I found the best book ever for helping you with season-spanning, continuous blooms in your perennial garden design: The Ever-Blooming Flower Garden: A Blueprint for Continous Color by Lee Schneller (Storey Publishing, 2009). It’s divided into four parts:
Part 1 – Creating your blueprint and buying all the plants
Part 2 – Case studies of five gardens
Part 3 – Her plant palette
Part 4 – Her flower catalog
There are five simple steps:
Step 1 – Draw your bed to scale on graph paper (the graph paper is included in the back of the book as well as an alternative method that skips the graph paper if you would prefer to work with square footage instead).
Step 2 – Roughly divide the bed into 3 parts on the graph: tall plants at the back, then medium, and short in the front.
Step 3 – Use her formula to see how many plants you need.
Step 4 – Transfer the plant quantities to her color-coded Blueprint Form under the appropriate category – tall, medium, short.
Step 5 – Use her Plant Palette to choose plants according to their bloom time.
Over-simplified, that’s the basics of her continuous bloom garden but she goes into using foliage plants, color combinations that work well, variety in plant height and flower shape, plant placement, and plant flower habits/shape.
The Plant Palette includes a limited list of specially recommended plants that grow in each season. It provides plant charts for Foliage, Spring, Early Summer, Midsummer, Late Summer and Fall. For each plant it shows: the plant height, how long it blooms, the blooming season, and the recommended Zones.
The Flower Catalog was limited to 220 plants she considered to be “the very best plants” that met certain criteria. Even then, she was very specific on what to use such as Achillea ‘Coronation Gold’.
The last few pages of the book was given over to an Appendix covering special conditions, plants with special problems and an index of common plant names.
I’m not sure that I would recommend the purchase of this book to a southern gardener. Instead, I would encourage them to look for this book at the public library. In limiting her selections to specific criteria, the author created a major bummer for southern gardeners. Only 31 of the 220 plants were good for Zone 9. Zones 10 or 11 had almost no plants. Nor did she include a section on tropical plants for Zones 9 – 11 in her Appendix. Nevertheless, I still found her overall concept very useful. A southern gardener could use her basic method using a perennial “encyclopedia” such as Perennials for Every Purpose: Choose the Right Plants for Your Conditions, Your Garden, and Your Taste by Larry Hodgson (2003) which includes a heat index and Sunset Books’ Landscaping with Tropical Plants by Monica Moran Brandies (2004).