This article was originally published in Garden Culture Magazine US02 under the title, “Grow Your Own: Rosemary” as part of the GYO Series.
The best tasting and most beneficial herbs are always freshly cut. Learn how to grow rosemary indoors using hydroponics or in containers for the best results.
A delightful herb with something to offer just about everyone, Rosemary originates from the Mediterranean region. Arriving in England with the Romans, the plant thrived just as well as in its native land. Prized since ancient times, Rosemary spread through many cultures. You now can find it growing in every country in the world.
There is no need for tracking down any special cultivars. Grow the original (latin: Rosmarinus officinalas). You will find an assortment of named varieties available. The differences they offer are purely ornamental, and would only be noticeable in landscaping and floral arrangements.
GROWING ROSEMARY INDOORS
GYO Fast Facts
- pH range 5.5-7.0 for best results
- Rosemary likes a normal humidity
- 69-74ºF (21-23ºC) best for leaf harvest
- 11-hour daylight minimum
- Harvest per sowing: 2-3
- Harvesting year round is possible
One of the best things about indoor growing is you can start new crops throughout the year, providing the seed or starter plants are readily available. Rosemary can be grown from both seed and cuttings. However, it is notorious for being difficult to impossible to start from seed. It also has a very low germination rate, yet some seed houses in the USA offer ‘primed’ rosemary seed that has great reviews for an excellent sprout rate. If it proves too difficult from seed, cuttings or a starter plant will work too.
Rosemary is a slow growing plant. Seed takes 4-8 weeks to germinate. The plants take 15 months to mature, and years to grow to full size. To speed up the process, many people start new plants from cuttings. In a greenhouse or grow room situation, this is not always the wisest choice.[/column]
If you do try starting it from cuttings, you want soft growth about 10 cm long that has been cut below a leaf node on an angle. Rooting hormone is not necessary, but media warmth is – maintain it at 24 C with a heat mat. Cutting stock may not be readily available year around. Herb plants are generally sold when in demand, during outdoor planting season in spring and early summer. Do remember to strip the leaves from the lower end of the cut stem before sticking it into your media.
The first harvest in the indoor garden will be 6 weeks in summer or 8-12 weeks in winter from the time of transplanting.
WHAT DO I NEED?
A native of the warm and sunny Mediterranean area, your plants require long day length and strong light. For best results, you’ll want rosemary in the indoor garden to be basking under lights for a minimum of 11 hours a day. High-Pressure Sodium (HPS) lamps are best at mimicking the strong sun in their native climate, but you can get by with compact fluorescent grow lamps too. If you choose the more budget-friendly CFL, it would be wise to run your lights a couple more hours a day. Skimping on the daylight hours causes lower yields, at best. Death from light starvation is also possible.
Rosemary does well in hydroponic systems. Use Rockwool starter cubes for germination. Sufficient root growth for transplanting takes 1-2 weeks after germination. Once you have roots penetrating the cube, transplant them to slabs or into the NFT trough. For frequent shearing, you’ll want them spaced 4-6″ (10-15 cm) on center.
If you’ve decided to grow this crop in traditional containers, start your seeds in an uncovered germination tray using peat or perlite as the cell media. Transplant them to growing pots at 2-3″ (5-8 cm) tall, and be sure to pick a quality soilless mix with good drainage. Rosemary requires a well-drained loamy soil.
Propagation temperature needs to be 75-84ºF (24-29ºC) with 75% humidity. Once your crop has been transplanted to grow on, maintain daytime temps used in propagating and nights at little cooler at 65ºF (18ºC). It’s preferred pH range is 5.5-7.0, and good air circulation is a must.
A light fertilizing periodically is all that is required. The thing that will be important for you to do is not over water. Mist the foliage several times a week.
Preserving your harvest is very simple with rosemary. It is still tasty and pungent dried, which is done by hanging loose bunches upside down in a dark place or in drying racks.
You can also freeze it by laying the sprigs on a baking sheet or tray and cover it before placing it in the icebox. The next day, simply strip all the frozen leaves off the stem into a freezer box. They will keep very nicely for up to 6 months and provide you with just picked flavor in cooked recipes.