Hortus Coronado - May 2020 ...

Don’t forget……..Sunscreen! Hats! Gloves!

Happy gardening!



Roses - Canned roses are good pickings right now at area nurseries.

Annuals To Plant - Ageratum, Amaranthus, Aster, Bedding Begonia, Bedding Dahlia, Candytuft, Celosia, Coleus, Coreopsis, Cosmos, Gloriosa Daisy, Impatiens, Lisianthus, Lobelia, Marigold, Nasturtium, Petunia, Phlox, Portulaca, Sunflowers, Sweet Alyssum, Verbena, Vinca Roses, Zinnias.

Vegetables - Beans, Beets, Carrots, Cantaloupes, Corn, Cucumbers, Eggplant, Kohlrabi, Leaf lettuce, Lima beans, Okra, Parsley, Peppers, Pumpkins, Radishes, Summer, Tomatoes, and Watermelons


We are probably at the end of any significant rain in the coming months. Make sure your irrigation is turned on and make any needed repairs.

Roses need about 1½ inches of water twice a week this month. The blooms have been spectacular this year. Thank you Mother Nature!

Epiphyllums are still blooming so continue to cut off faded blossoms and mist frequently in hot weather but don’t overwater. A good rule of thumb is to water when the soil is dry down to 1-1/2 inches.


Plants are continuing a big growth period so continue fertilizing. Remember not to overdo the feeding, otherwise your plants will grow too aggressively, resulting in softer growth and a thirstier plant during the summer months.

Watch for iron deficiency to show up in plants as yellowing leaves with green veins. After the rainy season the soil has been flushed, which is a good thing, but minerals will be lacking so we need to amend appropriately. Feed plants with a fertilizer that contains chelated iron combined with zinc.

Cymbidiums - May begins the main growing season. Good summer care is important. Keep the plants in semi-shade. Cut off bloom spikes and fertilize with your favorite orchid fertilizer. If you want to go a very easy route, fertilize with 2 or 3 tablespoons of Osmocote about once a month.  Fertilizer will be released each time you water. Have your cymbidiums outgrown their containers? Transplant no later than the end of June. If you wait, you may not get blooms next year.

Camellias, Azaleas and Rhododendrons - Start feeding with an acid fertilizer when they have stopped blooming. Use at half-strength so you can feed again two or three more times, fertilizing at 6-8 week intervals, finishing up at the end of September.

Dahlias - Give your dahlias a low nitrogen fertilizer to keep the plants strong for those beautiful flowers that will bloom in the summer.

Pest & Disease Control:

Head out to the garden in the early morning or evening to find snails and slugs. They are out in force and can do lots of damage in a short period of time. Move pots around to expose hiding spots. If the nights are damp, hunting is usually very fruitful, so get out there with a flashlight and find those little devils!

If you have planted your veggie garden already, chances are you will be battling leaf mold on your squashes. Typically, the cause is overwatering but coastal cool, damp weather can play a big part, too. There are a few theories about how to deal with this problem organically. One theory says to dilute skim milk 50% with water and spray on leaves. (Only use skim because the fat in milk will get stinky out in your garden!) 

Warmer weather means that garden pests are waking up, stretching and getting ready to feast on all the new, fresh growth in your garden. If you see aphids blast your plants with water first. Do this in the morning so plants dry off before nightfall. Ladybugs are good garden helpers to keep aphids in check but keep a spray bottle of Safer insecticidal soap handy so you can spot-treat when needed.

Watch for whitefly on your citrus, gardenias and hibiscus. Infestations signal weakness in plants and the honeydew secreted by whiteflies attracts black sooty mold and fungus which further weakens plants. Dressing the base of your plants with worm castings is a good practice to strengthen plants immunity and hopefully, keep infestations manageable.

Caterpillars are starting to appear so it’s important to stay ahead of an infestation. Some caterpillars will turn into beautiful butterflies, so don’t over react when you see your first one or two. On your roses, watch for rose slugs aka saw flies. Pay attention to the undersides of the leaves, looking for pale-green, caterpillar-looking slugs. They will strip a plant bare if you don’t pay attention. Spray your plants to wash these pests off, but if it begins to get out of hand, spray with BT, aka Bacillus thuringensis. BT is a natural bacterium in soil that acts as an insecticide that is a toxic to larvae, killing caterpillars only, leaving beneficial bugs alone.


If you haven’t done so already, it’s time to prune back frost damage on your plants.

Now that azaleas and camellias are finished blooming, it is time to prune. These plants bloom on year-old growth so if you wait too long to trim, you’ll disrupt the cycle for next year’s blooms.

It’s also time to prune your hibiscus, lantana and other sub-tropicals. These plants need shaping and can be cut back by as much as half, allowing you to shape them and clean out for a healthier plant. This also allows you to wash down plants more effectively if you get a whitefly infestation.

Pinch back your fuchsias, salvia and chrysanthemums to prevent legginess and promote fuller plant growth.

Thin out the new fruit on your deciduous fruit trees to about one fruit about every six inches.  This is easier said than done, because it’s hard to remove potential future fruit but you’ll get a better harvest for it and trees won’t get so stressed.

Don’t forget……..Sunscreen! Hats! Gloves!

Happy gardening!

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