Monarch populations

Traditionally, easter Monarch Butterfly populations have been measured by how many acres of land they cover when they overwinter in Mexico. In 1996-97, Monarchs were estimated to cover over 18 acres (approximately 1 billion butterflies). In 2014, that number had dropped to only slightly more than one-and-a-half acres. In simple terms, this indicates a 96% drop in population. Before we jump to any conclusions, it is important to understand that there have not been comparable drops in summer populations and scientists do not know why. 


Monarch butterfly feeding and breeding grounds​

Monarch Butterflies lay their eggs on certain types of milkweed. This is because those are the only plants the larval/caterpillar stage can eat. Popular rhetoric blames herbicides for killing these particular types of milkweed, but many regular Monarch habitats are flush with milkweed - and no Monarchs. There are mixed opinions on why this is and what it means.


As Monarch numbers initially dropped, people became worried and started planting milkweed and nectar plants to provide global corridors of food and habitat for the lovely Monarch butterfly. In less than one year, it was claimed that Monarch populations had risen from 1.6 acres to 2.8 acres as a direct result of these actions. This would be a great story, but it is not that simple. More Monarch populations are being found in previously unused areas. Some Monarchs are not migrating at all, staying where they are and feeding on popular tropical milkweeds that grow year round. Sounds great, right? Well, it is, and it isn’t.


In “normal” easterMonarch cycles, winters are spent in a state called “reproductive diapause”, in which means they are not sexually active. This is caused by hormonal changes that are believed to be related to daylight hours. Since native milkweed plants are dormant in the winter, everything was in equilibrium. The tropical milkweed (Asclepias curassavica) does not go dormant in winter, so Monarchs are able to stay in the same place year round and forego the migration, similar to the Santa Cruz populations. The only problem is, all that continuous feeding has led to the emergence of microbial parasite, called OE for short, that has the weaken significant numbers of an already stressed species…


What is a gardener to do?
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If you would like to help the Monarch Butterfly on its road to recovery, you can plant milkweed and nectar plants in your yard or on your balcony. Cosmos, marigolds and zinnias are all very easy to grow flowers that provide nectar, but you will still need to provide the proper type of milkweed to support monarch caterpillars. When shopping, look for native milkweed plants, not the tropical variety. If you already have tropical milkweed plants, you have two choices: rip them out and replace them, or trim them back 3 or 4 times a year, to interrupt the parasite’s lifecycle.


Have you seen any Monarchs lately? Please share your photos!

In the photo above, you can see a large number of established hemispherical soft scales. They suck sap from the twigs and leaves of the plant and then excrete a sugary honeydew that ants love. In fact, heavy ant traffic was what notified me of this very subtle, but potentially deadly infestation. As it was, I had to remove several branches.


The problem with infestations such as these is that the excreted honeydew provides a perfect growth medium for fungal diseases, such as sooty mold, and bacterial disease. As ants collect the honeydew and move from plant to plant, they can quickly spread disease throughout your garden.


Symptoms of soft scale infestation

One of the more inconspicuous insects, soft scale can build up a big infestation without anyone noticing. At first, you may simply see what looks like water-stress, leaves may turn yellow and drop earlier than normal, or leaves may die and stay attached.


To avoid the use of chemical treatment against soft scale, regularly monitoring woody plants and stripping any visible vermin away from twigs and leaves by hand are your best bet. You can also use a sticky barrier around the trunks of trees and shrubs to prevent the mobile first instars from establishing themselves on your plants and removing the protection provides by ants.

Easily recognized by their unusually large size (up to 4”) and horn-shaped tail, tomato hornworms (Manduca quinquemaculata) can strip your tomato plants of foliage and fruit in short order. 

Distinguished from their tobacco-loving cousins, Manduca sexta, by displaying white V-shaped markings, rather than single slash marks, both varieties are difficult to see until the damage is done. To learn more about the differences between these two agricultural pests, the University of Florida Extension Office has an excellent resource.

Hornworm damage

The first sign of hornworm infestation is usually stripped leaves and missing smaller stems on tomato plants. Hornworm caterpillars will also eat peppers, potatoes, eggplant and even jimsonweed ~ all members of the nightshade family. They prefer younger, new growth, but they tend to hide under larger leaves. Their bright green coloration provides excellent camouflage. 


Once they eat their fill of your garden delectables, hornworm caterpillars will return to the soil where they develop a hard-shelled pupal covering. Within their winter chalet, hornworms undergo a complete metamorphosis from worm to moth. In spring, the large (4-5”), heavy-bodied brown Sphinx moth will emerge to lay light green, oval eggs on upper and lower leaf surfaces. These eggs hatch and tiny caterpillars emerge, and the cycle continues. In some cases, a second generation can occur in a single year.

So what can you do if you find hornworm damage on your plants?

Handpicking hornworms from your plants is the best defense. They can be dropped in soapy water, tossed in a trash bag or, my favorite, fed to the chickens! Plants should be inspected at least twice a week through summer. If you happen to be lucky enough to discover a hornworm covered with little white packets, do yourself and your garden a favor: place the hornworm in a container covered with hardware cloth and leave it alone. The little white packets are the eggs of predatory braconid wasps. These beneficial wasps are too tiny to cause humans any problems, but they are your friends in the garden. As they hatch, they will feed on the hornworm body, as nature intended.


Since hornworms also feed on  in the nightshade family, you can reduce hornworm populations by keeping your garden weed free. Also, in the fall, till the soil where susceptible plants were grown to kill pupae and burrowing caterpillars.

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Green lacewings and lady beetles also prey on eggs and new caterpillars, so keep your garden predator-friendly with water, plants from the Allium family, and little or no pesticide use.

Farmers and gardeners in the NE and the Midwest don’t even try to grow the more delicate natured plants in the winter, but we Californians have the luxury of at least trying. We can protect our crops by using the USDA Hardiness Map to determine your planting zone (I’m in 9b) and learning when to expect frost to occur. According to the Cornell Cooperative Extension office, “Cool, clear nights with low humidity, often following a cold front, are signs of an impending frost.”
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UC Davis provides a helpful table that estimates when various areas of California can expect frost in the fall. Keep in mind that these are only educated guesses and that Mother Nature tends to kick our butts whenever we get careless or complacent. If you live outside of California, you can check with your local Cooperative Extension office or Master Gardener office for your first and last frost dates. Armed with this valuable information, you can determine which plants will need protection. You can also follow these helpful tips to reduce the negative impact of lower temperatures:

1. Select plants that are suited to your microclimate.
2. Irrigate thoroughly. Well hydrated plants are less likely to freeze.
3. Collect sheets (from your local thrift store) to cover plants during frigid nights. It is best if the fabric does not touch the plants directly. You can use plant stakes, umbrellas or any long handled tool to raise the fabric above the plant surface. Paper or plastic can be used, but they are not as effective. Cover plants in the late afternoon and then uncover them first thing in the morning.
4. Avoid chemical sprays. They do not work, no matter how convincing their advertising may be.
5. In severe cases, you can turn on the sprinklers. Just be sure to leave the sprinklers on until temperatures rise above freezing.
6. Container plants can be brought closer to the house, under a pergola, or brought indoors for the winter season if frost will be too much for them.

​How do you prepare your garden for winter?

In honor of the fact that we actually have water falling from the sky today, let’s talk about drainage.


Good drainage is crucial to plants, both containerized or in the ground, to avoid things like root rot, fungus gnats and, well, drowning. 


So, how do you know if you have a drainage problem? 


If you see pooling, puddling, or muddy spots, you may have a drainage problem. Water will either be held in the soil or it will go someplace else. Now, soil is pretty amazing. Picture the spaces between grains of sand. Water passes through those spaces easily. Loamy soil has medium-sized spaces that slow water movement a bit. Clay soil is made of really tiny bits that create lots and lots of tiny pockets for water to hang out in. We have mostly clay soil here in the Bay Area, so not enough drainage can be a real threat to plant health.


How can you correct a drainage problem?


Adding organic material to your soil is the best way to improve drainage. Period. It doesn’t matter what type of soil you have. Adding compost improves soil structure, the level and variety of nutrients available to plant roots and, hey, it reduces the amount of stuff in landfills! As long as it isn’t diseased, you can compost just about any plant material and use it to improve your soil’s health and drainage. By adding compost to sandy soil, you provide smaller bits of stuff that help hold water and nutrients in place. Loamy soil is already rock star material, but adding compost just makes it even better. When you add compost to clay soil, you create bigger pockets that allow air and water to move more freely, keeping the soil and your plants healthier.


Really big drainage problems can be resolved with swales, ditches, or French drains. Quite simply, you dig a trench that gets progressively deeper as you move away from the problem area. Gravity and surface tension pull the water away and deposit it in areas better able to handle that much water.

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One thing to keep in mind when considering drainage is what is in the water that is draining away. When water drains out of or away from your yard or garden, it’s not going out alone. Every drop of that water contains precious nutrients and microbes. When people use fertilizers, pesticides, herbicides or fungicides, those chemicals are also leached away. This nutrient soup is usually dumped into nearby creeks, rivers, lakes or oceans, disrupting the natural cycles of growth that take eons to evolve (and repair). Just sayin’…