Lavatera mallow, also known as Lavatera trimestris or rose mallow, is a fast-growing annual wild flower that grows indigenously throughout Europe. Lavatera mallow boasts deep green, erect foliage that is topped with 10 cm (4 inch) wide white or pink blossoms that are often mistaken for tropical hibiscus. These blossoms cover the Lavatera mallow plant from June to September. Lavatera mallow grows anywhere in the British Isles. For best results, wait to sow your Lavatera mallow plant seeds in the spring, when the soil has warmed to at least 20 degrees Celsius (70 degrees Fahrenheit).
Select a planting location for your Lavatera mallow plant that meets its cultivation requirements. Choose a location that receives six to eight hours of direct sunlight each day. It should also provide your Lavatera mallow with nutrient-rich, well-draining soil.
Cover the surface of the soil at your planting location in a 5 to 7.5 cm (2 to 3 inch) layer of equal parts aged manure and peat moss. Top this with an equal part of coarse builder's sand if you have heavy clay or slow-draining soil. Till the amendments into the soil to a depth of 10 to 15 cm (4 to 6 inches).
Scatter your Lavatera mallow seeds on the surface of the soil at your prepared planting location. Cover the seeds with no more than a 6 mm (1/4 inch) of amended soil. Lightly water the freshly sowed seeds to moisten the soil and encourage them to germinate.
Water Lavatera mallow a minimum of once a week in the absence of rain, soaking the soil to a depth of 10 to 15 cm (4 to 6 inches). Provide your Lavatera mallow with as much water as necessary to keep the soil evenly moist.
Fertilise your Lavatera mallow every two weeks during the summer, when the plant is actively growing. Feed Lavatera mallow with a half-strength solution of a balanced, water-soluble fertiliser that has been specially formulated for flowering plants. Follow the fertiliser label directions to ensure that the proper amount of nutrients are provided.
Pluck faded blossoms from your Lavatera mallow plant as needed to help it maintain a fresh, attractive appearance. Deadheading allows your plant to focus its energy on producing additional healthy blossoms.
Though Lavatera mallow is an annual plant, it typically reseeds for the next year by itself.
Make sure to sow your Lavatera mallow seeds directly where they will be grown, as it can prove difficult to transplant a Lavatera mallow plant to a new location.