Plant Isolation Required to Prevent Cross Pollination
Answered by: Conrad Richter
Question from: Joe Handley
Posted on: January 11, 2004

I am a new customer of Richters and I love your catalog and believe I will be very happy with the seed and products I have reciently ordered.

I retired in 2002 from the construction industry and in 2003 began selling at our local farmers market. I have always had a large garden and lots of family handed down herbs and perennials. I was amazed at the demand for herbs at our local market and that no vendor had sold herbs at our market. I could not meet the demand with my small stock and found a need for fennel, chervil, and cilantro which I normally do not grow.

I always grew a large patch of dill of an unknown variety given to me from my great grandmother. Market customer bought all the dill weed I could supply and begged for more,

When I was ordering from your catalog I found that Cilantro, Dill, and Fennel can cross pollinate and lose their unique flavor. I thank Richters for the information as I said you have a nice catalog.

We don’t say that in our catalogue. As far as I know, coriander, dill and fennel do not cross pollinate -- that is, they don’t pollinate across species. However, they will cross pollinate with another variety of the same herb if close enough. For example, if you planted our ‘Mammoth Island’ dill next to your great grandmother’s dill, you might get some cross pollination, and any seeds you collect could show characteristics from both varieties. But your dill variety will not cross with coriander; so as long as you don’t plant another dill variety, you can safely plant coriander and fennel and continue to collect seeds from your dill variety.

Finally the questions: How much distance between these varieties is required to stop cross pollination?

If you decided to grow a new dill variety along with your variety then you should separate the varieties. If you weren’t saving your seeds then cross pollination would not be an issue because even if two herbs cross pollinated, the quality of the harvest will be unaffected. The effects of cross pollination do not show up until the next generation is grown from the resultant seeds.

Pollination occurs by both insects and wind, so you probably need at least a half kilometer (quarter mile) to reduce the chance of cross pollination.

A. I have only a 1 acre garden so is isolation even a possibity?

No.

B. Does cross pollination affect the current years produce or only the plants produced from seed from the cross pollination?

No, it only affects the plants produced from the seeds.

C. Your seed is quite reasonable and though I usually save my own herb seeds I could order and reseed each year, with the exception that I would like to keep the viability of the dill I have grown for over 30 years. Are there any alternatives to plant isolation?

In general you can prevent the plants from flowering, but this is unrealistic in the case of these herbs. And, in any case, you want your grandmother’s dill to flower and set seed so you can keep the variety going. Probably the safest thingt is to avoid planting another dill variety.

Any information you can share would be appreciated. Thank you very much for reading my e-mail and Richters for their catalog. I am excited about the PotMaker I ordered from you folks and hope it works well for me.

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