Coleus Kong Lime Sprite is a new introduction from Ball Seed for 2015 and we're going to give them a try from seed. The seeds are expensive at about $2 apiece so we will be especially careful with them.
Introduced at the California Spring Trials the Kong Coleus are in a class all their own. You can click on this link to see the other new coleus introductions for 2015.
Many coleus varieties are advertised as being sun tolerant but in our area that means morning or half day unless you can baby them.
Karl Blume gets the credit for discovering Coleus in Java in 1853 and there have been many coleus fads over the years. I recall that in the 1970s in CA no home was without its obligatory container of coleus.
Ray Rogers' 2007 book, "Coleus: Rainbow Foliage for Containers and Gardens", is my go-to reference. If you've ever grown coleus and noticed that it has square stems, you automatically know that it is some member of the mint family.
Rogers points out that any coleus grown from seed is likely to be a prolific seed-producing variety and to realize that they will need to be pinched back to prevent seed formation.
With that said, he recommends starting the seeds 4-to-8 weeks before the average last frost for your area. Here that's April 15 so seed-starting would begin Feb. 15 at the earliest.
What's needed is shallow containers (3-inches is enough) with really good drainage, medium-textured seed starting mix, a super-fine material (vermiculite) for covering the soil surface before putting seeds on top, etc. The seeds need light to germinate so if the container is covered for germination warmth, use clear plastic or glass covering.
Disperse the seeds evenly but not densely over the surface, Rogers says. And, do not cover them.
Coleus seeds need: An even amount of moisture, a soil surface that never dries out, tepid rather than cold water, bright but indirect light, 60 to 75 degrees,as well as daily checking for germination and moisture needs.
Seeds take 4 to 14 days to germinate and if you are using fresh seeds, the germination rate will be very high. Within 2 or 3 weeks, the seedlings will be ready for their growing containers. Plan ten weeks from seed starting to planting outside according to this chart from IA State.
Coleus' preference for dry feet extends from seedling throughout mature plants in the garden and containers. Keeping the soil soggy around them causes insect infestations and wilting.