White-flowered hybrids between O. majorana and O. vulgare are common in cultivation. Those which resemble O. majorana in vegetative characters may be sold as Sweet Marjoram. They can be distinguished by the 5-lobed, 2-lipped calyx, often longer spikes, ovate leaves with longer hairs (c. 0.5 mm) and larger corollas; they seem to be intermediate in character between O. majorana and O. vulgare subsp. hirtum. Other hybrids are closer to O. vulgare subsp. virens and can be distinguished from this subspecies by their funnel-shaped, unequally lobed calyx, dense flower spikes, and leaves with shorter hairs; this hybrid (O. ×majoricum) may be sold as Oregano. The hybrid between O. majorana and O. vulgare subsp. vulgare (O. ×applii) has been recorded in Australia. Some hybrids are sterile, others not. It is relatively easy to recognise a plant as a hybrid between O. majorana and O. vulgare but the application of particular hybrid names to local plants is problematical.
Source: (2002). Origanum. In: . Horticultural Flora of South-eastern Australia. Volume 4. Flowering plants. Dicotyledons. Part 3. The identification of garden and cultivated plants. University of New South Wales Press.