Like several annual warm season bedding plants, oxeye daisy, Leucanthemum vulgare, is actually perennial. Also, some of the less extensively bred sorts disperse enough seed to naturalize and potentially become invasive. Increasingly popular modern varieties that are prudent with seed might not be true to type. Some might revert to more prolific forms.

Modern varieties should not get much higher than a foot and a half. They should also be more dense than the simple species, which gets a few feet tall. Foliage and form is quite variable among varieties. Stems are solitary or branched. They may be leafy or sparsely foliated above basal rosettes. Leaves might be lobed or serrate, with or without petioles.

The solitary, paired or tripled composite blooms of oxeye daisy are not so variable. They are classic daisies, with a dozen to three dozen clear white ray florets surrounding bright yellow disc florets. Without deadheading, fresh new bloom overwhelms deteriorating old bloom. Oxeye daisy is splendid as a cut flower. Spring bloom continues through summer, and can actually continue sporadically for as long as the weather is warm.

Toadflax really does look like baby snapdragon, which is its other common name. The tiny, half inch wide flowers are similarly bisymmetrical, and arranged in small trusses, although the diminutive leaves are distinctively narrow.

Common toadflax, Linaria maroccana, which is actually less common than the name implies, gets about one and a half to two feet tall and about half a foot wide. Two toned flowers bloom in summer in shades of pink, purplish pink, purple, blue, very pale yellow or red with yellow. ‘Northern Lights’ adds shades and bicolor combinations of yellow, orange and red to the mix. The more common ‘Fantasy Hybrids’ get only about half as tall and perhaps slightly wider, with earlier and slightly larger flowers in shades of yellow, blue, pink and bright pink, as well as white, mostly with slightly yellow throats.

Toadflax is a summer annual, but does not like to be too exposed to roasting heat and glare. If grown from seed, it should be sown as soon as possible after the last frost to get an early start.

Without becoming invasive, common alyssum, Lobularia maritima, can almost naturalize in favorable situations. It disperses seed profusely, so often appears where it is an asset to the garden. Since it is so docile, it subordinates to more vigorous plants that it mingles with. It does well on loosely set stone walls. If necessary, it is easy to remove or relocate. 

Common alyssum blooms with tiny but profuse white flowers. If they naturalize, varieties with pink or purple bloom eventually revert to white bloom after a few generations. Some varieties revert slower than others. Although popular as a warm season annual, alyssum can continue to bloom through next winter. Individual plants may survive for a few years.

Mature alyssum plants might get a bit higher than half a foot, but will get no higher than a foot. If they perform for more than a year, their progeny may begin to replace them before they get shabby. After removal, shabby plants, with a bit of shaking over bare spots, may share their last seed. Alyssum grows easily from seed, and is available in cell packs too.