While the lily plant grows with green leaves, the bulb is being recharged. The longer you can keep the lily growing, the better recharging and the bigger the bulb gets. You should continue to water the lily. Do not cut the stem back until the leaves fall off by them selves and the stem dies back. Sometimes, the stem will die back from disease, but most often you can get the lily to grow for a long time which is good. Do not cut the stem back before the lily stem has withered.
In your area, the temperatures may not be as low as to make the lily bulb "go to sleep" naturally and vernalize, cooling period which prompts the lily plant to bloom again. Therefore, if the lily has not started to show signs of going "back to sleep" nine months after flowering, you can put the pot ,and all, in a spare fridge set at a low temperature 33-35F. As low as you can without freezing. Gradually begin to withhold water.
Do not worry about lack of sunshine during this period. After the stem has died back, you keep the lily in the cold temperatures for six weeks and bring it back out. It should not be "programmed" to start growing again and flower.
Calla Lilies are most certainly perennial. In your region, a very mild usda zone nine, you can plant all your Calla Lilies in the ground and if you water and feed them they will all grow beautifully. It sounds like you are enjoying the blooms on your Callas. If you really want to impress your husband, memorize the following word "Zantedeschia", the scientific name for this is plant. There are two kinds of Calla Lilies/Zantedeschia.
One is the kind that loses its leaves when it rests. The other just stops flowering and doesn’t grow much, but it still has leaves. The first one is big and white, occasionally yellow. The second one is a little smaller and brightly colored. First, the "bulbs", which are really called "Rhizomes" , of deciduous, leaf-losing, Calla Lilies look completely different from the large, evergreen white-and-green florist Calla Lilies. Rhizomes of deciduous, colored Calla Lilies are flat, round wafers, typically with bulls-eyes or dark circles. They grow best in bright sun and can dry out between waterings.
If the flower on your Calla Lily is pink, red or plum, and it has finished blooming, and when is at the end of the growing season, the leaves will begin to turn yellow. That would tell you that you have a deciduous Calla Lily. The kind that loses its leaves when it is resting. Just water it once in a while. Don’t let it get completely dry. The leaves will drop and the plant will look like you have killed it. "This is normal". Don’t give up. Now, I must warn you: Even very experienced gardeners are rarely successful long-term with deciduous Calla Lilies.
But maybe you have the other Calla Lily. This one is the large, white florist’s Calla Lily. It is two too three feet tall and has solid green leaves. This one keeps its leaves and looks so beautiful, most people have to touch it to see if it is real, even when it is not blooming. The rhizomes are long and oval, with a larger end that is placed up when it is planted. These are strong and said to be hardy to zone seven. They need lots of water.
Remember, Ximelle,"all" Calla Lilies Must have a rest period. If you have the colorful, deciduous, slightly smaller Calla Lily described first, this is where many gardeners give up. That’s because keeping a dormant plant can feel like a total waste of time. You are sitting with a pot of dirt that seems to have absolutely no use whatsoever other than to take up space and occasionally fall over and spill its contents. Anyone you live with will think you can’t admit you have a brown thumb. The dog will knock it over and play with it.
At our house, the nanny considered all dormant potted plants utterly worthless. One weekend she did us the "favor" of throwing out a potted Amaryllis bulb; I rescued it just in time from the rubbish, but not before we argued as to whether there was anything actually growing in that pot of bone dry dirt under the pantry cabinets. A few months later, of course, there were green stems sprouting from the dry dirt. She was amazed. But that’s what happens.
A dormant potted plant, whether deciduous Calla Lily or Amaryllis, is not a pretty sight. Keep your pot in the coolest spot in the house that you can find without "Freezing", and you have the perfect winter location for your Calla Lily. Check it every so often for signs of life. Water it so that it does not completely dry out, once every two weeks or so. Now, your Calla Lily plant will go dormant sooner or later.
If it seems to be slowing down in the next few weeks, to try watering and fertilizing it through the summer. If you live in the Northeast, or somewhere that snow falls and it gets cold enough to skate on the local pond, you should keep it in the same pot all summer and make sure you water it faithfully. If you check the different colors, you will see that even thought they are all Calla Lilies, they bloom for different lengths, depending on the color/species. So don’t feel that you have to induce dormancy. It will tell You when it’s time for a rest.
Take care of your growing Calla until the end of the summer or at least until the leaves begin to yellow and wither. Slow down on the watering without letting it dry out completely and see if all the leaves fall off. And if it appears that you’ve killed it, keep the pot slightly moist and cool through the holiday season and don’t forget to water it. Remember, it’s the dormancy period where most gardeners throw in the towel.
Growing Calla Lilies need rich soil, bright light and moisture. Some people think Callas are good plants for beginners because it is so hard to overwater them, a common and fatal beginner’s habit for other plants and very helpful if you are growing a Calla Lily. Drying these out while they’re growing makes them go dormant. Drying them out totally while they are dormant will turn them into good additions to your compost pile. In the wilds of Florida and Louisiana, these plants thrive at the edge of a tropical pond or lake where it never dries out.
"White Flower Farm" success depends on explaining the keys to growing the plants they sell and I think they have done a good job on the Calla Lily. If you can get past the unfamiliar vocabulary, think of a "Rhizomes" as just a funny looking bulb that you plant sideways; with little bumps that sprout into plants, you can see why these Calla Lilies are so popular. The hardest part is the patience you need to get through deciduous dormancy, if of course that is the kind of Calla you have.
"The Spider Mites" are easy. These are indoor plant bugs. Put these plants outside and the Spider Mites will be wiped out in a day. They can’t take dryness and they can’t take cool weather. Then when you bring these plants in, mist them every day and try to keep the air in the house more humid. A few hours in the bathroom while you’re taking a shower will keep the Spider Mites from ruining your Callas.