This week as we study greenhouses we had a terrific field trip to T & L Nursery in Redmond, Washington. The general manager Andrej showed us through the shipping area, the propagation house, the old and the new greenhouses as well as the extensive outdoor growing area. It was fascinating to learn about the history of the greenhouses and how each one serves a specific purpose. Some are for warm growing in the winter, others just to keep rain off plants in the spring. We saw vents and side flaps, heating and cooling systems, irrigation and learned about the computerized environmental control system. Everyone enjoyed getting an inside view of this very successful nursery, which is in our own backyard!
At the end of winter quarter, students had the opportunity to sharpen their pruning skills by taking on one last project in the school arboretum. Each chose a plant to work on and took care of some early spring clean-up. Whether it was getting rid of dead, diseased or damaged wood, or formative shaping, the class helped to make the arboretum a more beautiful place. Good work everyone!
During the last week of October an exciting project took place in the arboretum. In conjunction with Cascade Water Alliance our Environmental Horticulture class installed an irrigation system in parts of the arboretum, covering the perennial beds, the native plant beds, the grass bed as well as the back lawn. With a group of highly organized experts in the field, headed by Mike Brent, our students learned about layout and design as they dug trenches in the rain throughout the arboretum. The irrigation components were all donated from two major suppliers, Rainbird and Hunter. We received a wide variety of fittings, heads and two separate control systems which will demonstrate the options available. This newly designed irrigation system is meant to become a learning lab in the future. The plan is for horticulture students, as well as outside groups, to come in and learn about an efficient irrigation system as they are exposed to an assortment of components, including a drip system. A special thanks to the dedicated team of Mike Brent, Water Resources Manager at CWA, Michael Laurie, Howard Stenn, Dave McGrath and Carrie from Seattle Tilth for making this all possible.
This summer we are carefully growing on many of the plants we had at our spring plant sale. These make up our stock plant collection from which we will take cuttings and propagate new plants for the 2015 sale. It's amazing that from a only a handful of bacopa plants we will create thousands of individual plants to sell in the spring. Because these few plants will turn into so many, we're watching them carefully. Tending them, pinching them, watering and fertilizing them.
Aphids continue to be problematic so we are still using beneficial insects as a biocontrol. Sound Horticulture is supplying us with several ravenous predatory insects. One of them is the green lacewing or Chrysoperia rufilabris. The eggs of the lacewings arrive stuck to little black tabs. They hatch quickly and the larvae are hungry! During their two to three week larval phase the lacewings can eat over 200 pests a week, earning them their nickname of aphid lion. The lacewing larvae is a versatile little biocontrol in greenhouses, field crops and orchards. Besides aphids it preys on thrips, spider mites, sweet potato and greenhouse whitefly, mealybugs, leafhoppers and the eggs and caterpillars of moths. After the larval stage the adults will live four to six weeks, feeding on nectar, pollen and honeydew. Females can lay up to 200 eggs attached to the top of a hair-like filament on the leaves and the cycle begins again.
In addition to our aphid lions, we are using other beneficial insects and also a microbial insecticide. Stratiolaelaps and Amblyseius cucumeris are both both predatory mites and they seem to be doing a great job of keeping thrips under control. The insecticide we are trying is Preferal. It's a naturally occurring fungus which infects many insect and mite pests on foliage and in the soil. The spores attach and penetrate the pests, eventually killing them. The Preferal seems to be working, although we can't seem to completely get rid of those aphids. Whether they are escaping in little hidden crevices or new aphids are constantly flying in, they really like the environmental horticulture program this year. One negative to using the Preferal is the cost. $130 for a 1 pound bag, which is only viable for one month after it's opened. So as we continue to grow our stock plants this summer, we will also continue learning new methods of care and control. That's what keeps life interesting!
Our spring field trip to the Elisabeth C. Miller Garden in Seattle was unforgettable. We spent an hour on a guided tour of this truly remarkable garden. To learn more about the garden, visit millergarden.org.
Normally growing aphids is a bad thing, but in respect to our beneficial insect program, it's a good thing. Here in the Environmental Horticulture Program at LWIT we grow and propagate thousands of plants in our greenhouses. Each year the students put on a huge plant sale that generates money that helps fund the program. This year we had a serious threat from aphids, which began appearing in November and stayed through the spring. Working with Alison Kutz from Sound Horticulture, we began a biological control program, using beneficial insects. We started to bring in good bugs to help us wipe out the bad bugs.
One of the insects that parasitizes aphids is the native wasp Aphidius matricariae. It seeks out aphids and lays an egg inside them, killing the aphid and producing another generation of wasp. Each female lays about 100 eggs, but may attack 200-300 aphids in the process. That's a lot of destruction from one tiny super-wasp. The larvae develop entirely inside of the aphid which turn a light brown and remain on the leaf surface. These aphid shells are referred to as 'mummies'. They aren't just found in greenhouses, I recently discovered an aphid mummy on my Japanese Maple. I was happy that nature was helping me keep my plants healthy.
Buying Aphidius frequently, however, can get expensive, so we decided to raise our own. A true baby wasp nursery in the greenhouse. It's called the banker plant system. We raised a type of aphid that only lives on grasses, so it wouldn't transfer to our greenhouse crops, and this provided a place for Aphidius to maintain and grow their populations. More wasps, less aphids...healthier plants. We had to build an exclusion cage to keep Aphidius out until the aphid populations were strong enough. We sprouted our wheat plants and left them in the exclusion cage for 2-3 weeks and them placed them on benches around the greenhouse. It was fascinating to watch the Aphidius we released near these plants. We could actually see them attacking the aphids, not a good viewing activity for the faint of heart. This is parasitism at its best. As our wheat matured we noticed more and more aphid mummies appearing on the plants. The system appeared to be working! Our aphid numbers did get too high at times and we still had to spray with insecticidal soap. Next year we will start our wheat earlier and get a strong population of Aphidius ready to engage in battle.
Written by Elaine Sawyer, May 2014
Last quarter the students took part in helping to increase wildlife habitat in our study arboretum on campus. Some students noticed some curious fungal growths coming from the base of a Douglas Fir. An assessment from a local consulting arborist told us that the tree had laminated root rot. Over time this type of rot will cause the main root system to die and eventually the tree will come down, likely in a wind storm. He recommended we turn the tree into a snag instead of cutting it all the way down.
A snag tree can be naturally occurring where the top breaks off or the tree slowly dies leaving a bare trunk inviting birds, small mammals and other wildlife. In our urban environments leaving dead trees is often frowned upon but we saw it as a huge learning opportunity and a way to bring more life to our arboretum.
The department of fish and wildlife has a great site with more info on the importance of snag trees for the dozens and dozens of species that depend on them. (Check out the link for more information http://wdfw.wa.gov/living/snags/)
We called in a local arborist to turn our Fir into a snag, which should hold up for many more years to come. He started by climbing and sawing off lower limbs leaving branches then worked his way up to the top removing it with a chainsaw. He then did some creative cutting to make the top appear rough, a though it had broken off. This will help initiate decay and create a more natural look.
The greenery was saved to make seasonal wreaths to raise money for student scholarships, the wood got chipped for mulch and the larger rounds will likely become firewood. All in all this was a great way to 'save' a tree and give back to our local community of birds. We have a thriving populations of birds including some huge Pileated Woodpeckers that will be thrilled with the new addition.
Fall certainly came back all of a sudden! The early and long summer abruptly ended for us Pacific Northwesterners in mid September.
I have found that life as a horticulturist is one of experience and observations.
Last spring I observed an increase in the amount of tent caterpillars on ornamental and fruiting trees. This
fall I am noticing many egg clusters adhered to the branches of trees.
Look closely at the young, 2 year old, branches of deciduous trees. You will notice a gray, translucent, shiny mass hardened on the stem. These are next year’s tent caterpillars. Tent caterpillars are cyclic and we have not had a bad infestation for 10 years or so.
I am now wondering if we will see tent caterpillar populations on the increase over the next few years. Start looking at your trees and let me know if you are noticing egg masses. My mode of pest control for the tent caterpillar has been to flick the egg masses off with my thumb nail and letting nature take care of it. All my caterpillar nests were either taken out by me or the birds this year.
Again, I am wondering, observing, studying. What type of winter this will be? Many plants are extremely drought stressed. The soils are powder dry. Even with the most recent rains the soil is very dry.
I keep observing, watching how plants are responding to our ever changing climate. Are you doing the same?
Our Spring Plant Sale is quickly approaching (April 26-27th & May 3-4, 9am-3pm) and we have been getting many requests for plant list. We know that planning the garden is half of the fun, especially this time of year on those rainy days, so here are the preliminary lists of annuals and edibles (click links to download the pdf). I've included slideshows with some pictures from previous years to help get the imagination going.
Follow the students on their journey through a year of Horticulture education...field trips, plant sales, muddy cold days and new learnings...