No, I haven't actually tried this - it's just an idea. Plants cannot "feel" or suffer from wind chill in the way that people do. The thing that really gets the Acacias and certain other Southern Hemisphere plants (many of them really, and some more than others) is the combination of wind, subfreezing temperatures and low humidity. Anytime we have east winds bringing modified arctic air into the region, you will notice the humidity drops way off to about 10-20% (except in the most maritime of locales, such as Port Townsend). In this situation, the plant is severely stressed because - air movement has a dessicating effect - super low humidity has a dessicating effect - being below freezing is obviously an additional stress. These Acacias etc. do endure very cold temperatures in the wild, in some cases down to 10F, 0F or even below. But whenever they have severe frost in the wild it is always with 100% humidity and no wind. So that is why I like my ice idea, even though I have never tried it. Sure the plants will be cold but there will be no chance of them getting dessicated. It is just that though, an idea. If you can trap humidity with plastic, that might work, until the plant gets too large. But you will have to seal it off pretty well for that to work! As far as 'drier soil' we could be talking about a couple of different things. #1 For many plants, there is an advantage to allowing them to dry out in late summer so they will harden off instead of growing into the fall, which would leave them susceptible to freeze damage. Such plants can still be rained on all winter and watered and fed generously in spring with no problems, as long as you stop in summer. #2 Many alpines, xeric plants, some western natives etc. show greater cold hardiness if the soil is really gritty so that it does not collect moisture in winter (better yet, a rain cover may be beneficial for some). But they too usually like to be watered generously in the spring. I would put Acacia and most cold hardy Aussie plants in category #1. Growing them a little tough is great...we don't need to water everything all summer around here.... growing them too tough might slow them down more than necessary.

My A. dealbata var. subalpina has got to be just about as tall as the Bremerton tree, but it is a lot skinnier. It set some seed this year for the first time. It is also putting up root suckers. I didn't really plan on that! Various places in the Northwest have had severe freezes with temperatures close to all time record lows since 1990. Eastern Washington in Dec 1996. Southwestern BC in Jan 2004. Southwest Oregon in December 1998. All of these freezes were less severe in the Seattle area. That is why I think the climate is not really getting warmer overall in our region, in a way that will enable us to get away with long term survival of more tender plants. The Seattle area is long overdue. That having been said... I also think the Pacific Northwest's best microclimates for marginally hardy plants, as well as the most idyllic gardening spots, are on the islands in the Strait of Georgia. As you go north from Vancouver, influence from the outflow of the Fraser Canyon diminishes, and the higher Coast Mountains more effectively block cold air from getting west. Tofino and Estavan point are mild, but cooler year-round than the southwest coast of Oregon and too stormy for my taste!

Ive grown some acacia tortilis from seed and they are about 6 months old now. I can't find anything online about how to care for them so Im wondering if anyone has some answers for me. What kind of fertilization do they need. What pruning is best? They are getting really tall and I don't want them to get too scraggly so I pruned the top a bit. Watering? Thanks for an help

Yes, those are the caterpillars of sulfur butterflies. I planted my senna to attract them. My bush's flowers only last a few weeks anyway, and the cats don't eat enough flowers or foliage to ruin the show. For camouflage, the caterpillars are usually greenish in color if they are eating the foliage; yellow like the one in your photo if they are eating the flowers. Although photos can be deceiving, yours appear to be about the size that they will wander and get ready to make a chrysalis. Below are some photos. The chrysalis can also range in color, usually from green or yellowish-green to red.