According to Hartmann and Kessler’s authoritative major text on plant propagation, “Success in grafting depends 45 percent on preparation . . . 10 percent on craftsmanship, and 45 percent on the aftercare of the grafted plant.” So while it is a lot of fun to work on your ninja knife skills, you should consider spending four times as much effort on aftercare!
To craft a good graft, you need to know its specific step-by-step—a whip and tongue is very different to make from a side-veneer. By contrast, aftercare is very similar for all grafts. You just need to know a few common-sense principles explained here.
Summary of Aftercare of Grafts
A graft is very much like a tender seedling. Have you ever done the early spring chore of moving home-grown vegetable seedlings out into your yard? That process of slowly acclimating the seedlings to the harsh outer world, called hardening off, is a lot like caring for a new graft. Moderation of temperature and moisture swings while guiding conditions to near mid-spring-like levels is the goal.
None of the steps are fancy; gardening is great like that. The pros use warm water in PVC pipe for heating and piles of sphagnum moss or sand for humidity.
Graft Aftercare Principles and Tips
Recheck wax in three to five days. Maintain a good seal on the graft. The seal is your first line of defense against humidity loss. Your graft is a living, growing thing. Expansion and temperature changes over time may crack your graft’s wax seal or make improper tying apparent. Check your grafts regularly, especially after a major temperature or humidity change event. Reseal them as necessary.
Try to keep humidity high. Humid, but not wet. We don’t want water droplets entering the graft; these can get between stock and scion and interrupt cambium contact. But dry air will draw water out of the graft and kill the scion. If you’re outdoors, there’s not a lot you can do except try to have shade (see below). Indoors, a water tray under your grafting area or, for the more hands-on, mist spraying nearby are ways to go.
Control temperature with high shade or other methods. If your grafts are out in the field and you can’t move the plants around, it is a good idea to have them under a leafy canopy from a nearby tree or from branches of the rootstock that you leave behind for the hotter summer, just to provide shade on the graft. Direct summer sun can heat-kill cells used to being shaded at that time of year, especially your tender graft tissue. No canopy nearby? Consider building a temporary tent of shadecloth purchasable from nurseries. Even a white bedsheet hung from laundry lines may work.
Suppress rootstock growth. The rootstock is a plant with roots, stems, and leaves or buds capable of producing leaves. The scion is a weakling compared to the stock it sits on. In order to keep the stock from sending all its energy to its own parts and not to the scion, you must cripple the rootstock. Aggressively prune off (or thumb out) rootstock growth below the graft union, including ground suckers. Do this quickly. Rootstock growth is wasted growth.
Watch for scion growth. Healthy growth from the scion means the graft union has taken. This is good to know, but your work is not done. You still need to be careful for a weak union that could brek in wind, and you need to keep directing as much stock energy as possible to the scion, via pruning.
Prevent girdling. Girdling happens when the growing scion expands and gets choked by the tight wrapping holding it in place. To prevent this, gently cut off the tape or string you tied with once your scion grows healthily. Do this once you see your scion leaf out.
Hartmann, Hudson T. and Dale E. Kester. Plant Propagation Principles and Practices, 7 ed. 2002.