University of Vermont Extension
Department of Plant and Soil Science
RENOVATING PERENNIAL BEDS
Dr. Leonard Perry, Extension Professor
University of Vermont
One of the main problems I hear from perennial gardeners, and one I
have myself, is perennial beds gone weedy. Or, as friend likes to
say, they’ve gone “natural” and reached their “goldenrod years”.
Where I used to have hundreds of perennials, all nicely organized
and labeled in neatly edged beds, now I only see the hardiest
survivors poking through goldenrods, nettles, grass growing in from
the edges, and a whole host of other invaders. If life has had
other priorities for you than keeping up with weeding, and your
perennial bed has become overgrown with less desirable plants, it is
time to think about renovation.
One option is just to live with your new beds and work with them.
Actually, all the “wildflowers” that have seeded in, plus the
remaining tough daylilies and phlox and such look pretty good—from a
distance. I have hundreds of daffodils interplanted in these beds,
so to totally dig up and renovate would destroy their spring effect
created over years. To go with this option, you need to appreciate
the “natural”, seemingly unorganized and “messy” meadow effect. The
diversity of plants actually is good ecologically as it harbors a
host of beneficial insects, plants for native pollinators, and food
To work with such overgrown beds, I merely weed whack them to the
ground in late fall so I can enjoy the cheery bulbs come spring.
For such beds I then “edit” out the worst offenders in early summer
as they start to take off, and I can tell what perennials I planted,
and what perennials nature put there. For this, use a heavy-duty
hoe, or perhaps perennial spade.
If you want to reclaim your beds though to their former organized
glory, just with “your” perennials and not ones from nature, you can
do a thorough weeding if they’re not too far out of control. If it
has been several years though, and they are beyond redemption,
you’ll need to renovate. This begins with assessing during summer
what is there that you want to save, and marking them with stakes
for digging the following spring. Peonies are an exception—they
should be dug in fall and either replanted in a holding area
elsewhere, or potted and overwintering in a non-freezing location.
If you want to go about the renovation properly, take some pictures
through the summer that you can study this winter. Measure the
beds, and roughly draw them on graph paper so this winter you can
plan your new plantings. Of course make a list of those perennials
you’ll be saving, so you know what you need to purchase this next
season. Note how big they are, and if you’ll be able to divide
I’ve found that if perennials are totally invaded by grass roots, or
roots of invasive perennials (like the silver banner grass,
goutweed, reed canary grass), it’s best to just discard them and
start over. Otherwise you’ll need to divide up such perennials to
the smallest portions, sifting through their roots for any invasive
roots. You’ll be sure to miss some, as I have, and end up in a few
years with the same weedy problems.
Fall is a good time for a soil test (kits are available from local
Extension offices and some garden stores), so you know what
nutrients to add next spring. If you need to add lime to the soil
to make it less acid, fall is a good time as it takes a few months
for this to work.
You also can begin in fall, after grass stops growing, edging the
beds with edging tool (manual or electric) or even square-tipped
spade. I often start by weed trimming the edges so I can see better
where I’m edging, and doing so more easily and in straighter lines.
Once you’ve analyzed your beds during the growing season, and made
your plans during winter, it’s time to go at the beds when you see
growth starting in spring. If you have one or more very large beds,
and you want to get the job done quickly or don’t have lots of time,
you might consider hiring a professional. Most state associations
(such as greenworksvermont.org) have lists of certified
professionals that have passed a rigorous test of their knowledge.
Or, for large beds if reworking them yourself, unless you have lots
of energy or help, consider tackling the bed in sections. This way
it won’t seem overwhelming.
First, dig out all those perennials you’ve decided to keep. Place
in the shade under burlap or similar if replanting very soon,
otherwise “heel them in” temporarily in another holding bed, or even
in pots, until ready to replant.
The next step is the most time-consuming but essential—digging out
all the rest of the plants, turning the bed with a fork to loosen
it, then sifting the top several inches of soil for any weed
rootlets. You can buy sifting screens, or make one simply with a
wood frame about one foot wide and two feet long, with coarse
hardware cloth wire mesh stapled to the bottom. Tilling the bed
instead will simply rebury these weed roots, and divide them up so
you have even more perennial weeds! Of course there will likely be
weed seeds in your soil, but mulch later and weeding or a hoe will
keep these under control.
For those plants you remove and weed roots, don’t dump them into
nearby fields if you don’t want them to take root in these areas,
nor near waterways where they can colonize stream banks. Unless you
have a really good and “hot” compost pile, don’t dump roots there
either as they can survive and reinfest other beds later.
Add any nutrients and gently rake them in. If you didn’t get a
chance to test the soil, you might just add an organic, balanced
fertilizer (such as 5-3-4). An inch or two of compost (well-rotted,
free of weed seeds) should be added, more if the soil is poor
(sandy, clay). This helps soil microorganisms, improves
water-holding as well as drainage, and provides some nutrients.
Most perennials don’t need much nutrition. Too much fertility can
make them grow only lush foliage with few flowers.
Divide and replant any perennials you saved, and put in new ones.
Beware of “gifts” from neighbors, and be careful with plant
sales—know what you are buying. Often there you’ll find those very
invasive perennials that are so easy to divide. If you’re
unfamiliar with perennials, take along a reference book, catalog, or
even plant app (increasingly there are ones for this) for a
smartphone, or look them up online on such handheld devices.
Water in well (deeply less often is better than frequent
sprinkling). Mulch with a couple inches of bark, shredded leaves
(whole leaves can compact and keep air and water from the soil),
pine straw, or similar. While some mulch is good, more is not
better for many perennials that like to spread. Mulching these,
such as yarrows, will kill them out over time and keep peonies from
blooming. To avoid having to start over again, make sure to keep on
top of weeds.
Spring and early summer is a key time to weed as much of the soil is
bare (perennials are just starting to grow) and the light makes weed
seeds germinate. A tip on using the hoe on weeds— just break them
off near the surface. If you dig too deeply, you’ll bring more weed
seeds to the surface where the light will make them germinate.
Since weeds need light to grow, and weed seeds to germinate,
planting large perennials or making sure they cover the soil when
mature, will minimize the weed pressure, as does mulch.