Archive for spring garden prep

Designers List of Shade Plants for Root Weevil Resistance

NE Portland Hostas with Root Weevil Damage

Root weevil damage distracts from an otherwise beautiful collection of shade loving plants.  

Designers List of Shade Plants for Root Weevil Resistance

Root weevil disfigure so many shade garden plants and can make a garden look ravaged. It’s disappointing to see hosta and other plant leaves looking all chewed up. Can we design a shade garden with beauty and style without using root weevil favorite snack plants?

“Well HELL that’s not much of a shade garden” is what I said after eliminating plants root weevil like to eat. I was disappointed in the tiny number of plants that would work and wandered off to write about something different, something a bit cheerier!!!! However, I’ve been thinking about it and yes, we have some great plants we can use. 

Evergreen Shrubs  

Fatsia japonica Spider's Web in SE Portland Residential Landscape Design

Sometimes choosing an interesting variegated leaf, such as this Fatsia japonica ‘Spider’s Web’ can hide the notching caused by Root Weevil (look close!)

Aucuba, Daphne and Fatsia are not root weevil favorites and if you select the variegated forms the notching doesn’t show as much. To be specific, Daphne odora ‘Marginata’,  Fatsia japonica ‘Spider’s Web’, and Aucuba japonica ‘ Gold Dust’ are varieties that I recommend.

I have never seen much leaf damage on our Native Huckleberry (Vaccinium ovatum) probably because the leaves are so tiny.  It doesn’t show which is what we are after.

Three Root Weevil Resistant Rhododendron for Part Shade 

Grant Park Garden Design Rhododendron with Root Weevil resistance

The fuzziness on the bottom of the leaves on some Rhododendrons reduce Root Weevil damage.

I’ve found  lists of root weevil resistant rhododendron less than helpful since most Rhododendron listed are sun lovers. Root weevil prefer part shade to shade loving plants.

Rhododendron ‘Clipiense’ is my best weevil resistant compact rhododendron for shadier situations. This rhody has fine hairs on the leaves so root weevil rarely bother it. It’s a slower growing variety and can take more shade than the other two I have listed but not deep shade.  Any rhododendron with a hairy or fuzzy leaf will be root weevil resistant.  Many of the hairier leafed plants are sun lovers but not all.

Rhododendron ‘Sappho’ is a tall white flowered w burgandy splotched flower.  Sappho does well in morning sun, dapples and afternoon shade.  

Rhododendron ‘Blue Diamond’ can take full sun but does well in full am sun and afternoon shade. It can get taller than wide.

Perennials   

NW Portland Sword Fern and Hardy Geranium in Residential Landscape Design

Sword fern (Polystichum munitum) and Hardy Geranium (Geranium macrorrhizum) do not show Root Weevil damage.

Sword fern (Polystichum munitum)  has a fuzzy frond (leaf) and root weevil don’t eat fuzzy leaves typically. Most fuzzy fronded ferns will be root weevil resistant and are an important player in a root weevil free planting. 

Hellebore argutifolius is perfect for NW Portland Landscape Designs

Helleborus argutifolius photo credit: Great Plant Picks

Hellebores are typically safe from weevil once they are mature plants. When the soft and munchable new leaves unfurl in February the root weevil have not hatched yet (here in Portland) so are not present until late April or May. The harder leafed hellebores like Helleborus argutifolius seem particularly impervious. 

Groundcover Plants   

Oregon Oxalis (Oxalis oregana) doesn’t seem to get a lot of weevil attention in my gardens and it is fun to add to salads. Same with our native piggy back plant Tolmiea menziesii. It has hairy leaves and is great for shade. For Saxifraga varieties, use the hairy leaved varieties for weevil resistance, the smoother ones are on the weevil munch list. Hardy geranium varieties that smell like cedar and have a fuzzy leaf are 100% weevil resistant – Geranium macrorrhizum for deep to moderate shade and Geranium x cantabrigiense for part sun areas. Another good bet is Sweet woodruff (Galium odoratum)

Last but not least, Euphorbia Rob’s spurge (Euphorbia amygdaloides var. robbiae) is a tough evergreen ground covering shade plant. I consider it a thug but it’s great to use in gardens where I have a path that doubles as barrier to their creeping roots. This plants roots must be contained or it will march right over your hostas. I’ve never seen any root weevil damage on this plant.

 Know Thy Enemy?   

Root Weevil have no natural predator here in the Pacific Northwest so it’s rare to find a shade garden without them.  We can cut the population of root weevil down to tolerable numbers and thus get our beautiful shade garden back. Read my blog “Attack of the Root Weevils”  to learn what can be done to reduce their population in your garden. 

 

Lace Bug Update

Azalea Lace Bug damageLast year I wrote a blog about a serious new insect problem for landscapes in the Pacific Northwest. It was serious because rhododendrons and azaleas make up a large percentage of the plants in most gardeners landscape. The easy way to control the insect was with a systemic pesticide that harms bees.  Many people were talking about removing all their susceptible plants rather than harm bees.

Here’s my latest report and what you can do to save your plants without killing bees:

Save bees and your azaleas and rhododendrons. How big a problem?
I have visited over thirty client landscapes in the Portland area since February – all the gardens but two had moderate to severe lace bug damage on rhodies and azaleas.  I was already expecting the 2015 lace bug plant damage to be a huge problem for my clients. Robin Rosetta, Associate Professor, Extension Entomologist, OSU says the lace bug hatch is a full month early.  This is very bad news unless you are prepared to start treating your plants now in mid-to-late April and early May.

Lace bug eggs waiting to hatch.  Photo by Robin Rosetta.

Lace bug eggs waiting to hatch. Photo by Robin Rosetta.

Strong blasts of water should be applied to the back of the leaves to damage the wings of the lace bug while it is in its soft nymph stage.  It can be a little difficult to hold your leaves steady to spray the back side, especially if it is a large rhododendron.  Portland Nursery has something called a Bug Blaster Head for your hose.  It’s easier to use and has a safer pressure for your plants’ leaves.  It also has a wand attachment that would make it possible to treat a large rhododendron.

Insecticidal soaps applied to the back of the leaves will also damage the lace bug nymph. These two methods are effective only while the nymph is soft.  Once it turns into an adult, soaps won’t work and water spray will not remove embedded eggs.

Green-Lacewing March Biological

Green-Lacewing March Biological

This may get confusing because the bad bugs that damage your plants are called lace bugs.  I’m about to introduce you to a good bug that eats the bad bug. The good bugs are called green lace wings.  If you don’t want to spray your plants because they are too big, there are too many plants or you want to work toward a long term solution; you need to purchase green lace wing larvae from March Biological  or go to Portland Nursery to order through them.  The green lace wing will eat the newly hatched lace bug and prevent the lace bug population from exploding.  Getting green lace wings in a high population in your garden will help with the next one or two lace bug hatchings that we expect this year.  My friend, Phil Thornburg, from Winterbloom has successfully diminished his damaging lace bug population. It took him a couple of years but he did it by applying green lace wings instead of pesticides.

Plants in full sun seem to be the most damaged from lace bug.
Basically they are stealing the green right out of the plants’ leaves and laying eggs that will hatch in another month adding insult to your already damaged plant.  Remember to water your rhododendron and azaleas regularly this summer –  they will need the extra support.

Question: What does lace bug on my rhododendrons have to do with bee colony collapse disorder?

Rhody Lutea March 2015 treated with bee killing spray

Rhododendron ‘Lutea’ in my client’s garden without any damage.  A rare occurrence.

Answer:  Systemic drenches often contain imidacloprid. It’s popular because it’s easy, the chemical is suppose to be safer for mammals (so humans, rats, bats are pretty safe) but the spray will harm or kill bees or any insects who feed on the plant.  For months afterwards bees take it back to the hive with the pollen so it’s not just harming one bee – it’s harming the colony.

The time to treat your plants without harming the bees is now!

 

Hydrangea Pruning Made Simple

Spring Hydrangea Pruning

A lot of my clients have asked me to help them with pruning their hydrangeas.

Hydrangea serrata 'Preziosa'

This blog addresses mophead hydrangea pruning.  Hydrangea pruning is simple and easy once you know the rules.  There is a link to a pruning video at the end of this blog produced by Cass Turnball of Plant Amnesty to help you feel more confident.  There are 5 kinds of hydrangeas.  This blog only addresses mophead hydrangea pruning.

 

Hydrangea serrata 'Preziosa'

Why prune hydrangea at all?

Why prune hydrangea plants at all?  Like most plants, pruned hydrangea shrubs will have a better shape so they look good regardless of the flowering aspect.  Many of us buy a hydrangea and think it will be 4’ x 4’.  Over time, many varieties will grow to 7’ tall.  It is very important to plant the right plant in the right place so you don’t have to be frustrated.  There are some varieties that are going to mature at and be easily kept in the 4’ to 5’ range.  We prune to achieve that height as well as a good shape.  If you have a variety that wants to be 7 or even 8 feet tall every year even with proper pruning, the best answer is to remove the plant and buy a variety whose size works for your garden.  Old Arts and Crafts homes with 6’ high foundations are perfect for the hydrangeas that are most cheerful at 7’.  They don’t work as well for homes with a 12” foundation or a small yard.Another reason we prune is to remove stems that no longer flower.

rabbit ears 2

Nicely pruned and open plant

We prune hydrangeas in early to mid March in the Pacific NW.  We start pruning our plants when they are about 3 years old or when you see the oldest stems are developing bark.  Remove the oldest woody canes.  On a young plant this might mean removing only 1 or 2 stems.  We remove dead stems and canes and we deadhead flowers back to the first lateral buds.  I think of these buds as rabbit ears.  I love this task.  I think it’s because I’m close to the ground and my soil smells good.  I typically see 2 colors of buds at this time.  The burgundy buds are just a bump on the stems.  The tiny green buds (the rabbit ears) are such a vivid green.  It says spring to me (and no it doesn’t rain every minute even in March).  These are days when a wool sweater and a down vest are perfect for comfort.

hydrangea 1 heads banner

Joy Creek Nursery Hydrangea Garden

There is more to the story about hydrangea pruning. Occasionally there are individual plants that didn’t read the rule book.  My garden coach client Mary followed the proper pruning techniques and she lost all her flowers for the year!!  AAACK!!  Her plants are 30 plus years old.  Since that debacle Mary only deadheads her plants, again just down to the first buds and she removes old woody stems.  Her plants always flower beautifully and are the focal point of her summer garden.  I’ve never had this happen to me but I’ve heard about it often enough from other professionals to know that some plants are probably genetically different than others.  If you don’t prune at all, your plants will get big and ungainly looking.  A build up of deadwood may diminish their flowering capacity.

For a detailed lesson on pruning mop head hydrangeas, see this video.

Garden Tips: Top 5 Spring Garden Prep Tips

Evergreen Orange Sedge with path light in Portland Oregon Landscape Design

Groom Evergreen Orange Sedge grass but DON’T cut them back

Garden Tips: Top 5 Early Spring Garden Prep Tips

Here are my Top 5  garden tips for things to do January to early March:

Cut back deciduous (gets dead looking in winter) grasses to 2″ tall stubble. Fountain grass, switch grass and japanese silver grass are just 3 that should be cut back this drastically.  Don’t cut back evergreen grasses-they grow  too  slowly  and  will  leave  a hole  in  your  plantings  for  a year.

American Switch Grass -Panicum Virgatum in a low water garden Raleigh Hills Portland Oregon

Panicum virgatum ‘Shenandoah’-American Switch Grass gets cut back in late winter.

 

Modern concrete paver patio design Sellwood Moreland Garden Design in Portland

Freshly installed hydropressed concrete pavers creates patio in shady back yard.

Scrub your flagstone

Scrub your flagstones, especially in the odd corners where they have become very slick. Same for concrete, where you don’t typically walk, it can be very slippery. Bleach will harm your stepables and if you track bleach in on your carpet, it will be a sad thing.  Some do use a 1 to 10 water and ammonia on their flagstone with stepables.  (10 is the water, 1 is the ammonia okay?) Chemicals to remove moss are harmful to your plants.

Cut back Lavender

Cut back Lavender to just above the lowest bits of new growth. Do this before mid March. February is best and as I like to say, January isn’t wrong.

Don’t prune your Rosemary now

Trim a bit of rosemary and make some good chicken soup but don’t prune your rosemary yet because it’s going to flower and our bees need all the help they can get. Prune it after it flowers.  Prune thyme, oregano, sage in February or early March.  Speaking of rosemary, the flu season has me making a lot of soup with rosemary. We have had our patience sorely tested waiting to get over this years flu (2011). Rosemary is both fragrant and flavorful. It lifts my spirits just picking it, I also like it with eggs and potatoes for breakfast, so simple, so good and so easy to step outside my door and snip.

Time to mulch?  Don’t bury your plants.

Time to start thinking about adding an inch or two of compost to place on your planting beds for as soon as you finish spring clean up or April 15 which ever arrives first. Do not bury the crowns of the perennials or other plants.  It can contribute or cause rotting.  Don’t fertilize unless you know what you are doing.  So many new plants and especially trees should not be fertilized their first year and many don’t need anything but good quality compost or mulch applied twice a year.

I hope these tips were helpful.  Please contact me for garden coaching if you are an existing or previous client.  Alana (associate designer and garden coach) and I want to help you have confidence in caring for your landscape.

Carol Lindsay