All posts by Jan Nelson

I am a landscape designer and consultant in the Santa Cruz mountains in California. I write a weekly gardening column for the Press Banner newspaper. I am also a Calif. Advanced Certified Nursery Professional and managed The Plantworks Nursery in Ben Lomond, Ca. for 20 years.
Design trends

This & That From The Internet

CZU wildfire smoke. Photo taken August 18, 2020 before the fire reached my house.

My friend Evan is a computer whiz and designed my website and blog. He is often researching on the internet and forwards me interesting tidbits of information about plants whenever he comes across something exceptional. I am always amazed what nature does to survive and prosper. Here are just a few interesting facts you might find fascinating, too.

Did you know that trees don’t like wildfire smoke anymore than we do? From a publication called The Conversation ( www.theconversation.com ) which features science and technology articles written by experts, I learned the following facts:

When smoke overwhelmed a research site in Colorado that was studying air quality and ecological effects of wildfire smoke, atmospheric and chemical scientists were able to watch in real time how the leaves of the nearby pine trees responded. Turns out “They responded a bit like us. Some trees essentially shut their windows and doors and held their breath”.

Plants have pores on the surface of their leaves called stomata which take in carbon dioxide and release oxygen as well as other chemicals in the air around them. Smoke from recent wildfires shows up even in grapes and affects the taste of wine.

When wildfire smoke travels long distances, the smoke cooks in sunlight and chemically changes. Mixing volatile organic compounds, nitrogen oxides and sunlight will make ground level ozone which can cause breathing problems as well as slowing photosynthesis in plants.

The research group in Colorado didn’t set out to study the effects of wildfire smoke on plants. As we know too well, 2020 was a bad year for wildfires. When thick smoke came through the field where they were working, they did their usual tests to measure leaf level photosynthesis of Ponderosa pines. They were surprised to discover that the tree’s pores were completely closed and photosynthesis was nearly zero. The trees weren’t inhaling the carbon dioxide they needed to grow and weren’t exhaling the chemicals they usually do. They were effectively holding their breath but not before having been exposed to the smoke.

It’s unknown how long the effects of wildfire smoke lasts or how repeated smoke events affects plants, including trees and crops.

From a newsletter called Aeon, I was reminded of the extraordinary complexity of plants behavior and the relationship with their environments, each other and with other living beings.

For instance, most plants respond to damage to their leaves by releasing volatile organic compounds (VOCs). Some of these activate stress related genes, some have antibacterial and anti fungal properties. Some VOCs specifically repel the attacking herbivore with nasty taste or toxins and some plants can identify which specific herbivore is attacking and produce different responses accordingly. Even more interesting, some VOCs attract predators of the insects that are attacking the plant. An attack by an herbivore can also induce the plant to produce more nectar which encourages insects easy from the leaves.

I won’t go into the philosophy of plant behavior outlined in the article but it was most interesting. But that’s all for now.

Design trends

All About Dry Creek Beds

Coming from a meeting with a client in Scotts Valley today I saw a really well designed dry creek bed. I didn’t get a picture today but I’ll go back, it was that good. How will this year’s La Niña affect our rainfall ? According to NOAA (National Oceanic & Atmospheric Administration) our chances of La Nina winter rains are average to slightly above. So with winter fast approaching you may be wondering how to channel that extra rain that runs down your property and do it with style. Here are some tips.

A dry river bed can slow runoff, spread it out and sink it back into the soil. Connected to a downspout they keep even more rainfall on your own property. sA dry river bed is a rock-lined swale that uses rounded river rock in addition to vegetation to allow runoff to soak into the ground. Make sure there is a 2% slope from beginning to end to ensure that water is conveyed away from your house to the desired location. Non-woven geotextile fabric is often used underneath the rock.

You can create a depression or rain garden at the end of your dry river bed and plant it with plants that tolerate wet feet in the winter. Both a dry river bed and a rain garden allow water to sink back into the ground. The plants remove pollutants from runoff from roofs or other impervious surfaces.

A rain garden might be a simple, shallow depression filled with plants that can flourish in both moist and dry conditions. The size and depth will depend on your how much water you need to capture in a winter runoff

Sometimes a dry river bed will receive so much runoff that a dry well or dispersal pit is installed at the end. If you have a high water table or clay soil the water may not always soak in fast enough and an overflow device like this is needed. The goal is to keep water on your own property and not in the street or the neighbors’ yard.

There are good looking dry river beds as well as bad looking ones. A quick Google image search will show you what I mean. Your goal is to create something that looks like it belongs right where it is. The plants, the accent rocks, the cobble, the location – all need to work together.

If your property has a natural slope follow the natural terrain if possible. You can install a dry river bed on flat land also by creating a channel for the river bed to follow. Keep in mind that even a dry river bed is more interesting if it is not all visible at once. Soft, flowing curves and bends create a natural look.

Start with the rocks and cobble. Rounded river cobble looks most natural for the creek bed. In nature, water flowing down a river would round off sharp rock edges to produce cobble of different sizes. A river never has just one size of rocks and yours shouldn’t either.

Accent rocks can be any type that you like as long as you get a variety of rock sizes and shapes. Use the larger stones to direct and channel water. Placing rocks on the outside of a curve creates a more natural look.

As in all gardens there is always a bit of maintenance to keep things looking and working great. Weeding in the first couple of months while plants become established is important. Replenish mulch as needed until the plants grow in.

Periodically remove leaves that have landed in your river bed and reposition rocks moved by runoff to keep your dry creek bed working for you when you need it. Also don’t start your dry creek bed too close to the foundation of your home if that area is flat. You can direct the water through a drain pipe connected to a downspout to a lower starting spot in your garden.

So whether you are adding a dry river bed to add interest to your lawn-free landscape or to double as catchment for winter storm runoff, make yours look like it’s always been there.

Design trends

What To-Do in the September Garden

Gaura – a perennial that attracts hummingbirds and blooms for a long time.

Summer is winding down. It’s still warm during the day but the nights are cool and there’s less and less daylight hours. The soil is still warm so it’s the perfect time to start thinking about planting. Like the saying goes, “gardening is a way of showing that you believe in tomorrow.”

Gardening makes us learn new things. If you water less frequently, some plants may decline or even die eventually. Remove those that do and replace them with plants that will thrive with less water.

Fertilize shrubs lightly one last time if you haven’t already done so last month. All shrubs, especially broad-leaved evergreens such as rhododendron, pieris, camellia, hebe, need to calm down, stop growing and harden off to get ready for the winter cold. Some plants have already set next year’s buds.

Roses especially appreciate a bit of fertilizer now, encouraging them to bloom another round in October. To keep them blooming make a habit of pinching and pruning off old flowers. Always cut back to an outward facing branchlet with five leaves. There are hormones there that will cause a new rose to grow much sooner than if you cut to one with only three leaves. You can always cut lower on the stem if you need to control height.

Deadhead flowering annuals and perennials in the ground as often as you possibly can. Annuals like zinnias and cosmos will stop blooming if you allow them to go to seed. The same is true of repeat blooming perennials like dahlia, scabiosa, echinacea and lantana. Santa Barbara daisies will bloom late into winter if cut back now. These plants know they’re on this earth to reproduce. If they get a chance to set seed the show’s over, they’ve raised their family. Try to remove fading flowers regularly and you’ll be amply rewarded. If you want to start perennial flowers from seeds this is the time so that they’ll be mature enough to bloom next year.

Now through October, divide summer blooming perennials like agapanthus, coreopsis, daylilies and penstemons that are overgrown and not flowering well. You can also divide spring blooming perennials like candytuft, columbine, astilbe, bergenia and bleeding heart but sometimes they don’t bloom the first spring afterwards due to the energy they use re-establishing themselves. If you’re on a roll out in the garden, go for it now.

It’s still a little hot to plant cool season veggies starts in the ground. They appreciate conditions later in September when the soil is still warm but temps have cooled. It is OK to plant seeds of beets, carrots, spinach, arugula, mustard, leeks, onions, peas, radishes and turnips.

If you aren’t going to grow vegetables in the garden this fall consider planting a cover crop like crimson clover after you’ve harvested your summer vegetables.
It’s never too soon to start planning for erosion control in those areas that caused you problems during last spring’s storms.

Cut back berries vines that have produced fruit. Canes of the current season should be trained in their place.

Spider mites are especially prolific during hot, dry weather. Sometimes you don’t even know how bad the infestation is until all your leaves are pale with stippling. Periodically rinse dust and dirt off leaves with water. Spray the undersides of infected leaves with organics like insecticidal soap switching to neem oil if they build up a resistance to one of the pesticides.

Grevillea lanigera ‘Coastal Gem’ , a goundrcover that attracts hummingbirds

Now that you’ve taken care of your chores reward yourself by adding perennials to your garden for color in late summer through fall. Take a look at the garden areas that aren’t working for you and replant. Good choices include aster, chrysanthemum, coreopsis, and gaillardia. Abutilon (Flowering Maple) come in so many colors that you probably need another one in your garden. Petite Pink gaura looks fabulous planted near the burgundy foliage of a loropetalum. Don’t overlook the color of other foliage plants like leucodtendron ‘Jester’ or Orange Libertia in the garden. A favorite ground cover that hummingbirds love is grevillea lanigera. Consider it for those hot areas.

One last to do: Make a journal entry celebrating the best things about your garden this year.