I received my order of paperwhites that I had ordered from a catalog and when I opened the boxes I saw that the bulbs have started to sprout. Should I get them into the ground now or should I store them, even though they are sprouting, until November. I received about 400 bulbs and want to plant them around all the trees on our property. We have three lots. I plan on planting Muscari around them on the outside of the tree perimeter. We live in Missouri City, which is located in the Houston area (Zone 9).
Plant them now. If they're sprouting, they're using their own stored energy to grow their leaves, so the more they use doing that, the less they'll have for putting out flowers in late winter or spring. They're probably not getting the water they need either, and that's also coming from what's stored in the bulb; once that runs out, they'll start to weaken and die.
On the other hand, if you have them in the ground outdoors, they'll have natural daylight for an energy source, and they'll be able to pull water and other nutrients from the soil.
Since they've already started growing, they'll probably flower sooner than they would naturally (it's common for paperwhites to be forced so they can be grown in pots indoors so that they bloom around Christmas). They should resume their normal flowering time in subsequent years.
Plant them as quickly as possible, outdoors, as Niall suggests. Paperwhites are Narcissi, and these particular bulbs really like to be in the ground by the end of August or very early September, which is when they will start to produce roots. Tulips are best left till November to be planted, other bulbs just in fall/autumn. Timings apply to cool temperate zones.