Ideeone / Getty Images Sweet Peas (Lathyrus odoratus) An old cottage garden favorite, rambling sweet peas in all shades of pastels take off when planted alongside a fence line or allowed to overtake a trellis. Plant in rich, amended soil and water deeply and regularly to encourage vigorous roots. To prolong flowering, pick stems or deadhead often. 2 of 10 Flowerphotos / Getty Images Geum (Geum coccineum) Dainty 1″ orange flowers form atop wispy stems in this prolific perennial.