Ask a Master Gardener: Here’s a checklist for your fall planting

Do you have a gardening question? The UC Master Gardeners of Santa Clara County can help. Our volunteers are part of the University of California’s Cooperative Extension program and we are trained to use research-based information to educate our fellow residents on sustainable gardening and landscaping practices specifically for our area.

Our monthly “Ask a Master Gardener” column will answer your questions and offer tips. Have a question? Email lifestyle@embarcaderopublishing.com.

Now that I’m pulling out my summer garden, how should I prepare my soil for winter? 

Answer: After harvesting remaining summer crops, add amendments such as blood meal, alfalfa pellets or fish emulsion to replenish nitrogen in the soil. 

Areas of the garden that are not actively planted for winter still need protection to support soil life and prevent soil erosion. Cover crops are one option. Their roots break up the soil, and if they are legumes, like fava beans, they add essential nitrogen. Mulches hold in moisture, moderate soil temperature, and help prevent weeds from germinating. Unlike rocks and synthetic mulches, organic mulches like leaves, wood chips, or straw also slowly break down, benfit soil organisms, and add nutrients to the soil. A top layer of an inch or two of compost will slowly work down into the soil, amending it with organic matter. Manure from herbivores can also be spread over the top of the soil. Even fresh manure, which could burn plants if applied directly, can be used over a bare area to decompose in place and be ready for the next planting season. But be sure to leave some areas of native soil available for ground-nesting bees! 

More Information: Keep Your Soil Healthy

October Gardening Tips 

Summer gardening may get the most attention but fall gardening can be just as busy and productive. You can plant winter vegetables, trees and shrubs, bulbs and native California plants, to name a few.  Here are some tips for October:

Plant winter vegetables

Now is a good time to plant winter vegetables so they have time to get established before cool winter weather arrives and the day length wanes. We recommend planting most cool-season vegetables in early fall. But you might still have luck transplanting leafy greens such as lettuce, arugula, spinach, and kale, and fast growers like radishes and cilantro even later. In our vegetable planting chart, you can see which months are best for planting which plants. Remember that vegetables need at least 6 hours of sun for strong, healthy growth.

Harvest persimmons

If you have persimmon trees, you’re probably seeing an abundance of fruit right about now. The skin of the fruit turns orange when fully ripe. The flat bottomed Fuyu persimmons will still be fairly firm when ready and can be eaten raw like a crispy apple or sliced up and cooked into an apple-style pie. Fruit that falls from the tree early may continue to ripen on the counter despite the green skin. Heart-shaped Hachiya persimmons turn almost jelly-like inside when ripe.  It is best to eat raw by cutting it in half and digging it out with a spoon. They can also be used in baking. If you eat an unripe Hachiya persimmon, you will gain a new understanding of the word “astringent”! To protect the persimmons from birds and squirrels, it is necessary to wrap the tree with bird netting or cover it in a structure made with chicken wire before the fruits are ripe.

More information: Persimmons in California 

Plant trees and shrubs 

You may be tempted to amend the soil when planting trees or shrubs, but it’s no longer recommended. If the soil in the hole is amended, it creates soil moisture differences that discourage the roots from growing into the native soil beyond the hole. For best results, dig a hole about twice as wide as the container. Rough up the sides to help the roots penetrate. Don’t loosen the soil in the bottom of the hole or the plant may settle too low. The goal is to keep the crown of the plant slightly above the surrounding soil, and then simply backfill with the native soil from the hole. 

More information: Planting for success

Plant garlic and shallots 

The time to plant most garlic and shallots is mid-October through the end of November. Fast-growing Dutch Red shallots can mature in just 90 days, so they can be planted again in late winter or early spring. Specialty growers guarantee disease-free stock and offer many more garlic varieties than you see at the grocery store –  from beefy Chopaka Mountain to beautiful Rose de Lautrec.

Choose the largest cloves and leave the natural papery wrappers on them. Plant them in moist, well-drained soil in a sunny location with the pointy tips up, about 1 inch deep. Space cloves about 4 inches apart to leave room for large heads to develop.

More information:  How to grow garlic  and  How to grow shallots

Plant bulbs

Bulbs that bloom in the spring are planted into the ground in the fall. These include those that are technically corms, rhizomes, tubers or tuberous roots, in addition to true bulbs ( babiana, crocus, daffodils, freesia, hyacinths, iris, ixia, sparaxis, and tulips). They can go into the ground in groups, into pots, or be tucked in amongst other plants. They need to be in a place that doesn’t stay wet because they will rot with too much water. It is important that the soil has good drainage. They flower best in full sun or filtered shade. 

Be sure to plant them with the pointy side up because new growth will come from that point. A rule of thumb is to plant them twice as deep as the diameter of the bulb but follow instructions for the specific flowers. Water them in at planting time.

This bulb planting schedule and these tips for growing bulbs can be helpful.

Plant ornamentals

Fall is the best time to plant most ornamentals in California. The soil is warm, but not hot, and winter rains are just around the corner. These conditions are ideal for promoting root growth and giving plants a strong start in your landscape. Since ours is a Mediterranean climate, select plants that grow naturally in warm summers and mild winters. They may be rootbound and look scraggly in the nursery because many are dormant by the end of summer. Don’t be deterred. Just look for healthy roots and loosen them before planting. You also can plant cool-season flowers now that bloom in the winter or others that grow slowly and then explode into fabulous spring blooms. 

Here’s how to give plants a head start with fall planting.

Do a fall garden cleanup

It’s an excellent idea to always keep the garden clean and to remove dead or dying plants or diseased material, yet there may be bigger seasonal cleanups when taking out plants that have finished producing or that need to be removed to make room for new plants. Trim woody or overgrown perennials. Remove plant debris that allows insects and diseases to overwinter and then reproduce. Always pick up fruit promptly from the ground to not invite critters or allow diseases to proliferate. It’s best to leave fallen leaves in place unless they are diseased. They provide a mulch layer while slowly breaking down and returning nutrients to the soil and then back to the plants. If the leaves are diseased, they need to be removed and put out with the yard waste. Monitor the health of your plants while you’re out cleaning up.

Check out this  Fall garden and landscape checklist to keep you on track.

Learn about spooky garden spiders

While we use spiders as spooky Halloween décor, spiders are beneficial insects and only spooky to the insects and other pests that they prey on. Spiders, such as orb weavers, catch our attention with their large, dramatic webs, while dwarf spiders are so small, we may not even notice them. Others, such as jumping spiders and flower spiders, hunt their prey without spinning webs. Widow spiders are indeed venomous, but they are also very shy and hide in dark places. Even though they are common, bites from them are rare. 

Watch this arachnophobia video to learn more about spiders and the myths surrounding them.

You can submit written questions to our Help Desk any time. Use this form to submit a gardening question. When submitting photos of an issue, please also include a picture of the overall plant. We’ll respond via email unless requested otherwise.

You can also subscribe to our monthly Tips and Events newsletter. San Mateo residents can also find gardening advice on the UC Master Gardeners of San Mateo and San Francisco website.