Varietal Differences In Marijuana Growth

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Ask Ed: Questions and Answers - Varietal Differences

Ganja Guru Ed Rosenthal answers a grow question about why plants from the same type of seeds may look significantly different.

I started two plants from the same seeds; they sprouted within one day of each other but they are growing differently. One has an umbrella-like canopy and the other has leaves that grow upward like a palm tree. They are both very healthy. Why are the plants so different?

- Cali, Colombia, Pedro-Newbie Farmer

You didn't mention where you obtained the seeds, but I suspect it was from a seed company. Most marijuana seed companies sell hybrids that vary quite a bit in their characteristics. Even though a certain package might claim the seeds are a variety, they are often really hybrid complexes with a spectrum of characteristics. The reasons for this are both genetic and logistical.

Logistically, classical breeding requires large numbers of plants and careful record keeping. Because of laws and other legal/security reasons the amount of space and number of plants is limited. As a result, available varieties are not inbred for five or six generations to make the plants more homogeneous.

F1 hybrids, made from a cross of two true breeding varieties, are uniform genetically but have a heterogeneous gene package: half their chromosomes come from each parent. When they are crossed, the second generation (the F2s) receives random assortments of genes resulting in plants that vary widely in their characteristics.

Sometimes seed companies say that there are two phenotypes and one is found 25% of the time and the other, 75%. The reason for this is that one of the versions of the alleles (gene) is dominant over the other. Thus, only the 25% of the plants that have the recessive version of the allele will exhibit that characteristic. The plants that have one of each allele will look almost the same as the plants that have two copies of the dominant version.

Seed companies expect that people are going to grow out as many seeds as they get and choose the best plant(s) as clone mothers. So, they figure, when the customer gets an assortment of versions of the "variety" s/he can choose the best for her/his situation. This, they say, gives customers the best chance of getting the right version of the "variety" for their needs.

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- written by Ed Rosenthal, Cannabis Culture