@Elestrial 7a you're welcome! Hume isn't difficult to root compared to many others but it isn't AS easy as the multiflora types. That thick cambium really does the job for rooting and budding. It's the tissue which calluses then differentiates and forms roots. It's what heals together with the cambium tissue on the back side of the scion to form new capillaries so nutrients can flow between that of the stock and the scion or graft. If you cleft graft fruit trees, you line up the cambium of the graft variety with the cambium of the stock. Cambium is not only the circulatory system of the rose but it's also stem cell material. If the plant is wounded, it forms scar tissue to seal and heal the wound. If a piece of one plant is inserted into a second plant, it knits together to form new circulatory tissue so the new part becomes part of the whole. If cambium tissue is exposed to cool, dark, damp conditions, it forms callus which then forms roots. When that tissue exists as a thicker layer under the bark in the entire plant, some wondrous things can be accomplished. De la Grifferaie is also multiflora type and it's the stock used to make 8' tall (and sometimes taller) weeping standards. Huey flows sap to about 3', 4' is pushing it. IXL has pushed it over 5'. Burling has created up to 6' tall weepers using Pink Clouds. I budded four buds of Baby Faurax in a 4' Hume whip in 1994 I rooted and they all took and grew. I gave that plant to a gardening client in 2015 when we sold in Encino and moved to the Central Coast. It isn't a multiflora type, but it's good to at least 4' in length in my experience.

How much heat? The San Fernando Valley north of LA gets HOT. It's considered a Zone 9b, as is where I am now, however they are worlds different. The Valley gets warm quickly and remains warm most of the day. Here, we're 9 miles from the Pacific and the ocean breeze keep it rather chilly. The "heat" shown on the chart below is in the full sun, for an hour, perhaps three on a really "hot" day. Then, the ocean breezes kick in and it's like standing in front of a walk-in freezer. In Encino, I planted my rose seeds in November as that's when the temperatures would traditionally be cool enough to allow for germination and maturation before the summer heat hit. Here, I can literally pollinate year round and plant most of the year because the temps remain low enough for germination as well as not so high it cooks the seedlings.

Old climate where there was heat.

Here.

I wrap cuttings to get them to callus then plant outdoors to allow them to finish rooting and growing. Huey and Fortuniana would not keep going after being unwrapped. IXL, De la Grifferaie and Pink Clouds do here. I obtained 44 rooted Fortuniana stocks and grafted to them in August when we CAN get heat. Everything simply turned black. The multiflora types all pushed growth.

Does that help give you an idea?

As for budding, Hume is best for "T" buds like Huey, where you have to wait for the stock to really be vigorously growing so the sap is flowing fully and the bark lifts easily. Pink Clouds and the other multiflora types can be "T' budded, but that thick cambium allows you to chip bud very easily and that is significantly easier for you to learn to do. It requires much less skill and practice. Burling has long promoted Pink Clouds because it remains in condition for budding much of the year. The heat lovers are best when the heat is highest so the sap is flowing fully. There are many tutorials on line how to chip and "T" bud. I have a blog post about it here, with photographs. http://pushingtheroseenvelope.blogspot.com/2014/11/chip-budding.html There are a number of other posts on my blog about what I'd budded with photos of how they turned out. And, if you're interested in wrapping cuttings for rooting, you can start here and then scroll forward to glean the discoveries and suggestions as they revealed themselves. There are even posts about rooting longer whips for standards. http://pushingtheroseenvelope.blogspot.com/2011/05/wrapping-cuttings.html