Shrubs That Can Be Greenhouse Forced

Shrubs That Can Be Greenhouse Forced

Last month, I sorted many common shrubs into “ease of forcing” groups, based on characteristics such as their visual impact in a container to disease problems.

To review, the first three were:

Group 1. Would not fit into a mixed container program for the spring. These include those with no outstanding features to their foliage (Forsythia ‘Golden Peep’) or susceptible to disease (Philadelphus ‘Manteau d’Hermine,’ Mock Orange). Since flowers were only formed on next year’s growth, forcing for flowers was out of the question.

Group 2. Will work for a spring program, but with numerous problems such as poor form, inconsistency of growth or flowering (sun rose) or unstable variegation (variegated Mock Orange).

Group 3. Plants that work, but will require a bit more time, more marketing, etc. These are excellent but generally slow (abelia, hydrangea paniculata).

Group 4. The last group consists of plants that are easily forced and catch the eye. This group proved to be the most uniform, most colorful and most appealing to the eye of the consumer.

We determined the need, if any, for cold for all the shrubs brought into the program and sensitivity, if any, to photoperiod for many of them. Rooted liners in 32 tray packs were subjected to 33ËšF to 37ËšF in coolers for zero, four, six, eight or 10 weeks. Photoperiod treatments (LD or SD) were provided after the plants were removed from the cooler, planted in gallon containers and placed on the bench. The research was conducted on many taxa over a period of three years. No growth regulators were applied.  

Quick Guide To Group 4 Shrubs:

1. Leycesteria ‘Golden Lanterns': An exceptionally bright golden shrub with eye Himalayan Honeysuckle appeal.

Comment: Cooling is not necessary, but limited cooling reduces time on the bench. Cooling more than 6 weeks resulted in significant plant death (17 to 42 percent). Photoperiodic manipulation is not necessary.
Recommendation: Receive rooted cuttings in November, place in the cooler for 6 weeks at lower than 40ËšC, then pot up in final container and move to the bench.
Result: A marketable plant after 8 weeks on the bench for 5-inch containers, 11 weeks for 1-gallon containers.

2. Sambucus ‘Black Lace’: A popular plant in the landscape today. ‘Black Lace’ provides Elderberry a handsome deep purple filigreed leaf.
Comment: Cooling is absolutely necessary for forcing. Cooling could be provided for a minimum of 6 weeks, but uniformity is poor (16.5 weeks required for 75 percent of the crop to reach marketable stage). Photoperiodic manipulation is not necessary.
Recommendation: Receive rooted cuttings in November, provide 8 weeks cooling <40ËšF, then pot up and move to the bench.
Result: A marketable plant after 8 weeks on the bench for 5-inch containers, 10 weeks for 1-gallon containers.

3. Physocarpus ‘Summer Wine': A wonderfully cold hardy shrub with handsome Ninebark coppery leaves.
Comment: Cooling is not absolutely necessary for forcing, but extremely beneficial to reduce bench time. Cooling should be provided for 8 to 10 weeks. Photoperiodic manipulation not necessary.
Recommendation: Receive rooted cuttings in November, provide 10 weeks cooling at lower than 40ËšF, then pot up and move to the bench. Growth regulators would be beneficial on plants cooled for more than 8 weeks.
Result: A marketable plant after 8 weeks on the bench for 5-inch containers, 11 weeks for 1-gallon containers.

4. Caryopteris ‘Sunshine Blue': A small shrub with bright chartreuse leaves. This was false spirea done in 5-inch containers only.
Comment: Plants do fill out larger containers well, recommend either two per gallon or one per 5-inch pot. Cooling recommended for vigor and to reduce bench time. Photoperiodic manipulation is not necessary.
Recommendation: Receive rooted cuttings in November, place in cooler for at least 6 weeks, pot up in 5-inch containers.
Result: A marketable plant after 9 weeks on the bench.

Next month, we’ll look at a few others that fit in Group 4, but because of funding limitations, we did not look at them as closely as the prior subjects.

Leave a Reply

More From Plant Culture...
Lavandula 'Meerlo' (Sunset Western Garden Collection)

March 3, 2015

Why You Will Still Grow Today’s Big Perennial 10 Years From Now

What will be the next big perennial? Breeders say it takes more than a splashy plant to distinguish itself in the market. Therefore, the question is not what will be the next big perennial, but rather what perennial performs well enough in the garden to have staying power in the market for years to come.

Read More

March 2, 2015

Avoid Surprises On The Delivery Dock

A call in advance about problems with a plant shipment to a retailer you supply goes a long way toward customer satisfaction.

Read More
Janeen Wright

March 2, 2015

Deliver Plant Quality That Trumps Price [Opinion]

The industry's goal is to have loyal customers who return to the same plants time and time again, not because of price, but owing to a plant brand that shouts top-notch garden performance and is synonymous with excellence, which gives them the secure knowledge that their investment will be worth every hard-earned cent.

Read More
Latest Stories

February 11, 2015

Infusion Technology Boosts Seed Performance, Study Sugg…

Seven-year-old wheat seed germination can increase by as much as 83 percent, according to a Vital Force Technology Study that looks at the effects of energy infusion technology on plant vitality.

Read More

February 3, 2015

American Floral Endowment Accepting Research Pre-Propos…

If you are pursuing a floriculture research project, now is the time to apply for funding through the American Floral Endowment. Research pre-proposal applications for 2015-2016 funding are due to AFE by June 1, 2015.

Read More

January 27, 2015

Marijuana’s Trajectory And Ascent To Horticultural Cr…

Marijuana growing is poised for change as growers and researchers focus on improving production practices.

Read More

December 9, 2014

Greenhouse Production: Two Years Of Basics & Beyond…

Greenhouse Grower's Basics & Beyond articles cover some of the latest news and research going on in greenhouse production. Here are article links for the last two years.

Read More
GrowIt! App Wins Gold At Design100 2014 US Mobile & App Design Awards

November 24, 2014

GrowIt! App Wins Gold At Design100 2014 US Mobile &…

The social garden app GrowIt! takes the Gold Winner award at the design100 2014 Mobile & App Design Awards.

Read More

November 10, 2014

The Perennial Farm Joins HGTV HOME Plant Collection

The Perennial Farm joins the HGTV HOME Plant Collection growers' network for 2015.

Read More
AmericanHort

November 4, 2014

AmericanHort Publishes Revised American Standard For Nu…

AmericanHort announces the revised American Standard for Nursery Stock (ANSI Z60.1) is now available for industry use. The Standard reflects the consensus of the industry regarding how nursery stock — living plants other than annuals — should be specified and sold within the trade.

Read More

September 26, 2014

Master The Art Of Watering

Watering is elemental to healthy plants, but one of the hardest concepts for new employees to master in the greenhouse. Recommend these tips to start them off right.

Read More

September 16, 2014

Ball FloraPlant’s Las Limas Facility Provides Gro…

Ball FloraPlant’s Las Limas farm in Esteli, Nicaragua, is one year away from full production, but sales and quality from the two-year-old facility are right on track.

Read More
Erysimum 'Cheers' from Darwin Perennials

September 15, 2014

Darwin Perennials Takes Production Offshore In Bogota, …

With its recent purchase of a farm in Colombia, Darwin Perennials is ready to amp up supply of its perennial genetics, to provide growers with tried-and-true varieties and comprehensive production specifications.

Read More

July 23, 2014

Plan Now To Prevent Bract Edge Burn On Poinsettias

Reduce fertilizer and water, and allow your poinsettias to develop slowly during the final four weeks of production to avoid bract edge burn.

Read More

July 11, 2014

Growing Your Crops Above Their Base Temperature

Lowering temperature set points in the greenhouse may help you combat rising heating costs.

Read More

May 1, 2014

Growers Report Nutritional Problems On Geraniums

In recent weeks, several growers have contacted Michigan State University Specialists about leaf discoloration on geraniums, especially the purpling of lower leaves.

Read More

April 22, 2014

How Two Postharvest Care Products Worked On Potted Plan…

What your potted plants look like at retail translates to sales or fails. North Carolina State University researchers report on how two postharvest care products performed.

Read More
Dianthus 'Passion' from Emerald Coast Growers

March 27, 2014

Growing Dianthus Successfully

Here's some advice on transplanting and producing this classic perennial favorite.

Read More
Aquilegia canadensis

March 10, 2014

Tips For Producing Aquilegia

Advice on planting, temperature, vernalization, lighting and more on columbine from Emerald Coast Growers' head grower Josiah Raymer.

Read More
Perennials in hoop house

February 21, 2014

Overwintering Perennials: Plan Ahead To Fungicide Drenc…

Demand for perennials has increased as consumers educate themselves and seek out new and improved varieties. Overwintering perennials can become an important profit center. Here's some advice on how to overwinter successfully.

Read More
Cold damage to ipomoea

February 11, 2014

Chilling Injury On Cuttings: What To Look For

During this young plant production season when many growers receive unrooted cuttings, liners and plugs for spring production. Cuttings shippers are delaying deliveries because the tender cuttings cannot withstand the frigid temperatures.

Read More