University of Maryland Extension

FAQs - Ornamental Plants (annuals, bulbs & perennials)

mixed flower bed

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This is the second year in a row that my daffodils produced leaves but no flowers. What is wrong?

My hostas have large ragged holes. What is eating my plants and how can I prevent this from happening?

Does mulch need to be applied more that once a year to a perennial bed? I already have 2-3 inches still in place.

My cannas have been hit by a frost and I know that I need to dig them up and store them.  What is the best way for me to do this?

Is it true that peonies need ants to help the buds open? I am trying to control the ants around them, but I was told I should leave them alone.

I planted mums in the front of my house last fall.  Now that spring is here they are totally brown, except I am seeing some green leaves at the base of the plant. How do I care for them now?

What perennials would you recommend to plant that bloom late summer into the fall? I would like to plant something other than mums and pansies.

The foliage of my black eyed Susan look terrible. This started earlier in the summer when I noticed they were covered with small dark spots that eventually took over the entire leaf. Right now they are very unsightly. What should I do and how do I prevent this from happening again?

My daffodils are finished blooming. Should I dig them up to divide them now that the leaves are turning yellow and dying back or should I wait until the fall to do it?

What is the best time to fertilize perennials?

This is the second year in a row that my daffodils produced leaves but no flowers. What is wrong?

There are a number of reasons why daffodils fail to bloom. If the bulbs have been in the ground for a number of years the area may have gotten too shady or the bulbs can be just too crowded. If so it is time to replant them to a sunnier spot or to divide the bulbs. Bulbs fail to bloom when foliage was cut back prematurely the previous year.  Bulbs need their leaves for photosynthesis and when removed the process stops and sufficient energy is not produced to form flowers. The foliage should be left alone until it begins to yellow and wither. You can cut off the flower stalks but not the leaves. Daffodils fail to flower for other reasons like lack of fertilizer (avoid high nitrogen fertilizers), the site has poor drainage, or they are stressed from replanting or division.

My hostas have large ragged holes. What is eating my plants and how can I prevent this from happening?

Slugs and snails love hosta. They are nocturnal pests, but usually leave slime trails that are noticeable during the day. There are many means of control. Simple traps can be made from overturned flower pots, grapefruit halves or small inverted containers.  Slugs will crawl underneath during the day to seek shelter. The slugs should be collected and disposed of. There are commercial traps and chemical controls available. See our publications for additional ideas, (PDF) HG 92 Slugs and Snails and (PDF) FS 822 Managing Slugs in the Garden and Beyond

Does mulch need to be applied more that once a year to a perennial bed?  I already have 2-3 inches still in place.

Theoretically, applying mulch to a perennial bed twice a year is a recommended practice but is not necessary to do. In the spring, adding new mulch improves the appearance of beds, keeps the soil cooler in the summer and suppresses weeds. Applying mulch in the late fall, after a hard frost and the plants are dormant, helps to prevent the roots from heaving out of the soil as it freezes and thaws. This is especially important for fall planted perennials. Typically 2-3 inches is a sufficient amount. In your case you can gently rake it to freshen it up. Be careful not to pile it around the base of plants, as it holds in excess moisture around the stems that can cause root and stem rot problems.

My cannas have been hit by a frost and I know that I need to dig them up and store them. What is the best way for me to do this?

Now that the tops of your cannas have died back, cut them back leaving a 6-8 inch stalk. Carefully remove them from the ground with a shovel.  Shake some of the soil off the roots and place them in a dry, frost-free area for a day or so to allow them to dry out.  Gently remove the remaining soil and place them in a box with dry sand or peat  moss.  Store them in a dry, airy location at about 40-50 degrees F. Check on them periodically and remove any rhizomes that are showing signs of decay.  In the spring, after the danger of frost has past and the ground has warmed up, split the rhizomes into sections and replant.

Is it true that peonies need ants to help the buds open? I am trying to control the ants around them, but I was told I should leave them alone.

This is one of many garden myths that get passed along from one gardener to the next.  No, it is not true that ants are needed to open peony buds. Ants are attracted to a sweet nectar that is produced on the surface of the buds. It is not known what its purpose is, however it does attract ants. The ants do not harm the peonies.  Ants are extremely beneficial insects outdoors; they help to combat termites and other insects pests. So, you do not need to worry and can just leave the ants alone.

I planted mums in the front of my house last fall.  Now that spring is here they are totally brown, except I am seeing some green leaves at the base of the plant. How do I care for them now?

Sometimes mums (Dendranthema x grandiflora) that are sold in the fall are not winter hardy in Maryland. Those are treated as annuals, but it sounds like your mums have successfully overwintered. In early spring, cut the dead growth back to just above where you see the green leaves (basal growth). Mums are generally easy-to-care for plants but benefit from a yearly application of fertilizer. To produce stockier, well-branched plants next fall, pinch off about 1 inch of the new growth when the plants get to be about 6-8 inches tall. This should be done 2-3 times up until the end of July. Water them deeply about once a week during hot, dry periods in the summer.

What perennials would you recommend to plant that bloom late summer into the fall? I would like to plant something other than mums and pansies.

There are many plants that add beauty to the fall garden. Ornamental grasses provide interest throughout the growing season, even after the first frost and into winter.  Muhlenbergia capillaries (pink muhly grass) is one outstanding ornamental grass that produces a mass of reddish-pink flowers that sway gently in the fall breeze. Panicum (switch grass) and Pennisetum (fountain grass) are also beautiful grasses for the fall. Asters, Joe-pye weed, Japanese anemone, sedum, Solidago (golden rod), Salvia elegans (pineapple sage), and the groundcover Ceratostigma plumbaginoides (leadwort or plumbago) will enhance your fall garden. Although zinnias are annuals, they are spectacular in the fall and are an excellent addition to a cut flower arrangement.

The foliage of my black eyed Susan look terrible. This started earlier in the summer when I noticed they were covered with small dark spots that eventually took over the entire leaf.  Right now they are very unsightly. What should I do and how do I prevent this from happening again?

Even though black eyed Susan is a Maryland native, they are very susceptible to a disease called Septoria. Once the plants are infected for the season there is little one can do. This disease does not kill the plant but is very disfiguring. Prevention is the key to trying to manage it. Cut back the plants at the end of the growing season and remove as much of the old plant debris as possible to reduce overwintering fungal spores. Next year, avoid overhead watering, prune or divide the plants to increase air circulation and keep mulch to a bare minimum around the base of the plants. A copper fungicide can be applied on the newly emerging leaves to help prevent the return of the disease.

My daffodils are finished blooming. Should I dig them up to divide them now that the leaves are turning yellow and dying back or should I wait until the fall to do it?

Yes, the timing is right to perform this task because the foliage is yellowing and the bulbs are beginning to go dormant. Take a spade and carefully lift the clumps. Discard damaged or soft bulbs. Shake the soil off the roots and place them in a single layer in a shady, dry spot to dry for a day or so. Separate the smaller bulblets from the parent bulbs and replant them all immediately. Make sure to water well. If they cannot be replanted right away, wait until the fall. Place them in an onion sack or some other type of container that has openings for air circulation. Store the bulbs in a dry, cool area that stays about 50-60 degrees F.

What is the best time to fertilize perennials?

There is no hard and fast rule for this. If you have a well-prepared bed that has good soil in many cases you need to nothing at all, or just perhaps topdress with an inch or two of organic amendment like compost, aged manure or LeafGro. Perennials differ in their need for fertilizer. Too much and many react by growing lush leaves at the expense of flowers. It's worth getting to know your plants.

Please send us a question at Ask the Experts if you have a flower question you would like answered. Digitial photos can be attached to your question.

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