Timing clones

I am growing 25 plants in a 32-square foot 4′ x 8′ garden lit by one 1,000-watt and three 400-watt HPS lamps. I place the plants into seven-gallon containers and grow them vegetatively for about a month in a peat-based soil that I enrich with organic fertilizers and lighten up with perlite. Then I switch into flowering for about 10 weeks. I have four varieties that ripen successively over a four-week period. When the first group comes out, it gives the rest more room to spread out. When the last plant is removed, I clean and wash the garden. Then I plant new clones.
My problem is that it takes me about 15 weeks per crop and I take clones from my plants just before I force them. The result is that I have clones growing for 10 weeks and they grow too big for the clone garden which is 2′ x 4′ and lit by four four-foot cool-white fluorescents. What are my options? Are there ways of controlling the growth?

Fred W,
Burnaby, British Columbia

There are several ways of slowing down the growth of clones. The first is to delay planting. You can store the cuttings in the vegetable chiller section of a refrigerator in a plastic bag, the way you?d store lettuce for about two weeks or longer. This will weaken the clones a little and they will have a lower strike ratio. However, it may be a worthwhile trade-off. After the clones are cut they can be left unpruned or trimmed for planting. Then dip them in a 1% hydrogen peroxide solution to sterilize them to prevent infection. A 1% solution is made by diluting one part drugstore hydrogen peroxide to two parts water that has been boiled and cooled. When you are ready to plant just take the clones out of the bag.

The cutting state is perilous for plants so a good environment that promotes active growth minimizes risks. Once the cuttings have formed roots and are growing new leaves, their metabolism can be slowed down. There are a number of ways to do this. Plant metabolism and light requirements slow down in a cool environment. At 45-50?F (8-10?C) the plants remain in a nearly suspended state. They require only 150 watts of fluorescent per square meter (15 watts psf) and very dilute fertilizer. When you are ready to jump start them, place them in a warmer environment with brighter light and more fertilizer. They will quickly respond to the change in the environment.

Even if you can?t cool the clones to 50?F (10?C), you can decrease the intensity of the light and provide diluted water-nutrient mix. The growth rate will slow.

Another possibility is to increase the size of your vegetative section just a little bit and grow the clones out a bit so they are larger when they are placed into the flowering section. This would decrease the time between harvest by three weeks or so, from 15 weeks to 12. After the plants are cloned they could be planted in one to three-gallon containers to encourage growth in the vegetative section. They are transplanted when the garden has been prepared.

You could increase the size of your vegetative section just a little bit and grow mother plants. You would take cuttings from the mothers only four weeks before they are to be transplanted into the flowering room. You only need 10 or so cuttings of each variety every three or four months. So you can keep the mother plants compact by trimming them back.

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