Expert: C.L. Fornari - 4/9/2007

Question
Hi. I live in Denver CO. Zone 5. I planted some morning glories in jiffy pots about 3-4 weeks in my kitchen. They have all come up and are about 3 inches tall. When is a good time to plant outside in my area? I plan on planting them on the south side of my house, were they will get sun most all day.  

Answer
Steve,
It's not so much the zone you live in but the last average frost date AND night time temperatures.  Morning glories are one of the tender annuals that do not like the night time temperatures to go much below 50 degrees.  

Since they are very tender if the temperatures dip into the 40's they'll be damaged, and if there is even a light frost they will die.  When I googled "Average Last Frost Denver CO" I got a range of dates that all clustered around the first or second week of May, depending on where in Denver you live, so my guess is that you won't be able to plant them until then.  But watch your long-range forecast and pay attention to how cold it is supposed to get at night...when those temperatures are at 50 and above consistantly, you can put them out.

My guess is that you'll have to keep them inside for at least three more weeks, and if you don't take measures they will soon grow into a tangled mess with each other...so plant the tiny peat pots into larger containers and put bamboo stakes in them for vine support - you'll probably have to tie the vines up with a soft, stretchy tie, and keep the pots far enough away from each other so that the vines can't reach the neighbors.

If you fertilize, only do so mildly and a minimum number of times until you plant them outside...fertilizer will just make them grow faster and be more prone to bugs indoors.

BE VERY ALERT FOR APHIDS - look for small bumpy insects on the tips of new growth, and very tiny white "litter" or stickyness on other leaves.  Treat with insecticidal soap at the first sign.

By the way, in looking for the last frost date for Denver I came across this article - looked pretty good: http://www.rockymountainnews.com/drmn/garden/article/0,2777,DRMN_23954_5453184,0...

all the best,
C.l.