“D” is for Delightful Dahlias and for December. That should help you remember that if you are a dahlia devotee, the growing cycle of the dahlia is from December to December. What we do with our dahlias in December directly determines the direction dahlias will develop. Dare you be a person that leaves dahlias alone? Or do you dig them in December?

 In Napa we are in USDA Plant Hardiness Zone 9b. That means we have mild winters that generally do not dip below 30-25 degrees. This is significant because dahlias do not like cold.  If the temperature drops below 25 degrees, dahlias left in the ground may suffer freezing cold conditions that turn the tubers into mush. Tubers may only be 1-4” below the surface and can be easily damaged.

If you decide to leave the tubers in the ground for the winter and you hear that there are reports of temperature dropping into the 30-25 degree range, you can protect the tubers with 3-4” layer of compost or blanket covers during those days and nights.

If you live up higher in the hills where it is colder than the valley floor, digging up the tubers may be your best bet to keep the tubers from freezing.  If you do dig them up, keep as much dirt around the tubers as you can. This will keep some moisture in the tubers as well as insulting them while in storage.

Cutting  straight down with a spade about 12-16” from the stem should give you enough dirt while not cutting off  or damaging the tubers. To really protect the tubers consider using two shovels or digging forks to pry up the clump. Do not pull them up by the stem as that can damage the necks of the tubers.

The next question is, What do you do with the clumps and tubers?

 

Your choices are:

Photo 1 is of freshly dug up tubers with dirt. Pick the whole clump up and place it into a large box with wood shavings, crumpled newspaper and/or peat moss to keep the clump slightly moist. Leave them there in a cool, dark place (e.g. garage) until the spring (March). Then separate the tubers and plant them.

 

Photo 2 is of tubers slightly cleaned up by water spray that can be stored in newspapers or shavings. This will leave some moisture on the tubers and reduce the risk of drying them out while stored. If left too dry for too long, the tubers will start to shrivel–not desirable.

 

 

 

 

Another alternative to the boxes of wood shavings is Photo 3.  Separate the tubers, clean them (clip the dry roots if you wish), then stack them flat in boxes filled with dry wood shavings or peat moss or vermiculite. The main stem is pointing straight up so if the eyes start to swell, they will be aimed in the right direction. In March you can put the whole bunch into the ground or a container.  

 

 

Or as shown in Photo 4 you can clean and trim each tuber with an “Eye”(the “Eye” being where the new stem will grow.) then label the tubers with a ink marker or plastic label then roll them up in plastic wrap with some shavings and store them wrapped. The advantage is they take up less space and  you can see how they are doing as well as being able to see the name of the tuber. You will also be able to see how the “Eye” is developing.

In all of these cases, store them in a cool, dark place where they will not be exposed to freezing temperatures.

In February and March you can work on the soil in anticipation of the spring planting. But how to do that, is a story for later issue.

Master Gardeners of Napa County are available to answer garden questions by email: mastergardeners@countyofnapa.org. or phone at 707-253-4143.  Volunteers will get back to you after they research answers to your questions.

Visit our website: napamg.ucanr.edu to find answers to all of your horticultural questions.

Photo credits:  Bob Niklewicz

We are now well into October and most of our rose bushes are fading with dull leaves, fewer blossoms and dropping yellow, brown or black leaves. The roses are getting tired and are trying to go to seed. It is time to keep the garden clean as it closes down for the winter, as short as winter may be in Napa. We continue to deadhead our flowering plants as part of that effort to maintain our garden.

Most gardeners have a passing knowledge of the term “deadheading” as it pertains to roses or other flowering plants. It is the removal of the fading or dead flowers from a plant. The main reason for doing so is to keep the flowers blooming and the bushes looking clean and healthy, as well as preventing fungal infestation in the spring. These are the primary reasons we do deadheading in the Fuller Park Rose Garden. We are trying to keep the energy from the leaves and flowers from producing more new growth in the plant's cycle of life. 

When our roses start to fade or just look sad, they grow seed pods called rose hips, and when they are swollen and fertilized (pollinated) they fall to the ground to reproduce copies of the parent bush in the wild. Or, they might be picked apart by birds that eat the seeds before they get anchored in the ground.                             

In controlled environments like our Napa gardens, we generally like to keep the beautiful flowers when they are in full bloom. In order to keep the blooms coming, we deliberately stop the life cycle by deadheading the blooms before the seed pod develops. When deadheaded, the plant will again spend energy to grow more seed pods (hips) in order to propagate themselves.

With some plants you can do the deadheading with just your fingers and thumb by pinching them off.  This is an especially good technique for smaller, younger plants where you Pinch off the top growth in order to stimulate more branches. Roses, because of the thorns, should be pruned with scissors or shears. If you choose to just take off the rose blossom high on the stem, a finger pinch would work, too. With roses, use your shears and make your cut just above the next lower leaves that have five leaflets on it.  If the flowers have been fairly large, you might consider going down to the second set of five leaflets. Make a clean cut just above the leaf.

When working with hybrid tea roses the above is the standard approach to deadheading. However, often you may find new “buds” coming up below the blossom. These are often disbudded (pinched off) in order to make the main blossom bigger. If you are to prune a floribunda variety of rose, often blooms are in clusters of 7-8 blossoms.  Some will fade before the rest. You may just cut away the spent bloom so the others can have more space and energy to grow.

In Napa we have mild winters and roses might grow all year. In colder parts of the country rose bushes go dormant. In Fuller Park, we have an aggressive protocol in January where we can reduce the bushes heights as much as two thirds of their normal size. In essence, we are forcing dormancy by doing this, that will lead to wonderful blooms by May.

There will  be a ZOOM course open to the public during the first week of January, followed by a hands-on class at the Fuller Park Rose Garden the following week. Watch the Master Gardener website ( https://napamg.ucanr.edu/ ) for more details if you wish to participate.

Remember: Toss plant debris into your city compost bin and NOT your own compost pile. The Napa City compost center produces high temperatures that destroy harmful spores while your backyard compost pile is unable to do so.

 

(Photo Credits Bob Niklewicz)

 

If you have questions about the Fuller Park Rose Garden and the Master Gardeners who maintain the Rose Garden, we are usually in the Garden the first Sunday and third Thursday of each month between 10:00 a.m. and 12:00 p.m., weather permitting, February through November. Thank you for your interest in the Fuller Park Rose Garden. See you there.

Napa Master Gardeners are available to answer garden questions by email: mastergardeners@countyofnapa.org. or phone at 707-253-4143.  Volunteers will get back to you after they research answers to your questions.

Visit our website: napamg.ucanr.edu to find answers to all of your horticultural questions.

 

September in the Master Gardeners' Rose Cycle chart (https://napamg.ucanr.edu/files/254549.pdf) has us continuing deadheading and cleaning out any suckers that grow up from the root ball. They generally do not produce any blooms, but they deplete precious nutrients and water from the established bush. The fresh mulch you added last June will be paying back its cost right now.

We had a tremendous amount of heat in July and August.  Many of our bushes suffered greatly from heat stress. Leaves turned brown, looked wilted and/or just fell off to preserve the moisture in the bush. Extra watering or, better yet, more frequent watering to keep the root ball moist is like CPR.

Leaves will also turn yellow from the heat or be susceptible to black spots.  Pick those off the branches and off the surrounding ground to reduce the fungus from spreading. Remember to sterilize your pruners after each bush to reduce the spread of the black spots. Note: We are not totally past severely hot days this summer; protect your roses.  Even putting a cover/shade or umbrella over them during the hottest part of the day will save them from the worst part of the heat.

You may also see aphids now. For the majority of cases, just using a high pressure hose spray will wash off those soft bodied pests. Do it every couple of days until the problem is reduced greatly or cleared. Also, make sure your irrigation systems is working correctly so that your plants receive proper moisture.

                                                 Rose of the Month:   Angel Face

Rosa 'Angel Face' is a floribunda rose. It has a wonderful mauve color that is from it's 'Lavender Pinocchio' x 'Sterling Silver' parents. It has been around for about 70 years. It produces clusters of 3-4” blossoms with a sweet and lemony fragrance. The established bush will have almost continuous displays of blossoms through most of the growing year. This rose has been a prize winner but it starts out slowly, so you may have to wait a year or more for the fully vigorous displays. It is located in two places, one near the NW fence as well as half way up the the north pathway of the garden.

Remember when pruning: Toss plant debris into your city compost bin and not your own compost pile. The Napa City compost center produces higher temperatures to destroy the spores while your backyard pile will not do so. When it comes time to add mulch, consider getting it from the Napa recycling center.

 If you have questions about the Fuller Park Rose Garden and the Master Gardeners (MGs) who maintain the rose garden, we are usually in the garden the first Sunday and third Thursday of each month between 10:00 and 12:00, weather permitting.

You can also go to our Master Gardner website: napamg.ucanr.edu for more details. 

Napa Master Gardeners are available to answer garden questions by email: mastergardeners@countyofnapa.org. or phone at 707-253-4143.  Volunteers will get back to you after they research answers to your questions.