Annual plants are those which take only one year to complete a full life-cycle of germination, vegetative growth, flower production, seed set, and death. Despite pruning, disbudding, and dead-heading, these creatures WILL expire once their year-long life-cycle is completed.
Most annuals realize they only have one life to live though, so they flower a LOT to produce as many seeds (babies) as they possibly can. That generally makes them good bedding plants and many of your plants for “seasonal color” come from this category: petunias, pansies and marigolds, for example.
Biennial plants, like the name implies, take two years to complete a life-cycle. Usually, the first year the seed germinates and produces mounding, basal (rosette-shaped), vegetative growth usually just above or at the soil line. This growth is evergreen and carries through the winter.
Year two, when temperatures and day length is right, the plant will send up profuse flowers and set a plethora of seeds which will fall to the ground, over-winter, and germinate the following spring, thus maintaining the circle of life.
Well-loved biennials include Forget-Me-Not (Myosotis spp.), Foxglove (Digitalis purpurea), and Hollyhock (Alcea rosea) to name a few. The trick with biennials is to initially sow your seeds two years in a row. That way you’ll have the plants you want every year! After that point they should self-sow. If they show up somewhere odd, move'em.
Bolting happens when certain plants get over-excited by the heat of summer. Brings out their inner teenager. You can thwart this by snipping off the part shooting upward, but your best bet is to find a bolt-resistant variety, do successive plantings, or just eat something else for a while.
Hardy. This is a term absolutely butchered by misunderstanding and misusage, so let’s clear it up. “Hardy” in the horticultural world is a term used to characterize a particular plant’s capacity to withstand COLD temperatures regardless if it’s a perennial, biennial, or annual. That’s all!
Granted, that’s with the understanding that it’s planted in the right soil with the right drainage, the right pH, the right nutrition, the right air circulation around it, the right amount and kind of light, etc. But even with all those caveats, it still describes only a “plant’s capacity to withstand cold temperatures”.
Seed catalogs still offer these old, field tested varieties because they taste good, and they survived all the pests and diseases without being a pain in the arse. There are a lot of exciting, new varieties out there, but the heirloom plants are like a little piece of the past that survived for us to taste and enjoy.
A word on looks: heirloom varieties were selected for flavor and abundance, not looks. While there are some very polite small, red and round heirloom tomatoes, get ready for the world of lumpy, pleated, and colorful. Super artful, super tastey.
That being said, different herbaceous plants can withstand varying degrees of extreme hot or cold temperatures. Your pansies usually make it through the winter but choke out in the heat of summer, don’t they? That’d make them a hardy herbaceous annual!
Master Garders are trained by the Extension Service of the U.S. Department of Agriculture (USDA). Master Gardeners assist with garden lectures, exhibits, demonstrations, school and community gardening, phone diagnostic service, research, and many other projects of their local extension service as a way to "pay forward" the education they have received. You can find more information and links to your local Master Gardeners groups through the American Horticultural Society's clickable map.
Perennial plants are those which, after germination, will flower and seed from the same root stock for two or more seasons. They’re not ever-lasting though. Short-lived perennials (like coreopsis and columbine) may only stick around for 3-5 years, while long-lived perennials (like peonies) can live over 100 years! Typically, we refer only to the herbaceous plants in our ornamental beds as “perennials” but technically it iscorrect to apply the term to trees, shrubs, and any other plant which lives for two or more seasons. You'll confuse other people, though.
Semi-woody perennials have woody stems, but they’re much less substantial than say a tree or shrub. Usually semi-woody plants get pruned heavily in the early spring to encourage branching and dense growth. For instance, Bluebeard (Caryopteris spp.), Lavender (Lavandula spp.) and Thyme (Thymus spp.) are all semi-woody perennials.
Suppose you want to grow lettuce, but you know lettuce bolts. To guard against your whole crop turning bitter and inedible, you'll sow a little bit of lettuce seed every week to 10 days. This way you'll have a supply of fresh baby lettuces in their tastey prime, even when the heat waves arrive and the more mature plants all bolt.
Tender trees, shrubs, and perennials are often originate from tropical or subtropical climates and can only be overwintered outside in the US in warm regions like Florida, Texas, Southern California, and other points south. (Of course, 'south' is relative. In zone 7, there are rosemary varieties that are hardy, but in zone 5, all rosemary is tender and comes inside for the winter. )
Tender plants are hardy in their native climates but can’t withstand northern winter temperatures where they’re often either brought inside for the winter and treated as houseplants, or planted in the garden during the growing season and treated as annuals (leave them in the garden to die). Think wax begonias, coleus, Persian shield, etc. That being said, there are tender perennials AND tender annuals. Keeps you on your toes.
Woody plants are all your perennials (including the trees and shrubs) which have so much hardened xylem tissue (the plant tissue which transports water and minerals all the way up from the ground to even the top-most leaf) within the central core of the stem that they help the plant retain most of its growth and shape from one year to the next. (Those can be cool shapes too: this image is a Japanese maple trunk.)
These plants also carry a protective covering around the outside of their stems and branches; Bark! (Woof.) The phloem (the plant tissue which moves food around and through the plant) from previous year’s or season’s growth has a chance to harden up and form this covering. Consider how our hair and nails are made up of dead skin cells and you’ll have some sort of decent comparison.
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