Like hats that Seuss characters would wear, Orostachys (or more commonly, Chinese dunce caps) is a fun succulent to grow.
Mix Orostachys with other low-growing succulents in a container and grow in full to partial sun. The additional succulents should be the stars of the show in early summer while this little number grows and forms tiny offshoots. By late summer, Orostachys will steal the show, which might have grown a little tired because it's that time of year when the rest of the plants are faking narcolepsy just to take a break from the heat.
If you have plant lights or a sunny window, Scilla madieriensis adds fascinating color indoors in early winter. I've had six bulbs all bloom any time from October to January, brightening up what is usually a very dull time of year.
For your outdoor garden, Kniphofia is one of the keys to that spiky look. The common name for this African native is "red hot poker," although it also comes in shades of yellow and orange. It can be tricky to grow, but once you find a location it likes, it will keep coming back and blooming every year. Three of my favorites are 'Echo Mango', 'Elvira', and 'Lemon Popsicle'.
Kniphofia 'Elvira' bloomed like crazy for three years straight in a semi-shady location with perennial Geraniums and coral bells, but I decided to give it more sun. It hasn't bloomed since. Takeaway: Some plants are picky about their location. If there is nothing wrong, don't try to fix it.
I planted Kniphofia 'Lemon Popsicle' in 2012, and although it hasn't spread, it's bloomed every year, which is pretty amazing, considering the fact that the plant is overrun by a clutch of peonies for the best part of the summer. It's considered a rebloomer, and for me it blooms in June, sporadically until September, when it presents a good clutch of flowers that are great in arrangements.
Itsaul Plants sent me four varieties of Kniphofias to try in spring of 2015. The strongest, most long-lived variety has been 'Echo Mango', which takes a rest only in the hottest periods of summer. It grows along with a coneflower called 'Solar Flare' that ironically was also hybridized by one of the owners of Itsaul Plants, Richard Saul. 'Solar Flare' is the longest-lasting Echinacea I've ever grown.
There are plenty more plants that provide that special vertical accent, but these three are among the most colorful and unusual.