Some guidelines to grow spring annuals
Plant annuals in the early morning or late afternoon when temperatures are cool, following guidelines below. To keep them blooming, cut or pinch off spent flowers.
Soil prep. Spread a 2-in. layer of compost and a few handfuls of organic flower fertilizer over the planting bed, then mix them into the soil. In containers, use a good packaged potting soil.
Plant prep. To pop plants from cell-packs, push up on the bottom of each cell. For larger containers, place one hand over the top of the rootball with plant stems between your fingers, invert the pot, then tap the pot's bottom with your other hand. If white roots are coiled at the botttom, cut or pull them off. Loosen matted roots with your fingers.
Spacing. Plant seedlings 9 in. apart, or roughly half the plant's mature size.
Planting. Dig a hole for each plant the same depth as its container and an inch or two wider. Plant so the top of the rootball is even with the surrounding soil. Firm the soil around the roots, then water each plant gently. Add a 1-in.-thick layer of mulch around the plants.
Fertilizing. Feed annuals about once a month during the bloom period.