. Since it involves the use of plant hormones and other chemicals in the auger, there is a higher probability of sports being produced in tissue culture.

This is a process also called the "Ross method" or "Rossizing" was developed by Henry Ross of Gardenview Horticultural Park in Strongsville, Ohio. It is designed to make hostas develop more buds and expand the clump more quickly. Basically, it involves gently uncovering the crown of a plant in the early spring. With a very sharp blade, you make a vertical cut on each side of the buds on the top of the crown. Apply some rooting hormone such as Rootone to the cuts. This injury causes the plant to respond with the production of more buds and more buds make for a larger plant.

This process is used on those cultivars which multiply slowly on their own. Care must be taken to not cut too deeply into the crown so that you destroy the bud. If you really mess up, it could kill the plant. Take care.

In recent years, people have experimenting with a lanolin paste product called BAP-10 which contains the chemical N-6-benzylaminopurine. This is applied to the crown of the hosta in the hopes that it will stimulate the formation of additional buds. The amount of success with this methods appears to be cultivar related.