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What to Plant in the May Garden in Southwest Idaho

May can be a confusing month for the gardener in southwest Idaho. There will usually be many warm days. It may seem that summer is here. But the wise gardener will never forget that the average last date of frost for southwest Idaho is mid May, with the potential of being as late as the first of June. Some seeds and seedlings can be planted, but not everything yet. Here is a list of seeds I typically plant in May, some of it succession planting, some of it first time for the year, and some of it because I didn’t get to it in April:

  • beets
  • cabbage, late or fall harvest for storage
  • carrots
  • dill
  • kale
  • lettuce
  • onions
  • potatoes
  • sunflowers
  • sweet peas
  • gladiolas
  • poppies
  • viola
A row of frilly, bright green lettuce needs to be thinned. Salad pickings!

A row of frilly, bright green lettuce needs to be thinned. Salad pickings!

I continue to watch the weather report diligently throughout May, being wary of any nighttime lows below 40°F for any warm weather transplants I have gone ahead and planted out. I know from experience that I will only have the time and memory to cover a certain number of tender plants, so mostly limit these plantings to things like tomatoes in my vegetable garden. Flowers or edibles planted throughout the landscaping will likely be forgotten, so unless I am willing to deal with this, I wait longer to plant those out. If you want some inexpensive ideas for ways to cover seedlings, you might like this article I wrote about it last year: Useful Pots for Late Spring Frost Protection.

IF the first half of May has been quite warm AND the weather report for the second half is predicted to be more of the same, I might go ahead and plant some of the warm weather crops toward the end of May. If the soil hasn’t warmed up enough or the spring weather has been particularly damp, many of the warm weather crops just won’t sprout, or might rot while trying. Raised beds or covering a garden with black plastic might raise the temperature enough to overcome slightly cool temperatures, but if there is a lot of rain it is best to concentrate on enjoying the plants that like the cooler moist conditions. June will come soon enough.

It is always a good time to consider keeping a few notes, written down or in your head, about what volunteers are sprouting around your yard. This is how I figured out that sunflowers can be planted much sooner than most of the packages say. This is true for other flowers, too. And potatoes. Try as I might, there are always a few potatoes in the ground that sprout the following spring. These types of natural germinations can be useful guidelines for when to plant, even the same year you see them.

To help set your mind at ease about waiting for warm weather, you might do an experiment with some open pollinated volunteers like I have done with tomatoes. Plant your seedlings out a bit early, keeping them covered and protected from cold weather as necessary. When the volunteers show up, let a couple of them grow alongside yours. You can do the same experiment with the same types of plants, either that you have grown from seed or purchased, but keep some in the pots and plant the others out in the garden. You will often find that the volunteers that came up later, when the weather was warmer, or kept in pots longer, grow to the same size just as quickly as the ones you tried to coax along in the cold garden.

A tomato I grew from seed was transplanted during the first days of May, but I will keep a close eye on the night time lows.

A tomato I grew from seed was transplanted during the first days of May, but I will keep a close eye on the night time lows.

Here is my list of warm weather vegetables that I usually wait to plant from seed until late May or early June:

  • green beans
  • dry beans
  • corn
  • cucumber
  • melons, like cantaloupe
  • pumpkins
  • squash, summer or winter varieties
  • basil

Tomatoes and peppers are usually transplants from my greenhouse starts.

It’s not like you don’t have anything else to do. There is plenty of weeding, sprinkler repair, and compost to spread. Plus, if your yard is like mine, there are tulips and irises blooming about now. I like to transplant and divide some of them this time of year when I can see their size and color. If you can get a big shovel full of dirt to go with the tulips, they might even keep blooming in their new location. Take some time to walk around and enjoy what is growing and blooming. Be glad that you don’t have to plant everything all at once. Enjoy the multi-season nature of gardening in Idaho.

The red tulips got transplanted here last spring.

The red tulips got transplanted here last spring.


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