Harris County Master Gardeners Releases May Gardening Calendar
Home & Garden

Harris County Master Gardeners Releases May Gardening Calendar

May 09 2023

By Karen Shook, Harris County Master Gardener

May reminds us why we need to get our gardening advice from local sources. We are preparing for the start of summer and harvesting from our spring gardens. For our Northern friends, it is time for spring planting.

While it “feels” like we’ve had lots of rain this year, through March we are about three inches below normal. The May forecasts I look at say to expect near historic averages in May (five inches of rainfall, 77° F average temperatures.)

Pests may be enjoying your plants as much as you are. Some damage is inevitable, but watch and limit (pick them off, spray them off).

Hurricane season is coming June 1. Now is the time to make sure trees are trimmed, no dead branches are waiting to fall.

Perennials and Ornamental Grasses

  • Continue deadheading (remove spent blooms). If blooms start to dwindle, consider cutting back by 1/3. Fertilize and water after cutting.
  • Fertilize your perennial beds.
  • Ornamental grasses can be planted through summer.
  • Divide chrysanthemums late April, early May.
  • Perennials that can stand our summer heat can be planted in May.


  • Clean out cool season annual beds, plant warm season annuals. Most transplants benefit from addition of compost to the soil at planting time.
  • Cut back petunias by 1/3. Fertilize and water.
  • Feed your annuals every 4 to 6 weeks.


  • Cut back yellow foliage of spring flowering bulbs. But not until yellow or brown color tells you the bulbs have replen- ished stored reserves. Dig, and reset the bulbs if desired.
  • Fertilize bulbs as needed to encourage vigorous growth.
  • Cannas and agapanthus are examples of summer bulbs that can be planted now. My cannas have been blooming and brightening the yard.


  • In your morning garden rounds, cut some roses (to first leaf with five leaflets) to enjoy indoors.
  • Continue to spray for blackspot, powdery mildew, aphids, etc., every seven to ten days through November. Fertilize every four to eight weeks (some sources say four weeks, others say eight weeks, so I say depending on health of the rose).


  • Prune spring flowering shrubs after they finish flowering. Azaleas are probably finished.
  • Other shrubs can be lightly pruned to shape.
  • Keep mulch several inches thick.
  • Fertilize camellias (lightly).


  • We are probably well into mowing season. Mow when grass height is 1/3 more than you want (don't cut more than 1/3 height each mowing).
  • Fill low areas with soil similar to native soil.
  • It is probably your last chance to apply broadleaf weed killer before it is too hot. Check the labels!

Groundcovers and Vines

  • Watch for snails, slugs in low growing groundcovers.
  • Dig and divide established ground covers


  • Prune spring vines after they finish flowering. Snip back, wind vines through support to keep looking neat.

Edibles (vegetables, herbs, berries, fruits)

Source: Harris County Master Gardeners Urban Dirt Newsletter (May 2023 Edition)

About Urban Dirt

Each month, Harris County Master Gardeners publishes an informative, resourceful newsletter entitled "Urban Dirt". This article was derived from the May 2023 edition. To read the May 2023 edition of this newsletter, click the button below.


Subscribe to Your


Stay current on local news and events with periodic emails sent straight to you!

Change Neighborhood

Select Your Region/Community