Professional gardeners know that creating continuous bloom in the mixed border can be challenging.  The secret to having flowers in the garden straight through until frost is incorporating Annuals, Biennials and Tender Perennials.

Annuals are those plants that grow, flower, set seed and die during a single growing season.  Some of the best annuals for the back of the border are Cosmos ‘Sensation Mix’, Cleome ‘Queen Series’ and Verbena bonariensis.  All of these plants grow quickly to more than 4′ and flower profusely into fall.  The daisy-like flowers of Cosmos do require deadheading to look their best.  If you want lower maintenance flowers, try Cleome or Verbena b.  The wiry stems and purple flowers of Verbena b. blend well with nearly everything!   TIP FOR SUCCESS:  Because annuals must complete their life cycle in one season, they tend to be heavy feeders.  Be sure to incorporate a time-release fertilizer formulated for flowering annuals into the soil when you plant them.  And don’t be afraid to follow up with a liquid fertilizer, if necessary.

Biennials are plants that form a basal rosette of leaves during the first growing season.  During the second season, they will flower, set seed and generally die.  Hollyhocks (Alcea rosea), Foxglove (Digitalis purpurea), and Lupines (Lupinus) fall into this category.  There are three ways to treat biennials.  As short-lived perennials: Cutting the flower stalk down before seeds mature, will often help the plant survive for several years.  As true biennials:  Leaving the seeds to mature on the plant and fall to the ground will normally give you enough seedlings in the spring to fill the area.  As annuals:  The best way to guarantee a great show is to replace them every year with high-quality plants.  TIP FOR SUCCESS:  Biennials tend to flower in early to mid summer.  If you don’t want a blank space in the garden when they finish flowering, be sure to plant mid-height  perennials in front that flower later in summer like Phlox (Phlox paniculata) or Turtlehead (Chelone).

Tender Perennials are marginally hardy or short-lived perennial plants.  Delphinium, Dahlias, Strawberry Foxglove (Digitalis mertonensis) and some tropicals fit into this category.  TIP FOR SUCCESS:  Marginally hardy plants like Dahlias and other tuberous plants can be dug up and stored in damp vermiculite over the winter and then replanted in early summer to avoid the possibility of freezing during winter.  During mild winters, a heavy mulch might be enough to protect some tender plants.  Some varieties are hardier than others, so experiment!

Most gardeners know the benefits that pruning provides trees and shrubs.  Less of us know how useful different pruning techniques can be for perennial plants.

Exceedingly tall or leggy perennials are one of the first groups of plants I think of that benefit from a quick shearing in early summer.  Eupatorium purpureum (Joe Pye Weed), for example, will grow upwards of 9′ tall, making it appear out of scale with smaller plants like Rudbeckia, Sedum, or Salvia. Cut it back by 1/3 in mid to late June to reduce the flowering height and create much fuller plants.

Another benefit of pruning perennials is delayed flowering.  Leucanthemum maximum ‘Becky’ (Shasta Daisy) is a popular plant on the island.  Shearing the plants at the front of a mass planting in late spring creates a tiered effect with taller plants flowering first at the back and shorter plants flowering later in the front.

Pruning can also be used to avoid some common issues with mounding plants.  These plants can fall open in the center as flowering peaks.  Nipponanthemum nipponicum (Montauk Daisy) is notorious for this problem.  Shear or pinch it a few times before mid-summer and you will be rewarded with a plant that holds its flowers in a compact mound.

A complete list of perennials that can be pruned in a variety of ways is available in Tracy DiSabato Aust’s book The Well Tended Perennial Garden: Planting and Pruning Techniques from Timber Press.  Tracy’s book is available at island book stores. But by all means, experiment!  If you remember a plant that tends to be leggy in your garden, it won’t hurt to pinch back a few stems and see what happens!  If you would like to enjoy your flowers a few weeks longer than last year, try shearing one plant early on to see how it reacts.

Happy Gardening!

Are you looking for a plant to cover a trellis, arbor or pergola?  Do you need something to scramble among your climbing roses or around the bare trunk of a tree?  Surfing Hydrangea Nursery offers one of the best selections of flowering and non-flowering vines on the island.  If you are interested in adding native plants to the landscape, vines can be an easy way to start; Wisteria frutescens is a late-flowering North American species that covers a pergola nicely, without being nearly as rampant as its Asian cousins; Campsis radicans (Trumpet Vine) is also a great choice for showy flowers later in the summer; Parthenocissus quincefolia (Virginia Creeper) is spectacular in the summer trained over a wall or wherever you have space!  Why not give one a try?  The wildlife will thank you!