Hi, and welcome. There are some bay area GWers that visit the CA forums that can give you more specific local information. I'm in the southern part of the state.

Generally a mature garden has had the plant material in the ground for a long enough amount of time (often measured in multiple decades) for the plants to be well established and near their maximum expected size, or at the latter years of their lifespan. Life spans vary greatly. The species matters--some trees are old and ready to die at 20, others remain strong for hundreds of years, for example.

The nuance of speech, and more information about what is in the garden and how old it might be, would help to determine the true meaning of what they were saying. By referring to your garden as mature, they could be admiring the stately specimens that were planted long ago, and hoping like crazy you don't tear the beautiful, historic plantings out. A nicely designed mature garden can be a valuable asset. Or they could be really commenting on how those plants are so large and overgrown for the location in which they were planted, that the roots are lifting the walk and the branches are crowding the eaves, the mature trees are shading out the sun-loving shrubs underneath, and that they should be pruned or removed. Or they could be thinking the plants are at the end of their life span, getting diseased and are in danger of falling over in a storm.

Growingwise, a mature planting will have an established root system and proven it's ability to take the growing conditions where it is located. New plantings require a more careful eye to how they are coping with the growing conditions while they are getting established. Younger plants are at a stage of their life when they have a quicker growth rate and thus require more pruning and training to help them mature into fine, mature plants. If a mature garden has been neglected for a long time, there may be some catch-up maintenance needed. But, generally speaking, a mature garden grows at a much slower rate and does not need as much time to maintain with pruning, weeding, etc.

Too much fertilizer can be far worse than none. The nutritional needs of plants depends upon a lot of factors, including the plant species and your soil. Your plants may not need any fertilizing at all. Is there something about the color of the leaves of your plants that indicates there may be a deficiency? If so, it is better to get a soil analysis, or determine the specific deficiency that might need correcting, rather than just indiscriminately fertilizing. In fact, I have had some plants begin to show evidence of new deficiencies with a discoloration of their leaves only after fertilizing with an all-purpose fertilizer, because it threw the balance of soil nutrients out of whack.

Finding a knowledgeable gardener is the tricky thing. In my area, the landscape maintenance field is awash with "gardeners" that don't know proper gardening techniques; topping, improper shrub pruning/hedging, and a lack of knowledge concerning fertilizing and pest and disease control is the norm. And sadly, most homeowners don't know the harm the maintenance crew is doing, because they see the same "look" all over town. Photographs of how they maintain their current maintenance contracts could be very telling.

Some photographs of your garden would also help the forum give you better information about your particular garden.

Good luck on finding a gardener, too many think sweeping the paths and removing debris is what you are looking for. You have been two years in this home and must have noticed well kept gardens in the neighborhood, talk to these home owners and try and get references of good gardeners. Even if they too busy to take on new gardens now get on their list for when they are available. A good gardener should survey your lot and make a list of what needs to be done, and the priority for doing it. Al

A true 'gardener' is very hard to find. Most services are nothing more than Mow-Blow-and-Go, and really don't want extra responsibilities. I agree with Al, look and ask around your area, but I bet most do their own gardening.

I also agree on the definitions for ' Mature Yard'. Could be good or could mean a lot of work down the road. Maybe your trees and shrubs need a good pruning. I suggest you find a registered Arborist and ask his or her opinion. Something else you might ask your neighbors about.

Thank you so much, all of you! This information is very helpful for me as I start to learn about the garden and how much I can take on vs. how much I would like a weekly gardener to do. Gyr_Falcon - thanks especially for your description of what our mature garden could be. I think we probably fall in the second category of having crowding and overgrowth issues... I don't think we are the "stately" garden or the "end of the life span" garden. We have had a weekly mow-and-blow person for two years but he hasn't wanted to do much more, and until I can make the leap from uninformed novice to educated gardener, I do need to ask around and find a more knowledgeable gardener.

Another way to increase the odds of getting some better quality help is to check out, or get referrals from, college horticulture departments, Master Gardeners, growers at the Fort Mason Community Garden, local garden clubs/societies, etc. They should be able to help you find someone that is experienced and knows their stuff.