University of Vermont Extension 
Department of Plant and Soil Science

Spring News Article

SPRING IN THE PERENNIAL GARDEN

Dr. Leonard Perry, Extension Professor, and
Andrea Luchini, Graduate Assistant
University of Vermont
 

In order for perennial gardens to look their best in summer, they require some care in spring before most plants begin to flower.

In the very early spring, if you ordered bare-root plants (just the plant and its roots) through the mail or internet, they may arrive.  Itís best to pot them into a container and let them get established in an outdoor, but sheltered, area before planting into the ground later.  If they are from a warmer location, with lush growth, you'll want to protect them from spring frosts.  Also, now is a good time to get your tools ready by cleaning, oiling, and sharpening.  Sharpening devices can be found at many complete garden stores, hardware stores, or online.

In the early spring, after most of the snow melts and temperatures are mostly above freezing, remove winter protection such as evergreen boughs, or other types of coverings and winter mulches.  Do so early in the spring because plants will begin growing under these.  Perennials need the sun, and to be exposed to cooler temperatures, to be fully hardy.  Uncover too late, and they may be easily burned by the sun or injured by dips in the temperature.  The mulches can stay on open parts of the perennial beds.

When you want to get out early in the season and garden it is hard to resist, but you donít want to start working in your flower beds if the soils are wet (especially clay soils).  This can cause compaction, which will make the ground harder for the plant roots to grow through, and it removes the necessary pore space for air and water.  You also donít want to step on newly emerging plants.

That being said, you shouldnít wait too long!  Any plants heaved up by frost action should be pressed back down into the ground. Before too many plants start their spring growth, start your spring clean-up by removing dead, decaying plant matter.  While it does provide organic matter to your beds, it can also harbor pests and diseases.  So itís best to remove this dead growth from last year, if you didn't last fall. Now, or later, you can add fresh compost or mulch for additional organic matter.

Some perennials such as tickseed, shasta daisy, garden phlox, asters, and coneflowers have green rosettes at ground level that overwinter and need to be exposed. Most perennials (such as perennial geranium, daylily, bee balm, and others) can be cut back almost to the ground, and they will regrow from there.

Once all the plants are cut back, you can start weeding!  By now, weeds will already be growing strong.  Itís the best time, and easiest, to get at them before they get too big.  Watch what you are doing as newly emerging plants (especially small ones you just planted last fall), and seedlings, can sometimes be confused with weeds.  If you know itís a seedling of something you donít want, go ahead and remove it.  If you want theseedling, but not in that spot, wait until it gets larger before trying to transplant it.

You can also start fertilizing and mulching your beds, again watching out for new plants.  Inorganic fertilizer shouldnít be necessary every year in perennial beds, especially if youíve been consistently adding compost, but older beds may need the added boost.  Organic fertilizers, which have fewer nutrients and are more slow release than inorganic ones, can be added each year.  Make sure to keep fertilizer off plant foliage to avoid burning it.

It's also better to apply too little rather than too much fertilizer.  Too much fertilizer may result in perennials growing lush foliage, with few or no flowers.  Too much fertilizer, and it may end up in surface or groundwater supplies.

When mulching your beds with fine pine bark or similar organic material, be careful not to over-mulch.   Two to three inches thick should be enough for open areas, and donít put any mulch on the crowns (base) of your perennials.  Some plants, such as peonies, wonít flower at all if their crowns are covered.  Other shallow-rooted perennials such as yarrow and many bellflowers may be smothered and killed by heavy mulching.

If you have plants that need dividing or moving, mid-to-late spring is usually the best time for this.  Keep in mind that many perennials wont need dividing unless they had few blooms the past season, or have open centers with no stems emerging.  Itís best to divide most perennials when they are about two to four inches tall.  If they are taller than that, you may want to cut them back to about this height. Try not to move or divide a plant when it is flowering.  This includes spring-bloomers such as lungwort and primroses.

While most plants like to be divided in the spring, some are best divided after bloom.  These include oriental poppies, Siberian iris, bearded iris, and true lilies (not daylilies).  Peonies are best divided in the fall.

Weeding, fertilizing, mulching, and dividing can all continue into late spring.  In general itís best to have the fertilizing, mulching, and dividing done before summer begins.  Staking plants with cages around them, or hoops as for peonies, should begin now before plants get too large. You can cut flowers off of tulips, daffodils, and other larger bulbs when they are finished bloom.  Leave the foliage though to die down naturally, adding nutrients back to the bulb for next year.


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