Home & Gardens: Growing lavender in winter | PostIndependent.com

Home & Gardens: Growing lavender in winter

Curt Swift
Free Press Gardening Columnist
Lavender Abstract
Getty Images/iStockphoto | iStockphoto

Earlier this week, the weather was quite nice, being in the 40s here in the valley. With such pleasant weather, gardeners can’t help but think about spring (though it’s still far away).

One task you should consider taking care of in the very near future is setting up your grow room in preparation for starting seedlings or rooting cuttings. Many vegetables should be no more than 5-7 weeks old when transplanted into the garden. Other vegetable seedlings can be up to 12 weeks old when set out in the garden.

Of course some vegetables are warm-season plants, and if transplanted to the garden before the last spring frost they can be killed. Other vegetables can be planted when the ground and nights are still cold, but regardless vegetable seedlings do best when planted at the right time and the proper age.

We know smaller, stocky plants that have not started to bloom and/or set fruit adapt to the garden more easily than leggy transplants that already have small fruits hanging on them. We also know tomato plants 4-5 weeks old yield better than older transplants.

“With such pleasant weather, gardeners can’t help but think about spring (though it’s still far away). “

Older transplants suffer more shock when transplanted to the garden and produce less of a crop over the course of the growing season than transplants of the proper size and age. Specifics on this were available from my website when I worked for Colorado State University Extension, but since that site has been closed down you will have to obtain the information from my blog at SwiftsGardeningBlog.blogspot.com . Scroll down the list of topics on the right side of the page and click on vegetables. Or send me an email and ask for information on vegetable planting times.

When you set up your grow room, you need to ensure the seedlings have adequate light but not an excessive amount. A window sill is not adequate for seedlings unless you supplement the light with a fluorescent figure, incandescent bulb, or high intensity discharge (HID) light. I realize many gardeners use their window sill and are happy with the results. But if you want to improve yield, the seedlings you plant in your garden or containers need to be the healthiest plants possible. And that means the proper amount of light. Research at the University of Arizona revealed a growth increase of up to 58 percent when seedlings receive supplemental lighting.

I have small lavender plants growing in my garage under fluorescent lights. These lights have a limited depth of penetration so they need to be close to the top of the plant. Using my photon sensor, a device that determines the amount of photosynthetic active radiation (PAR) provided by a lighting system, I was able to determine a significant drop in PAR from 127 to 47 on the meter. The higher number was one inch from the tubes; the lower number was four inches below the light tubes. These measurements are recorded in micromoles of photons per square meter per second, which is a concept hard to wrap your mind around. But in essence, it means the plants need to be within an inch of the light to receive the proper amount of photosynthetically active radiation. If I was using 1,000 watt high pressure sodium (HPS) lights, I would need to place the lights 26 inches about the plants to prevent burning, but that spacing does not work with fluorescent lights. Incandescent light bulbs can burn the plants, so it needs to be about three feet away.

Different lights produce different spectrums with blue light necessary for vegetative growth and red light necessary for flower bud development. A combination of red and blue light tends to produce the best transplants and for that reason I use a two-bulb fixture with one warm white and one cool white tube. This pretty much provides the same spectrum as a light designed specifically for plants and for a lot less money. Seedlings should receive supplemental light for 16-18 hours to receive their daily allotment of PAR, so plan on putting your lights on a timer.

I have always thought it would be neat to be able to harvest lavender flowers in mid-winter. That would require a setup of high pressure sodium lights for the red portion of the spectrum necessary for flower production. I would also need to reduce the length of time the plants receive light to increase the amount of flowers. Lavender under these light conditions might even yield better than the lavender growing outdoors.

That’s something to think about.

GJ Free Press columnist Dr. Curtis E. Swift is a retired horticulture agent with the Colorado State University Extension. Reach him at Curtis.Swift@alumni.colostate.edu, 970-778-7866, or check out his blog at http://SwiftsGardeningBlog.blogspot.com. He owns Swift Horticultural Consulting and High Altitude Lavender.

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