Caring For Your Perennials

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.

Perennial Planting

bullet 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., Cannas, 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 bed).
bullet 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.
bullet Rake 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.
bullet 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.
bullet 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.
bullet 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).

Perennial Watering

bullet 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.
bullet 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.
bullet Pay 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 months.
bullet Checking the soil is the only fail-safe way to know when to water.

Perennial Fertilizing

bullet Most 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.
bullet 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 growth.
bullet 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.
bullet The object is to improve the soil and its organic content so that nutrients are readily available for the plants.
bullet If 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 watering.
bullet If 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., Phlox, Daylilies, Daisies and Hibiscus) and they can benefit from being fed approximately every 45 to 60 days during the March to September time frame.
bullet To 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

bullet "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.
bullet "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 Salvias, native Texas Aster, Gaura and 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

bullet 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.
bullet 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, dry winds.

Perennial Transplanting & Thinning

bullet 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.
bullet Most 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 aggressively.

Perennial Staking

bullet One 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, Ox-Eye Daisy, Lindheimer's Gaura).
bullet If 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.
bullet Use 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 restricted.

Perennial Pests and Diseases

bullet  Usually 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.
bullet 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.
bullet Even 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).