It depends what you mean by "start". If that means seeding plants indoors, then the answer is yes. Only the hardiest plants can go outside at this point. There are only a few crops to be planted now, the main one would be peas.

I want to start my flower bed. I always seem to start in May (mother's day gifts:)) but this year we may put the house up for sale and I wanted to plant some plants, like sunflowers,mums,pansys, and geraniums. With the nice weather coming, I was wondering if you think I could plant sooner.
Thank you!
Deb

Deb, getting them started indoors would surely give your plants a head start ... if you have adequate space and light. Otherwise, how about wintersowing? Many varieties are suitable, and I don't think it's really ever too late to start. For detailed info from the experts, including lists of suitable varieties, check out the Wintersowing forum, and don't overlook the FAQ section - lots of good information there. I only tried it once (last winter) and was so overwhelmed with seedlings I didn't know what to do with them all!

Some well-chosen and healthy flowering plants, whether in containers or in beds, do make a house look fresh, cared-for, and inviting. Good luck to you!

What do you mean by start? When are you putting your house up for sale?
Forget about starting geranium and pansies from seed now. Well, pansies you could but they won't flower in time for this spring. You wouldn't put out any of the flowers you suggest now except maybe pansies. You gain nothing by starting sunflowers now unless you can do it indoors with a light setup that allows for tall seedlings. Otherwise, they are squirrel food.
If you are looking for early color, sometime in April, you can buy hardy annuals in flats like violas, pansies, snapdragons, forget me nots and maybe calendula and try them in the ground. You can also mix in some colorful lettuces. Also, I've seen winter heather for sale which I have in a container now. If it stays above freezing, you can do pots of cyclamen - the small florist type survive for me near 40 degrees. When it dips, I bring the pots in - usually night time. Bloody dock takes cool weather too. And there are pots of bulbs for sale. Again, I wouldn't leave anything hardy out in a pot once it gets close to freezing.

If you wintersow, you won't get your flowers earlier than buying in flats. Mother's day is the frost date but the nurseries are usually stocked before that with many things and the best pansies are usually gone if you don't go in April.
Did you want to grow from seed?