The Q&A Archives: Thinning Agastache

Question: I started Agastache (giant hyssop) from seed last year and they barely came up. This year they're booming - and are about 4 ft tall. How far apart should these plants be? Can I thin them now? Will they transplant at this size? My garden is shaded in the morning and late afternoon, with sun from 10 - 4. Thanks.

Answer: Agastache plants reach heights of 2'-6' and should be spaced about 12" apart. They self-sow readily, but can sometimes be hard to deliberately start from seed. The seeds can take from 30-90 days to germinate and prefer soil temperatures of 55F. You may have started your seeds in warmer soil, which might account for the poor germination rate you experienced. Now that your plants are up and growing, it would be best to divide them in early spring before they bloom, or wait until early autumn to divide them.

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