April in Sonoma County (Zone 9) is a bit of an in between time for gardening. Although gardeners are still able to do many tasks in our gardens we need patience with things like planting summer veggie plants. Our average frost season lasts from the end of October through mid April. In the Demo Garden frost can hit even through the first week of May. This year has been a warmer winter but after many weeks of no frost still we have had overnight frost warnings. This in between time means that some cool-season plants, like pansies, can be planted for color until the weather turns hot (pansies thrive in cool weather) but warm season plants, like zinnias need to wait to be planted until after frost season. Gardeners are growing veggie seeds up in greenhouses and on top of their refrigerators (for a little bottom heat) now and waiting to plant those seedlings when the soil temperatures are warmer and there is no danger of frost killing the little plants. Some seeds, such as peas, beets, radishes, and carrots can be planted directly into the soil outside anytime this month. Flower seeds, such as sunflowers and cosmos can be planted later in the month but can be started indoors at the beginning of the month to get a head start!
A note about tomatoes: Many people buy tomato starts too early in March because they see them offered at the nursery and think that it's time to plant them. This means the young tomatoes have to be protected when frost is forecast, they also struggle to thrive in the cold soil. Here's a tip to save time and heartache-buy tomato plants in April when the selection is good but keep them in the 4 inch pots so you can put them in the sun during the day and bring them in at night to protect them from the cold. Then, plant tomatoes in late April. I plant my tomatoes in the first week of May. Planted at this time the tomatoes usually surpass the size of the plants that were planted with the possibility of overnight cold. Of course, some gardens may have an unusually protected spot or frost free, sunny area that could make tomatoes happy sooner. Experiment with your garden!