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Plant diseases

photo 2Plant diseases are infuriating! – It is just horrifying to see all our hard work withering on the vine. Preventative medicine as opposed to treating symptoms after they have become a problem is always the best approach so here are a few tips to keep your garden healthy and disease free:

When shopping for plants look for disease resistant varieties and choose plants that are vigorous and healthy. Shopping with a reputable grower is always a wise choice.

If you notice any sign of disease on plants immediately remove damaged parts and if necessary the entire plant. Composting will not always kill pathogens which can spread to additional plants or even overwinter in the soil so diseased plants should be sent out with the trash or burned.

Choose the right plant for the right location – If a plant is stressed because it is in the wrong spot – has too much sun or too much shade it will be more susceptible to disease. The same it true of water and fertilizer – the wrong amount of either one can cause more damage than good.

Rotation of vegetable crops will help break the cycle of disease by eliminating the build up of diseased organisms in one spot.

Over crowding of crops can create too much humidity and fungal disease. Keep air flow moving by good planning and thinning.

Keep the garden tidy by turning under finished crops before disease causing organisms can take over. And clean tools and especially pruners in between uses to keep from spreading disease from an infected host.

Preventative treatments like dormant sprays can be a safe way to protect plants – be sure to follow instructions carefully.

Because of our high rainfall and mild climate fungal and bacterial diseases are the most common problems in Portland. Here are a few to keep an eye out for:

Botrytis blight
This fungal disease looks like a grey powdery mold. It primarily appears on vegetable, bulbs and some perennials. Strawberries and zucchini are especially susceptible. Look for wet looking spots on leaves or fruit which will turn into a powdery grey mass. The entire plant can sicken and die so deal with it as soon as you spot it.
Air circulation is the best defense as this fungus prefers warm and humid areas. More sun also helps so pruning neighboring plantings can be useful so avoid wetting the leaves of susceptible plants while watering. Finally – remove and destroy any infected plant parts and wash tools and hands after.

Powdery mildew
Another fungal disease that commonly affects PNW gardens is powdery mildew. Late Summer is the time to look for white powder splotches that envelop leaves and stems. Cucumber, beans, zucchini, squash and roses are among it’s favorite victims. Although it can cause serious damage if left unchecked it is possible to minimize spread and still reap a harvest from infected crops.
Making space for air flow and maximum sun is essential. Well watered plants are less likely to fall victim but be sure to water from below and avoid water on leaves. Remove and destroy damaged foliage. A solution of 1 T baking soda to 1 gallon water and a tad of liquid soap spayed onto the leaves will also help.

There are a gob of different fungi that produce rust but the prevention, identification and treatment is similar. Orange to yellow spots present in speckled formation on the leaves. Spring or late Summer is the usual time for it to appear as the fungi prefer mild days and cooler damp nights.
Again overhead watering should be avoided to restrict the spread of rust. More sun also helps. Remove rusted leaves and garden debris to prevent the cycle of reinfection.

Commonly attacks apples and pears in the Spring right after flowering. It looks just like it sounds with with yellow to brown to black blotches on the leaves and sometimes the trunk. Leaves can eventually drop and in extreme cases defoliation may occur. Fruit can also appear scabbed but is still edible.
Remove and destroy damages areas. Pruning for air circulation is helpful but in extreme cases a copper spray can at lease prevent against another infection the following year.


Ramorum blight and tip dieback
The symptoms vary widely according to the host plant but generally look for bark cankers especially ones that are bleeding or girdle the entire circumference of the trunk. Leaf spotting or blotches appear in areas of the leaf that can collect water such as at the tips or the midribs.
This disease only first appeared in 1995 but has quickly spread. It can affect many types of native oaks, rhododendrons, myrtle, bay laurel, madrone, cascara, redwood, douglas fir, kinnikinnick, salmonberry, and evergreen huckleberry. It also attacks viburnum, camellias and pieris among others.

Root rot
The risk of root rot comes in the winter as water drenched soil robs roots of oxygen and makes them susceptible to this soil fungus. Signs may not appear on the plant until the early summer when the plant is unable to draw water through its damaged roots. Plants may appear wilted with leaves eventually browning but adding water will not help. Prevention is the best approach start with healthy plants and create good drainage before planting. A mycelium application will improve soil conditions and root health. Mulching can also help to discourage spread by cooling the soil. If unable to recover replace plants with a resistant variety that is suitable to the location.

Verticillium wilt
Look for one single branch showing signs of stress – wilting or the leaves turn brown while the rest of the plant looks perfectly fine. Often a long canker will also appear in the affected area and a ring will be present in the cross section of a cut branch. This soil borne fungus will attack many plants but maples are especially at risk. Complete lists are available online.
A similar disease attacks tomatoes, peppers and eggplants.
Established trees can sometimes be saved by removing affected branches and building the up soil health. Apply a thin compost but avoid high nitrogen, potassium is better. Clean tools immediately after use as the disease can be easily spread to other plants. If the plant needs to be removed replace with a resilient species.

Bacterial blight
Rapidly wilting leaves and dark splotches that manifest in the rainy spring can mean a bacterial infection. Remove and destroy affected parts and plants. Wash tools between each cut to avoid spread and wash hands before moving to another area of the garden.

This bacterium can move quickly and so the symptoms progress rapidly. Leaves and entire branches can redden and drop within days. Affected areas should be removed and burned as soon as detected. Cuts should be made at least 12 inches below the affected area. Tools need to be cleaned between cuts. This bacterium is transmitted by pollinating insects and infected plants can act as hosts and spread rapidly to other plants.

The Pacific Northwest Plant Disease management handbook is available online and has an exhaustive list of diseases. It is organized by host so it makes identifying the disease a little easier. Be sure you have the right diagnosis before beginning a treatment and please try natural methods before resorting to harsh chemical applications.


Growing air-plants

airplantsAn Air-plant or Tillandsias is part of the Bromeliad family. Air-plants are native to the americas and have an amazing range from the southern US all the way down to south America. There is an astonishing variety of air-plants that have developed out of their diverse habitats. Tillandsias like many bromeliads get their nutrients and water primarily through their leaves and therefore do not need soil to survive.

It is practically impossible to overwater an air plant since they only absorb the moisture they need. But they do need to be able to dry between waterings. A soggy location is not healthy for the plant and they should never be left in a position so that water accumulates in the center of the plant as this will cause rot.

Frequent misting works just fine for air-plants but they really love at least a weekly soak in lukewarm water and can even occasionally soak overnight. Be sure to shake out excess water after each soak. Watch the plants closely to determine how often you should be watering as different homes and even parts of the home will vary in humidity.

Signs that your air-plant is under watered.
Tips of the leaves may turn brown.
The natural curvation of the leaves will increase.
Leaves will feel stiff.

Air-plants do not like to dry completely and prefer a humid environment. If it seems under watered they can be revived with a good soak. When moved to a new environment even from one room to another they will often shed their bottom leaves – don’t despair as this is just part of their acclimation process and they will often recover.

Tillandsias like a litter fertilizer once a month or so. You can use a bromeliad or orchid fertilizer look for foliar feeds and follow the instructions on the bottle for amount.

Location and light
Air-plants seem to do best when paired with other plants. I tuck them in and amongst my other plantings but am sure to not place them directly in the soil where they might set in water for to long and get soggy.

There are many species of air-plants and some require more light than others. Like most houseplants they enjoy a nice bright but diffused light. Of course here in the northwest light in the winter is a premium so they may need to be moved to a sunnier location during winter months.

Many people like to keep their air-plants in the bathroom so they can take advantage of the extra moisture. And while this is true you will still need to water the plants. Unless you live in a dorm with people showering around the clock most bathrooms do not retain enough moisture to keep air-plants happy. Another consideration is light, many bathrooms have very little light so unless you have a nice big window the bathroom may not be the best spot for your tillandsias. One last consideration is heat. Bathrooms in older homes tend to be a bit chilly and air-plants enjoy consistently warm environments.

You can mount air-plants onto wooden boards, natural logs or driftwood.They also work well on ceramic or brick mediums. When attaching an air-plant avoid copper wire or superglue as they will poison the plant. Moss can hold a lot of water so use caution so that your air-plant doesn’t stay to soggy. Air-plants are often placed in all sorts of containers. The main things to remember is that they will need some air flow and never want to be in standing water.

Tillandsias produce offshoots called pups. They shouldn’t be removed until they are about 1/3 of the size of the parent plant. You can leave them together to form a nice clump or if you decide to divide them gently pull in a twisting motion. Some varieties will die after blooming but will often send out tiny pups at the same time, leave the mother plant intact until it dries completely.

Thicket is offering several classes on Tillandsias this summer so stay tuned to our events page and come in to make your own mounted air plant project.

June tips

June can be a scorcher or we can lapse into “Juneuary” with cold temperatures and dreary days that make us long for a real summer. But either way June is a great month for gardening. The weather has warmed enough to get those new plant starts growing and it’s not too terribly hot so we can enjoy being outside and keep those garden projects moving along comfortably.

It was an insanely dry winter and now our farmers and agricultural families are paying the price so please do your part and conserve water! Here are a few easy tips.
Water in the morning when less will evaporate and the plants are taking up water more efficiently so less is lost.
Direct water close to the roots where it is needed most instead of overhead.
Consider installing a drip system to save water and your precious time.
See more watering tips in posts from July 2013.

Pests and diseases:
This is the season for the pests to thrive. Prevention is much better than reactive control. Specific plantings and building bug houses are a great way to help those beneficial bugs.
You can visit our pest management post to help identify pests and comprehensive ways to deal with them effectively. Look for caterpillars, aphids, slugs, thrips, whiteflies, flea beetles and cutworms – boy there are a lot of them out there!  As a last resort start with the least invasive treatments:
– Insecticidal soap
– Horticultural oils
– Botanical insecticides
Fungal problems such as black spot or powdery mildew appear this time of year treat where appropriate with anti fungal solutions, trimming and by thinning to creating air flow.

Vegetable garden tips:
Start cooler weather crops like greens and cilantro in a shadier spot like behind your row of tomatoes or under your bean pole so they will get a little protection from the hot sun to come.
Deadhead garlic blooms so that growth energy is focused on the bulbs and use the scapes in a stir fry.
Pick those strawberries! If left to rot they will invite disease.
Cage, trellis or stake tomatoes and vines before they get to big and unruly.
Invest in a dandelion weeder and save your back.
Feed starts with and organic fertilizer or a composted manure or bio-mulch.
Thin your plantings of greens, beets, radishes and onion to use as micro-greens.
Adding a mulch can conserve moisture and help keep weeds at bay.
Squash (or any of the curcubits) blossoms may drop but not to worry this is a natural process where the first flush of male flowers drop after pollination. The second flush of flowers are the female blooms and they are the ones that will develop into fruit.
Resist the urge to cut suckers on fruit trees as it will only encourage more growth now.

Seed outdoor:
For your rotation plantings add – arugula, asian greens, beets, broccoli, carrots, chard, green onions, kale and lettuces.
For the first round of seeding – basil, beans, corn, cucumbers, melons, pumpkins and squash are all ready to go out.

Starts for direct planting:
Just about everything can now go in the ground! arugula, asian greens, basil, beets broccoli, brussels sprouts, carrots, chard, cauliflower, chives, corn, cucumbers, dill, eggplant, green onions, leeks, kale, lettuces, melons, peppers, pumpkins, squash and tomatoes.

The veggies are really coming in now! Greens galore, peas and broccoli, cabbages and herbs oh my! Eat up and enjoy all that hard work!

© thicket 2017