Tree cuttings using home-made heat mat

In January I set up a home-made under-heated cutting tray.

My purpose was to root cuttings of apples and pears. Normally these are reproduced by grafting (reproduction from seed does not give true cultivars – desired characteristics are lost). If it’s easy to grow from cuttings then this should be a faster and cheaper way to produce large numbers of trees. It’s not clear how large they will grow (normally the size of grafted trees is controlled by selecting the rootstock). I’ve got plenty of space so I want to find out. It’s not clear how soon cuttings will fruit – hopefully similar to grafted trees (which should be a load sooner than trees from seed).

I used a 137 watt waterproof LED light rope buried under the soil in a 8cm deep tray. I covered the tray with bubble-wrap and poked the cuttings (dipped in rooting hormone) through into the soil. I poked a funnel through so I could water occasionally. I placed the whole thing in an unheated out-building (by a window to give a lot of natural light. I measured the soil temperature occasionally and it was always in the low 20s (Celsius)  which I think is about right.

Results:

  • Grape vine, fig, red and white current cuttings had a good degree of success. I have propagated these before without heat so I’m not sure how much the hear really helped.
  • Two of the many apple and pear cuttings I took, that’s less than 2%. Not a good rate of success but it shows that it can be done.
  • Nothing else rooted – I tried various shrubs and trees (not huge quantities of them, so this result isn’t statistically significantly worse then the apples/pears).

Thoughts for the future:

  • Might be simpler to put the light rope under the soil tray instead of in it, like this.
  • A deeper tray would hold the heat and moisture better and would allow longer cuttings.
  • Maybe I should have sprayed the cuttings to increase moisture, the air was very dry (and the bubble-wrap on the soil surface meant very little evaporation). Or used a lid over the tray instead of the bubble-wrap on the soil)
  • The apple tree cuttings I took were mostly very thin (less then 5mm) pruning off-cuts. Thicker cuttings might have been more successful.
  • I didn’t have a thermostat, it might have been too hot or too cool.
  • Maybe I should have set it up in a warmer place (in the house instead of in an outbuilding)
  • Lots of discussion here on the soil (or other medium) to use. I used a mix of course sand and peat-free seed compost, possibly I should have used something more free-draining (also my trays had no drainage holes, I relied on watering just enough so as not to water-log but not to let it dry out – but it was under bubble-wrap so hard to tell how moist it was)

I’ll try again next year – hope for better success rate with apples and pears.