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This Month in Your Garden
MAY |
Roses |
 This is a really fun month for
roses; they are blooming and usually
vigorous enough to resist most
diseases, although it’s important to
keep checking for problems to get to them early.
Black spot looks exactly like it sounds,
black spots on the leaves, with the leaves turning
yellow. It spreads easily to new growth so it is
important to remove any affected leaves from both
the plant and the ground. Rust is easy to spot on a
rose by the rust-colored powder on the underside of
the leaves. This will spread easily, and when you
remove the leaves you can actually see the powder
fall to the soil or to other parts of the plant. A fungicide
formulated for roses (follow directions exactly!)
is usually quite effective, or for a more organic
treatment mix one tablespoon of baking soda
with one tablespoon of horticultural oil to a gallon
of warm water. Spray this on new growth early in
the day, when temperatures are less than 90 degrees.
Keep an eye out for insects also. Aphids
are green soft-bodied insects that love to feast on
new buds. They can be blasted off with water in
the morning (it’s never a good idea to get rose foliage
wet in the late day, after the sun can’t dry them
quickly-wet foliage is more susceptible to disease.)
For thrips, make a solution of insecticidal
soap (follow directions on packaging) and spray
buds just as they begin to color to discourage adult
thrips from laying eggs in them. This should be
done in early morning and not in hot weather.
Of course, another organic way to fight
pests is with beneficial insects, such as ladybugs
and green lacewings. Remember to use pesticides
judiciously if you release beneficials. |
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Perennials and Shrubs |
 May is the month that starts
the transition from spring to summer
in the garden. Many of the
shrubs that been putting on a show of flowers for
months are turning back to green, or in the case of
many of our California natives, brown, for the rest of
the year.
This is the best time to cut back those shrubs
and perennials that have flowered all spring long and
are now declining. By pruning some of the plants
now, you will be rewarded with a second, lesser
bloom.
If you love pink jasmine (Jasminum polyanthum)
in the winter and early spring, and want to keep
loving it, now is the time to get it under control. Otherwise
it will smother everything in sight in no time at
all. And you won’t even realize it is happening because
it will charm you all the while. Then it will
leave you with spent blossoms all over that look like
your plants have been slimed. Cut it back now and
show it who’s boss and it will reward you with another
bloom, but without getting out of bounds this
time!
Speaking of taking over everything, be sure to
trim the long whips on your wisteria that want to wrap
around each other. Cut them back to two nodes for
maximum blooms next year. Cut back any vines that
are creeping under eaves or other places that they
could cause damage.
As lavender starts to complete its bloom cycle,
trim it into neat little spheres so it won’t develop
woody undergrowth. It will think it’s in the south of
France!
This is also the time to prune camellias and
azaleas. Trim back camellias to keep their shape and
size. Azaleas are best tip-sheared with hedge clippers
so they will give a full show of flowers next year.
Both of these shrubs will need to be fed with a fertilizer
high in acid for the first time this year. Follow up
again in another month for both, and that will be all
for the azaleas and a third time in another month for
the camellias, and they will be done for the year too.
As the days start warming up it is time to start
resuming watering duties and therefore you should
have already put down a thick layer of mulch around
your perennials and shrubs to keep the soil cool and
damp between watering. Of course you wouldn’t
want those conditions for your California native
plants. Most natives can handle some light irrigation
throughout the summer, but will suffer from root rot
with any more water than once every few weeks.
Although planting has been in full force for
many plants for months now, this is the best time to
plant tropical plants. Bougainvillea, brugmansia, cannas,
bananas, and citrus will all take off once the
warm days of summer hit, if they have been established
in the middle of spring. If you complain about
burnout in your garden at the end of summer, try putting
in some beautiful combinations of the new colors
of bougainvillea along a fence or wall. Or try a weeping
standard form of the plant. They can be gorgeous
when nothing else can stand the heat! |
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Fruits, Herbs and Vegetables |
 Horticultural scientists are
continually working on methods
to improve the symbiotic relationship between
our plants and the micro-organisms that sustain their
life. Thanks to this research, it is now possible to
boost growth rate by increasing mycorrhizae fungi in
the soil. Mycorrhizae are beneficial fungi that live in
association with plant roots. They synthesize growthregulating
hormones by developing hyphae that attach
to and enhance the function of a plant’s root system.
The plant then takes up more water and nutrients,
facilitating vigorous and healthy growth, more
productive yield and resistance to drought stress and
disease.
These beneficial organisms can be introduced
into the soil by way of inoculant products that are available in combination with fertilizers, or in powder
or tablet form. A mycorrhizal inoculant should specify
that it has been propagated in a sterile environment
and should contain a variety of endo- and ecto-
species. The plant-compatible species of fungi will
develop, and inactive spores will simply remain dormant.
Application is best made at seeding or transplanting,
but it is possible to bore to the root zone and
apply inoculant to established plants as well. Better
nurseries have these products or you can find them
on-line searching mycorrhizal fungi, or go to rootbooster.
com. Follow directions and your veggies will
truly thrive.
Plant pumpkins and winter squash this month
and a second crop of corn. Do a final thinning of carrots,
beets, and radishes. Pull every other onion
whenever you need scallions, to gradually thin the
crop. Remove all but 2 seedlings per hill of squash
and melons. Follow thinning directions on seed
packets for beans, corn and other crops. Pull out
weeds and apply a side dressing of fertilizer to 3”
seedlings. Top with a 2” layer of mulch. Check irrigation
systems to verify adequate moisture and begin
a regular schedule of Bt or insecticidal soap applications.
Thin fruit trees early this month, and identify
any insect infestations and use appropriate controls.
Flash tape or discarded CDs tied to deciduous fruit
trees will discourage hungry birds. Espaliered
trees should be pruned now and throughout the summer
to direct and maintain their form. Cane berries and
blueberries need generous watering as they begin bearing.
Continuous picking, adequate water and a shade
covering can keep strawberries productive too. Feed
citrus and avocados their second application of the season.
Scratch the fertilizer into the top inch of soil and
water well after feeding. |
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