University of Maryland Extension

Care of Annuals and Perennials

Click on the highlighted word to find information on the planting and maintenance of bulbs, groundcovers, and vines

Watering

  • Do not rely on summer rainfall to keep flower beds watered. Plan from the beginning to irrigate them. This is particularly important in the case of perennials, which are permanent fixtures in your landscape.
  • Moisten the entire bed thoroughly, but do not water so heavily that the soil becomes soggy. Allow the soil to dry moderately before watering again.
  • A soaker hose is an excellent watering system. It allows water to seep directly into the soil without waste and without splashing leaves and flowers. Drip systems are also good.
  • Hand-watering with a water wand or nozzle allows you to custom water plants and monitor them at the same time. Direct water to the root systems of disease-susceptible plants. Give new transplants or other vulnerable plants extra water.
  • Water from sprinklers wets the flowers and foliage, making them susceptible to diseases. Soil structure may be destroyed by the impact of water drops falling on the surface; the soil may puddle or crust, preventing free entry of water and air. Avoid sprinklers whenever possible.

Fertilizing

If you incorporate organic matter, i.e., compost or rotted manure, into your soil on a regular basis, your plants may be adequately nourished. With less fertile soils, add fertilizer according to recommendations given by soil sample analysis. Apply fertilizer in the spring so it will not leach out before plants can benefit from it. Water the bed after applying fertilizer. This washes the fertilizer off the foliage, preventing fertilizer leaf burn, and makes nutrients available to the plants quickly.

Your garden may need additional nitrogen if you use straw, raw sawdust, or wood chip mulches because microorganisms decompose the mulch, taking up available nitrogen in the process. If soil test results indicate it, add lime in the fall so it will have time to raise the pH.

  • Annuals: Once annuals have germinated and begin to grow, they may need additional fertilizers. You can use a complete granular fertilizer, like 10-6-4, compost tea, or one of the soluble plant foods.
  • Perennials: Perennial plantings can rob the soil of its natural fertility. A light fertilization program gives a continuous supply of nutrients to produce healthy plants. Place 5-10-5 fertilizer in beds, at the rate of 2 pounds per 100 square foot of bed space early in April. Repeat twice at six-week intervals. If perennials begin to lag a bit in mid-summer, use a water-soluble foliar fertilizer or compost tea as a boost. Apply another treatment of fertilizer to late-blooming plants in late summer. Organic fertilizers, such as cottonseed or alfalfa meal, can be used as well.

Mulch 

Mulch gives an orderly look to the garden and cuts down on weeding. In addition, mulches maintain uniform moisture and temperature conditions in the garden. Organic mulches add some nutrients and humus to the soil, improving tilth and moisture-holding capacity.

  • Apply organic mulches after plants are installed, when soil is damp. It’s best to mulch after the soil has warmed up.
  • Grass clippings make a good mulch for annuals if they do not mat.
  • Other attractive organics for mulching include bark, pine needles, or shredded leaves.
  • Spread inorganic mulches such as black plastic before planting, when soil is damp.

Mulch and Perennials

Perennials generally are permanent plants. They need special care to protect them against repeated freezing and thawing in our unpredictable Maryland winters. But be careful—improper mulching can damage the plant. Don’t pile mulch heavily over the plant’s crown, as this encourages rotting or root development into the mulch. Wait until late fall, after several killing frosts, to apply mulch. If you apply it too early, the retained warmth may cause new growth to start, resulting in severe damage to the plant. Remove winter mulch when growth starts in the spring, assuring the plant of much-needed light.

Weeding

  • After plants are set out or thinned, cultivate only to break crusts on the surface of the soil.
  • When the plants begin to grow, stop cultivating and pull weeds by hand. As annual plants grow, feeder roots spread between the plants. Cultivation is likely to injure these roots. In addition, cultivation stirs the soil and uncovers weed seeds that then germinate.

Deadheading (removing old flowers) 

Remove spent flowers and seed pods to maintain vigorous growth of plants and ensure neatness and continuous blooming.

Staking 

Tall-growing annuals like larkspur, or tall varieties of marigold or cosmos, need support to protect them from strong winds and rain.

  • Stakes can be made from wood, bamboo, or reeds large enough to hold the plants upright but not large enough to be conspicuous. Stakes should be about 6 inches shorter than the mature plant so that their presence will not interfere with the beauty of the bloom.
  • Begin staking when plants are about one-third their mature size by placing stakes close to the plant, taking care to minimize damage to the root system. Secure the stems of plants to stakes in several places with paper-covered wire, twine, or other material that will not cut into the stem.
  • Plants with delicate stems (like cosmos) can be supported by a framework of stakes and strings in crisscrossing patterns.
  • Tie the plant by making a double loop of the wire with one loop around the plant and the other around the stake. Never loop the tie around both stake and plant. The plant will hang to one side and the wire may girdle the stem. Add ties as the stem lengthens.

Pinch Them If You Love Them!  

It’s a good idea to snip the tops off perennials several times during the growing season to encourage bushier growth and reduce their tendency to fall over. For fall-blooming flowers, the first pinch is usually done in early May. Maintain a 6- to 8-inch height until early July. Perennials that profit from a little pinch include chrysanthemums, sedum, and asters.

 

 

 

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