This month in the garden – May



Mid-Atlantic Region

May Maintenance Guide


May brings the end of pollen and summer begins – at least Memorial Day weekend – the official kick off of summer.



  • Every garden has room for container gardens. Find some fabulous pots and fill them with whatever you fancy. Know the amount of sun you get and when. It matters when you select your plants. Remember they need extra watering and fertilizing.


  • It’s safe now to plant the Amaryllis from Christmas. It will not likely bloom again this year, but should do so next year. Mine from previous years bloom mid month.  Here’s a little Amarylis planting how-to.
  • Now that the soils have warmed, plant Caladium bulbs or those potted and already in leaf. They like it warm and can be damaged by a cool weather, not just a frost. They are also big feeders so they will need consistent watering and fertilizer during the growing season.
  • Actually, any tender summer bulb such as cannas, dahlias, ginger lilies, and tuberoses can be planted now.
  • Oh, the Irises are blooming their little heads off. Recently, I cut some for a friend. She took a whiff and realized for the first time, bearded Irises have a lovely scent. They are nice to bring inside to enjoy the smell. After blooming, cut flower stalks to tidy up the plant.
  • Cut the flowers stalks of daffodils. Try to ignore the leaves as they die a natural death.
  • Add Bacillus thuringiensis (Bt) as a natural way to rid this pest.


  • With the frost behind, annuals can be planted with abandonment.
  • Visit public gardens to see the variety available for planting in our area. The JC Raulston Arboretum is an All-American Selection (AAS) display garden exhibiting the most recent selection winners.
  • Direct sow zinnia seed at intervals to have cut flowers through frost.


  • May is not the ideal time for planting perennials, but they are oh, so available. Plan to plant, but pamper. They will require extra watering to help get established.
  • English Ivy is leafing out. English ivy sure seemed like a good idea at the time it was introduced to the USA, but this non-native is very invasive.
  • Seeing the Chinese wisteria escaped in the wild brings a feeling of wonder. Yes, the color and flowers cascading down from the trees is beautiful, but they ain’t supposed to be there. Think twice about planting one. Instead, the American wisteria, ‘Amethyst Falls’ blooming a little later, is a good choice.


  • May is Southern Magnolia’s bloom time. They give so much and we need to do so little for them in return. I like to pluck a Magnolia bloom and float it in a bowl of water near where I read or enjoy the magnolias-21garden at the end of the day. It last but a day, but what a day it is.
  • The Endless Summer Hydrangea is the first Hydrangea to bloom on old and new growth with the ability to rebloom all summer long. I planted my Endless Summer in 2005 and I find the reblooming ability to be weak. Perhaps it will improve with age. To encourage reblooming, cut the blooms for drying or to put in vases for a fresh arrangement. This will also encourage the plant to set new buds.
  • Prune rhododendron and azaleas right after flowering.


  • Roses are in full swing right now. Let your roses flush out and take shorter pruning tactics in May so they grow taller. This is usually good advice for the first couple of cuttings. Then you can prune at will remembering to cut at an angle at the next 5 leaflets. Remember, Roses are heavy feeders – both food and water. I fertilize once a month and give each rose about 5 gallons of water each a week or about an inch a week. Water at the base of the plant and in the morning to help discourage black spot.


  • Plant an herb garden! If not for you, then for your garden friends. The Tiger Swallowtail butterfly larvae love parsley and fennel. Let those ‘green worms’ eat it all. Or plant enough to spare. If you don’t want them, call me at 781-0199 and I will rescue them to my gardens.
  • May, in my garden, is Lavender peak bloom time. Each May, I’m lavendar-april-27-2008-0621reminded of why I grow Lavender. It can look ratty many month of the year. After it flowers, cut back and shape.


  • To encourage flowering, a fertilizer low in nitrogen and high in phosphorus is best. The fertilizer’s 3 main ingredients are N-P-K with N for Nitrogen, P for Phosphorus and K for Potassium. 10-10-10 means there is an equal proportion of each N-P-K. Hydrangeas like a low N and a high P, thus a combination of 10-40-10 would be ideal. My general rule of thumb to remember what the numbers mean is to start with the first number and apply from the top of the plant to the bottom. As such, N – is for the green; P – is for the bloom; and K- is for the root.
  • To refresh your understanding of pH, pH refers to the acidity of the soil and is measured by the number of Hydrogen ions present in the soil. pH is a logarithmic scale based on the power of ten. As such, pH of 6.0 is 10 times more acidic than pH of 7.0! Thus, even a little change in pH can make a big difference. A pH of 7 is neutral, less than 7 is acid, greater than 7 is alkaline. Most plants like a pH between 6.5 and 7. All hydrangeas like it more acid than most plants.


  • Keep your gardens cool, less thirsty, and reduce the amount of weeds,  top dress your garden beds of mulch. I can write volumes on the benefits of mulch. I am really mulch crazy. I believe in the power of mulch.
  • For my Roses, I use mini-nuggets, but for my perennial gardens, I used composted leaf mulch.
  • Picking up a load reminds me of how important it is to make sure your yard waste is separated from your trash. This is not only good stuff once it is composted, but the conservation practice is in all our best interest! Confessions of a Stainable Gardener – Part 3 Mulch


  • Spring is prime growing time for weeds too.  The best advice is to stay on top of them with a weekly weeding event.


  • Now that we are past the last frost, irrigation systems are firing up. My appeal to you is not to water if you don’t have to. Most people OVER water, not underwater.
  • Remember, don’t water because it’s Tuesday or Saturday or any particular day of the week. Water when the top 2 or 3 inches of soil feels dry and then only if the plant looks thirsty.


  • Keep your wildlife coming back for more. Fill your feeders, replenish the water in the birdbaths, don’t spray pesticides.


  • For Your Continual Gardening Education, look for garden tours going on this spring, summer, and fall. There is also a fantastic winter garden tour at the JC Raulston Arboretum in February each year. Garden tours are a great way to see how others use certain plants and garden accents, and they can give you endless ideas. If you are new to this area, this is a must for practical purposes and pure pleasure. Garden owners opening their garden are putting their hearts on their sleeve to share with you their passion and giving back to the gardening community.  Support our local gardeners who are giving us so much. During the Garden Conservancy’s Open Days tours also benefiting the JC Raulston Arboretum, you may be surprised to know all the notable gardeners and garden writers who come. Even some the most veteran gardeners attend, those who are smart enough to know there is always someone new to learn from and new pleasures to be found.


Guide and photos by Helen Yoest

Gardening With Confidence



  1. Jan said

    You have some great reminders in the post, and not just for your area. Even down here in the Deep South, these can be helpful.

    Always Growing

  2. Michelle said

    Great and informative post.

  3. […] For Your Continual Gardening Education, look for garden tours going on this spring, summer, and fall. There is also a fantastic winter garden tour at the JC Raulston Arboretum in February each year. Garden tours are a great way to see … Read more from the original source: This month in the garden – May « Gardening With Confidence ™ […]

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