As overwintering western monarch butterfly (Danaus plexippus (L.)) numbers have decreased, conservation groups have urged agencies and private citizens to plant milkweed to support monarch larvae. However, demand for native milkweed plants has outpaced availability in nurseries and seed companies, especially in the western United States. Gardeners have planted the milkweed that they could obtain, often resulting in large numbers of non-native milkweeds in residential gardens. In Chapter 1, I conducted a survey of a set of neighborhoods in the eastern portion of the San Francisco Bay Area of California to understand changes in the prevalence, species composition, and spatial distribution of milkweeds planted by gardeners in an urban matrix. These neighborhoods are adjacent to two monarch overwintering sites and have hosted winter breeding monarchs in recent years. To understand the changing milkweed landscape, I surveyed gardens from October 1 to November 24, 2020, and resurveyed the same parcels from October 14 to November 30 of 2022. I recorded the presence or absence of milkweed plants in the genus Asclepias and in related genera Gomphocarpus and Oxypetalum in each garden, along with detailed information about all milkweed plants and monarch larvae observed. Milkweed gardening expanded over the two-year period with a higher percentage of gardens containing milkweed in 2022 versus 2020. Only four species of milkweeds were regularly found in gardens. More gardens contained native milkweeds in 2022, with the percentage of milkweed-containing gardens with Asclepias fascicularis and Asclepias speciosa both increasing by 4.5 percentage points over the two years. Many gardens still contained non-native milkweeds in 2022. The percentage of milkweed growing gardens with Asclepias curassavica decreased by 4.8 percentage points, but the percentage growing Gomphocarpus physocarpus increased by 7.3 percentage points. These patterns likely reflect the changing availability of native milkweeds and lack of clarity surrounding outreach about non-native milkweeds. For Chapter 2, I documented the winter availability of milkweeds in the same region during the winter of 2020-2021. I re-visited gardens identified during the fall of 2020 and followed how milkweed plants were maintained throughout the winter. After recording if non-native milkweeds were cut back during the winter, I classified the degree of pruning and recorded the presence or absence of monarch larvae. Additionally, I conducted more detailed counts of larvae and eggs on select plants. For gardens containing non-native milkweeds, I found that approximately 18% of such gardens are well pruned close to the ground leaving little to no vegetation, an additional 15% have plants that are partially pruned, and approximately 67% appear to not be pruned at all. Monarch adults, larvae, and eggs are present in local gardens throughout the duration of the winter but are less common in late January through mid-February. Many larvae present in the first two weeks of January 2021 were fourth and fifth instar larvae remaining from the previous year. Large concentrations of eggs became common in early March of 2021, with high egg densities on many plants. While non-native milkweeds were available to and used by monarchs during winter months, some native Asclepias fascicularis and Asclepias speciosa plants retained green vegetation into mid-January of 2021, calling into question the assumption that all native milkweeds die back during the winter. In Chapter 3, I documented common predators of monarch larvae in urban gardens in the San Francisco Bay Area. From the summer of 2021 through the fall of 2024, I recorded all observed fatalities of monarch larvae in a set of experimental gardens. I also conducted structured predation trials from August through mid-October of 2023. Almost all documented monarch fatalities were caused by predation by invasive Polistes dominula wasps. During extended day and nighttime observations, I observed two species of vertebrate predators consuming monarch larvae: a scrub jay (Aphelocoma californica) and a dusky-footed wood rat (Neotoma fuscipes). Other species documented attacking or consuming monarch larvae were a yellow sac spider (Cheiracanthium spp.), Argentine ants (Linepithema humile), and yellow-jackets (Vespula pensylvanica). Attacks by Polistes dominula wasps would sometimes result in monarch larvae dropping from plants and escaping into dense ground cover or weedy vegetation around plants. However, most attacks were fatal and resulted in larvae being skinned, gutted, and dismembered and delivered to wasp nests with repeated trips until only gut matter and head capsules remained. High fatality days generally occurred on hot days in the late summer. Attacks were almost always mounted by a single wasp that had encountered the plant. In earlier summer trials, attacks were less common on monarch larvae in two gardens dominated by agricultural plants despite the wasps being ubiquitous in those gardens. Polistes dominula on these days could often be seen hunting along crops in the Brassicaceae, potentially searching for lepidopteran larvae of other species. My study provides important data on habitat used by both larval and adult monarchs for a poorly understood portion of the western monarch butterfly population. My study also provides an example of ways to conduct science that are place-based and conducted by researchers who are part of the regional community. Conservation practitioners should consider the future impact of rising temperatures on the growth of all species of milkweed. Future efforts should also focus on control of Polistes dominula wasps and working with gardeners to locate wasp nests early each season.