Kaliteri Oregano

I purchased some Kaliteri Oregano from you about 4 years ago. The plants are now well established and bustling. How and when can I harvest parts for use?

You can harvest leaves just about anytime. When the plant is just coming into flower you may notice that the flavour and aroma are the strongest; and traditionally herbs harvested for drying at this stage. But Kaliteri's leaves are richly flavourful virtually anytime. The only time you should hold back cutting is when the plant's growth is slowing down or when it is dormant, as will be the case in winter.

My success story! You describe them as tender perennials. Well I am in California's High Desert area near Victorville at an elevation of about 3600 feet. These plants have withstood snow, and bright sunlight with temps up to 115 degrees. I have the plants on the east side of the house to limit sun exposure to mornings and early afternoons.
The size is about three-feet tall, four feet wide and the ground area where planted contains hard sandy soil that I amended with compost. I usually toss more compost on the soil once to three times each year. No fertilizing.

Thank you very much for your feedback on Kaliteri oregano. It truly is a special plant and we are very proud that we introduced it to North America. It is great to know that the plant does so well in your conditions. According to the USDA hardiness zone map you are in zone 8. We rate Kaliteri oregano to be hardy in zones 6-11, so you are firmly in the middle of the plant's hardiness range.
When we use the term "tender perennial" that is used relative to our zone 5 location in Goodwood, Ontario. Here, Kaliteri oregano is not hardy, so we call it a tender perennial. We are using the USDA zone system now, but our labels and databases still have the older "tender perennial".