Perennial Garden / Flower Care

What Is a Perennial?

A perennial plant will live for more than two growing seasons; while its roots remain persistent, with clumps of stems or buds at or below ground level.

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

The care and maintenance of your perennial garden need not be complicated or daunting. Much of good gardening is a combination of some basic horticultural principles with common sense and a good eye

A host of perennials respond best to a tidy spring cleaning and are seemingly rejuvenated from the practice. Other perennials favor a quick cutting-back before winter sets in, so that they can get right down to business in the spring, unimpeded by last year’s growth.

The trick to doing this the right way is to know when to cut what.  The following is a list of some of these basic perennial care principles.

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.  

When you want to get out early in the season and garden it is hard to resist, but you don’t 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 don’t want to step on newly emerging plants.

That being said, you shouldn’t wait too long!  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 it’s 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.

Once all the plants are cut back, you can start weeding!  By now, weeds will already be growing strong. It’s the best time, and easiest, to get at them before they get too big.  

You can also start fertilizing and mulching your beds, again watching out for new plants.  Fertilizer shouldn’t be necessary every year in perennial beds, especially if you’ve 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.

More Basic Perennial Garden Care Info

Site

Know the site conditions–light, temperature, soil, slope, drainage, and air circulation.

Soil

This is the single most important factor in growing healthy plants. Most perennials grow best in soil that is well drained with good fertility and a pH of 6.0 to 7.0. Adding organic matter to soil improves the fertility, texture, and water-holding capacity. Apply a two to three inch layer of mulch to conserve water, reduce the need to weed, and keep soil temperature cool.

Plant Selection

Knowing the needs of each plant in the garden is essential. Does it need sun or shade? Should the soil be dry or moist? Know the size of the plant when it reaches maturity so the plant can be properly placed. A garden that is too densely planted is difficult to maintain. Plants whose mature height is 3′ or above should be planted 2′ to 3′ feet apart, and plants 2′ to 3′ tall should be spaced 1.5′ to 2′ apart. Below 2′ tall, spacing should be 1′.

Dividing & Thinning

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 won’t need dividing unless they had few blooms the past season, or have open centers with no stems emerging.  It’s 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.  

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.

Fertilization

Most perennials do not need much fertilizer. Many overfertilized perennials will produce excessive soft growth and produce very few flowers.

Staking

Some plants need staking to prevent flopping over in the garden. Plants with heavy flower heads or long thin stems tend to blow over or are beaten down by heavy rains. Staking should be done early in the spring to allow the plants to grow through and around the stakes, usually hiding the stake by midseason.  Staking plants with cages around them, or hoops as for peonies, should begin now before plants get too large.

Mulching

Mulch  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 don’t put any mulch on the crowns (base) of your perennials.  Some plants, such as peonies, won’t 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.

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.

What to do when

March

  • Cut back tall grasses
  • Prune roses
  • Test soil

April

  • Gradually remove winter protection
  • Weed, mulch, and edge
  • Thin and divide plants
  • Plant bare root plants
  • Prepare stakes and cages
  • Weed

May

  • Weed
  • Finish mulching not completed in April
  • Water newly-planted plants
  • Fertilize as per soil test when establishing new beds or planting new plants
  • Pinch plants back
  • Stake
  • Thin plants

June

  • Weed and water as necessary
  • Scout for pests
  • Pinch and deadhead
  • Cut back
  • Stake

July

  • Weed and water as necessary
  • Fertilize heavy feeders such as ever-blooming daylilies and mums
  • Deadhead (stop pinching mums in mid-July)
  • Stake

August

  • Weed and water as necessary
  • Deadhead
  • Stake

September

  • Edge beds
  • Water as necessary
  • Move and divide plants
  • Cutback

October/November

  • Weed and water as necessary
  • Mulch
  • Winterize the garden after the ground is frozen (late November or December depending on your area)

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