Question
Hi,
I live in Rhode Island. My mom bought me a "Primula" plant for Easter. Can I plant this outside now? My dad always told me to plant my flowers after the 1st full moon in May but I am reading that Primulas are cold tolerant. Also, is that a good rule of thumb for impatiens and begonias to plant them after the 1st full Moon in May?
Thanks!

Answer
Those pretty Primroses are technically hardy, but it is too early to put them outside right now -- one basic frost and the blooms will be damaged.  For best results, keep them cool and lit, but frost-free.

I have not heard your father's rule of thumb re the 1st full moon of May, but it certainly does sound like a reliable benchmark.  Native Americans called that the 'Flower Moon'.  Lunar Gardening in general maintains that the Moon's gravity exerts a pull on moisture flowing through plants and in Soil.

The Ed Hume Garden Almanac uses the lunar phases to recommend optimal dates for sowing Seeds, watering, lawn mowing, growing houseplants, transplanting, fertilizing, etc.  The Full Moon of any month is considered the best time to do certain things 'by the light of the Moon', including repotting, planting Seeds and fertilizing.  Garden writer Marion Owen reports that an English gardener has done his own system test, and finds they are quite effective:

'R.J. Harris, the head Gardener at a private estate near Cornwall, England, conducts his own experiments.  Each year he cultivates a selection of crops in opposition to the best practices of moon-gardening methods.  Crops planted according to the lunar cycle fare much better, he said.'

Here's her website:

www.plantea.com/planting-moon-phases.htm

Impatiens and Begonias would be planted on the same schedule as your Primulas, apparently.  It is most imperative, however, that you not expose these plants to a sudden, unexpected frost; these are not cold hardy, and you will seriously damage them, or lose them, if you are not careful.

Thanks for writing,

L.I.G.