Since You Asked...Dean Hill

For the inaugural Q&A, I thought it appropriate to chat with the co-author of Weatherproofing Your Landscape...the book. Emmy-nominated landscape architect Dean Hill is co-host of the popular DIY Network program, Grounds For Development.

(You just never know where Dean will pop up next! Catch him on the Rachael Ray show next Monday, September 26th. Check your local listings for the time. And keep up with Dean on Twitter @greendeantv.)

Q. Dean, as far as extreme-weather events are concerned, what are the advantages of using trees and shrubs that are native to a local area?


A. One of the biggest advantages is that native plants can be genetically and historically adaptable to extreme weather events. For example, there are oak trees that survive and thrive after being involved in a fire event, and there are bald cypress trees that thrive in flooded, low areas.


The most important consideration is to find out what plants are native in your area, ecoregion and/or ecological community. (Plants adapt to specific areas,  known as ecoregions or ecological communities. That’s logical—plants that like water are going to grow where there is water, and plants that like dry are going to grow where it is dry! All of the plants that grow together in these specific areas form a community. These communities are where you can get ideas for your plantings.)


And always remember to put the right plant in the right place!  Don’t take a plant that grows in the wet and expect it to grow in a dry area.  Look around at natural areas where you live and emulate nature.     

Welcome to the Friday question-and-answer feature. Feel free to leave your own questions related to weatherproofing your landscape—or recovering your landscape from an extreme-weather disaster—in the "comments" section on any Weatherproofing Your Landscape posting.

Q. How difficult is it to convert a conventional landscape to native?

A. Conversion is not difficult. The best part is that it can be exactly the same as designing for a “conventional” landscape. Natives lend themselves to easy incorporation into mixed planting beds, perennial beds and even shady, woodland plantings!


As an added bonus, native plants that are incorporated into shady, woodland settings are less likely to be eaten by browsing deer that can be an extreme, ongoing problem.

Q. Can the conversion to a native landscape take place in stages, over several years?

A. The conversion can easily take place in stages. For do-it-yourselfers, if you have limited or no experience with native plants, start small! 


Do some online research. Choose a couple of attractive native perennials that you like, and plant them in a favorite bed. Keep expanding your knowledge and your plant palette.


Make sure to look for state native-plant organizations and associations. Some of these advocate groups—of  which you don’t have to be a professional to be a member—have annual sales of native plants that come with no-cost expert advice.


I have found native plants to be infectious...almost obsessive. Any time I travel to a new place or design in a new area, the first thing that I look for is information on the native plants of the area. This gives me insight into the local context, and also helps me understand why this place is unique and different from the next place!

Killer Mulch

Lately, I've been amazed and disheartened to notice how many trees die of mulch. That's right: mulch.

With extreme-weather events growing more and more prevalent, landscape trees and shrubs must contend with hurricanes, tornadoes, ice storms, droughts, wildfires, flooding, lightning...sometimes it's like a war zone out there.

But since mulch has become a decorative addition to many landscapes, surpassing its purely functional purpose of the past, what should be a benefit to plants is increasingly becoming an outright killer. The problem is with "coning"—piling mulch in a deep cone shape against the trunk.

You've seen this practice for years in shopping-mall landscapes. Now it's becoming a common sight in residential landscapes.

Coning puts a plant at risk in three ways. First, piling mulch around the trunk can cause trunk rot. Second, mulch that is piled deeper than four inches can suffocate roots, especially those of young transplants. And third, new roots can grow directly into these mulch cones—then, because mulch dries faster than soil, those roots are quick to die during drought conditions.

To prevent this from occurring, keep mulch at least a foot away from the trunk, and limit it to four inches deep. Use light materials, such as cedar mulch, to promote air circulation (yes, roots do "breathe"). And pull mulch materials back altogether during persistent wet spells.

Landscape plants are threatened enough by extreme-weather events. It's downright painful to think of them dying because of what was intended as an act of kindness.

A Burning Question

This summer, I planted a new crape myrtle inside a walled, sun-blasted courtyard. With little root system to sustain it, the young shrub wilted badly under temperatures that reached 100F to 110F degrees in the shade day after day. Tender leaves began to go brittle.

With unrelenting, record-setting heat for three months running, this summer has been especially brutal to even established landscape plants. I've seen outer leaves on the crowns of mature Japanese maple trees fried to a crisp. And then there are the sunscorched evergreen hedges grown next to reflective surfaces.

A wall—or even a parked vehicle—exposed to direct summer  sunlight can turn that area into a broiler. Any plant grown in close proximity to reflective surfaces during periods of extreme heat is in danger of scorching. For low-growing plants, there is a short-term remedy.

Once I began tossing a sheet over my crape myrtle during the heat of the day, it perked up and made it through the summer in good shape. Low-growing hedges can benefit from the same protection. (Plants growing near reflective surfaces need more water, but watering won't prevent sunscorch.)

Unfortunately, there isn't much you can do about a large tree that is suffering sunscorch, other than make a better choice of species the next time. Most trees that suffer burned foliage during extreme heatwaves are either too tender for such extremes—or are understory species, adapted to filtered sunlight, that were planted out in full sun.

As summer draws to a close, it's time to take stock. If sunscorched  twigs are brittle, they've died and need to be pruned away. If the twigs remain flexible, wait until spring to see if they sprout new foliage. If the same problem occurs summer after summer, the long-term remedy is to remove the plant and replace it with a more heat-tolerant species.

As for my crape myrtle, I expect the fast-growing crown to be above the top of the courtyard wall by next summer, safely out of range of the reflected heat.