The Guerrilla Gardening Guidebook – Perennials and Biennials


“Tomato Soup” – Whitney Avenue – Wilkinsburg, PA – Echinacea is a favorite of my girlfriend and I… I grow it everywhere I can… Available in a variety of bloom styles and colors… Drought tolerant once established… Often self seeds but the colors typically fade or completely revert to purple…


This post is part of a larger body of work titled ”The Guerrilla Gardening Guidebook”. For the introduction and table of contents please click here

Although some guerrilla gardens are intended to only last a year, some can last for a long time. Plant selection, coupled with continuing community support can make a community garden last for years with minimal maintenance.

A perennial is any plant that lives for three or more years, many live much longer. The garden flowers called perennials technically should be called herbaceous perennials because they lack the woody stems and branches of shrubs and trees, which are called woody perennials. Most herbaceous perennials die to the ground during winter, but their roots remain alive and send up new growth in spring. The tall tops of some perennials die in fall and the plant will develop ground-hugging rosettes of leaves that survive the winter. A few perennials, such as bergenia and epimedium, are herbaceous, but have evergreen or semi-evergreen leaves.

Most perennials bloom for two or three weeks at a specific time of the year, and their foliage remain till frost. Some cherished perennials, such as threadleaf coreopsis and fringed bleeding-heart, are long-blooming, producing flowers for 8 to 12 weeks. Others, such as garden phlox and delphinium, can be encouraged to rebloom after cutting back the first flush of flowers after the blooms fade and before they set seed. Many perennials with short bloom times have cool foliage that lasts well beyond the flowers, leaf color and shape should therefor be considered as well.

Many perennials spread, forming larger clumps every year. Some fast growing plants need to be dug up and divided periodically or the plants will become stunted. Aggressive spreaders must be continually hacked back or they will take over the garden. Some plants, like peony can grow for 50 years without ever needing divided.

Perennials are cold hardy to different degrees, some can’t survive winters north of Washington DC, others flourish in Minnesota and the Dakotas. Some thrive in the hot and humid summers of the south, while others will simply wilt and flop over in anything remotely hot.


Living for only two years, biennials germinate from seed the first year and put all their energy into growing foliage and strong root systems. They often live through the winter as a rosette of ground-hugging leaves… The next growing season… They send up flowering shoots… Set new seed… And then die… But biennials can be unpredictable, not always sticking to the intended lifestyle. Some behave as short-lived perennials, flowering for two to three years before they die.

Many biennials, like foxglove and hollyhock, reseed themselves so successfully that they seem to be perennial in your garden… They will return year after year… Oftentimes perennial seeds will germinate the same year they fall to the ground, allowing it to germinate the following year. You can help this along by simply shaking the seed heads over the ground where you want the plant to grow.

Container grown plants can be put in the ground any time of the year they are available. To remove the plant from its container, first water it, then turn it upside down, holding your hand under the root ball so when it slides out you can easily catch it. If the plant won’t budge, whack the bottom and sides of the container until it does… As a last resort you can cut the container off…

Roots of container-grown plants frequently encircle the surface of the root ball. Unless you interfere, the roots may keep growing around and around in the hole. Lay the plant on its side on the ground, holding it at the top with one hand, firmly rake the entire surface of the root ball with a weeding claw. Cut into the root ball with the tines of the claw to loosen and sever the roots. The cut roots will eventually branch and grow out into the surrounding soil.

Dig your hole wider and deeper than the container the perennial came in, you should be able to comfortably fit the plant in the hole while in the pot. Fill the bottom of the hole with at least an inch of soil. Place the plant in the hole and adjust accordingly so the plants crown is level with the existing soil level. Refill the hole with soil, firm the soil, water it…

A good starter list when beginning your guerrilla garden perennial research, all of the following plants will grow relatively well without much human intervention – Yarrow, Hollyhock, Golden Marguerite, Columbine, Butterfly weed, Fall Asters, Astilbe, Indigo, Bergenia, Mountain Bluet, Bugbane, Turtlehead, Coreopsis, corydalis, Delphinium, Chrysanthemum, Bleeding Heart, Foxglove, Echinacea, Blanketflower, Hardy Geranium, Lenten Rose, Daylily, Heuchera, Rose Mallow, Hosta, Iris, Dead Nettle, Shasta Daisy, Blazing Star, Lilyturf, Lupine, Forget-Me-Not, Catmint, Evening Primrose, Peony, Oriental Poppy, Russian Sage, Phlox, Balloonflower, Lungwort, Salvia, Stonecrop, Goldenrod, Lambs Ear, Foamflower, Verbena, Speedwell, Viola.

Continuing care of herbaceous perennials varies from plant to plant. For my general article titled “caring for herbaceous perennials”, please click here

plant petunias and question everything – chriscondello

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