Dip your toe in the Dipladenia pool

Thanks to social media, plants that never received much attention before are gaining more time in the spotlight. Like Dipladenia.

An annual, Dipladenia (aka rocktrumpet) is sometimes used interchangeably with Mandevilla but they are different. As Brian Krug and Jamie Gibson, technical leads with Syngenta Flowers, noted at the most recent Cultivate event, Mandevillas are more vine-like (although some new Dipladenia varieties are now available with vining traits). Dipladenia tend to be bred for more rounded, controlled habits and are more like shrubs, though.

“There is growth potential” for Dipladenia, Krug said. “It has continued popularity, it’s programmable, it has minimal pest issues and it has outstanding shelf life. Consumers like it because it has tropical feel – it’s a high value-looking plant. It’s very durable and likes hot, humid weather. It can be successful anywhere in the country.”

Those looking to grow and sell Dipladenia were provided with some helpful guidelines from Krug and Gibson, the latter of whom said the “key parameters for success are a reputable supplier with pest-free, properly fertilized mother stock.”

Gibson went into the finer details of adding this plant to your offerings. First, keep your cuttings “warm” (not below 48º). Shipping can stress cuttings, especially with warm or delayed shipments, which can lead to tip breakdown. Try to avoid long-term storage (more than 24 hours) of cuttings. Be sure to use an early fungicide spray to help prevent foliar diseases.

Dipladenia cuttings’ rooting time is five to six weeks, which is slower than most other annuals. Gibson suggested trying callus cuttings to reduce rooting time by two to three weeks. Keep growing temperatures between 70º and 74º. Continue light misting until good root formation occurs – and wait until the leaves flatten out to finish misting.

“Long days of high-quality light are necessary, otherwise they’re just green and stringy,” Gibson said. More than 14 hours of daylight are required. He noted that higher quality and higher quantity light may accelerate nutrient utilization, though, so be aware of that. Varietal differences do have different nitrogen demands. And while LEDs warm the plants, they may not warm their substrates.

The program timeline totals 20 – 22 weeks from propagation to production, and the last 10 weeks are the most critical. Gibson said growers “don’t need maximum flower to sell, but they need some color.”

Pinching is recommended during propagation or after transplant, as it results in more rounded plants and less vining. If you are pinching in propagation, do it only on cuttings that are well-rooted. PGRs are highly recommended during propagation too.

Pre-finished Dipladenia programs from more southerly locations are available to avoid common propagation and flower development challenges in more challenging northern climates for spring sales.

When finishing, growers should aim for daytime temps of 74º to 80º, and 66º to 70º at night. Growing media should sit within a pH range of 5.6 to 6.2.

PGRs are generally not needed during finishing. Adequate heat and light intensity are crucial for optimum quality, however. And be mindful of your irrigation practices – extreme over-watering or extreme drought stress can cause bottom leaf yellowing on young plants.

To increase branching, pinch above the node with the most recently expanded leaves. Be sure to maintain good fertility (with greater than 150 ppm nitrogen). And implement the best environmental conditions you can (as mentioned above).

For PGR branching, Gibson recommended Configure® sprays to improve lateral breaks. Other PGRs can be used to control height. He said you’ll need a PGR toolbox for different phases of Dipladenia growth.

Throughout all this, scouting for insects and disease is still necessary. Thrips parvispinus (aka pepper thrips) is a concern. “Monitoring with sticky cards up front is so important. Have a very attractive sap for thrips,” Gibson said.

Spider mites are also commonly seen. Take the time to look underneath leaves for these pests.

Diseases to be on the lookout for include southern wilt and bacterial Pseudomonas savastanoi. Also watch for leaf spots and Botrytis.

If you want to dip your toe into Dipladenia growing, Krug and Gibson said the keys to success are simple: long days of light, proper temperatures and quality fertilizer.

by Courtney Llewellyn