Plant some things now; others have to wait until after last frost—or longer

by Connie Oswald Stofko

Here is a question that I received from a reader:

Hello, I saw that the last frost for my area (in Hamburg) is possible as late as May 22; should I really wait so long to plant anything? 

Mariely Ann Ortiz

Actually, there are lots of things you can plant outside right now!

But some things have to wait until after the last frost — or even longer.

And that date you have of May 22 isn’t actually the last possible date for frost for the Buffalo area.

What you can plant now in WNY

For some ideas on when you can plant various plants, check out this list from Cornell Cooperative Extension in Tompkins County. John Farfaglia, extension educator with Cornell Cooperative Extension in Niagara County, said the dates are pretty close to the dates for the Buffalo area.

Perennials and trees

Any perennial that is hardy in your garden zone can be planted now, said
Mark Yadon, vice president at Mischler’s Florist and Greenhouses.

See what garden zone you’re in here.

Perennials are plants that come back the following year, growing from the same roots. You can see a list of perennials here that will be offered in the59-cent perennial sale at Mischler’s. The sale will take place from Friday, April 26 to Friday, May 3.

Although he doesn’t carry trees, Yadon noted that trees can also be planted now.

Get some tips on choosing a tree for your landscape here.

Cool-weather annuals

When we talk about annuals in this context, we mean things that we have to plant every year because they die in the winter. They might be perennials in other parts of the world, but here we treat them as annuals.

Here are some annuals that you can plant now, and are even flowering:

• Pansies
• Osteospermum daisies
• Calibrachoa
• Nemesia
• Diascia
• Ranunculus

There are also some annual phlox that can be planted now. These include ‘Phloxy Lady’ and ‘Giesel’.

“You can plant them now, and they will last through a frost in the fall as well,” Yadon said.

You can plant these cool-weather annuals in a pot. You can also plant them in a garden bed as long as your soil is dry enough to be worked. Scoop up some soil and squeeze it in your hand. If it forms a glob, it’s too wet. If it’s crumbly, it’s good.

Vegetables and herbs

There are many cool-weather vegetables that you can transplant outside now or start from seed now, said Jen Weber, vice president and manager of Mike Weber Greenhouses.

Start with leafy greens. You can transplant spinach, kale and cabbage outside now.

Lettuce likes cool temperatures, but not frost. You can plant it outside if you if you cover it with a sheet of plastic or a cloth to protect it from a frost.

You can also plant these leafy greens from seeds now, too.

If you want to transplant peas outside, wait until the nighttime temperatures are above 32 degrees, Weber said. The foliage can’t take a frost.

To start peas from seed, Weber said you should sow them on Good Friday, no matter whether that falls in late March or sometime in April. It has to do with cycles of moon. She does this every year and says she never has a problem.

Onions and root vegetables can be planted from seeds or transplanted outside now.

Now is also the time to transplant broccoli and cauliflower outside, or to plant them from seeds. While they don’t carry potatoes, she noted that this is the time to plant them, too.

Get your cold-weather vegetables planted by mid-May or at least by Memorial Day. They not only tolerate the cold, they actually like it on the cold side, Weber explained. If you wait until it’s too warm, they won’t grow as well. The broccoli and cauliflower might get just one floret instead of a big head and they won’t be as sweet. And the warm weather will make them go to seed too soon.

Corn is kind of fussy, Weber said. If you want to start corn from seed, do that in the house now. Transplant it outside the first of May, but cover it. It can’t take air temperatures below 40 degrees at night. It doesn’t like being wet, so err on the dry side for the soil.

Perennial herbs can be planted now. These include chives, parsley, oregano, lavender, hyssop and horehound. Sage and rosemary can be planted outside when night temperatures are above 40 degrees.

Wait until after last frost — or longer — for these plants

Annuals

Most annuals shouldn’t go out until after the last frost. This includes plants such as begonias and marigolds, as well as all types of impatiens (walleriana, New Guinea and SunPatiens).

However, some plants should wait even longer to be planted outside, Yadon said. In the Buffalo area, wait until Memorial Day for coleus, sweet potato vine and tropical plants such as mandevilla. It’s not just that these plants can’t take a frost; they don’t even like the cold.

“They really suffer,” he said. “It’s just the cold nights and cold soil temperature.

“They will wilt from the cold, but people think they need water and will water them. Then the water rots the roots.”

Vegetables and herbs

“I can never get people to wait on tomatoes; I don’t why,” Weber said. “I’m getting calls now about tomatoes.”

Some people think they can plant tomatoes on Mother’s Day weekend, but Weber insists they should wait until Memorial Day or even June 1 in the Buffalo area. That goes for peppers and cucumbers, too.

Weber said the first week of June is the best time to plant them because the ground is warmer, the air temperature is warmer and we’re past the last frost. Tomatoes, peppers and cucumbers want nights that are at least 60 degrees Fahrenheit.

If you have your plants out in poor conditions, it may take time for the plant to recover.

“If you plant too early, you could stunt your plant,” Weber said. “You might get a setback instead of that head start you think you’re getting.”

The cloudy days and moisture can cause mold and the plant will rot. Frost can kill the plants. When there are frost warnings, gardeners scurry outside to cover their plants to try to protect them.

“If you just wait until the first week of June, you won’t have to cover them,” she said.

Herbs other than the perennial herbs mentioned above should wait until the end of May, Weber said. Those more tender herbs, such as cilantro, prefer nights that are at least 50 degrees Fahrenheit.

Basil likes it even warmer– nights should be 70 degrees.

When is the last spring frost in WNY?

“It’s hard to pin down” when the last frost will occur in your area, said John Farfaglia, extension educator with Cornell Cooperative Extension in Niagara County. “There are a lot of variables. There are microclimates along the lakes, in valleys, in deep valleys and in urban areas.”

You can find charts to give you a point of reference, but these dates aren’t etched in stone. The dates are averages.

Note that the chart lists dates at 32 degrees and 36 degrees Fahrenheit. A susceptible plant can be damaged by frost at 36 degrees and sustain more damage or be killed at 32 degrees, Farfaglia said.

Also note that the chart lists probabilities of frost. For the Buffalo area, the last date that is listed is May 22. That’s when there is a 10 percent chance of having a frost after that date. Looking at it another way, the odds are that in one out of ten years, the Buffalo area will have a frost after May 22.

Farfaglia said that a different chart lists Lockport as having an average last date for frost between May 7 and 10. Yet he remembers in the last five years having frost as late as May 23 in Lockport.

Even when it comes to predicting the last date of frost for a particular area, “There are so many variables, to come up with a really tight date is not feasible,” he said.

In general, on average, the last frost in the Buffalo area is around May 22. In the Lockport area, it’s about a week earlier than Buffalo. In the Southern Tier, it’s a week or two weeks later than the Buffalo area. (The chart on freeze and frost probabilities puts Jamestown as having a 10 percent chance of having a frost after June 25.)

Yadon from Mischler’s, which is in the Buffalo area, says he waits until May 10 or 12 to see what the 10-day forecast is. If there’s no frost in the forecast, he will bring the more tender plants out.

Weber also recommends watching the weather. “I try to tell people, ‘don’t go by a specific date, go by the temperatures,'” she said.

It’s hard to get an accurate long-range forecast of the weather.

“That’s the crazy gambling part of gardening,” Farfaglia said.

How to get your questions answered

Readers often contact me with questions that I can’t answer. I’m not a gardening expert– I’m a writer by profession. I interview knowledgeable people in order to provide you with great articles on Buffalo-NiagaraGardening.com.

So when someone asks a question, sometimes I interview people and write an article.

Or I post the question to see if other readers can chime in with helpful information. That’s good if a reader is looking for a wide range of opinions and doesn’t mind waiting for the answer. If you want to try this route, email the question to me at connie@buffaloniagaragardening.com and I’ll pose it to my readers in an upcoming issue.

However, don’t send me questions:

• To find out what is wrong with your plant
• To identify a particular plant or insect
• If you need an answer quickly

For those questions, ask the Master Gardeners with Cornell Cooperative Extension or turn to your local garden center. They can give you the information you need.

Note: If you want to know what garden center has a particular plant in stock, contact the garden center directly.