Ask Mr. Smarty Plants

Scutellaria ovata (Heart-leaf skullcap) is a perennial, evergreen in winter, 1-3 ft. tall, and blooms blue, violet from April to June. According to this USDA Plant Profile map, it does not grow natively in North Central Texas, but rather in Central and East Texas. We are not sure what you mean as "dormant," perhaps the non-blooming period after June? If that is true, we will presume you are looking for a companion plant that will provide color in the area into the Summer and Fall. 

We will look at plants native to North Central Texas, both annual and perennial, and assume they can do well in the same environment in which your skullcap is located. On our webpage on this plant (which you can read in full by following the plant link above) is this information:  "Native Habitat: In open woodlands, along roads, and on brushy slopes in East and South Texas. Moist sand, loam, clay, limestone." Also on that page are the Growing Conditions for skullcap:

"Light Requirement: Part Shade , Shade
Soil Moisture: Moist
Conditions Comments: Heart-leaf skullcap is an under-utilized plant for gardens. The showy blue flowers bloom on spikes similar in form to Salvia sp. It colonizes vigorously by underground, fleshy roots. Oily glands on the leaves make it possibly deer resistant. In winter, heartleaf skullcap displays evergreen foliage. Nectar source for adult butterflies."

In terms of planting other plants in the same bed, we would call your attention to the sentence "It colonizes vigorously by underground, fleshy roots." This plant is a member of the Lamiaceae, or Mint family, which is well known for vigorous colonization, if not invasiveness, sometimes impeding the establishment of other plants. We will go to our Recommended Species section, click on North Central Texas on the map; then, on the right-hand sidebar, select on "herb" (herbaceous blooming plant" under General Appearance, and the blooming months of June, July, August, September and October, and Narrow Your Search, which gave us 37 choices. We have four examples of plants that we like below; you should read every webpage on those four, and then look at other possibilities, paying attention to the amount of sunlight and moisture available.

Conoclinium coelestinum (Blue mistflower) - perennial, 3 ft tall, blooms blue July to November

Eryngium leavenworthii (Leavenworth's eryngo) - 3 ft. annual, purple July to September

Machaeranthera tanacetifolia (Tahoka daisy) - 1 ft., annual, blooms blue June to October

Melampodium leucanthum (Blackfoot daisy) - 1 ft., perennial, blooms white March to November

From our Native Plant Image Gallery:

Conoclinium coelestinum

Eryngium leavenworthii

Machaeranthera tanacetifolia

Melampodium leucanthum