It all depends on your point of view! All these perennials are hardy and colorful. and some are prolific reseeders. Pictured is Erigeron karvinskianus (Santa Barbara daisy). It will bloom all summer with very little care, but you have to decide if you want it everywhere or if it’s worth it to pull out the little seedlings. The same can be said for Gaura, Geranium incanum and Euphorbia wulfenii.
Another category consists of the plants that spread by rhizomes. A prime example is Oenethera speciosa (Mexican primrose). The delightful single pink flowers abound spring into summer, but with a little water and nourishment, they will overtake their neighbors. And then there’s Origanum “Hopley’s purple”. Like many other ornamental oreganos, it sports lovely mauve-purple flowers in profusion – it just doesn’t know where to stop! Salvia darcyi is spectacular with its bright display of red flowers all summer. Fortunately, the runners that appear are usually welcome, but if not, they are quite easy to remove.
Coreopsis adds a lovely bit of color to the garden. These are tough plants that need little to moderate water and they seem to bloom almost endlessly, especially if deadheaded. They also tend to self-sow, so be prepared for either even more color or a bit of weeding.
Perovskia, or Russian sage, is not a true sage, but it has some similarities. It needs little water, is very tolerant of heat and requires good drainage. Sprays of purple flowers appear in late spring and summer.
Echinacea, or coneflower, is a tough plant that blooms for a long period in summer and autumn. Recent breeding has produced flowers of many colors and plants of varying heights. These plants are suitable for the garden or containers.
Nepeta, or catmint, is a very useful little plant. Most varieties get about a foot tall, but ‘Six Hills Giant’ can grow to three feet. Grey-green leaves and spikes of purple flowers are characteristic. Bees love Nepeta and deer tend to leave it alone. N. cataria is catnip, the herb of choice for many cats. …
Achillea (yarrow) Green or gray ferny foliage and lots of colors to choose from! White (‘Calistoga’), yellow (‘Sunbeam’ or ‘Moonshine’), crimson red (‘Red Beauty’) and orange red (‘Faust’ and ‘Terra Cotta’). They all endure the hot summers and cold winters. Water needs are low and bloom time long.
Centranthus, or Jupiter’s beard, is a great perennial, but be prepared for its rather vigorous self-sowing. It is very tolerant of most conditions and needs little water. Flower color ranges from crimson to pink to lilac to white, with a very long bloom period. Gophers do not seem to like it, perhaps because of its…