rose geranium and lemon verbena cuttings taken oct and potted in sand indoors under lights. doing great. new tip growth which i pinch out and side shoots which i am leaving on until they get as high as main top stem. should i start feeding them in addition to water. they have another 5 months indoors. i don't want them to get big and gangly. i just want them strong and ready for outdoor transplanting. i'd prefer not to move them into soil pots now. what do you think? they are about 5-6 " high. thanks
I was always taught to pot cuttings up as soon as good root growth had been established. This would be partly because of the feeding issue. As growth would slow down during the winter months naturally, you are correct in not wanting to feed them much now. That means very little nitrogen. I generally use a weak kelp emulsion, which has limited nitrogen in it, over the winter months to promote good root development while not promoting top growth. You also want to be careful about not over watering for the next few months.
Rocky--growing stuff under lights in the winter often presents this problem. Things can grow so rapidly it's hard to keep them under control enough so they will even fit under there before they can get planted out in spring. Personally I do give my stuff some liquid fish (despite the smell inside!) every so often, since a nitrogen deficiency won't produce the best plant either...some kelp other times, and just enough of these to keep the plants looking green and healthy. Keeping plants dry is good in the greenhouse where they have very short daylight periods right now, but under the grow lights they need a bit more moisture as they are not dormant. Interestingly, Carl Whitcomb has done decades of research on fertilizing, and found much better rooting and subsequent plant growth of almost all species using some osmocote and trace minerals right in the rooting medium. I have started to experiment with this and seem to find this is true, cuttings stay greener and healthier than those in an inert rooting mix.
It's the same as not fertilizing newly planted stock because it's newly planted. If there is a deficiency, the plants need to be fertilized, whether they are newly stuck cuttings or newly planted finished plants. Cuttings will have been living off whatever was in them when they were first taken and are probably like bears coming out of hibernation by the time they have made new roots and started top growth--as are overwintering hardy plants in spring. The well lit rooting setup is providing an artificial summer, your geraniums are far from dormant and should be given the full treatment.
Oops---my mistake. I apologize. Missed the "under lights" bit. I use a regimen of fish (somewhat weaker than normal) and kelp emulsions alternately under lighted conditions. One of the reasons I use the kelp is because of the trace minerals in it. I have had much better results with seedlings holding back a bit on the nitrogen and promoting good strong root growth. The plants are slower to achieve top growth at first, but they more than make up for it later on. They also generally are much healthier plants.
