The Collinsia grandiflora is an annual herbaceous plant, native to North America; produces thin rigid stems, 30-60 cm high, poorly branched, which bear small oval or lanceolate leaves, dark green, rough and leathery, crossed by showy roughness. From April, until July-August, it produces a myriad of small flowers, similar to snapdragons, bilabiati, with clear upper lip and bilobate lower labellum, pink or purple. The flowers of the hills bloom together in small circular crowns. This plant, still little cultivated in Italy, is very suitable for informal flowerbeds, both in a sunny place and in the shade.
The Collinsia grandiflora produces small flowers that develop without problems in any position, from the full sun to the shade under the trees; in areas with very hot and dry summers it is advisable to choose a semi-shaded or shaded position, to avoid that the heat of June makes the plants suffer excessively. In fact, these plants can suffer if they are subjected to direct radiation during the hottest hours of summer days. The specimens of Collinsia grandiflora develop without problems until the temperatures remain above 15 degrees, they cannot survive below.
These herbaceous plants are annual, so after flowering they develop only for a few weeks, the coolness of September-October generally causes their complete desiccation.
To obtain the best flowering, during the vegetative period, water regularly, and in abundance, avoiding the soil to dry completely between one operation and another, but without causing water stagnations that would be harmful. Every 10-15 days, provide small doses of fertilizer for flowering plants, mixed with the water used for watering.
The specimens belonging to this variety prefer soft, rich in organic matter, well-drained and fairly fresh soils; avoid stony or very clayey places.
It is good to check that the substrate used provides sufficient drainage, to avoid the formation of stagnant water that these shrubs would do badly. They settle in March-April, but it is also possible, during the month of April, to sow the plants directly.
To obtain new shoots, the multiplication process takes place by seed, at the beginning of spring, or in a heated seedbed, already starting in February. These plants produce small oval fruits, which contain many fertile seeds; generally they self-seed easily, so every year new plants tend to appear in the same area of the garden giving the impression that these plants are perennial. If you decide to grow new seedlings, in winter, you need to keep them sheltered until the outside temperatures are no longer mild and do not fall sharply.
Collinsia grandiflora: Pests and diseases
The plants belonging to this variety prove to be very resistant and, usually, they are not subject to the attack of pests and disease, making preventive treatments with specific plant protection products superfluous.