How Do I Care for my Perennials?
Although many very low maintenance
perennials are available, most perennials require some maintenance to
perform at their best. We will attempt to outline the primary maintenance
considerations for perennials.
Carefully evaluate the drainage of the area to be planted. If a site
does not drain, it will not support healthy plants. Poorly drained
soil is responsible for more plant failure than any other single
cause. One way to check the percolation of the soil is to dig a hole
approximately 2 feet deep and fill it with water. Let the water drain
away and then refill the hole. If the water drains away twice within
an hour, the soil is well-drained and will support most any plant that
insists on impeccable drainage (e.g.,
Calylophus). If the water
drains within 6 hours, it is suitable for plants that will accept
heavy soil (e.g.,
Flame Anisacanthus). If
water stands beyond 6 hours, consider building a raised bed or install
a subsurface French drainage system (perforated PVC pipe in a gravel
Prepare the soil by excavating as necessary to remove all weeds and
grass. Preparation may required a 3 to 4-inch depth be removed in a
heavily infested area (especially in Bermuda lawn grasses). In areas
which are clear where no grass or weeds exist, no excavation is
necessary. Next, add a 4 to 5-inch depth of organic material (compost)
to the soil in the area to be planted. Till or fork the organic matter
into the existing soil to a depth of 4 to 5 inches. This procedure
provides an 8 to 10 inch prepared planting zone.
out the beds to remove all debris and to smooth the grade. Also, grade
the beds so that a crown exists (higher in the middle). Grading to a
crown will help to ensure positive drainage in the planting bed.
Lightly moisten the prepared areas before planting begins. Determine
the proper spacing for the mature size of the plant. Lay out the
plants, still in pots, on the ground and make any adjustments
according to individual preferences and site lines.
Start planting. If roots are matted or pot-bound, tear the outer edges
of the root systems so that the roots will grow outward. Set the
plants level with the surrounding soils (i.e., plant so that the top
of the root ball is even with the surrounding soil). Setting plants
too low will cause drowning and/or rotting.
Water the plants thoroughly. Add a layer of mulch to the beds using a
1 to 2 inch depth of organic material (e.g., shredded hardwood,
cypress, compost). Add additional mulch as needed to maintain a 1 to 2
inch layer (generally twice a year - early spring and early winter).
Water only when the plants need it. Do not water on a fixed
schedule. Let the plants dry out between watering (however, don't let
them get bone-dry or wilted). Probe the soil and if it is dry in the
top 4 to 5 inches, then it is time to water.
Remember, plants may show the same symptoms from being over-watered as
from being under-watered (e.g., yellow leaves and/or wilting). There
is no other way to determine when a plant needs water other than to
monitor the soil moisture. Make sure to water perennials separately
from lawns if you are using an automatic watering system. Early
morning is the best time of the day to water. Late evening or
nighttime watering may encourage mildew and/or fungus. Water deeply -
a general rule of thumb is to provide (from rainfall and irrigation
combined) a 1 to 2 inch depth of water every week in the summer; a 1
to 2 inch depth of water every 2 weeks in the fall and spring; and 1
to 2 inches per month in the winter. Use a rain gauge to determine how
much water is being applied.
attention to seasonal variations. When changing over from spring to
summer, for example, the quick cutoff of all rainfall can be brutal to
plants. Watch out for both over- and under-watering in the winter
Checking the soil is the only fail-safe way to know when to water.
perennials do not require large amounts of fertilizing. In fact, many
will respond to over-fertilization by becoming excessively tall and
produce minimal or no flowers.
Assuming that bed preparation has been performed as outlined above
using a 4 to 5 inch depth of organic compost, most perennials will
need minimal to no additional fertilizer during the first year of
Top-dressing with compost appears to be the best method for providing
sufficient nutrients for perennials. Generally, top-dressing should
take place in mid to late February. Use a 1 to 1-1/2 inch depth of
compost every 2 to 3 years. Take care to scratch or incorporate the
compost lightly into the soil.
object is to improve the soil and its organic content so that
nutrients are readily available for the plants.
you cannot invest in the labor and/or material to accomplish
top-dressing with compost, then consider feeding with composted,
organic fertilizers (composted poultry or cow manure, cottonseed meal,
etc.) or sulfur-coated, slow-release synthetic fertilizers. If you do
use synthetic fertilizers, work the fertilizers lightly into the
soil or apply below the mulch layer so that there is less likelihood
of these being washed into storm sewers by heavy rains or excessive
you feel the need to use supplemental fertilizers, these applications
should be made during the period March through September. Fertilizer
needs and rates of application ideally should be based on soil tests.
If you cannot perform timely soil tests then apply according to
fertilizer labels approximately every 60 to 90 days. There are some
perennials that are heavy feeders (e.g.,
Hibiscus) and they can benefit from being
fed approximately every 45 to 60 days during the March to September
recap - proper initial preparation of beds with organic matter is
critical to the future health and fertilization regime with regard to
perennials. If the soil is rich and well prepared, little or no
supplemental fertilizer is required for most perennials. Top-dressing
with a 1 to 1-1/2 inch depth of good aged compost every 2 to 3 years
is the best approach to providing nutrients to most perennials.
Perennial Deadheading and Shearing
"Deadheading" is the removal of dead flower heads. This
process should be performed to encourage the production of new flowers
rather than seed. Although deadheading is not strictly required, the
procedure can lengthen and intensify a perennial's bloom season.
"Shearing" is the cutting back of a plant all over. Shearing
stimulates new growth. Many perennials benefit from this process. Some
perennials such as the larger
Mexican Mint Marigold will benefit
from shearing back one-third to one-half at midseason to keep them
dense and encourage strong late-season bloom.
Perennial Winter Protection
Mulching after frosts have "hardened off" perennials is helpful (a 1
to 2-inch layer). Do not mulch too early or the mulch may encourage
new growth, which can be killed by a sudden hard freeze. Prune woody
perennials back after light frosts have hardened off the plant. This
process will reduce the exposure to hard freezes. Herbaceous
perennials, in general, should be cut back as late as possible (mid to
late February) so that pruning will not stimulate new growth which may
be killed by late winter, hard freezes.
Water perennials deeply before a hard freeze is expected. This
watering will protect roots which may be exposed to cold air pockets
in the soil and will help prevent plant tissue dehydration from cold,
Perennial Transplanting & Thinning
Perennials, in general, should be transplanted during the season
opposite of when they bloom. That is, transplant spring and
summer-flowering perennials in the fall and transplant fall-flowering
perennials in the early spring. It is best to cut back the plant by at
least one-half to two-thirds before transplanting. Use a sharp shovel
and keep as much root ball as possible. Water in the transplant
immediately. Plants may need to be shaded for several days if
transplanting is done during a period of high temperature.
perennials will give you signs when thinning or division is in order.
Tell tale signals are the flowers get smaller over the years; a clump
may take on the appearance of a tangled up mess; the plant may develop
a hole in the center; the plant may generally have less vigor; the
plant tends to flop over as it ages; or the plant may be spreading
way to avoid having to stake perennials is to select shorter-growing
varieties or to choose those that are self-supporting. Unfortunately,
sometimes staking is unavoidable in order to keep some perennials from
"eating their neighbors alive" (e.g.,
Mexican Bush Sage,
staking needs to be done, do it early. (All you tomato gardeners know
what we mean.) The stems of the plant need to be sturdy and flower
buds should not be formed yet. Stakes placed early are easily hidden
by subsequent maturing foliage.
natural materials (for example; bamboo, branches) whenever feasible.
Use ties such as jute or string that blends well and are
biodegradable. Don't tie the stems of plants so tightly that they look
Perennial Pests and Diseases
few major pest and disease problems will arise in perennial gardens if
the right plant has been chosen for the right place. That is to say,
choices of acclimated plants for the correct cultural matches (light
requirements, drainage, soil type, root competition, etc.) will result
in little or no major pest and/or disease problems.
Monthly inspections for insects, diseases and over/under watering will
keep you aware of potential problems. Just seeing several insects on a
plant does not mean you have a problem; they may be beneficial
insects. Observe the details of their appearance and make written
notes. Next use an expert or a reference (county extension agent,
nursery, gardening book, etc.) to identify the insect and determine if
treatment is necessary.
the presence of a number of harmful insects won't cause significant,
lasting damage, if a sufficient number of predators are present to
consume them. If treatment is required, apply the least toxic
materials (including the use of bacterial sprays and organic methods).