The Ins and Outs of Frost Blankets, Award-Winning Penstemon and a New Geum

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News and commentary for the perennial market GrowerTalks MagazineGreen Profit Magazine

Friday, March 10, 2017

Paul Pilon Subscribe
Perennial Pulse

Above-Average Temps
Do Frost Blankets Really Work?
How Much Protection Do Blankets Provide?
Managing Coverings in the Early Spring
Geum Solid Gold Dancer
This Penstemon is Pentastic
Cultivate Registration is Open

Above-Average Temps

It’s hard to believe winter is almost over. This weekend is daylight savings time (so don’t forget to turn your clocks ahead at 2:00 a.m. Eastern time Sunday morning) and the beginning of spring is less than two weeks away.

It might be just me, but winter didn’t seem so bad this here. Sure, there was some really cold weather for a while there, but in my travels, the winter seemed relatively mild and with less snowfall than I’m accustomed to seeing.

March 2017 temperature outlook. Areas not shaded have an equal chance of above- or below-average temperatures. (The Weather Company, an IBM Business)

The mild winter is going to continue for most of us. The Weather Channel is predicting above-average temperatures for much of the country. Only a small sliver of the Pacific Northwest is expected to have below-average temperatures.

Do Frost Blankets Really Work?

That’s a great question! It can be difficult to determine how beneficial frost blankets can be, but believe me when I say that frost blankets really work. Here's a couple of great examples showing how well they can protect plants and prevent injury.


The image on the left shows what can happen when the blanket is not properly secured or anchored. A large portion of this blanket blew off and the exposed lithodora died from cold injury. The plants that remained covered had no injury and are beginning to flower.

The image on the right shows a large group of plants that died from cold damage. In this case, the mortality occurred in locations on this bed where there were large holes in the blanket.

In both instances above, you can clearly see live plants where the plants remained covered and significant losses in locations where the plants were uncovered for either short (wind) or long (holes in the blanket) durations.

How Much Protection Do Blankets Provide?

The following info was originally shared in the Perennial Pulse I sent out on April 12, 2016, but I thought it's also relevant to include here.

There are several grades of frost blankets available. They're sold by the amount of weight they have per square yard, which also provides an indication to the amount of cold protection they're likely to provide.

Blanket Weight  Cold Protection
0.5 oz. per square yard Up to 4F (2.2C) warmer than outside temperatures
1.0 oz. per square yard Up to 4 to 6F (2.2 to 3.3C) warmer than outside temperatures
1.5 oz. per square yard Up to 6 to 8F (3.3 to 4.4C) warmer than outside temperatures
3.0 oz. per square yard Up to 10+F (5.6C) warmer than outside temperatures

As you can see, frost blankets can offer a significant amount of protection. Depending on the covering used, frost blankets can provide five to 10 degrees or more of cold protection. The blankets can be placed directly over the top of plants for short durations or on frames above them for extended time periods.

Frost blankets come in various lengths and widths. Most growers use either the 1.5 or 3.0 oz. per yard fabrics. Frost blankets can be obtained through various horticulture distributors.

Managing Coverings in the Early Spring

While on the topic of protecting plants from cold using protective coverings, here’s a few guidelines I thought I’d pass along.

Perennials that have de-acclimated from cold temperatures have broken their dormancy and/or are actively growing are very susceptible to injury from freezing temperatures. It’s probably more important to protect plants from below-freezing temperatures now than it was in the middle of the winter. As the outside temperatures become warmer in the early spring, it’s often necessary to manage or remove the coverings and recover the plants from time to time.  

Besides being used during production, frost blankets are also beneficial during unexpected cold snaps in retail settings.

As beneficial as frost blankets can be, they can also have some negative side effects unless they're managed properly. Many protective blankets used to provide cold protection can be very heavy when wet. The weight of the covering in combination with little air movement underneath and through the blanket can be detrimental to any crops that remain evergreen or semi-green throughout the winter months, as well as crops that have emerged from dormancy. These plants are highly susceptible to foliar diseases, temperature fluctuations and high humidity levels that build up under the coverings. Leaving the blankets on too long can be very detrimental to some crops (especially during the early spring).

Evergreen varieties should only be covered (with any material) during the coldest periods of the winter. Removing the covers whenever the temperatures warm up (consistently above 40F/4.4C during the day and above freezing at night) will decrease optimum conditions for disease development. The coverings can remain longer on crops, such as daylilies, that go completely dormant during the winter months.

It’s best to pull the coverings off in such a manner that they can be pulled back over the plants to provide frost protection when freezing temperatures return. In a typical spring, it’s often necessary to remove and recover the blankets several times before the temperatures remain warm enough to keep them off altogether. Frost blankets can provide great amounts of protection from cold when they're properly managed in outside sites, as well as inside coldframes, Quonsets and other structures.

Geum Solid Gold Dancer

Here’s another great-looking geum from breeder Brent Horvath of Intrinsic Perennial Gardens. Solid Gold Dancer is the 17th addition and the first gold-colored geum in the Cocktail series. Flowering begins in late April or early May and continues for up to four weeks.

This mover and shaker develops compact 10- in. tall by 12-in. wide clumps with 15- to 18-in. flower stems. This hybrid Zone 4 to 8 geum is longer lived than the older chiloense varieties.

Apparently, Solid Gold Dancer is named after the popular '80s dance show. Check this video out or search it on YouTube if you've never heard of the show. Although it's not actually named after a cocktail, Brent created a refreshing summer drink just for this great geum: Reposado tequila on ice with three fresh-squeezed lemon wedges. Sip and enjoy!

This Penstemon is Pentastic!

Last year at Spring Trials, Histil introduced a new series of penstemon called Pentastic from Concept Plants. It received rave reviews then and just recently received the Best New Variety in the Herbaceous Perennials category at the UK Grower Awards 2017.

The plants in the Pentastic series have large, dense, colorful blooms held nicely on their compact growth habit. There are three colors in the series -- rose, pink and red. They're well branched, easy to grow and don't require vernalization for flowering. However, this great series isn't for everyone; the Pentastic cultivars are only hardy in Zones 7a to 10. 

Cultivate Registration is Open

Registration for AmericanHort's Cultivate'17 opened at 11:00 a.m. on March 7. Cultivate’17 will be held at the Columbus Convention Center July 15 - 18. Cultivate is one of our industries largest events, typically having over 10,000 attendees, which includes a huge trade show with over 800 exhibitors, more than 140 educational sessions and tons of networking opportunities.

Registration is streamlined into a simple four-step process:
1) Select Your Conference Package
2) Increase Your ROI (sign up for additional tours and workshops)
3) Book Your Hotel
4) Make Your Own Agenda (map your trade show route and narrow down your educational choices)

Click here to learn more and to register for this great event.

Thanks for reading. Feel free to update me as the new growing season begins. 

Take care,

Paul Pilon
Perennial Pulse

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