Agastache: Production Advice
Media. Agastache prefer a well-drained media such as a 50/50 peat-perlite or pumice mix. Drainage holes in the pots should err on the larger side. Taller pots, like standard gallon pots, give the plant a better capillary column for drainage, and the soil weight should keep the plants from blowing over in the wind.
Planting. Plant one 72-cell liner per 4-inch, 6-inch or gallon pot. Plants may be trimmed for mechanized planting. Agastache are not as sensitive to planting depth as other perennials since they are from the Lamiaceae (mint) family and readily root up the stem. It is advised, however, to make sure the top of the liner matches evenly with the top of the soil in the pot to prevent stem and crown rot. Fungicides at planting are usually not required. Those who prefer pot mulches should use non-organic mulches like turkey grit, or pot covers. Filbert shells, used in the Northwest, are fine as they take years to decompose.
pH/EC. Maintain an acid pH of 5.5 to 6.5 and an EC of 1.5 to 2.0 using the pour-thru method. This means testing the pH of the liquid that drains from a pot rather than testing the media itself. Water plants normally and wait one hour. Then take a half cup of distilled water, pour it over a pot that can be placed in a plastic bag or saucer, tilt the pot and collect the solution to treat. pH and EC pens are cheap and accurate these days. Agastache do tolerate mildly alkaline conditions.
Temperature. A 50°F to 55°F night and a 70°F to 75°F day are ideal for agastache. In areas of the South, where nights are warm, place this crop on the ground rather than benches, as it can be 10°F to 15°F cooler. They can take higher heat than many crops but should have a nightly cool-down for better growth.
Light. Agastache need full sun and do best with 35 to 50 mol/m²d. Plants will stretch and flower much less in shade.
Fertilizer/Watering. Supply a low- to medium-rate of constant liquid feed at 100 to 150 ppm. Nitrogen of 20-10-20 balance can be used. Too much nitrogen will cause lush, soft growth that is more susceptible to disease. Make sure to dry down plants between irrigations because wet-dry cycles prevent root-rot pathogens. Do not feed at the typical annual plant rate as it will create plants that are too vigorous with fewer flowers.
Pinch/PGRs. Pinching the plants one to two weeks after planting helps produce full, well-branched plants with more flowers. Mechanical pinching can be replaced by the use of Florel at 200 to 400 ppm. For growers that are new to Florel spray or agastache, Terra Nova Nurseries recommends application at a lower rate with more frequent applications. For example, two applications at 200 ppm, one to two weeks apart instead of once at 400 ppm. Remember that efficacy of Florel is dependent on the pH of the spray solution (it needs to be an acidic 4.0 to 4.5) and for the length of time the solution is allowed to dry.
Pests/Disease. Aphids, mites and thrips are the major insect pests of agastache, with mites being the worst. As with any crop and pest, scouting and prevention are keys to success. Make sure to rotate chemical controls to prevent resistance. Downy mildew (particularly this year) is the main problem for nurseries in terms of disease resistance. Prevention is the key when combating downy mildew as it often discolors entire leaves. In extreme cases it can lead to defoliation and death. Be sure to give these plants plenty of space for proper airflow and apply fungicides preventatively.
Scheduling. Finish time from 72-cell liner to 4-inch pot is four to six weeks. From 72-cell to 1-gallon pot, the finish time is eight weeks.