Hello all. I did a bit of searching and didn’t find any topics on this, though I’m sure they are on here! I’m going to be bench grafting some apples and pears and had planned on doing so mid April when I think I can move them outside. I purchased my scions and rootstocks from Fedco who will be shipping them out mid March.
1: Should I store the scions and rootstocks in the root cellar until mid April, or should I graft them then store them in damp sand till April, or should I graft them and boot them outside as soon as I get them?
2: I’m planning to experiment with potting some for a season and putting some in nursery beds (as was suggested here). When is too early to put them outside? What temperatures are too low for freshly bench grafted trees?
3: Should I heavily mulch the trees with straw until late spring?
I really don’t have a ton of room for these guys to be inside and my root cellar doesn’t stay that cold (in the low 50’s) as it is below the floor of my house, which used to be a general store 140 years ago and I’m sure was kept much cooler than I keep it now.
I’m in Northern Illinois, Zone 5b. I get my apple and pear rootstock a little before April 1st. When they come, I dig a hole in my garden bed. Then put the roots in the damp soil. Pack them in a little. April 1st I bench graft. The next day I put them in individual buckets, but an exterior bed is probably better. The apples always get 90%. Last year a heat wave came, none of the pear made it. Either plant out the pear for a year and then graft, or graft onto a side branch and leave as much of the rootstock as possible.
I’d say they can be put outside a couple or three weeks before your last frost date. Apples and pears are pretty resilient. I’d graft them up as soon as you receive them and hold them indoors cold (like 40-55 out of light) in damp sawdust or sand if you can. They will start the graft callousing process. When the buds start to push I plant them outside.
Great response, I do similar with all my potted plants I cover them with a dark trash bag for about 3 weeks in my greenhouse, the more you can give them temperature well above freezing to about 70F the quicker they callous. My greenhouse gets down to 40F at night but goes up to mid 60s each sunny day. If a cloudy day it stays about 40-42F but callousing is not interrupted as long as it’s not freezing.
Dennis
Kent, wa
The reason for covering is to preserve the limited stored energy in the scion, remember it got its energy stored as sugars doing photosynthesis! It cannot replace any energy until callousing is complete and the xylem/ Phloem plant cells are connected thru the graft union. When callousing is complete the scion can efficiently replenish its energy need to push buds to growth because fluids can now flow freely back and forth from rootstock to the scion. It usually takes most fruit types about 3 weeks at optimum temps to fully callous, thus denying sunlight just keeps the buds calm until you are ready to initiate bud break. This way the grafter controls when it happens.
Callusing temperatures of Fruit and Nut trees
Try it!
Dennis
People ask me what are optimum callusing temperatures to ensure a good percentage of viable grafts.
Nectarines/Peaches – 18-26 deg C. ( 64.4 to 78.8F)
Apricots/Cherries – 20 deg C. ( 68F)
Plums – 16 deg C. ( 60.8 F)
Apples/Pears – 13-18 deg C. ( 55.4 to 64.4F)
Walnuts – 27 deg C. (80.6 F)
Grapes – 21-24 deg C. ( 69.8 to 75.2 F).
Figs - 23.9- 29.4 deg C. ( 75-85 F).
Do not forget tissue damage for most temperate fruit will occur at temperatures over 30 deg C. (86 F). So if you use electrical tape or any dark materials to graft, cover them with aluminum foil to prevent the sun from killing healing tissues.
Temperatures either side of the optimum will also work, but the percentage take will be reduced. See graph below for walnuts.
Dennis, when letting the trees callus I assume it’s ok to keep them damp but unplanted? Since my materials are coming in mid March, I’ll get them grafted and let them callus up in a cool dark room for about three weeks. Should I then move them into a cold area 35°- 45° F until they are ready to go outside in late may?
Is coconut coir a suitable medium to keep them moist in?
Hi Luke
Coconut coir, sawsdust, spagnum moss are all great Mediums. I would keep them in the dark room callousing until the chance of dipping below 32F at any time of the day has passed. Callousing can take much longer in a cool vs warm room, but if you are expecting in your area a long cold spring with frequent freezes, the cool room may be better since a warm room just like sunlight will encourage buds to swell. You are wise to have a plan. So consult your historic weather to determine the average lows during the months of Mar to Apr for your location and plan on storing your rootstocks until grafting makes sense. Perhaps a delay of grafting is your best bet, you can best determine your course of action once you study you historic weather data. Apples and pears are pretty forgiving, a little late is better than grafting too early
My thoughts.
Dennis
